THIRD INTERNATIONAL CONFERENCE ON PERMAFROST TROISI~MECONFERENCE INTERNATIONALE SUR LE PERG~LISOL
Edmonton, July/juillet 1978
ENGLISH TRANSLATIONSOF THE FORTY-NINE SOVIET PAPERS, THE ONE FRENCH PAPER, ANDTHE THREE INVITED SOVIET THEME PAPERS
VERSIONS ANGLAISES DES QUARANTE-NEUF MEMOIRES SOVI~TIQUES, DU MEMOIRE FRANCAIS,ET DES TROIS RETROSPECTIVES PRESENTfES PARDES CHERCHEURS SOVIfiTIQUES
PART I: ENGLISH TRANSLATIONS OF TWENTY-SIX OF THE SOVIET PAPERS (Published in Vol. 1 of Conference Proceedings)
PARTIE I: VERSIONS ANGLAISES DE VINGT-SIX M€MOIRES SOVIETIQUES (publi6es dans le Vol. 1 du Compte rendu de la Confgrence)
OTTAWA, March/mars 1980 NRCC 18119 Part Iof two Partie Ide deux Published by the NATIONAL RESEARCH COUNCIL OF CANADA
Copies obtainable from: The Executive Secretary,Third International Conference on Permafrost, c/o National Research Council of Canada, Ottawa,Ontario, K1A OR6.
Price: $35.00 (Parts I and 11) ~-Part 1 Part I1 ISBN 0-660-10520-9 ISBN 0-660-10521-7 NRCC No. 18119 NRCC No. 18119 Cat. No. NR15-6/1978-3-1 Cat. No. NR15-611978-3-2
NOTE:
Volumes 1 and 2 of the Conference Proceedingshave the following identification:
Vol. 1 ISBN 0-660-01735-0 NRCC No. 16529 Cat. No. NR15-6/1978-1 Vol. 2 ISBN 0-660-50401-4 NRCC No. 16529 Cat. No. NR15-6/1978-2
PubliC par le CONSEIL NATIONALDE RECHERCHES DU CANADA
On peut obtenir des copiesen s'adrcssant au Secr6taire administratif, TroisiPme conf6rence internationale sur le pergilisol als du Conseil national de recherches du Canada, Ottawa, Ontario, K1A OR6.
Prix: $35.00 (Parries I et 11)
Partie I Partie I1 "
ISBN 0-660-10520-9 ISBN 0-660-105h-7 CNRC No 18119 CNRC NO 18119 No de cat. NR15-6fl.978-3-1 No de cat. NU15-611978-3-2
-~REMAR-: Les volumes 1 et 2 du Compte rendu de la ConfGrence sonr identifigs come suit:
Vol. 1 ISBN 0-660-01735-0 CNRC iJ0 16529 No de cat. NR15-6/1978-1
vol. 2 ISBN 0-660-50401-4 CNRC NO 16529 No de cat. NR15-611978-2 PREFACE
The Third International Conference on Permafrost was held in Edmonton, Alberta, in July 1978. It was sponsored by the National Research Council of Canada through its Associate Committee on Geotechnical Research (Chairman - Dr. L.W. Gold, Associate Director, Divisionof Building Research, National Research Council of Canada). The Proceedings of the Conference, published in two volumes, included 139 submitted papers (Vol. 1) and 8 invited special theme papers (Vol. 2). This present publication (in two Parts) contains the49 submitted Soviet papers, the1 submitted French paper, and the 3 Soviet theme papers. The papersaxe in the same orderas they appear in the Conference Proceedings.
This record is dedicated to the memoryof Mr. Valery Poppe, a noted Russian interpreter and translator with the National Research Council of Canada. For many years he provided invaluable interpretation and translation services in the permafrost field which greatly assisted contacts between North American and Soviet scientists. He played an active role at the Third International Conference on Permafrost only weeks before hissudden and untimely death in September 1978. The NRC Associate Committeeon Geotechni- cal Research and the Divisionof Building Research wish to take this opportunity to express their sincere appreciation of Mr. Poppe's many contributions to the workof the Division and the ACGR through the years.
Their thanks are here recorded also to the other translators for their services in the preparationof these books: P.J. Hyde and Associates, Walter Kent,Josef Nowosielski, Hazel Pidcock, Victor Popov, RobertSene, Donald Sinclair, and Tania Thorpe. The technical editing was done by R.J.E.Brown, Division of Building Research with assistance fromT.W.H. Baker of the same Division. Dr. Brown was Chairman of the Conference. The work of Lise Esselmont, NRC Translations, in organizingall the translations and producing the final typewritten manuscripts is also gratefully acknowledged.
Ottawa C.B. Crawford March 1980 Director, DBR/NRC La TroisiPme confgrence internationale sur le pergelisol a t5tg tenue 2 Edmonton, Alberta, au mois de juillet, 1978. Elle a et6 parrain6e par leConseil national de recherches du Canada par l'entremise de son Comitg associgde recherches ggotechniques (Prgsident - Dr. L.W. Gold, directeur adjoint, Division des recherches sur le bztiment, Conseil nationalde recherches du Canada). Le compte rendu dela Confgrence, publiE en deux volumes, comprend 139 mgmoires (vol. 1) et 8 rgtrospectives spgciales (vol. 2). La prgsente publication (en deux parties) comporte49 mgmoires sovigtiques, le mgmoire franqais etles trois rgtrospectives sovigtiques. Les mgmoires apparaissent dansle mEme ordre que celui du compte rendu de la Confgrence.
Ce document estdiSdiG a la memoire deM. Valery Poppe, interprste et traducteur russe distingug quia travail16 au sein du Conseil national de recherches du Canada. Pendantphsieurs annees, il a fourni un service d'interprgtationet de traduction inestimable dans le domaine du pergEliso1, qui a grandement les aid6 rapports entre les scientifiques nord-am6ricainset sovigtiques. I1 joua un rljle actif lors de la Troisisme aonference internationale sur le pergglisol quelques semaines seulement avant sa mort soudaine et prgmaturge sur- venue au mois de septembre, 1978. Le ConitE associg de recherches ggotechniques duCNR et la Division des recherches Issur bgtiment profite de l'occasion pour exprimer leur gratitude pour les nombreuaes contributions deM. Poppe au travail de la Divisionet du CARG au cours des annges.
I1 remercie ggalement les autres traducteurs pour leurs services lors de la pr6paration de ceslines: P.J. Hyde et associgs, Walter Kent, Josef Nowosielski, Hazel Pidcock, Victor Popov, RobertSerrG, Donald Sinclair, et Tania Thorpe. La rGvision techniquea 6t6 faite par R.J.E. Brown, de la Division des recherchessur le bztiment avec l'aide de T.W.H. Baker de la mzme Division. Le Dr. Brown gtaitle prgsident de la ConfGrence. Le travail de Lise Esselmont, des Services de traduction duCNR, pour l'organisation de toutes les traductions et la production du document final est aussi grandement appr6ciG.
Ottawa C.B. Crawford mars 1980 Directeur, DRB/CNR TABLE OF CONTENTS (Parts I and 11)
PART I
Balobaev, V.T. Reconstruction of Palaeoclimate from Present Day Geothermal Data ...... Gavrilova, M.K. Classification of the Relationship Between Climate and Permafrost-Climatic Regions ...... Moskalenko, N.G. et al. The Effect of Developing a Territory on the HeatBalance and the Thermal and Moisture Regime of the Ground in the Northern Partof Western Siberia ...... Pavlov, A.V. Thermal Physics of Permafrost Terrain ...... Kudryavtsev, V.A. and Melamed, V.G. Geophysical Aspectsof the Development of Permafrost ...... Kvlividze, V.I. et al. An NMR Study of the Phase Transitionof Water in Models andin Frozen Clays ...... Savel'ev, B.A. Investigation of the Structure and Propertiesof Bound Water ...... Shvetsov, P.F. Conditions and Geothermal Consequences of the Moisture Exchange Between the Lithosphere and the Atmosphere in Permafrost Regions ...... Zhestkova, T.N. Results of Experimental Studies of the Freezing Process in Very Fine-Grained Soils ...... Chizhov, A.B. The Role of Highly Mineralized Groundwater in the Cooling of the Lithosphere at Depth ...... Ershov, E.D. et al. Experimental Investigation of Heat and Moisture Transfer During Sublimation- Desublimation of Water in Fine-Grained Soils ...... Ershov, E.D. et al. Water Migration, Formation of Texture and Ice Segregation in Freezing and Thawing Clayey Soils...... Fotiev, S.M. Effect of Long-Term Cryometamorphisrn of Earth Materials on the Formation of Groundwater ...... Romanovskii, N.N. et al. Long Term Dynamics of Groundwater Icings ...... Baulin, V.V. et al. The Role of Tectonics in the Formation of Permafrost on Low Plains ...... Page
Gasanov, Sh.Sh. Cryolithogenesis as an Independent Hydrothermal */ Type of Sedimentary Process ...... 225 v'
Gravis, G.F. Cyclic Nature of Thermokarst on the Maritime Plain in the Upper Pleistocene and Holocene ...... 245 Jy'
Grechishchev, S.E. Some Aspects of the Mechanics of Frost Fracturing of Soils in the Permafrost Zone ...... 259 c."" Konishchev, V.N. Mineral Stability in the Zone of Cryolithogenesis ...... 279 /' Romanovskii, N.N. Principles of Classification of Polygonal-Vein 297 Structures ...... *>..' Are, F.E. Offshore Permafrost in the Asiatic Arctic ...... 311 f*'
Baranov, I. Ya. Structure of the Northern Circumpolar Permafrost Region ...... 3 2 7 vd'" Dubikov, G.I. More Precise Position of the Southern Permafrost Boundary Between the Urals and theOb River ...... 34 7 /"" Gorbunov, A.P. Permafrost in the Mountains of Central Asia ...... 357 p Kudryavtsev, V.A. et al. Zonal and Regional Patterns of Formation of the Permafrost Region in theU.S.S.R...... 371 /'"'
*/ Popov, A.I. et al, Cryolithological Map of the U.S.S.R. (Principles of Compilation) ...... 391 v/
PART 11
Vtyurin, B.I. Principles of Cryolithological Regionalizationof the Permafrost Zone ...... 1
Grave, N.A. and Sukhodrovskii, V.L. Terrain-Forming Processes in the Permafrost Region and the Principlesof Their Prevention and Limitation in Territories under Development .... 11 Anisimova, N.P. Hydrogeochemical Investigations in Permafrost Studies ...... 25
Avetikyan, Yu. A. Use of AC Current Surveys in Permafrost Studies ...... 43 Page
Kudryavtsev, V.A. and Maksimova, L.N. Forecast of Changes in Geocryological Conditions during Economic Developmentof thePermafrost Region ...... 57
Kudryavtsev, V.A. and Kondrat'eva, K.A. Geocryological Survey Methods ...... 71 Mel'nikov, V.I. and Gennadinik, B.I. Electrical State of a Permafrost Cross Section ...... 85 Garagulya, L.S. et al. Thermal Interaction of Pipelines with theGround ...... 103
Aguirre-Puente, J. Present State of Research on the Freezing of Rocksand Construction Materials ...... 117 Dokuchaev, V.V, et al. Ice Rich Soils as Bases for Structures ..... 133
Frolov, A.D. Problems and Possibilities of Studying the Processes of Dynamic Relaxation in Frozen Earth Materials ..... 149
Maksimyak, R.V. et al. On the Role of the Components of Frozen Clay Soils in the Developmentof Strength at Different Temperatures ...... 169 Vyalov, S.S. Kinetic Theory of Deformation of Frozen Soils ...... 185
Baulin, V.V. et al. Permafrost Investigations in Pipeline Construction ...... 199 Biyanov, G.F. and Makarov, V.I. Characteristics of the Construction of Frozen Dams in Western Yakutiya ...... 213
Buchko, N.A. et al. Seasonally Operating Units and Their Use in Northern Construction ...... 227
Makarov, V.I. et al. Construction of Multi-Storey Buildings on Cold Piles in the Cityof Mirnyi ...... 241 Peretrukhin, N.A. Strength and Stability of Railway Subgrades in Permafrost Regions ...... 255
Popov, B.I. et al. Construction of Earth Embankments for Highways in Western Siberia ...... 269
Porkhaev, G.V. et al. Construction by the Method of Stabilizing Perennially Frozen Foundation Soils ...... 283
Vyalov, S.S. Long-Term Settlement of Foundations on Permafrost .... 297
Maksimov, V.M. Hydrodynamic and Hydrochemical Assessment of Explosions Used in Testing Low-Output Wells in Permafrost Regions ...... 313 Page
El'chaninov, E.A. et al. The Stability of Underground Workings in Permafrost ...... 32 1
Emel'yanov, V.I. and Perl'shtein, G.Z. Water Thawing of Frozen Ground for Open Pit and Underground Mining in the Northeast ofthe U.S.S.R...... 339
Mel'nikov, P.I. Permafrost - Hydrogeological Zoning of Eastern Siberia ...... 355 Vyalov, S.S. Interactionbetween Permafrost and Buildings ...... 379
Tsytovich, N.A. et al. Design, Construction and Operation of Earth Dams in Arctic Regions and under Permafrost Conditions ...... 407 -1-
RECONSTRUCTION OF PALAEOCLIMATE FROM PRESENT DAY GEOTHERMAL DATA
V.T. Balobaev ' Permafrost Institute, Yakutsk
Earth materials are a medium in whichthermodynamic disequilibrium processes at a given moment of timedepend not only on parametersof the state of these materials and the gradients of these parameters at that moment of time, but also on the state of thematerials during earliers stages, i.e., theirprehistory. Thus one might say that such a medium has a memory.
The memory has the property of attenuation, which is defined as weakening of the memory concerning much earlierstages of theprocess. The evolutionof the state of materials in time is described by theLiouville equation (Dei, 1974), fromwhich it follows that notonly are the details of the initial state forgotten with time, but they are descrf bed with a steadily decreasing set ofparameters. For different mediaand differentprocesses, the time scales of attenuation vary over a wide range.
We shall examine only the thermal state of earthmaterials, which depends on temperature and heat fluxes (or temperature gradients). Earth materialsare media with low thermal conductivity. Hence, heattransfer in them takesplace slowly in both time and space. The space factor is extremelyimportant asfar as the attenuation of memory is concerned, A thick mass of earthmaterials contains a vast amount ofinformation on thermal prehistory and thermal states in former times. Attempts toextract this information by analyzingthe thermal state of the ground outside of the permafrostregion have not been successful, The effect of the former epochs on the present day temperature field of earth materialslies within the accuracy of interpretation, and the latter is difficult because of our
Proceedings Third International Conference on Permafrost, VOI. 1, pp. 11 - 14, 1978. -2-
The situation is different, if heattransfer in earth materials is accompaniedby phase changes, i.e.,by freezing of wateror melting of ice. Indeed, it followsfrom the equation of thermalconductivity that the dimensionlesstime of temperaturestabilization inthe frozen tone is describedby the Fourier criterion Fo = ar/E 2 , where a isthe thermal conductivity of earthmaterials, r isthe time, and 6 isthe thickness of permafrost. At the same time, it followsfrom the condition ofenergy conservationat the phase boundary (theStefan condition), that the time of stabilization of this boundary depends on the complex criterion hTr/S2Q, where X is thethermal conductivity of earth materials, T is thetemperature and Q is theheat released or absorbed duringthe phase transition.This criterion can be represented in a different way: (ar/S2) x (hT/aQ),where the first termrepresents the same Fourier criterion.
The second term is always lessthan unity. It isclose to unity for densesedimentary and crystallinematerials and is 10 to 50 timesless forweakly cemented mat,erialscontaining water. This means that in the first case the rate of heat transfer and the rate of movement of the phase boundary areabout the same. Inthe secondcase, however, theheat transfer is much fasterthan the movement ofthe phase boundary.Here thetemperature field is almostcompletely dependent on the phase processes. In moist, freezing-thawingmaterials, the memory attenuatesvery slowly. Their present day thermalstate carries much infomation on theformer temperature conditionsover a longperiod of time.
A change inthe temperature field of the ground generallystarts at the surface, since the most dynamic factor of temperatureformation is the climatewhich changes considerably. Warm epochs arefollowed by cold periods of glaciation.
If we couldextract information on theformer thermal state of frozen,weakly cemented earthmaterials, we couldform an opinion on the -3- climates inthe past. The more recentthis past, the more completeand accuratethe information. It is now possibleto extract this type of data fromcontemporary disequilibrium permafrost which occurs over large areas in the northern part of the U .S.S.R.
The analysis of its thermalstate shows very clearly that our time is warmer than the most recent epoch. It ispossible to single out three types of temperature fields of d.isequilibriumpermafrost (see Figure 1). The firsttype refers to low temperature, homogeneous, disequilibriumpermafrost characteristicof Central Yakutia and theextreme northern part of Tyumen' Oblast'. The second type is characteristic of practicallynon-gradient, homogeneous, disequilibriumpermafrost whose temperature is the same as the meltingpoint of pore and fissureice. This type is widely present in the northernparts of Tyumen' Oblast' and some partsof Yakutia adjacent to the middle and lowerreaches ofthe Vilyui River.
Figure 1 'C
M
Types of temperature fields in disequilibrium permafrost.
The third type is found inrelic permafrost which does notextend tothe surface and thawsfrom above. The main characteristic of all types of disequilibriumpermafrost is the fact that at present it thaws frombelow because the flow of heat towards the lower phase boundary in unfrozen soils -4- exceeds the outflow of heat from this boundary infrozen ground, .i.e., qt ’ 9,.
Recent geothermal investigations, in which specialattention was paid to the thermal state of earthmaterials at the phase boundary, indicate quiteclearly that the climate in Westernand Eastern Siberia, as well as in Yakutia is getting warmer.The pronounced warming trend is indicated by a considerablediscrepancy between the thermal state of permafrost and the temperatureconditions on thesurface. The climate has been getting warmer slowly and over a long period of time,since the temperature field in permafrost and in theunderlying unfrozen material is quasi-stationary within the experimental error,i.e., it has sufficient time to become stabilized. Thewarming trend was not complicated by prolonged cold spells of considerable amp1 i tude,since the thermal process now observed in earth materials has been proceeding in one direction only. This does not exclude thepossibility of short-periodtemperature fluctuations lasting less than 500 - 1000 years, which cannot have any effect on the lower phase boundary. The warming trend occurredover the entire northern part of the U.S.S.R. and was probably of global extent,since similar disequilibrium permafrost formationsare found in theentire permafrost zone in sedimentaryrocks of post-Jurassic age. Such arethe qualitative deductions which follow from the analysis of available geothermal data. These data were alsosubjected to quantitativetreatment but this proved to be very difficult. As a first step, it was required to solvethe problem of permafrost thawing from below due to theintraterrestrial heat flux and thetemperature changes on the surface. An approximate solution was given by us earlier on the assumption that the temperature field in the unfrozen zonewas quasi-stationary (Balobaev, 1971; 1973). As an initialcondition, we assumed that in the middle of thelast climatic minimum, thethickness of thefrozen zone corresponded to the ground temperature at thesurface, while thetemperature field of earthmaterials was stationary. In other words, = -qt, qt > 0, where To is thetemperature of the ground surface during the climatic minimum, Am isthe thermal conductivity of permafrost, and c0 is the thickness of thefrozen zone during the same period. Such a moment invariably occurs if a cooling trend is followed by a warming trend. It does not coincideexactly with the middle of the coldperiod but isslightly displaced depending on thetemperature. -5-
As a boundary condition, we took a 1 inearincrease in the surface temperaturebeginning with the end of the cold period, when thetemperature field became stationary and up to thepresent time: T, = To + gr, where T, is thetemperature of the ground surface, r is the time and 6 is theaverage rate of temperature change. The actualtemperature increase in the thousands of yearssince the last glacial period was, of course, not linear. But then the problem is so difficult because we do not know what form the temperature increase did take in thepast. The 1 inear approximation is the simplest and, in the absence of trueinformation, perhaps the best assumption. Apart from time, it introduces only one other unknown parameter - therate of change in thesurface temperature of the ground. A morecomplex approximation would have required a much 1arger number of unknown parameters making a sol ut: 09. L:? the problem impossible. Even with our simpleassumption we could not ar~ice at a closed system of equations and find a correct solution.
In the given case we obtain:
where
6 is thepresent thickness of permafrost; 6 is the unit weight of dry soils, while W and c are the water content and the specific heat of earth materials respectively.
In this equation To and B are unknown. If they were known, we coulddetermine 6 and r. Thus in any given case we haveone equationwith two unknowns. An unambiguous solutionrequires a second equation but we could not derive it for thedata available to us. The equationdescribing the temperature field within frozen or unfrozen ground would be suitable for this. However, as was mentioned earlier,the present temperature field contains no traces of former changes. The phase processesalone provide some -6- information,since we analyzed geothermal data for very thickpermafrost, and the information required extends over tens of thousands of years.
In recent years much has been done in thestudy of theabsolute chronology of climatic changes in the Late Pleistocene andHolocene of Siberia (Kind, 1974). It was determined that the stationary regime of permafrost at the transition from the last cooling trend to the warming trend was evidently established 18,000 - 20,000 years ago.
In this casethe suggestedequation will dependon only one variable - thesurface temperature of earthmaterials during thelast (Sartan) glaciation, which was very close to the minimum temperature.
Use wasmade ofgeothermal data from 12 points in thepermafrost regionof the U.S.S.R. Seven of these were in Yakutia, one in Eastern Siberia and three in Western Siberia. The initial geothermal dataare given in Table I. The watercontent and theheat absorbed during phase transitions were not measured directly but were calculated from otherdata. It is these parameters thatare responsible for the main calculationerror. It was establ ished that changea in Q of 20 - 30% resulted in a temperature difference of 1 - 2OC. It will beshown laterthat this error is quite acceptable and amounts to 10 - 15%.
During the period covered by the calculations, thawingfrom below was takingplace in the Cretaceous and Jurassic sandstones of Yakutia, the Cretaceoussands and clays in the area aroundTurukhansk, and in the Palaeogene clays in the northern part of Western Siberia. This is the reason for considerabledifferences in thecalculation parameters(Table I).
Even a brief examination of thedata helps to establishthat abnormally thick contemporary permafrostcould have been formed only at surface temperatures of -8OC to -1OOC in Yakutia, -6OC in EasternSiberia and -7OC to -9OC in Western Siberia.
The calculatedsurface temperatures of permafrost, its thickness and the average rates of temperature changes 20,000 years ago are shown in Tab1 e I I. At that time permafrost was 7OC to 14OC colder than now and its -7- temperaturereached -14OC. Therewere no significanttemperature differences between pointsin Yakutia and, for example, Western Siberia. The cooling trendevidently extendedover the entire permafrost region but was less severe inthe Lena Valley (Namtsy, Yakutsk,Promyshlennyi). We shouldnote that even now thetemperatures there are slightly higher than in the adjacent areas. The average rateof increase in the temperature was 0.5OC per 1000 years, It was higher in Western Siberia and lower in Yakutia. We should remember, however, thatthe points in Western Siberiaare 2OC - 3OC farther north(approximately at the ArcticCircle) than the points inYakutia. Duringthe Sartan glaciation, the thickness of permafrost in Yakutiareached 800 m. As isthe case at present, it variedwithin a widerange from place to place,depending on thegeological conditions. In the course of 20,000 years,earth materials with a highwater content thawed not more than 100 - 150 m, while denser and less porous materials thawed 250 - 300 m. The average rate of thaw rangedfrom 0.6 to 1.5 cm peryear. At present it is 1.5 - 2.5 cm per year.This means thatin the initial stage of thaw the phaseprocesses were proceeding at a slower rate than now. If thepresent conditions will remainlargely unchanged, approximatelythe same length of time will elapsebefore the thickness of permafrost is stabilized.
We alsocalculated the palaeotemperatures ofpermafrost 15,000 years ago. They followedthe same patterns,but for obviousreasons were slightlyhigher (bynot more than l0C for most points),This indicates that it ispossible to analyzethe palaeoclimate, even if theestimated time of the climatic minimum contains a significant error.
The palaeotemperaturesare a function of theair temperature, which is themain characteristic of theclimate. Hence they are also a function of thepalaeoclimate. To determinethe exact difference between the temperature of the groundsurface and that of the air, it isessential to know suchparameters as radiation and thethermal components of the exchange between thesurface and the atmosphere, the dynamic characteristicsof the atmosphere, and precipitation(especially in winter) at thetime of the climatic minimum. It ishardly possible to obtain .these data, hencea simplerapproach is required. We shall assume thatthe differences between theair temperature and thetemperature ofthe groundsurface has remained unchanged. Inactual fact, this difference was probablysmaller inthe past than it is now. -8-
m -E 9"m 24
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OONrnI. *q?f????? Lnr-lmFacu--NwToo IIII Ill
U .r c h 0 .r Y) m U E 0 r W a m r 3 -9-
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At presentthe mean annual temperature of the ground surface at all investigatedpoints is 7OC - 8OC higherthan that of air. Bearing this in mind, we estimate that 20,000 years ago the mean annual air temperature in thenorthern part of Western Siberia and in Central Yakutia ranged from -17OC to -2l0C, which is approximately 10°C to 13OC lower than at present.This points to a pronounced warming trend which led to a decrease in the permafrostthickness everywhere in the U.S.S.R.
The calculated average rates of increasein the temperature (Table 11) differsignificantly, although for adjacentpoints they are almost the same (e.g.,Vilyuisk, Kyzyl-Syr, Nedzheli). It is unlikelythat there were differences in the warming trendwithin a relatively small area of Central Yakutia.
Most 1ikely the warming trend was uniform. In this casethe differences in 8 should indicatethat the heat exchangebetween the ground surface and the atmosphere had its specif iccharacteristics at each point in Central Yakutia. This applies first of all to vegetation and topsoil. The same is true of Western Siberia.
Our assumption concerning a gradual and continuousincrease in the ground temperature from the middle of Sartanianglaciation and up to the presentdid not allow for the effect of the Holocene optimum on the development of permafrost which lasted for several thousand years. The reason for this is as follows. Firstly, thawing of permafrost from below depends on thetemperature at the surface as long as the latter remains below O°C. When this temperature rises above O°C, permafrostbegins to thaw from above. The permafrost base continues to move, as if thetemperature at the surface is still O°C, sincethe heat flux in permafrost will be equal to zero as long asthe upper and lowerphase boundaries do not merge, i.e.,as long as permafrost does not thaw right through (seecurve I11 in theFigure).
Secondly, the abundant geothermal data available at present do not contain any evidence that the Holocene optimum had any effect on the ground temperature. In Yakutia this was due to thefact that in the Holocene the ground temperature never rose above O°C. Therefore any influence of this optimum was very soon obliterated by theslight coolingtrend which has - 11 - persisted until thepresent. That this is indeed the case is indicated by the presence of ancient ice wedges near the surface of the ground.
If we assume thatthe averagetemperature of the ground surface during the Holocene optimum was 2OC higher than at present,this should have resulted in thawing to a depth of 60 - 80 m. Since the optimum was followed by a slight and briefcooling trend, this talik should be present still and have a temperature close to O°C. In places where the presenttemperature of the ground surface is O°C, thecurves of type I1 (see Figure) should indicate the presence of thetalik. In our analysis such curves were present (Turukhansk, Yubileinoe,Urengoi), but they showed no signs of the Holocene optimum. Futureresearch should concentrate on the phase composition of the upper permafrost horizons where the temperature is O°C.
According to some sources, unfrozen layers havebeen discovered in permafrost in thecourse of drilling. However, this could not be confirmed by any other methods, if we disregardthe contemporary unfrozen zones the upper layers of which have a temperature below O°C. No complex calculations are required to show thatthe age of a 10 to 15 m thickfrozen layer is 200 to 400 years and not thousands of years.
The effect of the Holocene optimum on the thermal state of permafrost is still not fully understood. - 12 -
REFERENCES
BALOBAEV, V.T. 1971. Characteristics of geothermal processes in permafrost regions. In: Geokriologicheskie issledovaniya, Yakutsk, pp. 9-17. BALOBAEV, V .T. DEVYATKIN, V. N. and KUTASOV , I. M. 1973. Contemporary geo- thermal conditions of the existenceand development of permafrost. Proc. I1 International Conference on Permafrost, Yakutsk. For English translation see U.S.S.R. Contribution to the I1 Inter- national Conference on Permafrost. NAS, Washington, D.C. 1978. DEI, U.A. 1974. Thermodynamics of simple media with a memory. "Mir" , Moscow, 190 pages. - 13 -
CLASSIFICATION OF THERELATIONSHIP BETWEEN CLIMATE AND PERMAFROST-CLIMATIC REGIONS
M.K. Gavrilova PermafrostInstitute, Yakutsk, U.S.S.R.
Climate is one of the basic factorsin permafrost formation. The Earth'spermafrost regions are restricted mainly to the polar andsubpolar regions,and in southernlatltudes, to high altitudes, i.e., to thecold regions.
Permafrost is a good indicator of climate,especially of changes inits territorial and temporal limits. A depth of hundreds or even thousandsof metres reflects not only yearly (in the upper layer) but also epochal fluctuationsin climate. The history of theearth's climate with its cooling andwarming periods,the variety of present-day climates and the tendencies of bothnatural and man-made climatic changes aremanifested in thetemperature regime of the permafrost. Therefore, this regime becomes an indicator of the influence of all the climatic elements.
However, despitethe fact that the relationship between climate and permafrost has been studiedover a longperiod, many aspects of the problemare still far fromsolved. This is due as much tothe complexity of theproblem as to a number of objective and subjectivecircumstances. For example, thereis a paucity of qualitativedata andabsence of exhaustive theoretical work. However, thedevelopment of contemporarygeocryology requiresthat a number of questions be answered withregard tothe interaction of climate and permafrost.
ProceedingsThird International Conference on Permafrost, Val. 1, pp. 23 - 28, 1978. - 14 -
From the Russian, Soviet and foreignliterature, it can be -seen thatthe approach tothe problem of correlatingclimate and permafrost has differed at variousstages. This reflects a dialectic"spiral": a progression from a simpleto the complex with an ensuingreturn to the originalposition but on a higherplane.
Scientific study of the correlation between climate and permafrost has developedfrom qualitativediscussions of a globalnature in themiddle of theXVIIIth century to today's precise measurement of theheat balance in the microclimate.
It should be notedthat the failure of several individual attempts to establishthe relationship between climate and permafrost has ledto some pessimism withregard to this problem. Thisfailure can be explained by a lack of sufficient knowledge and thesmall amount of materialavailable at thattime.
Thus the"discrepancy" between mean air temperatures and the geocryologicalconditions in such concretesituations (wider than the microclimate) in the '30s and '40s suggested thatthe main factorin the occurrence and development of permafrost is notclimate, but the geological conditions .
However, meteorological at stations (open location)air temperature is measured at a heightof 2 m, butthis does nottypify conditions near the ground surfacewhich isitself the upper limit for temperaturedistribution in the soil. From 0 - 2 m thereare considerable changes in meteorologicalconditions. Moreover, it must be takeninto accountthat the air temperature at this height is the result not only of vertical changes butalso of a horizontal change due to theintermingling of neighbouring air masses. Inshort, the air temperature measured in the meteorologicalgrid is notthe result of thethermal processes at a given point,but of processes takingplace over a relativelylarge area of tens or hundreds of ki1ometres .
The most significant factoringeocryology must be the more locationallyrestricted ground surfacetemperature rather than the air - 15 - temperature. Unfortunately, measurements of this phenomenon made within the meteorological grid are still not sufficiently reliable.
Thus, air temperature is not the most important criterion when estimating microclimatic conditions of a geocryological situation in specific locations. However, this phenomenon should not be overlooked when analyzing the general geocryological regime of large regions. In sunmation, the air temperature is nothing more than a measure of thethermal state or the result of a heat balance over a relatively wide area.
Recently there was a resurgenceof this "pessimism" with regard to data on heat balance as well. This is primarily due to the difficulty of measuring these phenomena, and also to the fact that the indicators are not always in accordance withthe geocryological conditions. As radiation features are related to astronomical factors,they have a tendency to latitudinal distribution to which permafrost conditions are not always subject. For example, the coldest ground is in northeast Yakutiya and not on the arctic coast and islands, where there is the smallest annual radiation balance.
Such a "disconcordancell is related to a breakdown of latitudinal cl imate zonal ity with a1 1 its consequences: circulation factors, cl imate formation, or the degree to which the climate is continental. A preliminary analysis of our research shows that general summer thawing regimes display the greatest concordance with the data on heat balance. The characteristics of winter freezing coordinate best with the intensity of temperatures. On the other hand, in microclimate research the heat balance characteristics are a good indicator of the thawing and freezing of earth materials on different types of terrain in a single locality. Data on the heat balance are also essential for any theoretical interpretations of the thermal processes which take place on Earth.
A significant "anomaly11in the permafrost distribution at a given latitude is brought about by the following factors: altitude above sea-level , terrain, and bodies of water. This also holds true for climate formation and its consequences. - 16 -
Thus the exclusiverole of climate in theoccurrence . and development of permafrostas an externalcause of the thermal conditionof theearth's crust, both in the past and at present, is not in doubt. However, therelationship between climate and permafrost is very complex. In some instances, the determining factor is the thermalregime which has become establishedover a largearea; this can be adequatelycharacterized by the air temperature. In otherinstances it is the local thermalregime. This demands detailedresearch into all components of theheat balance between the lithosphere,the soil and the atmosphere.
A differential approach to the climate-permafrost problem is needed in accordance with the specific tasks at hand. One occurrence or another of geocryologicalfeatures could be connected with completely differentgenetic climatic phenomena. Before coming to any conclusionsabout theclimate-permafrost relationship, there must be further investigationof theformation of the cl imate itself and 1 i kewise of its influence on the thermal or temperature regime of earthmaterials in general and of frozen ground in particular.
We proposea classification of the climate-permafrost relationship on the basis of six genetictypes of climate: cosmic, planetary, macrocl imate, mezocl imate,microclimate and soil cl imate (Table). Each type of climateinfluences the permafrost conditions in its own way, or has its own geocryol ogical probl ems.
The cosmic climate (or more preciselythe cosmic factors of climateformation) beingdetermined by theinteraction of theearth with othercelestial bodies, points to a basicrelationship between the sun and theearth's thermalregime. All major fluctuations in the earth'sclimate are dependent on the intensity of solarradiation, to which thecooling and warming trendsof the Glacial and the Interglacialperiods are also related. This in turn is reflected in thegeocryological conditions. Formation of permafrost, its age,thickness and temperature regime at great depths are all related to the cosmic climate.
The planetaryclimate, or ratherthe climate of theplanet Earth is to a largedegree determined by its shape and rotation. With this a.re - 17 - associatedthe uneven exposure to radiationat different latitudes and- the changes in the intensity of this radiation with season and time of day. This causes thegeneral distribution of permafrost to be mainlywithin polar and sub-polarlatitudes and bringsabout periodic fluctuations of temperature in the upper layers. The presence of theEarth's atmosphere, which becomes more dense withproximity to the Earth, is apparentfrom the weakening ofsolar radiation as it approaches theEarth's surface. The history of theformation of theEarth itself is notwithout importance, The Earth'sinternal heat determines the vertical limits of permafrost in the lithosphere.
The division of theearth's surface into oceans and continents leads to uneven heatdistribution within a givenlatitude. It givesrise to circulationor heat transfer from the oceans tothe continents. Since land has a lowerthermal conductivity, it is cooled more easilythan the ocean. Thisexplains why permafrost isrestricted tothe continents. Further redistribution of heat on thecontinents is associatedwith the processes of themacroclimate or the climates of thecontinents. The greaterthe distance fromthe oceans the more severe become theclimatic and geocryological conditions.This is intensified by therotation of theearth. This also accounts for the west-east transfer of air masses or the strengthening of the continentalnature of climate from west to east inthe northern hemisphere. In Eurasia, for example, theAtlantic ocean exerts a significantinfluence, withwhich is associatedthe curvature of thecontinent's permafrost boundaries.This isalso the case on the SouthAmerican continent.In this way, themacroclimatic processesdetermine thecharacter of thecontinental distribution of permafrost
The mesoclimate is connected withlarge mountain formations, with bodies of water and withdiffering height above sea-levelwithin one locality,et. It determines"abnormal" strengthening and weakening of permafrost in a given zone. Thus inthe southern latitudes of Asia, Africa and SouthAmerica, thepermafrost phenomenon restrictedto high mountains is a phenomenon of the mesoclimate. The less intensepermafrost in earth materialsunder the northern seas and waterbasins is similarlyassociated with the mesocl imate. - 18 -
The greatvariety of geocryologicconditions is broughtabout by microclimatic phenomena causingvariations in temperature for different physico-geographicconditions in any one locality. The questionof seasonal freezing and thawing ofearth materials on differenttypes of terrain and also under structures is connected with microclimaticprocesses.
And finally there is the soil climate or the climate of deep earth materials. All the formertypes of climate were externalfactors in determiningthe heat exchange between the earth's surface and the atmosphere. However, furtherredistribution of heat in the upper layer of the earth's crust,or the final formationof a temperature field at a given location, is dependent upon the lithological composition, on the structure and humidity of theearth materials themselves or on their thermo-physical properties. Therefore, when heatapproaches thesurface, the temperature regime will vary accordingto the type of localearth materia. For example, moistsuglinoks , dry sands,etc. Subsurface water substantially modified the temperature field.
In thetable, the numeration oftypes of climate is on thebasis on distance from the sun. Each climateoperates against a backdrop of the precedingtype. However, this still does notaccount forthe ensuing weakening of theinfluence. In individual cases, the second of two related climates canhave the greaterinfluence on thefinal geocryological outcome. For example, largequantities of subsurfacewater (a factor of soilclimate) can bring about the formation of open taliks, even against a backdrop ofthe most severemacroclimate. However, thelatter creates the potential. And so we acknowledge that ground water found in smallerquantities under the conditions of the relatively mild macroclimate ofSouthern Siberia could lead to the formation of anopen talik, but would not do so in the severe macrocl imate of Yakutia.
It is characteristicthat some typesof climate can play a dual role depending on the backdrop against which they exist, and also on the season. For example, forests in thenorthern and southernregions form "warm" or"coldtt microclimates respectively. In winter,icings, bodiesof water,etc., protect earth material5 from freezing and in summer impede their warming up, etc. - 19 -
Permafrost terrain can be divided into genetic climate-permafrost classes in accordance with the role that type plays in the climate permafrost relationship. Seven characteristic types are noted.
1. Macroclimatic field. Permafrost brought about by macroclimatic conditions, Meso- and macroclimaticrelationships are intensified or weakened by the permafrost regime but are not a determing factor.
2. Meso-, macroclimatic field. In accordance with the macroclimatic conditions, the permafrost should be continuous, but under the conditions of the mesoclimate it can become discontinuous or island type, or might'disappear completely. This is characteristic of the arctic continental shelf.
3. Macro-, meso-, microclimatic fields. All three can be decisive in either maintaining permafrost or causing it to disappear. These coincide with the northern discontinuous permafrost region.
4. Mesoclimatic field. On the basis of the macrocl imate, there should be no permafrost. Its occurrence is related to the conditions of the mesoclimate. The microclimate is not a determining factor. It coincides with the southern, continuous permafrost region.
5. Meso-, microclimatic field. Both can be determining factors. Coincides with the southern discontinuous permafrostregion.
6. Microclimatic field. Permafrost is not caused by either the macroclimate or themesoclimate. Only the conditions of the microclimate are a determining factor.
7. The field of the corresponding soil (earth material) climate. This is not determined by present day macro-, meso- or micro-cl imatic conditions, but the established thermal regime of the earth materials helps to preserve the remains of ancient permafrost. Coincideswith the distribution area if relict permafrost. - 20 -
The methodology of solving these and other geocryological problems depends on the type climateof and its related geocryological phenomena.
Associated with the problem of climate-permafrost interaction are many real problems of present-day geocryology such as prediction of the natural trend of permafrost development on the earth, prediction of changes in permafrost conditions upon the opening up of terrain, protection of the environment, cl hate me1 ioration, etc. At present, man is capable of consciously influencing the geocryological (temperature) conditions of the upper (seasonal) layersof earth materials by modifying the conditions of the microclimate (regulation of the insulating role of the Earth's surface). Partly with regard to the mesoclimate (creation of large reservoirs) and the soil (regulation of moisture retentive earth materials). On a more planetary and cosmic scale the processes of the macrocl imate cannot yet be controlled by man.
And. so, an overview of the climate-permafrost classification shows that the problem is a frequently encountered aspect of a wider problem, namely the sun-earth relationship. At the same time, it is so complex that it requiresthe work of specialists in different fields: astronomers, meteorologists, glaciologists, soil scientists,forestry specialists, agriculturalists,specialists in land improvement,specialist from all branches of engineering, etc. Thisimportant and extremely interesting 'subject of the interaction between the earth's climate and permafrost can only be conclusively resolved by the concerted efforts of the above mentioned and other specialists. - 21 -
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THE EFFECT OF DEVELOPING A TERRITORY ON THEHEAT BALANCE AND THETHERMAL AND MOISTURE REGIME OF THE GROUND IN THENORTHERN PART OF WESTERN SIBERIA.
N.G. Moskalenko, V.B. Slavin-Borovskii and Yu.L. Shur A1 1-Union Research Institute of Hydrogeology and Engineering Geology, Moscow and N.A. Lazareva, S.P. Malevskii-Malevich MainGeophysical Observatory, Leningrad
Studies of thesusceptibility of permafrost to changes resulting fromindustrial andeconomic activity are made necessaryby the requirements fardeveloping the vast territories of the northern part of Western Siberia and forpredicting the engineering andpermafrost conditions in areas undergoingdevelopment.
The studies areconducted in two maindirections: a study of the heatbalance, and observations of thestate of thepermafrost and of the seasonally thawed layer in different terrain conditions.
Thecomponents of theheat balance and of thethermal and moisture reglme of theground are studied intest areasunder undisturbed terrain conditions and at artificially preparedsites (sites devoid of vegetation).
Parallelobservations at undisturbed and disturbedsites make it possible to estimatethe changes inthe conditions of heat exchangeand thawingwith removal of surfacevegetation. Such studies were conducted in 1975and 1976 in the forest tundra zone in shrubcovered, mossy andlichenous peatlands, in patchyshrub covered, lichenous open areas of predominantly larch and in patchyshrub covered, mossy andlichenous tundras.
Proceedings Third InternatSonal Conference on Permafrost , Vol 19 pp. 55 - 60, 1978. Studies ofthe thermal and moisture regime of thelayer of seasonal thawing havebeen conducted since 1971 in thenorthern taiga, the southern and northernforest tundra and thetundra. nowWe have resultsfor more than 200 microfacies of thetypical natural landmarks of these zones (Moskalenko and Shur, 1975b; Slavin-Borovskii,1975).
In a number of theareas helicopter surveys of the a1 bedoand the radiationtemperature of theactive surface were conducted. The resulting information makes it possibleto estimate the variability of conditions at thesurface in different natural complexes (Malevskii-Malevich, 1965, 1968).
The above-described activitiesare carried out in the sumner months by expeditionarydetachments. In winter,intermittent observations of the snow cover are made in thedetachments' areas of operations. The ground temperaturesare observed in boreholesthe year round (atintervals of 5 to 15days).
When conductingthe observations and during their subsequent processingstandard procedures are used wherever possible.
In theheat balance studies provision wasmade for a multipleset of observations in orderthat a1 1 of its components could be determined independently. For measuring the ground temperature a special thermometric unit incorporating a non-heat conductingcore was used with resistance thermometers installedat predetermineddepths. The non-uniformity of the subjacentsurface was accounted for by an additional thermometric unit and a thermocouple. In gradient and actinometric measurements thenon-uniformity of thesurface is automaticallytaken into account.
In additionto the normal four times a day measurements a further series of measurements were conducted six times a day, At the leeward extremity of thedisturbed site additional observations were conducted at a height of 2.0 m.
Direct measurement of the heatfluxes in the ground took the form of an experiment. The reduced calculatedvalues were derived from thermometricinvestigations. - 31 -
Alsoby way of a test of the new procedures,empirical relations between theheat fluxes inthe ground and theglobal radiation were derived from the results of integration.
An estimate of theaccuracy of measuringthe depth of thaw was made on thebasis of multiplesamplings with a probe. The calculations of thedistribution pattern of the derived values showed that for fairly large samples with a volume closeto that of thegeneral population (n = 100; 50) thedispersion S2 is 100 with a measuringaccuracy of 2.5 cm. A tenfold sampling is consequently accompaniedby a mean deviationfrom the general population of theorder of 10% of the measured value (0.5 - 1.0 m), The multiplesampling of thedepths of thaw is governedby itsprobability character(Grechishchev, 1975).
The heatbalance
The informationderived from parallel observations at disturbed and undisturbed sites is used forcalculating the components of theheat balance. In areascontaining patches the heat flux in the ground and the depth of thawbeneath clayey-siltypatches far exceed these valuesbeneath thevegetative cover. Accordingly, the mean values of theflux wereused in thecalculation. These consisted of theweighted values for the patches and thevegetation. The weight of thepatches was takento be equal tothe proportionof them in thetotal surface area, i.e., about 20%. The results of the measurements and thecalculations make it possible to determinethe sums of the heatbalance components throughoutthe period of thawing. In Tables I and I1 thesedata are adduced for two areasduring the 1975 period of t hawi ng+
Inthe Tables the following symbols are used: R isthe radiation balance, LE are the expenditures of heat on evaporation, P isthe turbulent heat flux, B isthe heat fluxin the ground, A isthe heat balance discrepancy .
The closurecondition of theheat balance can serve as a checkon thereliability of thedata presented, since all of its components are determinedindependently. An exceptionare the data for the disturbed site - 32 -
in the peatland where additional procedural difficulties made it impossible to derivereliable results for thevalues of LE and P. In this case they were determined from a prior assumption of the balance closure on thebasis of thedata for R and B. At all of the remaining sites, asfollows from the data adduced in the lower line of Tables I and 11, theresulting discrepancy
The possibility of using informationderived from short series of measurements in order to calculatethe heatbalance is problematic. The correlation between theradiation balance and the expenditures of heat on evaporation proved to be very weak: r(R, LE) ranged from 0.25 to 0.67 for the undisturbed sites and from 0.15 to 0.54 for thedisturbed sites. The evaporation is evidently 1 imi ted by the energy capabil ities and by the conditions of moisturetransport to thesurface. It is probable that only under conditions of extreme moisture (bogs and artificial covers)that short series can yieldsufficient information for studying thestructure of the heatbalance.
The comparisonbetween the values of the heat balance components at the two sites under undisturbed conditions illustratesthe local differences caused by thevarious types of subjacentsurface. Most noticeableare the differences in the distribution of thequantities of heat expended on heat exchangebetween thesurface and the atmosphere in the clear and latent form (the P and E correlation). Whereaswhen theconditions are those of a lichenous cover in suglinoks a turbulent heat flux is the predominant component, in thecase of mossy vegetation in peatlandsthe bulk of the heat is expended on evaporation. In suglinoksthe heat fluxes in the - 33 -
TABLE I Heat bajance of shrub-coveredlichenous open areas of predominantlylarch, Kcal/cm forthe period of seasonalthawing (July 1 - September 29, 1975).
Undisturbedsite Disturbed site Month R I LE I P I B I LE+P+B I A, % R I LE I P I B I LE+P+BI A, % VI1 6.42 1.62 3.52 1.19 6.34 -1 6.39 2.17 2.22 1.69 6.08 -5 VI11 4.07 1.53 2-18 0.81 4.52 +11 4.65 3.17 1.89 0.50 5.57 +2O IX IX 2.06 1.36 0.69 0.37 2.42 +18 2.30 1.47 0.26 0.20 1.92 -1 8 c 12.542.37 6.39 4.52 13.28 13.34 6.80 4.37 2.39 13.56 Mean diurnal, cal/cm day 50 71 140 50 26 148 76 49 27 Heat bal ance discrepancy for the season + 6% + 2%
TABLE I1 2 Heatbalance of shrub-covered, mossy, lichenouspeatland, kcal/cm for the period of seasonalthawing (July 4 - September 25, 1975).
. . .. .- " - Undisturbed site Disturbedsite Month R I LE I P I B ILE+P+B I a,% . R 1 LE I P 1 B VI1 5-82 2.52 2.20 0.98 5.70 -2 3.986.70 1.20 1.52 VI11 3.74 2.48 1.13 0.38 3.99 +5 4.44 3.87 -0.09 0.46 IX 1.95 1.76+162.25 0.26 0.23 2.48 1.40 0.77 0.30 c 11.52 6.77 3.56 1.62 11.95 13.62 9.24 1.89 2.29 Mean djurnal , cnl/cm day 137 81 42 19 162 110 22 27 Heat balance discrepancy for the season +4%
groundare appreciably greater than in peats and thedepths of seasonal thawing are in agreement with this. The differencesin the radiation balance are inconsequential. - 34 -
In estimating the effect of a disturbance in the properties of the subjacentsurface on theheat balance the following conclusions seem to be most important
When development is in progressthe radiation balance changes very littlewith the denudation of suglinoks (6%) and verysubstantially in the case of peatlands(18%). This is because in the latter case theinfluence of two factorsis being felt: a pronounceddecrease in boththe albedo (from 15-17% to 10-12%)and theeffective radiation, whereas when removing a lichenouscover from the surface of suglinoksthe albedo remains practically unchanged.
The values of theturbulent fluxes of heat and moisture change markedlywith development. theIntypes of surfacesdiscussed, with elimination of thevegetation an increase inthe moisture fluxes, amounting to severaltens of percent, and a decrease inthe heat fluxes is typical Of greatestimportance from thestandpoint of thecryogenic processes are the changes in theheat flux inthe ground. If thetotal flux values for the season areconsidered, the markedchanges in the conditions for thepeatlands areparticularly striking (anincrease of B by almost oneand a ha1 f times duringdevelopment). At the same time, inthe case of thesuglinoks cumulativedifferences for the season arenot manifested. If theindividual periods of the season of thawingare considered , however, it then becomes evidentthat when development is in progress there is a marked increase in theheat fluxes in the ground during the initial period of thawing(July) with the result that the rate of thawing at the disturbed site is much higher than atthe undisturbed site, although the ratio between thefluxes then becomes reversed and throughoutthe season as a wholethese differences almost disappear.
From theresults of theinstrumented observations in 1976 the dependences between some ofthe components of theheat balance and thetotal (incoming)radiation are derived.
Thus, in comparing thegraphs reflecting the changes in thedaily totalsof short-wave radiation and the mean diurnalvalues of the heat flux in theground occurring throughout the summer of 1976, it can be seen that - 35 - there is an overall trend towards an increase in these values, while in individual time segments they can change oppositely.
In order to ascertain the relations between the incoming radiation Q and the radiation balance of the undisturbed Ru and disturbed Rd sites in the northern forest tundra the correlation coefficients of these values were calculated and the following linear empirical equations were formulated:
R = 0.08 + 0.440 Q; r = 0,703 U Rd = 0.11 + 0.490 9; r = 0.786
Similar equations were derived for the heat fluxes in the ground:
Bu = 0.007 (1 + 4.3 Q); r = 0.723 Bd = 0.027 (1 + 5.4 9); r = 0.835
It is typical that the value of B correlates better with Q than does R and the values of R and B are better for the disturbed site than for the undisturbed site. The graphs of these dependences are presented in Figure 1 .
Figure 1
Empirical dependence of the radiation balances R(1) and heat flu3es in the ground (11) on the short-wave radiation Q at 14 hours (cal/cm min), - 36 -
The fact that Rd > RU and Bd > Bu during daylight, as determined from the derived dependences, emphasizes the displacements in the heat balance occurring with removal of the vegetative cover. On considering the arbitrary remainders of the radiation balance R-B it follows that when 2 Q > 0.1 cal/cm min the expenditures of heat on evaporation and the turbulent heat exchange are higher at the undisturbed s'ite. These dependences, however, were derived for the "dry" sumer of 1976 when the role played by evaporation in the heat balance was evidentlyless than normal.
The use of summarizing recorders for measuring Q and E? made it U possible to tracethe relations between the three hourly (during the daylight period) and diurnal sums of these values.
Thus, for the three hourly sums of 3 B an d 3Q the findings were r = 0.64 and the following empirical linear dependence:
3B = 3.2 + 0.154CQ.
For the daily sums the dependence is also linear:
CB = 0.175 Cg - 2.6 diurnal diurnal
The correlationcoefficient r = 0.749. The values of and CfJ and the graphs of the empirical dependences are presented in Figure 2. diu nal
Figure 2
Relation between the (I) three-hourly and (11) djurnal sums of incoming radiation c Q and the heat flux in the ground cB, cal/cm for the sumner of 1976. - 37 -
Time consumingand complicatedheat balance studies can only be conducted in certain of the wide variety of subjacentsurfaces occurring in regions under development. For this reason a very urgent task is that of describing the heatbalance conditions for particular a territory characterized by a variegationof terrain. For this purpose,steady state observationsare supplemented by occasionalsurveys along special routes. These surveys are accomplishedboth by normal surfaceobservations and by helicopter.Helicopter surveys make it possible to obtainthe spatial distributions of the albedo and temperaturevalues at the surface. Measurements of 8 types of naturalterritorial complexes (NTC) indicated closelysimilar values of thealbedo (15-17%) for the overwhelming majority of types of subjacentsurface. Onlytwo of them are distinguished by a noticeably lower albedo: pine forest and scorchedpeat mounds, in respect of which thesurface temperature during the daylinghours is 5-10' higherthan in theother NTC's. The dataobtained make it possibleto estimate the values of the radiationbalance of various NTC's and thevariations of these values, amounting to as much as 15%.
'Presented in Table I11 are thefollowing results of theradiation survey by he1 i copter:
A is thealbedo, t - the surfacetemperature, D - the dispersionof the correspondingvalues within each variety of terrain, and Rn/RO - the ratio of the calculatedradiation balance in the nth terrainto the radiation balance of thecontrol site. The Rn/RO ratio was calculated from the formula - In for the control site: Rn = Ro + Q(AO - An) + Io ca 1 Q = 0.90 cm2min; A. = 15%, t = 25OC - 38 - and the effective radiation:
ca 1 ca 1 10 0.15 -3 cm m n RO = 0.61 cmzmin
TABLE I11 Results of he1 icopter surveys of the radiation and a1 bedo
Natural complexes (NTC) A,% D(A) t,'C D(to) Rn/RO
Flat shrub-covered, mossy, lichenous peatl and 15.7 0.4 26.4 I 1.03 Sedge and Sphagnum bog 15.5 0.7 24.6 0.9 1 .01 Peat and mineral moundsand ridges containingshrub-covered lichenous open areas of predominantlycedar 15.1 0.5 33.1 1.8 0.88 Mineral mounds and ridges containing shrub-coveredlichenous open areas of predominantlycedar 16.0 - 33.8 I 0 "88 Sparse forest consisting of birch and spruce 11.8 1.3 27.7 2.1 1.01 Open area consisting of larch,spruce and birch 16.3 0.2 26.4 1.5 1.03 Coarsehillocky shrub-covered lichenous peatl and 16.4 1.2 24.4 1.1 1 .01 Denuded peat mounds 13.0 1.1 29.3 3.4 1.02
The temperature regime of the ground
Studies of thetemperature regime of the layer of seasonal thawing in variousnatural complexes have shown that it is subjectto significant changes. These changes are mainly associated with the non-uniformity of the microrelief and thevegetative cover under undisturbed conditions and with the disturbance which is caused to theproperties of the ground and the subjacentsurface in areas undergoingdevelopment. Presented in Table IV are data on thetemperature of the surface and the upper levels of the soil and ground to a depth of 3 m throughout the sumner for five of the most widely distributed NTC's in two natural tones (the northern taiga and theforest tundra). - 39 -
TABLE IV Temperature regime of earth materials in various natural complexes underundisturbed and disturbed conditions.
1 2 3 4 5 6 7 8 9 10 11 1214 13
Forest Tundra, 1975 A 0.85 -3.2 a 10.1 17.3 2.6 8.7 6.6 4.0 3.0 -0.4 -1.7 -2.6 0.51 b 10.8 21.9 2.5 7.0 5.3 3.5 2.9 -0.7 -1 -9 -2.6 0.63 B 1.3 -3 .O a 9.5 16.3 2.4 8.7 7.1 4.0 1.5 -0.4 -2.0 -2.6 0.51 b 10.7 22.9 1.2 5.4 3.6 1.42.5 -1.0 -2.2 -2.9 0.44 C 1.6 -3 .O a 10.3 21.9 1.8 7.7 5.9 4.7 1.4 -0.6 -1.9 -2.5 0.48 b 10.0 21.1 1.0 5.4 3.0 - 1.3 -0.8 -2.0 -2.6 0.38 D -2.0 a 0.0 9.9 19.2 4.2 8.6 8.3 8.0 7.2 1.7 -0.5 -1.5 1 .26 b 0.159.7 19.3 2.7 7.2 5.1 4.8 3.6 c - I 1.2 C 0.05 10.6 21.6 1.3 5.6 4.2 - 3.5 1.8 -1.1 -1.8 1 *l E -2.0 a 0.0 10.2 18.5 4.3 9.0 9.0 8.0 7.4 1.9 -0.9 -1.7 1.4 b 0.02 10.8 19.1 4.1 8.3 7.7 7.0 7.1 1.3 -0.8 -1.5 1.3 Northern taiga, 1973 F 1.05 -0.8 a 11.0 22.6 4.5 10.5 9.0 4.97.5 -0.1 -0.4 -0.6 0.6 b 11 .o 25.9 2.4 6.9 4.6 3.4 2.6 -0.4 -0.6 -0.7 G 1 .o -0.8 a 11.8 20.6 4.9 9.2 7.9 6.1 5.4 -0.1 -0.5 -0.8 0.7 b 11.4 21.4 5.5 9.5 8.4 6.1 6.0 - I I 0.6 H -0.4 a 0.211.5 23.9 3.7 8.5 7.0 5.1 4.5 3.8 0.0 -0.2 1.3 b 0.1 12.1 26.1 2.2 6.9 4.9 4.3 3.7 2.5 0.01.15 -0.2 I 0.0 13.1 25.5 5.1 12.4 12.1 11.010.1 5.8 1 .O -0.4 -0.4 2.35 J 0.7 -0.7 a 11.7 23.0 4.1 9.7 7.4 5.0 3.4 -0.1 -0.5 -0.6 0.59 b 12.4 30.1 2.5 4.47.1 2.33.2 -0.4 -0.5 -0.6 0.5 K 0.412.0 21.5 4.1 10.1 8.4 7.2 6.1 -0.1 -0.5 -0.5 - 0.74
" . Explanation: 1 - Naturalcomplexes: A - shrub-covered lichenous peat mounds (a - shrub-covered, green massy, lichenous hummock; b - shrub-covered, lichenous hummock); B - flat, shrub-coveredlichenous peatland (a - shrub-covered, lichenous hummock, b - lichenous strip between hummocks); C - flat shrub-covered, lichenous, Sphagnum peatland (a - shrub-covered, sphagnum - 40 -
TABLE IV Explanation: (cont Id) hummock, b - 1 ichenous strip between hummocks) ; D - smoothed area on northern slopeof hill with patchyshrub-covered, lichenous open areaconsisting predominantly of larch(a - patch of suglinok, b - shrub-coveredlichenous humnock, c - lichenousstrip between hummocks); E - the same areawith vegetativecover removed (a - suglinok, b - suglinok in whichpeat has formed); F - flat, shrub-covered, sphagnous, lichenouspeatland (a - shrub-coveredlichenous hunmock, b - lichenousstrip between hummocks); G - the same peatlandwith vegetative cover removed (a - hummock, b - strip between hummocks) ; H - mineral mound with shrub-covered, 1 ichenous open area consistingpredominantly of cedar (a - shrub-coveredlichenous hummock, b - lichenousstrip between hummocks); I - the samemound withoutvegetation and with sand on thesurface; J - mineral and peat mound with shrub-covered, sphagnum, lichenous open areaconsisting predominantly of cedar(a - shrub-covered, sphagnumhummock, b - lichenousstrip between hummocks); K - the same areawithout vegetation and withpeat on thesurface. 2 - Thickness of peat 1ayer, m. 3 - 12.Temperatures of earthmaterials (mean valuesfor July-September) atthe surface: 3 - mean, 4 - maximum, 5 - minimum at the followingdepths in m: 6 - 0.05, 7 - 0.1, 8 - 0.15, 9 - 0.2, 10 - 1.0, 11 - 2.0, 12 - 3.0. 13 - Mainannual temperature at a depth of10 m. 14 - Thickness of seasonally thawed layer, m.
These dataindicate that in undisturbed conditions where there is a 1ayer of peatextending to a depth of 10 cm and more, thetemperatures of theupper layers theof topsoil are fairly close to one another, notwithstandingthe differences inthe composition of the subsoil and the parentrocks from which the soil is formed, as compared withthe areas devoid of surfacevegetation. At the same timethe temperatures of the upper layers of topsoilin areas of limitedextent where thereis no vegetation (non-sortedcircles) differ only slightly from the temperatures of the much 1 argerareas underdevelopment. Thisindicates that the temperature of the upperlayers of the topsoil depends in large measureon the properties of the near-surfacelayer and on the local properties of thesubjacent surface.
It hasbeen found that a fairlystable relation obtains between the sums ofthe summer air temperatures and the denuded surfaces of the ground. Thus, Inthe peatlands, bogs and supersaturated sands of northern slopes of embankments therelation between the sums of the summer surface temperatures and the sum of theair temperatures is 1.05; inthe peaty surfaces of heaving hummocks it is 1.1; in dry sands 1.2 and on thesouthern slopes of the embankments 1.3. - 41 -
The depth of seasonal thawingdepends heavily on the composition and properties of the ground constitutingthe active layer. Thus, at closely similar temperatures of thesurface and upper layers of topsoil the depth of seasonal thawingcan differ by two or more times. In peatlands, after rmoval of thevegetative cover, as a rule there is a slight increase in this depth, The largestincrease in this value as a result of development is observed in sandy areas.
Insummer, the influence of the microrelief and the mosaic pattern of thevegetative cover on the temperature regime of the soil is traced within the facies to a depth of 1 m.
Clearly when discussing the temperature regime of thesubjacent strata the boundary at this depth can be taken to be general for the facies.
The region of our investigationslies within the zone of surplus moisture. In June and July, however, evaporationoften exceeds precipitation, which leads to drying out of the upper part of theactive layer. For example, in the course of the surrmer, in the upper layer measuring 5 cm thick and situated in the northern taiga in a flat peatland covered by shrubs, Sphagnum and lichens, in undisturbed conditionsthe reserves of moisture vary by one and a ha1 f times (1 7 to 24 mm),, and in areas where thevegetat 5 ve cover has been removed - by almost three times (1 0 to 28 mm). In peatsthe seasonal variations in the moisturecontent of thesoil embrance a layer measuring 30 to 40 cm.
In sands, removal of thevegetative cover leads to a decrease in their moisture content throughout the wholeof the layer of seasonal thawing. Thus, thereserves of moisturein a layer measuring 0.5 m are 130 to 140 mm in an area covered by shrubs and lichens, and 60 mm in an area without vegetation, In all cases an increase in themoisture content is noted immediately atthe boundary of seasonal thawing (Dostovalov and Kudryavtsev, 1967).
Snow gauging observationsindicate that the distribution of the snow is quiteintricately linked with thenature and extent of the disturbance caused to theterrain. In peat or mineral earthmaterials - 42 - without a vegetativecover the density of thelower layers of snow is -much higherthan it isin undisturbedconditions. Furthermore, in a number of areasthe snowwas seen to disappear later from grounddevoid of vegetation. In open places removal of the vegetative cover usually leads to a decrease in thethickness of the snow cover. Near embankments of linearinstallations the snow cover is much lessuniform,
The variationin the mean annualground temperatures, especially in the initial yearsfollowing the development of a territory,is associated with changes inthe thickness and densityof the snow cover. As will be seen fromFigure 3, removal of thevegetative cover often 1eads to a decrease in the mean annualtemperature of the ground. In thos areas, however, where by virtue of thelocal conditions, removal of thevegetation has not caused a decrease inthe thickness and a substantialincrease in thedensity of the snow, the mean annualtemperature of the ground rises. It should be noted thatthe absence of methods of predicting changes inthe characteristics of the snow coverassociated with the development of a territory reduces the accuracy of forecasting procedures.
Figure 3
Mean annualtemperatures of the ground at depths of z, in m in (a) undisturbed and (b, c and d)disturbed conditions. b - without vegetative cover; c - without a layer of peat; d - without vegetative and snow covers. I - flat peatland; I1 - mineral and peat mound; I I1 - mineral mound - 1 ; IV - mineral mound - 2.
The study of thethermal and moistureregime of the ground in areas where there is no evidence of such processes as erosion and thermokarst showed that removal of thevegetative cover and destruction of thepeaty - 43 - layer, which has no noticeable effect on therelief and the regime of .the surfacewaters, leads to an increase in the depth of seasonal thawing. This can be very substantial in some types of NTC's. At the same time, these disturbances give rise to changes in theproperties of theactive layer and in thethickness and density of the snow cover, with theresult that in the majority of cases the mean annual tempeature of the ground does not rise.
The processes involved in the thawing and neogenesis of permafrost takeplace slowly and do not evolve to the point where theinfluence of the restoration of the terrain components that were disturbed during development begins to be manifested. Foremost among these is thevegetation (Moskalenko and Shur, 1975a). Because of the slow rate of change the thermal state of the ground is easily checked and canbe controlled at any stage in the use of an installation.
Our study also indicates that the fulfillment of a small number of on the whole, easily accomplished requirements for studiesin permafrost would substantially decrease both the range of variations in the depth of seasonal thawing and the temperature of the ground and the amplitude of the changes occurring in theterrain as a whole.They obviously includethe well known requirements for laying winter roads and linear installations in such a way that the snow is compacted rather than cleared. At the same time, removal of the peat in areascontaining permafrost cannot be regarded as desirable. - 44 -
REFERENCES
DOSTOVALOV, B.N. and KUDRYAVTSEV, V.A. GeneralGeocryology. Moscow State University, p. 404, 1967.
GRECHISHCHEV, S.E. Optimalprecision of geocryological forecasts basedon physical and mathematicalconsiderations. - "Methods of geo- cryologicalinvestigations." MOSCOW, pp. 4-16, 1975. MALEVSKII-MALEVICH, S.P. Procedures of conductingactinometric observations from a helicopter.Transactions of the MainGeophysical Observatory, No. 161,1965. Idem. 1968. Temperature and radiationregime of irrigated rice fields. - "Actinometry and atmosphericoptics." Tallin. MOSKALENKO, N.G. andShur, Yu.L. Forecasting changes in theterrain in areas of permafrostunder development. "Methods of geocryological investigations", MOSCOW, pp. 34-45, 1975a. Idem. 1975b. The temperatureregime of the surface and the layer of seasonal thawingon the lacustrine alluvial plains of the northern part of Western Siberia. - "Geocryologicalinvestigations", MOSCOW, pp. 76-96. PAVLOV, A.V. The heat exchange between freezing and thawingground and the atmosphere. Moscow. "Nauka", p. 296, 1965.
SLAVIN-BOROVSKII, V.B. Some results of a comparativestudy ofundisturbed and disturbedareas of terrain in the northern taiga. - "Methods of geocryologicalinvestigations." Moscow, pp. 45-53, 1975. - 45 -
THERMAL PHYSICS OF PERMAFROST TERRAIN
A.V. Pavlov Institute of Permafrost Studies, Yakutsk, U.S.S.R.
The thermal physics of landscapes reveal the relationship between individual components of a landscape (terrain) or between various terrain types. Of central importance here is the energy (heat) balance method, which makes it possible to describe quantitatively the processes of heat- and mass-exchange in the terrain of the earth's crust. The study of the thermal physics of terrain types focuses on the near-surface layer of the atmosphere, the surface cover (snow, vegetation, water, etc. ) and earth materials. The essential difference and also the complexity which characterizes I. themophysical studies in permafrost terrain is that in this case it is necessary to take into account the seasonal phase transformations of ground moi sture.
This integrated approach in studying the processes of heat- and mass-exchange in terrain types is typical in geocryology and is often lacking in the allied sciences of hydrometeorology, geothermal investigations, the physics of the near-surface layer, etc. (Pavlov, 1975). The most effective method of understanding the thermophysical processes is to conduct long-term observations of all of the heat exchange parameters in the system comprising the ground, the surface cover and the atmosphere in terms of their daily, seasonal and yearly variations. The author has conducted studies of this type since 1957 at the V.A. Obruchev Institute of Permafrost Studies (Moscow) and also at the Institute of Permafrost Studies of the Siberian Branch U.S.S.R. Academy of Sciences (Yakutsk). The studies encompassed a region of seasonal ground freezing (Zagorsk) and areas with unstable (Vorkuta, Igarka) and stable (Yakutsk; Syrdakh, 100 km to the northeast of Yakutsk; Solenaya, 300 km westwards of Noril'sk) permafrost (Pavlov, 1965, 1975).
Proceedings Third International Conference on Permafrost, VOI.1, pp. 69 - 74, 1978. - 46 -
One of the most important components ofthe terrain is the snow cover. In cornpardson withother natural formations, it isdistinguished by its seasonal character and the extreme variabilityof its properties, texture and thicknesswith space and time,which together characterize its effect on the heat exchange between the ground and theair. At permanent installations thefollowing dominanttypes of heat exchange inthe snow cover were experimentallystudied: conduction, diffusion and thepenetration of short wave solarradiation (Pavlov, 1975).Despite prevailing opinions, an abrupt variation(up to twofold) was revealed in theheat and mass exchange of the snow cover in the O°C to -3OOC temperaturerange. Processing the experimental data made it possibleto obtain the following formulae for determining the coefficients of macroscopic diffusion D and thermalconductivity A:
D(t) = D(0) + at + bt2, (1)
where D(0) = 0.92 x lo-' m2/sec; a = 2.91 x lo'* l/OC: b = 5.61 x lom41/(°C)2;
are coefficientsof thermal 'air, 'ice*Pair and pice the conductivity and the density of the air and ice respectively;
The first factor in the right hand part of formula (2) characterizesthe heat transfer by trueconduction, the second - thatwhich is causedby diffusion of watervapour. Inthe central regions of the European partof the U .S .S.R., throughoutthe whole of thewinter, diffusion accounts for about 1/4th of the totalheat transfer 9,. In thenorthern regions, where thewinter temperaturesare lower duringthis season, heattransfer caused by diffusion does not normally exceed 1/5th to l/lOth of 9,. - 47 -
We will assess theapplicability of the above formulae for calculating the coefficient of thermal conductivity of the snow cover, without takinginto consideration the temperature dependence (Abel 's Proskuryakov, Iosida,Iansson) . Plotted on thebroken 1ine in Figure 1 arethe two extreme curvescharacterizing at a definitedensity the lowest and thehighest values of the coefficient of thermalconductivity of the snow cover(corresponding to theconductive and effective thermalconductivity at a temperature of about -1.2OC). The formulae of Kondrat'eva,Iosida and Sulakvelidzefall outside the range of possible variations of X at any temperature. The most acceptable formulaeare those of Proskuryakov,Iansson and Piotrovich, and also Porkhaev'scalculated data, since they lie wholly within the range of possible variations of A.
Figure 1
Comparison of formulae for calculating the coefficient of thermal conductivity of the snow cover X as a function of the density P. 1 - after Kondrat'eva, 2 - Iansson, 3 - Proskuryakov, 4 - D'yakova and Serova, 5 - Abel's, 6 - Piotrovich, 7 - Iosida, 8 - Sulakvelidze, 9 - Porkhaev'scalculated data. The hatched area indicates the range of.possible variations of X (according to observations at Yakutsk and Igarka).
Now that we have 9 better understanding ofthe physics of theheat exchange processes in the snow cover, we will make a quantitativeestimate of - 48 - the intensity of the heat exchange between the groundand the atmosphereboth seasonally and as an annual totalfor what might be calledstandard natural terraintypes. They are taken to be open areas of terrain with a continuous snow cover and we shallprovisionally refer to them as "meadows".They are the most fully studied with respect to thesurface heat exchange, since it is here that the network of hydrometeorological stations is situated.Presented in Table I are the averagedvalues of all of the components of theheat exchange between the ground and the atmosphere both for a period with an above-freezing ts and a below-freezing tw air temperature and also for the year t and arethe total and reflectedradiation, Ieff the Yr' Qs S is effectivesurface radiation, R is the radiationbalance, P is theturbulent heatexchange, LE are theexpendi-tures of heat on evaporation (E is the evaporation, L = 600 cal/yr), and B is the heat flux in the ground. In Table I the observationsites are arranged in increasingorder of latitude (Vorkuta and Igarkaare situated at approximatelythe same latitude). The observations at Vorkuta arecharacterized by disturbedrather than natural conditions of heatexchange, as here thestation was situatedat the boundary of the town, where the influenceof technogenic factors is considerable(darkening of the surface by coal dust, etc.). All the remaining stations were situatedoutside the built-up area.
In summer, the albedo A of "meadows" is comparatively stable. In high and middle latitudes its value is usually between 16 and 25%. Shaded ground with a sparse herbaceous cover and also flooded areas are characterized by lower albedovalues, while some types of light herbaceouscovers containing pockets of cottongrass have highervalues. No zonation is observed with respect to thedistribution of thealbedo for the U.S.S.R. as a whole during the warm season. On the averagefor the year the value of A, ranging from 30 to 57% increases with latitude. This is due to thefact that the ground remains snow covered for a longerperiod of time in high latitudes - the snow cover being characterized by a higherreflectivity - than is thecase with herbaceous associations and soil.
The effectiveradiation of thenatural surface of a "meadowtt is 23 to 32% of the total radiation. During the warm season thehighest value of 2 theeffective radiation Ieff (about 20 kcal/cm ) is observed at Yakutsk. - 49 -
Table I Components of the heat exchange between the ground and the atmosphere for "meadows".
Components Kcal (season cm 2] %K r r I rw year rs I Zagorsk (1 957-1 959) Qs 63.7 16.5 80.2 100.0 100.0 S 14.5 11 .o 25.5 22.8 31.7 Ieff 16.2 6.9 23.1 25.4 28.8 R 33.0 - 1.4 31.6 51.8 39.5 P 6.1 - 1.6 4.5 9.6 5.6 LE 25.0 1.3 26.3 39.2 32.7 B 1.3 - 1.1 0.2 2 .o 0.2 Yakutsk (1970-1973) 62.4 27 .O 100.0 100.0 Os 89.3 S 11.8 18.1 29.9 18.9 33.5 Ieff 19.9 9.0 28.9 31.9 32.4 R 30.7 - 0.1 30.6 49.2 34.1 P 19.1 0.4 19.6 30.8 21.9 LE 9.3 1 *o 10.3 14.9 11.5 B 2.1 " 2.0 0.1 3.4 0.1 Igarka (1971-1974) Qs 44.2 32.5 76.7 100.0 100.0 s 10.1 21.1 31.2 22.9 40.7 Ieff 13.0 7.8 20.8 29.4 27.2 R 21.1 3.6 24.7 47.8 32.2 P 7.3 3.0 10.3 16.5 13.4 LE 11.3 1.7 12.0 25.6 15.7 B 2.5 - 2.3 0.2 5.7 0.3 Vorkuta (1 959-1961 ) .o Qs 38.2 26.2 64.4 100.0 100 S 6.1 13.3 19.4 16.0 30.2 I eff 9.5 10.9 20.4 24.7 31.6 R 22.6 2.0 24.6 59.3 38.2 P 9.8 2.6 12.4 25.7 19.3 LE 9.6 0.8 10.4 25.2 18.9 B 3.2 - 2.0 1.2 8.4 1.9 - 50 -
Table 1 (cont'd)
Sol enaya (1 974-1 975) 37.5 35.4 Qs 72.9 100.0 100.0 S 9.3 32.1 41.4 24.8 56.9 Ieff 8.7 7.9 16.6 23.2 22.8 R 19.5 - 4.7 14.8 52 .O 20.3
P 9.9 c 1 29.9 -
LE 6.6 c I 17.6 I B 1.7 - 1.6 0.1 4.5 0.1
Note: The characterof the vegetative and mineralcover atthe observationsites was asfollows: Zagorsk - clover andherbage, sandy silt; Igarka - reedgrass (Calamagrostis), very fine clayey silt; Vorkuta - hummocky tundrawith dwarf Arctic birch, heavy clayeysilt; Solenaya - moss and lichen hillocky tundra, clayey silt and sandy silt.
For the warm season theradiation balance R of thenatural surface of a "meadow" is abouthalf of Q, (49 to 52%). The ratio between theannual values of R and Q ranging from 20 to 40%, decreasesas thelati tude S increases. The anomalouslylow albedo and theincreased value of the R/QS for Vorkuta is to be attributed to the heavy pollution of the atmosphere with coal dust at the boundary of the town.
The resultsobtained confirm the existence of a welldefined latitudinalzonation with respect to the territorial distribution of the radiantheat exchange characteristics, as revealedby calculations and data fromweather stations (Atlas of theHeat Balance, 1963; Pivovarova,1966). Thiszonation is due to the decrease in the influx of totalradiation and the increase in thelength of timethat the ground remains snow covered as the 1ati tude becomes greater.
The expendituresof heat on evaporation LE vary in relation to Q, within wide limits:from 15 to 39% in sutrmer and from 11 to 33% inwinter. While no regularpattern is to be seen inthe spring-summer variationin the percentage of radiationheat expended on evaporationthere is a noticeable tendency for LE/R to increasetowards autumn (Table 11). The reason for this is that whereas in spring and sumner a part of theradiation heat is taken up - 51 - by the ground, by September the ground is releasingheat, which provides additional energy resources for evaporation.
Table 11
LE/R
P1 ace Month IV V VI VI I VI11 IX Zagorsk 0.45 0.74 0.72 0.75 0.73 0.84 Yakutsa 0.36 0.30 0.29 0.19 0.40 0.46 Igar ka 0.51 0.15 0.48 0.57 0.58 0.69
Vorkuta 3 0.14 0.38 0.40 0.43 0.69 Sol enaya - - - 0.45 0.44 0.49
Research at the A. I. Voeikov Main Geophysical Observatory (Budyko, 1956; Zubenok, 1966) has shown that the geographic distribution of surface evaporation is governed mainly by. thefollowing factors: the energy resources (radiationbalance) and the moistureconditions of the ground. In middle latitudes and especially in southernlatitudes, where the influx of radiation heat is considerable,evaporation is almost whollydetermined by the moisture conditions. When the precipitation is sufficient,expenditures of heat on evaporationarethe main outgoing component in theheat balance. In particular, in thewestern and centralregions of the European part of the U.S.S.R. up to 60 to 80% of theradiation balance is expended on evaporation. As thelatitude increases the radiationbalance decreases, which gives rise to an overall trend towards a decrease in evaporation. In thetundra zone (Igarka, Solenaya, Vorkuta) it is not onlythe evaporation that decreases but also,despite the supersaturation of the ground, the LE/R ratio, which here amounts to 34 to 54%. This is due to thedecrease in the air temperature and the ground surface temperature, which can be regarded as secondary energy indices in relationto R and tothe low yield of water from the mossy and peatycovers that are widely prevalenthere. Thus, during theentire summer the LE/R ratio reaches a maximum (60 to 80%) in the middle latitudes (45 to 55'N). becoming smaller towards the south because of the insufficiency of moisture and also towards the north due to the low yield ofwater from the - 52 - ground. Thisgeneral pattern inthe distribution of the LE/R ratio may be greatlydistorted in some regions(for example, Yakutsk)on account of an absence of zonation associated with the high moisture content.
In summer theturbulent heat exchange ranges from 6 kcal/cm2 (Zagorsk) to 19kcal/cm2 (Yakutsk) or, inrelation to Qs, from 9 to 31%. The P/LE ratio (Bowen's ratio) is characterized by minimum values in middle latitudes and becomes greatertowards the north and south.There is a relationship between Bowen's ratio and the total precipitation. As indicated by thedata for Vorkuta and Igarka, where P/LE - 1 , thetotal annual precipitation r = 450 to 480 mm isevidently critical for estimating the prevailingeffect of currents of turbulentheat or expenditures of heaton evaporation. At Zagorsk (r = 644 mm) P/LE << 1, at Yakutsk (r i 202 mm) P/LE 2.
At thesites of therecording stations the accumulation of heat by the ground B duringthe period with above freezingair temperaturesranged from 1.3 (Zagorsk) to 2.5 kcal/cm2 (Igarka).During thisperiod a characteristicproperty of theheat balance components of "meadow" terrain is a substantialincrease inthe groundheat fluxin the permafrost region. Here, its value can be as high as 5 to 6% in relation to Q, and 10 to 15% in relationto R. In thepermafrost region there is a sharp peak inthe amount of heataccumulated by the ground and this coincides with the beginning of its thawing.During this period the heat flux in the groundcan be as much as 1.4 to 1.6 kcal (monthecm2 ) in some years. An abrupt decrease in the accumulation of heat by the groundthen occurs. Inregions where there is no frozen ground a smoother variationin the value of B duringthe summer is noted(Zagorsk). The release of heat by the groundoccurs unevenly with time. It is greatest atthe beginning of thewinter. During October and November the ground may expend more than 50 to 60% of all of the heat losses throughout the winter.
Of course,the mean long-termconditions are such thatthe heat fluxin the groundapproximately equals the expenditure. The remaining components of theheat balance (R, P,LE) are from halfto one orderless duringthe twperiod than during the tSperiod; quantitatively speaking they areapproximately equal (see Table I). Duringthe coldest months of the - 53 - winter,effective radiation predominates over theinflux of total radiation, the duration of this period increasing as thelatitude becomes higher. The period with a negativeradiation balance is even longer. Radiation cooling leads to an air temperatureinversion above the snow cover. R. Geiger (1960) was evidentlythe first to notice this. As a result of theinversional temperature distributionthe turbulent heat flux isdirected towards the surface of the snow cover and partly compensates for theheat losses by radiation. For thegreater part of thewinter turbulent heat exchange is an 5 ncomingcomponent and expenditures of heat on evaporation an outgoing component of the heat balance. Evaporation of the snow cover is normally slight in comparison with the totalreserves of snow and it cannot be taken into account in hydrological calculations. At the Yakutsk recording station, however, it was as much as 8 to 26% of the snow reserves (according to data from a six-year period of observation).
Experimental data indicate that the thermal turnover in peatlands is smaller than in mineral terrain. In particular, at Igarka thedecrease in thethem1 turnover in peatlands as compared to clayey silts was 9%. The comparatively small decrease in the thermal turnover is due to thefact that steep temperature gradients, intensifying the accumulation of heat, form in it because the frost table is near thesurface. P.F. Shvetsov (Principles of Geocryology, 1959) has proposed a more general theory that thereis an increase in thermal turnover as thelithological composition of the ground changes from mossy peatlands to gravel and shingle. Under natural conditions, however, ground consisting of coarse-grained particlesis usually less moist and is not necessarilycharacterized by larger thermal turnovers, as the latterare caused not only by periodicvariations ‘in ground temperature but also by expenditures of heat on phase transitions of ground moisture with freezing and thawing. ”In situ data indicate that the thermal turnover is greater in clayey silts than in sandy silts and sands. Thus, the dependence of thermal turnover on thelithological composition of the ground is highly c omp 1ex .
The positive and negative items of the thermal turnover in the ground originate under conditions of asymmetry of its thermal properties in the frozen and thawed state. The observations at the permanent recording - 54 - installations showed that under naturalconditions, as a result ofmarked fluctuationsin moisture content, the coefficient of thermal conductivity of the active layer may vary more appreciably during the annual cycle than during thetransition from the frozen to the thawed state (Pavlov, 1975). This stronglydistorts the temperature shift At which V.A. Kudryavtsev (1958) has defined as the difference between the mean annualtemperature at the base of theactive layer and thetemperature at theground surface. Under natural conditionsthevalue of At, even in clayey silt and especially in coarse-grainedmaterials, frequently remains within the range of accuracy of its experimentaldetermination. Specifically, according to thedata from long-terminvestigations at the permanent installations,the value of At was: Zagorsk and Yakutsk +0.2'C, Vorkuta -0.6OC and Igarka -0.3OC. In mossy-peaty earthmaterials, however, the change theincoefficient thermalof conductivity as a result of phase transitions of moisture is much greater than when there is a change inthe moisture content. The temperature shift in them is accordinglyclearly defined. Thus, at Solenaya station the value of At was -1.5OC.
The studiesresulted inthe discovery of a new general ruleS characterizingthe regional pattern which is manifest in the effect of the snow cover on theheat exchange processes between the ground and the atmosphere. As a resultof the marked decrease in thecoefficient of thermal conductivity of the snow with a loweringof the temperature,the insulating role of the snow cover inregions with severe winters is more pronounced than in regions with mild winters.
In comparison with open 'areas,the conditions in Siberia are such that water bodies and forest comprise the more common types of terrain.
In some regionscontaining frozen ground, waterbodies account for up to halfof the total area. They are a uniquelandscape which exerts an influence on thenatural processes and inparticular, on thetemperature and thicknessof permafrost.
Few systematic observations of waterbodies have been conductedand almost all of them failto encompass thewinter. To quotethe widely - 55 - prevalentmetaphoric term, the aqueousenvironment (1 ike the forest cover) is a "trap"a for radiation. A generalisationof the results of actinometric observationspertaining to the waterbodies of the U.S.S.R. indicatesthat in sumner the radiationbalance of waterbodies Rwat is 20 to 40% higher than the valuefor treeless landareas Ro and that in the autumn theopposite relationship is observed(Kirillova, 1970). The ratio between the sumer totals of Qat and Ro becomes greater on the whole towards the south. The reflectivity of waterbodies tends to decrease and the radiationbalance increasesas the water bodybecomes deeper. Year round investigations of the thermalphysics of water bodies were conducted by the author in a small lake in the vicinity of Zagorsk and in adeep thermokarst lake at Syrdakh. We will compare the data on the albedo of Lake Syrdakh and that of the shallowlakes of Central Yakutiya during the ice free season(Table 111). The noticeable decrease in thealbedo of Lake Syrdakh (by 4 to 7%) is both on accountof the increase in depth (and consequently in the absorptivecapacity) and the decrease in transparency of the water,
Table I11 Albedo of the lakes of CentralYakutiya, %.
~ ". .. - .- . . .. - Lake Years I Months I Mean
Syrda k h 1974-1 975 6 7 8 14 7 Tyungyulyu 1963 11 12 15 24 14 Kradenoe 1968 8 12 13 17 11
Pro khl adnoe 1969 I 9 11 16 11
~ - .. -. . Note: The data on the a1bedo of Tyungyulyu, Kradenoeand Prokhladnoe lakes were derived by M.K. Gavrilova (1973).
The ratio between the albedoof the water body during the season with an exposed watersurface Awat and thealbedo of the surroundingtreeless areas of land A, does not exceed 1/3 during the summer months (Figure 2). In winter the differences between A,,,at and A, are minor and the value of laatI > IR61, sincethe temperature of theactive surface is higher and the radiation is greater. Taking thetotal for the year, Rwat H (0.9 to l,l)Ro. - 56 -
At approximatelyequal annual values of theradiation balances of the water body and the ground, the circulation of heat in the water body is 6 to 8 times greater, which leads to the formation of taliks beneath the waterbodies in the permafrost region.
Figure 2
Annual variation in the ratio between the albedo of a lake A1 and of a treeless area A, 1 - a lake situated near Moscow; 2 - a lake at Syrdakh.
In the U.S.S.R. althoughforested areas occupy up to 35 to 40% of the overallarea, in contrastto %eadowsI1 , their thermal physics have hardly been studied atall. The first complete group of long-term observations conducted in thepermafrost region comprised pineforest at Yakutsk, birch forest at Igarka and larchforest at Syrdakh. Of specialvalue are the investigations of the larch forest, which in many regions of Siberiaoccupies up to 80% of the forested area.
The reflectivity of forestcover over the year (with theexception of the late spring period, when the snowon the ground meltscompletely but still remains in the forest) is lower than in thetreeless area. Thea1 bedo of the lightconiferous forests of Siberia is 10 to 13% in summer, while that - 57 - of the larch forests is 14 to 19% (Table IV). In summer the ratio between the forest albedo Af and thealbedo of the open area is 0.5 to 0.8; in winter it does not exceed 0.6 (Figure 3).
Figure 3
Relatiorship-between the a1 bedo af a forest Af and the a1 bedo of an open area A,. 1 - birch forest (Igarka ; 2 - pine forest (Yakutsk 1 ; 3 - larch forest (Syrdakh).
Table IV
Albedoand radiation balance of Siberian forest cover.
Season Pine Larch Birch forest forest forest Albedo, % ts 10-1 2 10-13 14-19 13-1 4 14-15 20-21 tY. Radiationbalance, kcal/cm2 42 45 24 ts t 51 50 34 Yr - 58 -
The decrease in thereflectivity of forest cover as compared to "meadows" leadsto a substantial increase in theirradiation balance.
In order to estimatethe radiation balance of aforest Rf as compared to an open area Ro, Yu. L. Rauner (1972) used observationaldata for closestands of larch andmixed forest at Zagorsk and Kursk during the warm season. The estimate wasmade from dailytotals averagedover aperiod of severaldays. The dependence of Rf on Ro was obtained by the linearequation:
where
2 FI = 1.05, 6 = 30 cal/(day cm ).
For coniferousforests (pine, spruce), Rauner gives other - 2 parameters of regressionequation (3): a = 1.1, 6 = 35 cal (day cm ).
The observations of theradiation regime of thepine and larch forestsafford basisa for determining the closeness of the correlation between the dailytotals of Rf and Ro under the conditions in Siberia(Figure 4). The correlationcoefficient was 0.94. The parameters of equation (3) proved to be as follows for the light coniferous forests of Siberia: i = 1.37; 2 6 = 10 cal/(day * cm ).
The increase in the radiationbalance of the forest during the winter R3 is 5 to 6 kcal/cm 2 for the larch and deciduous forests of Siberia and 7 to 8 kcal/cm2 for the pine and spruceforests. Taking into consideration AR3 the annual valueof the radiationbalance of forested landscapes can be calculated from the formula:
( Rf)year = ( zRo)f f btf .
The results of the observations and also the published data (Rauner, 1972; Gavrilova, 1973 et al.) show that within a single regionthe difference between theseasonal and annual values of the albedo A and the - 59 - radiation balance R of thesubjacent surface for various types of terrai-n can be greater than the difference between the same types in differentregions. Thisenables us to use the values of A and R as leading factors when making an energy estimation of naturalterrain types (Pavlov , 1975). Based on these indices the various types can be placed in a sufficiently well defined correspondence with "meadows".The relation between the remaining components of theheat balance (P, LE, B) of the various types and the Ilmeadow'l is 1 ess definite. On the basis of thetheories whichhave been considered, a general energy classificationis compiled with respect to the most typical types of terrain. This classification is comn to the forest-steppe,forest and forest-tundra zonesof the U.S.S.R. (Table V).
Figure 4
WO
300
200
100
Correlation between the radiation balance of a forest Rf pd the radiation balance of a treeless area Ro (cal/(day I cm )) 1 - pine forest; 2 - larchforest; 3 and 4 - direct regressions from experimental data of the author and Yu. L. Rauner (1972) respectively. - 60 -
Table V
Energy classification of naturalterrain types.
Season Pine and spruceLarch forest Birch and mixed Water body Icingarea forest forest Albedo (relative to the open area) tf 0.55 - 0.6 0.55 - 0.65 0.6 - 0.85 0.45 - 0.55 1.0 - 2.0 0.4 0.45 0.85 tYr - 0.45 - 0.55 0.5 - 0.65 0.70 - 1.05 - 1.25 Radiationbalance (relative to the open area) tf 1.3 - 1.4 1.25 - 1-35 1.1 - 1.2 1.05 - 1.15 0.7 - 0.9 1.6 1.7 1.4 1*5 1.3 1.4 0.85 1.15 tYr - - - - 0.5 - 0.7
REFERENCES Atlasof the Heat Balanceof the Globe. 1963. Editor M.I. Budyko, MOSCOW, 69 pages.
BUDYKO, M.I. 1956. The heatbalance of theearth's surface. Leningrad, Gidrometeoizdat , 225 pages. GAVRILOVA, M.K. 1973. The climate of CentralYqkutiya. Yakutsk, 119 pages
GEIGER, R. 1960. The climate of theterrestrial layer of air. MOSCOW, Izd-vo IL , 486 pages. ZUBENOK, 1.1. 1966, The role of evaporation in the hwit ba'lpnce of theland. In: ContemporaryProblems In C1 imatology. Leningrad,Gidrometeoizdat, pp. 67-82.
KIRILLOVA, T.V. 1970. The radiationregime of lakes d artificial reservoirs. Leningrad, Gidrometeoizdat, 28 3 pages. KUDRYAVTSEV, V.A. 1958. The effect of variouscovers on the de th of seasonal freezing and thawing. In: Aspects of t e Physical Geography of PolarCountries, Itd-vo WGU, firstR edition, pp. 28-34. Principles of Geocryology , part 1, 1959. MOSCOW, Ird-vo AN SSSR, 431 pages. PAVLOV, A.V. 1965. The heat exchange between the atmosphere and freezing and thawingearth materials. Moscow, "Nauka", 254 pages. - 61 -
PAVLOV , A .V. The heat exchangebetween the ground and the atmosphere in the northern and middle latitudes of the U.S.S .R. Yakutsk, 302 pages. PIVOVAROVA, Z. I. 1966. A study of the solar radiation regime in the U.S.S.R. In: Contemporary Problems in Climatology. Leningrad, Gidrometeoizdat , pp, 41 -56. RAUNER, Yu. L. 1972. The heatbalance of the vegetative cover. Leningrad, Cidrometeoizdat, 210 pages
- 63 -
GEOPHYSICAL ASPECTS OF THEDEVELOPMENT OF PERMAFROST
V .A. Kudryavtsev and V .G. Melamed Faculty ofGeology, Moscow State University, U.S.S.R.
Net radiationat the surface is the basis of thethermal state of theearth. It determinesthe climate ofthe atmosphere and lithosphere and, inparticular, the temperature regime of the nearsurface layers of the lithosphere. As is known, thethermal radiation regime of theearth's surface depends on thesolar constant, the latitude and characteristics of the geological and geographicalenvironment of each givensection of this surface. The first two factorsare sufficiently stable and if they change at all, then onlylittle and overlong periods of time. At the same time, changes inthe geological-geographicalenvironment are both considerable and rapid, and this above all is thereason forall main changes inthe thermalstate of the earth,the climate of the atmosphere and temperature ofthe nearsurface layers of thelithosphere. Indeed,such phenomenaas theatmospheric circulation, warm and cold sea currents, distribution of oceans and continents on theearth's surface, the structure of thesurface of thecontinents (folded regions,lowlands) , amount of icein northern and southern seas, andmass exchange inthe ground, and condensation ofmoisture in the atmosphere and lithosphere - all these phenomena determinethe climate of the atmosphere and lithosphere,thethermal state of differentregions, as well as the geographical and altitudinal zonal ity.
The existence of different cycles in weather conditions and climate is well known. There areshort period fluctuations (lasting for hours, days and months) , eleven-yearcycles (which depend on solaractivity), 1850-year cycles,etc. There are also long term fluctuations with periods of several hundredthousand and millions of years,which are related to thegeological
ProceedingsThird Internatlonal Conference on Permafrost, VOI. 1, pp.100 - 105, 1978. perlods of glaciation and theinterglacial periods. Since the climate of the atmosphere and thelithosphere is due to one and the same cause, thenet radiationat the earth's surface, theaforementioned fluctuations themselves areinterrelated. It followsthat one can talk aboutthe aforementioned periodic changes in thetemperature field of the earth and its dynamics.
The cryol ithosphere exists in places where the soil temperature is O°C or below as a result of specificcharacteristics of the heat and mass exchange on thesurface of the earth. Depending on theduration of the existence of theaforementioned temperature field, there may be shortterm, daily, seasonal orperennial freezing of thenear surface layers of the 1 ithosphere lasting for hours , days, months, years andthousands of years respectively. The periodicityin the changes of thenet radiation at the earth'ssurface determines the dynamics of thetemperature field in theupper horizons, as well as the formation and thehistory of development ofthe cryol ithosphere.
In the studytheIn of the dynamics and development of the cryolithosphere, ft is essential. to acceptthe view that the development of thetemperature field of the earth and the cryolithosphere has been continuous and is the result of continuous changes in the net radiation at the surface of theearth. This makes it essentialto reject the ideas of the steady state, quasi-steadystate, etc., according to which the changes in thetemperature field at depthconstitute a disturbance of thesteady state and terminate relativelyquickly. In other words, because of continuous changes in the climate and thesurface of theearth, a continuityof motion and development 4s an essentialprerequisite for the temperature field in thenear surface layers of thelithosphere. The stateof rest is simply a special case of motion.
The theories in whichthe steady state plays a centralrole are based on fieldobservations of the permafrost temperature, which show that at greatdepths this temperature remains stable for 20 or 30 years.That this approach is wrong becomes evident ifwe considerthat although the amp1 itude of thesurface temperature fluctuations attenuates rapidly with depth, there are,nevertheless, corresponding changes in thetemperature field in layers of - 65 - considerablethickness. In spite of thefact that the absolute value of these fluctuationslies within the experimental error, it is thesefluctuations whichdetermine on the geological time scalethe dynamicsof development of permafrost.
The situation is similarwith respect to the dynamics of the permafrost base. Inthe casewhere theformation andexistence of permafrost isrelated to longperiod fluctuations extending over tens andhundreds of thousands of years,there will be changes inthe thickness of permafrost of several mil 1 imetersor even fractions of a mil 1 imeterper year. This , of course,creates theimpression that thetemperature field within the permafrost is steady.
Thisoften leads to the assumption that it is quite proper to apply steadystate problems in generalpermafrost studies. However, the use of such problems results in utterly wrong conclusions on thepatterns of formation of permafrost(in particular, the time of permafrostformation determined in this way is far too low).
Inthe well-knownstudies by D.V. Redozubov basedon theideas of the steadystate, it is stated that permafrost up to 600 m in thickness can be formed inthe course of 3000 years. At the same time, it followsfrom the solutionof the Stefan problem without the initlal conditions describing the dynamics of perennialfreezing inthe presence of periodic changes inthe surfacetemperature (Table) that even inthe case oflong period temperature fluctuations of lowamplitudes, the permafrost formed is now thickalthough its age is considerable.
It followsfrom the Table that the thickness of permafrost increasesrapidly with the increase in the amplitude of fluctuations. On the other hand, thethickness of permafrost is greatly dependent on thegeothermal gradientg. It increases as g decreasesand reaches a maximum of g = 0 (i.e. , in places where theinflux of subterraneanheat is blockedby deep seated permafrost). The role of thegeothermal gradient increases rapidly with an increase in theperiod of fluctuationsof the surface temperature and becomes noticeableat periods of theorder of severalthousand years. Thephase - 66 - transitions (i.e. , the moisture content of earth materials) also influence the formationof permafrost but to a lesserextent (in terms of quantities) than theaforementioned factors.
In thepresenceIn of differentfluctuations of thesurface temperature,the temperature field theof near surface layers theof lithosphere and, inparticular, formation and existence of permafrostare the result of thetotal effect of all thosefluctuations. The temperature field in permafrostcontains traces of periodicreplacements of warming trendsby coolingtrends from differentperiods, which leads to a simultaneous occurrenceof aggradation and degradation ofpermafrost at different depths. A goodexample of this is offeredby geocryological conditions inthe West Siberian Lowland,where deep-seated (70 - 200 m) relic permafrost is buried underunfrozen materials 30 to 100 m in thicknessthe upper part of which froze to a depthof 20 - 80 m at a laterdate (Zemtsov,1962; Baulin et a1 ., 1967;Sharbatyan, 1974; Gruzdov et a1 . , 1972).
It is evident that the rhythmic nature of temperatureconditions at thesurface leads to periodic changes inthe heat exchange inthe permafrost. The warm and coldperiods are related todegradation and aggradation respectively. Thus, inprinciple, there are no differencesin this dynamic of the temperature field within and outside the permafrost region.
Inspite of this, however, theliterature contains references to thefact that cold is accumulated inthe ground inthe permafrost region, whileoutside this region the ground accumulates heat (positive and negative heatbalance ofthe soil). This isobviously wrong, sinceotherwise the temperature inthe permafrost region would drop to absolutezero, while outsidethis region heating would go on indefinitely and theearth materials would me1 t.
Hence, in any area and region,the dynamics of permafrost and the history of its formation anddevelopment arerelated to fluctuationsof the heat exchange on the surface of the earth and the causes of these fluctuation. The study of the dynamics of development of permafrostrequires a comprehensiveanalysis of historythe of surrounding the - 67 - geological-geographicalenvironment and of changes inthe entire complex of geological andgeographical factors affecting the heat exchange on theearth's surface and theformation of permafrost. Thus thehistory of formation of permafrost becomes a page inthe history of development of thegiven region which isrelated to the palaeogeographical conditions in this region andon theearth as a whole,and inparticular to the periods of glaciation and the interglacialperiods. Inthis casethe investigators should pay special attentionto the effect of variousgeological and geographical factors on the heat exchangeand theformation of permafrost. This makes it necessary to determinethe specifics of thethermophysical patterns of formation of the thermalstate of theupper layers of theEarth indifferent geological structures(mountain countries, lowlands and plains, uplands, plateaux, geosynclinalregions, denudation and sedimentaionregions, and indifferent 1ati tudi naland geobotanical zones).
TABLE
Thickness of permafrostforming for variousamplitudes A and periods T of fluctuationsin temperature at the surface when there is a geothermalgradient of 0.01 and 0.03 deg/m (inbrackets) for the volumetric moisture content of earthmaterials of 25% (numerator) and 50% (denominator)*
7,36(6,96) 11,8(11,4) 15,1(14,5) 102 "" """_ "I 5,23(5,04) 8,40(8,16) 10,7(10,4) 21,9(18,6) 35,8(31,6) 45,9(41,1) lo3 "- "" 15,9(14,2) 25,8(23,7) 33,0(30,6) 58,1(38,6) 99,0(72,4) 129(97,9) I"" 104 """ I"" 44,5 (3x7) 74,4(S9,l) 96,3 (78,8) 119(56,0) 224(120) 304(174) ___fl___I" "" 101(52,8) 184(110) 245(155)
* Depths of permafrost for thecykle obtained under the condition that the temperature at the surface is 0 C, the coefficient of thermalconductivity and thethermal cagacity of theeagtg materials in frozen andthawed states 4.19 kJ/m/h C and 2095 kJ/m C. respectively. - 68 -
Inthe folded mountain regions, the most important factors are the altitudinaltonality, the geological and structuralcharacteristics of rocks, theformation of terrain and ofdeluvial-proluvial deposits on theslopes, as well as thestructure of theintermontane depressions. There are many types of thermalinteraction of groundwater withpermafrost due tothe effect of closedartesian basins, different conditions ofsupply and discharge of groundwater in thesebasins, as well as ofits chemicalcomposition. On the plains of thePlatform, it isthe latitudinal zonality and thestructural features of thecryogenic depositions and the Quaternary deposits extending overvast areas, which are the most clearly observable. Comparatively varied hydrogeologicaland geothermal conditions create a hydrogeothermicbackground againstwhich the influence of thelithological composition and moisture regime of the earth materials is superimposed.
All of thesefactors, to onedegree or another,leave their markon the formation of the geocryological conditions of the region anddetermine the peculiarities of its composition,cryogenic texture, andlikewise the temperaturefield, the thickness of thepermafrost, and theprocesses and phenomena whichoccur within it. The dynamicsand historyof permafrost development infolded regions are characterized by theirgreat complexity. The imposition of a series of fluctuationsin surface temperature under these conditionsis complicated by the dynamic nature of thegeological-geographical conditions,landscape features, sedimentation and denudation, and neotectonic movements. On theplatform and on theplains, the historical development and the dynamics of thepermafrost are less complex, and periodicfluctuations in temperatures at the surface are clearly manifest.
All of the above offerconvincing evidence of thenecessity for a strongcorrelation between the geophysical I thermophysical and the geographical and geologicalaspects of thedevelopment of permafrost, i.e., the study ofthis phenomenon must be realizedin a broadgeophysical perspective. The thermophysicalaspect must be examined for each given geologicalcircumstance; thiscan be accomplishedonlynot by the specification of extremeconditions and characteristics of theenvironment, butalso by theselection of a general schema forthe formulation and derivation of basicdifferential equations. - 69 -
The dynamics of temperaturefields of earthmaterials subjected to freezing andthawing within the framework of a continuumare best described by theStefan problem. A characteristicfeature of the abovementioned problem that has many applicationsin various fields of science and technology is the presence of internal,mobile boundaries separating the frozen andthawed zones (fronts),for which the law of dislocationis not known beforehand.Except for the steady state case, the associated specific non-linearity (in the sense of boundaryconditions) ofthe Stefan problem excludes the possibility of usingthe principle of superimpositionof solutions and greatly complicates researchinto patterns of occurrenceunder natural conditions.
In accordance withthe aforementioned, which are typical of the freezing and thawing ofthe materials, there is their simultaneousoccurrence atdifferent depths during the periodic formation and disappearance of frozen andthawed layers(due to seasonaland perennial fluctuations in theclimate); this 1eads to a mu1 ti-fronted Stefan problem with a variable number of fronts. Inthis case, as wellthe near eutectoid phase transitionsof free and gravitationalmoisture, the conversion of bound poremoisture occurring in the diaparone at subzerotemperatures isof substantial importance.Moreover, duringfreezing in damp, fine-grainedmaterials, mass exchange (migration of moisture) 1 eading to theformation of cryogenic textures andheaving plays an importantrole. No lesssignificant is the mass exchange in coarse-grained materialsduring filtration and infiltration.Finally, the study of patterns of formation of geothermal fields is alsocomplicated by the dependence of the thermophysicalproperties and permeability of materials on thecomposition and texture of thesubstance: factors which undergo change duringfreezing and t hawi ng
All ofthe aforementioned led to the fact that during calculations on freezing and thawing,the approximated results ofthe Stefan type of problem in very simp1 e formulationswere we1 1 developed (Lei benson,1931 ; Krylov, 1934, 1940; Charnyi, 1948, tyk'yanov,Golovko, 1957; Porkhaev,1970; Fel 'dman, 1963and others). Of greatimportance atthe present time are the well known formulae and "express methods" for fieldcalculations (Kudryavtsev et a1 , 1974). These allowquantitative research to be carriedout on the freezingand thawing processes inearth materials during the periodic - 70 - establishment of regimes(Stefan problem without the initial conditions). with respectto individual geological-geophysical factors.
Despitethe considerable success attained with the help of the givenapproach forsolving a widerange of problemsongeocryological forecasting and therational useand protection of theenvironment, satisfactory answersneed to be found to a wholeseries of important quantitative patterns of formationand development of permafrost.
Substantialsuccess in mathematicalresearch on the Stefan problem has only been attainedrecently. As a result, and also due to therapid development of computers inrecent years, a wholeseries of mathematically based algorithms of thesolution of theStefan problem have been proposedand arebeing used moreand more (Melamed, 1958; Vasil'ev,Uspenskii, 1953; Samarskii, Moiseenko, 1965; Budak et a1 ., 1965, 1967). Of greatimportance areself model 1 ingsolutions to theStefan problem for general equations and also systems ofquasilinear equations (Melamed, 1969),which allow not only research on theanalytical and physicalfeatures of a givenprocess, but also evaluation of therole of its numerous parameters. All of this opens wide perspectivesfor mathematical simulation of givengeological processes on digital computersand for associated questions based on solution of theStefan problem. A similar approach, when thereis a strongcorrelation between the formulation of theproblem and thegeographical and geological conditions, givesthe possibility of researchingboth general and individualpatterns of the complex geological phenomena and for them to be characterized quantitatively.
The mostdeveloped are the various methods forsolving the one dimensionalStefan problem forlinear parabolic equations; a problemwhich describesthe phase transitionsof moisture that are similar to eutectoid transitions. As was shown inthe work of Chudovskii(1 954, 1976),Martynov (1959),Ivanov, (1970) and others, the given formulation is a sufficiently completemathematical model of thefreezing andthawing processes occurring in naturalconditions in various types of coarse-grainedmaterials (bedrock and semi-bedrock,shingles and gravelswith sandand debris, sandyloam fillers, sands, etc.). One of themost effective algorithms for solving the given - 71 - multi-frontedStefan problem is the method of reducing the Stefan problem to a system of ordinarydifferential equations (Melamed, 1958).Unlike the differentalgorithm, the proposed method notonly allows a solution to the problem to be found when there is a change in the number of fronts as a result ofthe formation or disappearance of zones, but also, withgiven accuracy, determinesthe dynamics of heat flow in timefor anysection. This allows the possibilityof using the algorithm developed in the study as an effective instrumentfor solving variousproblems in geothermal and permafrost forecasting, when thereare occurrences ofeutectoid phase transitions in the materials due tonet radiation at the earth's surface. In particular, as a result of finding a periodicallysteady solution to the Stefan problem under examination(variable number offronts during harmonicfluctuations of temperature atthe surface), it was decidedthat, in time,the heat flow q in the layer of freezing (thawing) experiences interruptions of the first kind of discontinuityat the moment offlow-through by the front at the depth being investigated. The sizeof the interruption q andlikewise the inflow value Q' and the outflow value of 9- of the constituent heat exchanges during the cycle decreasewith depth. When this occurs,the heat exchanges aresharply reduced as they pass throughthe base of the layer of freezing(thawing).
Withthe help of theproposed algorithm, the feasibility of determiningthe inflow and outflow components of heat exchanges inmaterials duringthe cycle has made it possible to find annualfluctuations of "temperatureshift" that are characteristic of the layer andwhich, forthat cycle,link the mean temperature atthe surface with that of the layer of freezing(thawing). Results derivedbythis method of investigationof temperature shift wereused by V .A. Kudryavtsev (1958) to obtainthe we1 1 known approximationformula.
The efficiency of this method for solving the Stefan problem with a variable number offronts, has allowedresearch to be conducted intothe near surfacelayer ofthe earth; a fieldthat is formingas a result of superimpositionof fluctuations in climate during various periods. All of this opens widepossibilities for research intothe cardinal question of generalpermafrost studies: the creation of a retrospective model of the historical development of permafrost. - 72 -
Inslightly moist, fine-grained materials, wherephase transitions of non-freezingwater are very important inthe freezing andthawing processes,the dynamics of thetemperature field are described by a Stefan typeproblem for a quasilinearparabolic equation. At thepresent time, there are a number of suggestedmethods forthe solution when thereare weak restrictions on thedata, as isthe usual case (Melamed, 1976).Comparison of serialcalculations of thegiven problem (for actual materials with various types of iceformation in the spectrum of subzerotemperatures) with the correspondingsolutions of the Stefanproblem for eutectoidtransitions examinedabove shows thatduring thawing, calculation of phase transitions of non-freezingmoisture (all conditions being equal) leads to a substantial reductionin the depth of thawing and to a sharp risein the temperature of thepermafrost (observable even in fine-graineddust-particled sand).During freezing,the aboveeffect is considerably weakerand should, inpractice, be consideredonly infine-grained materials when thereisnatural moisture imperceptibly exceeding the maximal molecular moisture content.
In verymoist fine-grained materials (where thefreezing processes areclosely associated with the migration of moisture that leads to the formationof various cryogenic structures and heaving),the dynamics of the temperature field(with a few approximationsbasically associated with disregardfor the questions of thermorheology)are best described by the type of Stefanproblem for a system ofquasilinear equations (Melamed, 1966, 1969; Takagi,1970). Inthis case, theheat- and moisture exchange characteristics of materials (in particular the coefficients of heat- and potential diffusity) depend substantial 1,y on thetotal resulting moisture. As mathematical research has shown, thegiven problem fully describes a number ofimportant characteristics of the phenomenon beingsimulated that are shown from experimentsand fie1d observations.
At thepresent time, the algorithms proposed are for a solution of theproblem when thereare weak restrictionson input, for both arbitrary extremeconditions and self model1 ingcircumstances. Comparison of results of mathematicaland laboratory simulation of the freezing process inkaolin clay showed thatthe solution to theproblem offreezing, when there is migration of moisturein a1 1 problemsexamined , isbest described by heat and mass exchange in freezing,moist, fine-grained materials, with a verysatisfactory degree of accuracy. - 73 "
Calculationscarried out for the above problem show that in contrast to conventional methods forcalculating the depth of freezing (where thedetermining factor is the hourly frost degree index) in moist, fine-grainedmaterials, it is necessary togive detailed consideration to the characterof changes in thesurface temperature during thewinter months. In particular,determination of icecontent throughout the section of frozen ground is closely connected with the non-monotonic natureof the surface temperature and is expressed in thesuccession of warmingand coolingperiods. This is most clearly manifested in the first half of theperiod of freezing. The resultingpossibility of establishing a quantitative dependence of the cryogenicstructure of permafrost on climaticconditions permits an indirect approach to the solutionof the problem concerning the occurrenceof paleotemperatureconditions for formation of permafrost throughout the given section. Wide horizonsare opened by thesolution to this problem when: calculationsare made of ice accumulation and associated heaving in various regimes of suprapemafrost water.
The self modellingsolution to the problem offreezing when there is moisturemigration allowed a number of important general characteristics of this process to be revealed and clarified. Related to it, for example, is research into the dependence of the moisture at the heave threshold on extreme conditions,primarily the temperature of freezing; this is widely applicable in permafrostengineering studies for estimating the susceptibility to heave in earthmaterials. This was later used extensively in the working outof new methods forcalculating standard depths for 1 ayingfoundations (Kudryavtsev, 1971). Moreover, with thehelp of thesolution obtained, it was possible not merely to elucidatethe concept expressed by M.N. Gol'dshtein in 1948 concerningoptimal conditions for segregated ice formation, but a1 so to solve thequestion quantitatively. In particular,calculations carried out for a number of actualfine-grained materials with physicalproperties substantially different from those of water, showed a non-linear dependence of the optimum temperatureof segregated ice formation and heave on naturalmoisture; this increasesstrongly with the growth ofthe latter. In the sameway, research into generalpatterns of maximum excess iceformation, conducted on thebasis ofthe self-modelling solution to the problem of theStefan type for a system ofquasilinear parabolic equations, opens up thepossibility of studying the - 74 - historical development of fine-grainedpermafrost and for the development of ways of control ling their cryogenic structure.
Of considerableinterest are the recently obtained solutions to variousproblems of the Stefan type, which describe the processes of freezing andthawing during changes inthe surface level according to the given law. The greatestcomplexity in this case callsfor research into the temperature dynamicsof the constituent systems when thereis interaction of therock matrixwith the layer forming on its surface. An importantfeature of the aboveclass of "contact"problems ofthe Stefan type is the fact that the number of frontsof freezing and thawing inthe given problem was hitherto unknown. The solution to a widerange of problems ofthis type in the self modellingformulation notonlyallowed research intothose general quantitativepatterns of development of thefreezing and thawingprocesses in the systemsunder investigation, but also into questions concerning control of theseprocesses during various types of excavations(preparation of ground in open pit minesand placerareas, rubble mounds duringconstruction of embankments and earth dams, etc.),optimization of snow accumulation,etc. Solution of Stefantype problems in accordancewith the given lawI when there is mobility of the surface, alsoallows the possibility ofindirectly calculatingthe temperature field of thenear surface layers, of the lithosphere causedby sharp changes inclimatic conditions, transgressions and regressions due tosedimentation and denudation. Thus, the use of the methods examinedabove for solving one dimensionalStefan problems allows quantitative researchto be carried out on a number of importantgeneral patterns of permafrostdevelopment indifferent types of earthmaterials, depending on a wholecomplex ofgeological and topographicalconditions. The solution of the givenproblem is also of greatimportance for the creation and evaluation of "express"calculation methods widelyused in permafroststudies. Finally, solution of the onedimensional problems of theStefan type plays a very importantrole inperfecting methods of geocryologicalforecasting and environmentalprotection and, particular,in in the workingout of scientifically based implementation of compl ex permafrost , permafrost-engineering-geological and hydrogeologicalsurveys Inthe Soviet Union,where permafrost-hydrogeological forecasting is verywidely developed, theabove research methods forpermafrost processes based on theStefan problemhave been successfully employed for many years inthe solving of I - 75 -
importantnational economic problems arisingfrom industrial development of thevast territories of theNorth andNortheast U.S.S.R. All ofthis is convincingconfirmation of thecorrectness and expediency ofthe broad geophysicalapproach to researchinto the permafrost processes and phenomena examinedabove.
A combination of thetraditional determined systemsbased on the solutionof the Stefan problem (examined above) and statistical systems has wideperspectives for solving the problems of geocryologicalforecasting in vastregions. Use of thelatter (in particular with input of data by the Monte Carlo method, A.S. Tytkevich)permit the determination of the limits of fluctuationsin the temperature regime of materialsin the territory under examination,with regard to the influence of variouslocal factors (facies; consistencyof materials both by depth and areally; changeability of snow and vegetation cover areally and temperorally;fluctuations from year to year in cl imatic conditions, etc.).
As well as theintense implementation of the solutions that are being examined (solutionsto the various one dimensionalStefan problems), when studyingindividual problems permafrostof studies, solutions to multi-dimensionalStefan problems on digital computersare also employed. In this case, it is usual for theso-called integral-interpolation (equilibrium) methodsassociated with finite elements to be used. Apartfrom the extreme awkwardness of such solutions, their use to date in permafrost forecasting has been restricted bythe absence of a demonstration of theexistence of a classicsolution to even thesimplest multi-dimensional Stefan problem. Consequently,use of the above mentionedalgorithms demands extreme care.
Futuredevelopment of quantitativequestions in permafrost studies is primarilyassociated with the complex study ofthe mechanics of various processesof heat and mass exchange occurringin the earth materials. Among theseshould be noted such important problems as the interaction of permafrost withthe supra- and subpermafrostwater, the thawing of materialswith regard to infiltration and settlement,migration in permafrost,etc.
Mathematicalcomputer simulation of the phenomena under investigationplays an enormous rolein the solving of givenproblems. The - 76 - most important problem, along with the demonstration of the existence of a classic solution, is the working out mathematicallyof fundamental, efficient algorithms for the solutionof multi-dimensional problems of the Stefan type. Future perfection of analog computers of a type such as the hydraulic integrator system of V.S. Luk'yanov, which played such a large rolein the development of the mathematical model of permafrost processes and phenomena, is extremely important.
All of the above characterize to a sufficient degree the current state of the problem of the geophysical foundations of permafrost studies that explain the role of heat and mass exchangein the formation and developmentof seasonally and perennially frozen materials, their connection with the net radiation at the surface, with internal heat sources and with peculiaritiesof the formation of the geological environment and the physical geography. Research into these questions will in the final analysis, allow an approach to the creation of theoretical bases for permafrost studies in the broad sense of the word.
Obviously the problem must be solved in stages. Thus, at the present time, work must be done on the following main problems:
1. The establishing of a quantitative link between the net radiation at the Earth's surface and patternsof formation of seasonally and perennially frozen materials;
2. clarification of quantitative estimates of the influence of geological and geographical environmental factors on the developmentof the permafrost region;
3. Quantitative research into heat and mass exchangein earth materia S during freezing and thawing;
4. determination of the dynamicsof the temperature field of seasonally and perennially frozen materials due to the historica development of the region being researched; - 77 -
5. determination of thegeophysical (heat and mass exchange) conditions of formation and development of cryogenic structures ;
6. the working out of thegeophysical bases of theconnection between the development of the permafrost region and paleogeographicalconditions;
7. development of a theory on evolution of the permafrost region as a global phenomenon due to latitudinal zonal ity, altitude and specialstructural features of ourplanet and the geological history of theearth;
8. the working out of the principles of geocryological fore- casting, and applications of control of thepermafrost processes causedby changes in the natural historical conditions and by anthropogenicaction.
REFERENCES
BAULIN, V.V., BELOPUKHOVA, E.B., DUBIKOV, G.I. and SHMELEV,L.M. Geokriologicheskieusloviya Zapadno-Sibirskoi nitmennosti. (Geocryologicalconditions of the West Siberian Plain). M., Nauka, 1967.
BACHELIS, R.D. and MELAMED, V.G. Reshenie kvasilineinoi zadachi tipa Stefana metodom pryamykh. (Sol ving the quasi 1inear Stefan typeproblem by thestraight line method).VINITI, NO. 3941-72 Dep.,pp. 1-17, 1972.
BUDAK, B.M., VASIL'EV, F.P. and USPENSKII, A.B. Raznostnyemetody resheniyanekotorykh kraevykh tadach tipa Stefana. (Differential methods of solving some marginalStefan type problems). Inthe book: Chislennye metody v gazovoi dinamike.(Numerical methods in gas dynamics) No. 4.3 Izd-vo MGU. pp. 139-183, 1965.
BUDAK, B.M., VASIL'EV, F.P. and EGOROVA, A.T. Raznostnyi metod s lovlei fronta v uzelsetki dlya zadachi Stefana c nemonotonno dvizhuschchimsyafrontom. (Differential method with the capture of the front into the node of the network for a Stefan problem with a non-monotanical ly mobile front). In. the book: Vychislitel'nye. (Computingmethods and programing). No VI. Izd-vo MGU, pp. 231 -141 , 1967. - 78 -
VASIL'EV, F.P. and USPENSKII, A.B. Raznostnyi metod resheniya dvykhfaznoi zadachi Stefana. (Differential method for solving the two- phase Stefan problem). Vychizlitel 'naya rnatematika 4 matematich. fizika., Vol. 3, No. 5, pp. 874-886, 1963. GOL'DSHTEIN, M.N. Deformatsiya zemlyanogo polotna i osnovanii sooruzhenii Dri sromerzanii i ottaivanii. (Deformation of road beds.. . and . foundations during freezing and'thawing). . Trudy Vsesoyuz. 1n-a "zhel .-dor. transp.,No, 16, Transzheldorizdat, p. 258, 1948, GRUZDOV, A.V., TROFIMOV, V.T. and FIL'KIN, N.A. Osnovnye zakonomernosti rasprostraneniya stroeniya tolshch i temperatur mnogoletnemerzlykh tolshch Tazovskogo poluostrova. (Basic distribution patterns of structure and temperatures of permafrost in the Taz Peninsula). In the book: Prirodnye usloviya Zapadnoi Sibiri. (Environmental conditions of Western Si beria)., No. 2, Izd-vo MGU, pp. 115-133, 1972. ZEMTSOV, A.A. Mnogoletnemerzlye porody v poime r. Enisei. (Permafrost in the floodplain of the Yenisei River). Trud In-ta merzlotovedeniya
Iim. Obrycheva, Vol. 19, Izd-vo AN SSSR,epfiT 92-74, 1962.
KRYLOV, M.M. K teplotekhnicheskomu analiru promerzaniya grunta. (Thermo- technical analysis of the freezing of earth materials). Vestn. inzhenerov tekhni kov , No. 1 , pp. 466-467, 1934. KRYLOV, M.M. Raschety promerraniya i ottaivaniya. (Calculations of freezing and thawing). Vestn. melioratsii 1 gidrotekhniki , No. 1 , pp. 58-63, 19407 KUDRYAVTSEV , V .A. Novaya metodi ka opredel eniya gl ubiny setonnogo promer- taniya gruntov. (New methods for determining depths of seasonal freezing of earth materials). Osnovaniya, fundamenty i mekhani ka gruntov. No. 6, pp. 35-36, 1971 . KUDRYAVTSEV , V .A. , GARAGULYA, L, S., KONDRAT ' EVA, K .A. and MELAMED, V .G. Osnovy merzlotnogo prognoza pri inzhenerno-geologicheski kh issledovaniyakh. (Principles of permafrost forecasting in geological engineering research). Ird-vo MGU, p. 431, 1974. LUK'YANOV, V.S. and GOLOVKO, M.D. Raschet glubiny promerzaniya gruntov. (Calculation of depth of freezing of earth materials). M., Transzheldorizdat, p. 164, 1957. MARTYNOV, G.A. Teplo- i vlagoperedacha v promerzayushchikh i protai- vayushchikh gruntakh. (Heat and moisture transfer in freezing and thawing earth materials). In the book: Osnovy geokriologii (merzlotovedeniya), (Principles of Geocryology/Permafrost studies) Pt. 1, Ch. 6, M., Izd-vO AN SSSR, pp. 153-188, 1959. - 79 -
MELAMED, V.G. Svedeniezadachi Stefana k sistemeobyknovennykh different- sial 'nykhuravneii. (Reducing Stefan problems to a system of ordinarydifferential equations). Izv. ANSSSR. Ser.geofiz. NO. 7, pp. 848-869,1958. MELAMED, V.G. 0 chislennomintegrirovanii classicheskoi zadadchi Stefana prinalichii fatovykh perekhodov v spektretemperatur. (Numericalintegration of theclassic Stefan problem in the presence of phase transitions in the temperature spectrum) Izv. AN SSSR, Ser. geofit. No. 2, pp. 340-344, 1963.
MELAMED, V.G. Matematicheskayaformulirovka tadachi promerzniya vlazhnykh gruntov s uchetom migratsi i vlagi i usloviyaobrazovaniya ledyanykh prosloev.(Mathematical formulation of theproblem offreezing of earth materials with regard to migration of moisture and the condition of formation of icelayers). In the book: Merzlotnye issledovaniya (Permafrost Research). no. 6, Izd-vo MGU , pp. 28-38, 1966.
MELAMED, V.G. Avtomodel'noereshenie zadachi teplo- i vlagoobmena v promer- zayushchikhtonkodispersnykh porodakh pri zadannom zakone izmeneniya urovnyapoverkhnosti. (Self modellingsolution to the problem of heat and moisture exchange in freezing, very fine-grained earth materialsfor a givenlaw of change in surfacelevel). In the book: Merzlotnoeissledovanie (Permafrost Research). No. 15, Izd-vo MGU, pp. 27-37, 1967. PORKHAEV, G.B. Teplovoevzaimodeistvie zdanii i sooruzhenii s vechnomerzlymi gruntami (Thermal interactionof buildings andstructures withperennially frozen ground). M. , Nauka, p. 206, 1970.
SAMARSKII , A.A. and MOISEEMKO, V.D. Ekonomicheskaya schema skvoznogo scheta dlya mnogomernoi zadachiStefana. (Effective schema for complete calculationfor the multiple Stefan problem). Vych slitel 'naya matematika i matematich. fizika. Val. 5, No. 5, pp.816-827, 1965. FEL'DMAN, G.M. Metody raschetatemperaturnogo rezhima merzlykh Sruntov. (Methods for calculating the temperature regime of frozen earth materials). M., Nauka, p. 254, 1973. CHARNYI, I.A. 0 prodvizheniigranitsy izmeneniya agregatnogo sostoyaniya priokhlazhdenii ili nagrevaniitel. (Advance of the boundary of the state of aggregation during cooling or warming of a body). Izv.tekh. nauk., No. 2, pp.187-202, 1948. CHUDNOVSKII, A.F. Teploobmen v dispersnykhsredakh. (Heat exchange in veryfine-grained materials). Gostekhizdat, M., p. 444, 1954.
CHUDNOVSKII, A.F. Teplofizika poch. (Thermophysics of soils). M., Nauka, p. 351, 1976. SHARBATYAN, A.A. Ekstremal 'nye otsenki v geotermii i geokriologii. (Extreme estimates in geothermy and geocryology). M. 9 Nau ka p. 122, 1974.
TAKAGI, S. A an ly is f icelens formation. (Water Resour. Res. VOP. t, io. E.
- 81 -
AN NMR STUDY OF THE PHASE TRANSITION OF WATER IN MODELS AND IN FROZEN CLAYS
V.I. Kvlividze, V.F. Kiselev, A.V. Krasnushkin, A.B. Kurzaev and L.A. Ushakova f~loscow StateUniversity, Department of Physics, U.S.S.R.
Studies of theprocess occurring at thewater-solid interface are ofgreat interest to geocryology and many otherareas of scienceand technology. Numerous studies on theproperties of water in dispersed systenls unequivocallyevidence stable co-existence of ice and mobilewater phase within a largeinterval of negative temperatures. In the literature there are, however, contradictoryviews regarding the nature and the mechanisms of structural changes inthe surface water phase, as well as theproperties of that phase.
The useof nuclear magnetic resonance (NMR) techniques opened up new possibilities for thestudies of phase transitions. The effective use of NMR in studies of thesolid-liquid phase transitionis due to thewidth of the NMR spectrumdecreasing by severalorders in the course of the transition (Abragam, 1963). The lattercircumstance permits us to use the NMR spectra fordetermining the phase composition ofthe sample. In this paper we examine theresults obtained from a NMR studyofthe ice-water phase transitionin models (bothinorganic and biological) and clayswith the purpose of elucidatingthe nature of thedrop in the melting point of ice in dispersedsystems, infrozen earth materials in particular.
Objectives of the studx
In order to solve theproblem specified, we studied the state of water in porous, as well a s non-porousadsorbents at thein terface w it h - ProceedingsThird International Conference on Permafrost, Vol. 1, pp. 114 - 118, 1978. - 82 - hydrophilic and hydrophobic sol ids, as we1 1 as at the ice-vapour interface. The following systems were selectedas objects of study: dispersedice; waterdispersions of polyfluoroethylene,silica powder, montmorillonite and kaolinite;adsorption films on thesurface of silica powder, silica gel and kaolinite, as well as proteinsolutions.
The properties of the samples were as follows. The specific surface of dispersed ice was S - 30 m2 /g. The technique used for preparing ice samples, was described in detail in an earlierpublication (Kvlividze et a1 , 1974). Dispersion of polyfluoroethylene was prepared from spherical particles with an averagediameter of 35 mv, Themethod used forpreparing the dispersion of polyfluoroethylene was described by V.A, Pchelin(1970), specifications of the samples - by A.B. Kurzaev et al,, (1973). The dispersionof silica powder consisted of particlesaveraging 20 mmp in diameter, which corresponds to S ~140m2/g of silica powder; the surfaceof 2 theparticles came to 40m per 1 g of water(Kvlividze et a1 1974). In preparing the dispersion of montmorillonite, we used Na - moulds of askanite gel (S N 600 m2/g). The surface of theparticles was a30 m2 per 1 g of water. Kaolinitedispersions were prepared from a sample of kaoliniteclay (S -25 m 2 /g) in calcium moulds. In order to reduce the contentof OH-groups, the mineral was partlydeuterated. We studied samples with the watercontents of 3.3 and 30 m mole per 1 g of dryclay, V.I. Kvlividze et al., (1972) provided a detaileddescription of theCa-kaolinite samples. The SKS*-3 silica gel used is a uniformly coarsely porous adsorbent 2 (S -340 m /g; averagediameter of the pores 7 my; moisturecontent of the sample 44 m mole H20/g silica gel (Kvlividze and Kiselev, 1967)).
Apart from that we investigated 2.5% proteinsolutions, i .e. a1 bumen from human serum (Kurzaev et a1 1975).
In order to obtain NMR spectra,the samples were placed in glass ampoules and sealed. In the case of the samples containingadsorbed water the ampoul es were fi1 led with he1 ium inorder to improve theheat exchange duringthe freezing of the samples.
* Trans1 iteration. Brand name. (Translator). - 83 -
Techniquesused to obtain NMR spectraand in processingthe results.
The main measurements ofthe NMR spectrawere obtained in a broad-bandautodyne spectrometer. The instrumentrecords the derivative of theadsorption signal; the operating frequency of thespectrometer is 12.5 MHz. The measurementswere taken inthe 80 - 272 K temperature interval. The Av width of thenarrow bands was measured inhigh-resolution spectrometers.
The protonmagnetic resonance spectra of theadsorbent-water systems commonly consisted of severalsignals belonging to the stationary H20 molecules(the broad band) mobile H20 molecules(the narrow band) and protonsfrom the OH groups of theadsorbent, respectively. Inorder to obtainthe spectrum of thewater molecules as such, the band of the OH-groups mustbe deducted from the totalsignal. Failure to takeinto account the contributionof the OH-groups to the NMR signalrecorded may lead to the erroneousconclusion that mobile water molecules exists even theat temperature of liquidnitrogen, as was done by Pearson and Derbyshire in their work(1974). If thespectrum is composed of several bands varying in width(Figure l), the relativeintegrated intensity of each individual component makes it poss ible to calculate the fraction of the nucle i producing it.
Figure 1
Derivative of the NMR adsorptionsignal of theNa-montmorillonite aqueous dispersion at differenttemperatures.
1 - thenarrow component; 2 - the broad component. - 84 -
In a broad-bandspectrometer we commonly observeremodulation of thenarrow componentand, consequently,distortion of the shape of theline. Remodulationof the lineintroduces, however,no errorinto the determination of itsintegrated intensity, since the proportionality betweenthe integrated intensity of theline and theamplitude of modulationpersists even at greatermagnitudes of modulation, when the shape of theline is distorted. Thiscircumstance is of greatimportance in the case of the complexspectrum examined: relativeintegrated intensities of the components ofthe spectrum areindependent of the amp1 itude of modulation. The fractionof mobile moleculescan thus be determinedfrom the spectrum recorded inthe course of remodulation of thenarrow line. The relativeintegrated intensity of the narrow 1 ine was calculatedwith the he1 p of a computerby way of digital integration.
In takingtemperature measurements of NMR spectra it is imperative to keep in mindthe possibility of temperature hysteresis, i.e., theresults Of the measurements may be affectedby the preceding temperature regime of the sample. In order to avoid ambiguous results,the temperature evolution Of thespectra was alwaysstudied under standard conditions, where the sample was heatedfrom 77 K tothe temperature specified for the experiment.
Results of theexperiment
At T = 77 K the NMR signal of waterprotons consists in all the entities underinvestigation only of thebroad component producedby immobile frozenwater molecules. The featurescharacteristic of temperature changes in thespectra of all the systems studiedare the appearance of a narrow component (the mobilephase of water)at temperatures below 273 K and the simultaneouspresence of thenarrow and broad components of thespectrum within a definitetemperature interval. As an example we present inFigure 1 spectra of the water-Na-montmorillonite system at different temperatures. As may beseen from that diagram,the intensity of thenarrow component increaseswith the rise in temperature,while that of thebroad component decreases - 85 -
Figure 2 280 240 220 200 T,K 1 I 1 1 Nn, '1 %
20
10
5
2
1
0.5
1) - thecontent of themobile phase of water as a function of inversiontemperature for dispersions of polyfluoroethylene; 2) - silica powder; 3) - Na-montmorillonite; 4) - Ca-kaolinite; 5) - 2.5% proteinsolution - serum albumen; 6) - dispersedice; - andsamples with a film of wateradsorbed on silica powder; - and on Ca-kaol inite.
Figure 2 shows the relativecontent of mobilewater molecules Nn as a function of inversiontemperatures for different entities. The initial pointsinthe low temperature region correspond tothe narrow component recordedwith confidence. If theonly boundaries present in a heterogeneous systemare ice-vapour or ice-hydrophobicmaterial, the emergence of mobile watermolecules is noted at temperatures above 250 K, i.e.¶ 15 - 20 K below themelting point of ice undernormal conditions. If theice is in contact withhydrophilic materials, including protein macromolecules, then the
mobi 1 ity . of moleculesappears at temperatures of 170 - 190 K, 1' .e., 50 - 100 K below the melting point of ice. - 86 -
Inthe T < 260 K region (see Figure 2) thelaw governing changes in Nn isthe same forall the hydrophilic materials. In the 180 - 260 K temperatureregion the dependence of the number of mobilemolecules is subject to the equation
where E is theenergy causing the change of molecules tothe mobile state, and R isthe gas constant.For this temperature interval El r~ 6.7 - 7.5 Mjoules/kmole,i.e., differsbut little from theheat of fusion of ice (6.1 Mjoules/kmole). The sharpincrease in Nn at T > 260 K corresponds tothe beginning of melting of the main bulk of ice.
It is interestingtojuxtapose the results obtained for the adsorbedwater and waterdispersion at the same adsorbent. We can make this comparisonfor silica powderand kaolinite. As may beseen from Figure 2, thegradient of the straight lines log Nn (l/T) is the same forwater dispersions and adsorptionfilms. This circumstance suggests that the mechanism governingthe appearance of mobilewater molecules inadsorption films, where thewater-vapour interface exists alongside the solid-water interface, is the same as thatin water dispersion systems, where there is no such interface. It shouldbe noted thatthe absolute quantity of mobile 2 waterper 1 m ofadsorbent's surface coincides at thegiven temperature in theadsorption film and frozenwater dispersion within the margin of errors of theexperiment.
Inaddition to the temperature dependence ofthe concentration of mobilemolecules, we examined variationsin the width of the line of the narrow component. The data on the dispersion of silica powder and kaolinite are shown inFigure 3. In the T < 260 K regionthe width of thenarrow NMR line Av for all.the hydrophilic systems issubject to a dependence ofthe followingaspect: - 87 - where E2 isthe energy initiatingmolecular motion. The magnitude of E2 is 18 andMjoules/kmole19 forsilica powder and kaolinitedispersions, respectively, wherease El determinedfrom equation (1 ) does not exceed 7.5 Mjoules/kmole.
There are severalhypotheses regarding the nature of themobile watermolecules reccrded: a) diffusion of moleculesover the surface without theformation of a new phase(Resing, 1967, 1972); b) diffusionof defects insidethe ice crystals; c) formation of theincipient liquid phase(1 iquid "embryos"),i.e., thebeginning of melting of theice. A discussion regardingthe first hypothesis was publishedearlier (Kvlividze, 1971). As may be seen fromthat paper, this hypothesis cannot explain the total conjunctionof experimental facts. Themechanism of the volume diffusion of defectsalso fails to correspond to the fact observed (Kvlividze et a1 . 1972): El (theenergy initiating the formation of defects)in equation (1) should be greaterthan Ep (theenergy initiating the motion) in equation (2), whereas it is obvious from thevalues of E, and Ep presented above that we are dealing with the opposite ratio.
Figure 3
1) - temperature dependences of the width of thenarrow line of thespectrum in aqueous dispersions of si1 ica powder; 2) - and Ca- kaol ini te. The third mechanism, i.e.,melting of thesurface phase of ice, is themost probable one. Thisis supported first of all by theevidence from thestudies into the thermal capacity ofthe adsorbent-water systems for non-porous(Plooster, Gitlin, 1971) and porous(Berezin et al., 1972) adsorbents. These studies have demonstratedthe presence of a heatcapacity anomaly related to the melting of ice in the adsorption space.
Measurements of thewidth of thenarrow conponent‘s 1 ine may be used toobtain assessments of thecorrelation time which characterize the degree of mobility of thewater molecules contribution tothe narrow component of the NMR spectrum.For example, forthedispersion of polyfluoroethylene at T = 270 K thetime of correlation is rc < lom1’c; for dispersedice it is rc$ low1’c at the same temperature(Kvlividze et a1 ., 1974).Let US mentionfor the sake of comparison thatpure water has rch* 1 0-l2 c, and crystal 1 ine ice rc- c,Unfortunately we havebeen unable to obtain reliable assessments of rc for frozen earth materials or for any other systemsbecause theobservable width of the proton resonance line is determinedbyparamagnetic impurities (Krasnushkin, Kvlividze, 1971; Pfeifer, 1972,1976) orother secondary factors rather than by thenlobility of water molecules .
If we neglect to takeinto consideration the broadening of the lineson account of thesefactors, the values of correlation time obtained fromcalculations will be as much asseveral orders of themagnitudes too high. Inreality, however, we canonly obtain the maximum value of the correlation time (which is or the order of 10’’ c)) for complexheterogeneous systems withparamagnetic admixtures.
In comparingthe data fordispersions varying in concentration and for samples with adsorbedwaterp it has been establishedthat the absolute quantity of mobi le molecules atthe given temperature and in the presence of adequate possibilitiesis not a function of thetotal water content in the system. It may therefore be assumed thatthe liquid phase forms atthe phase interfacerather than within the ice. It may thus be seen fromthe informationpresented above that mobi 1e mol ecul es representrudiments (“embryos”) of theliquid phaseand appear atthe ice-hydrophilic surface - 09 - interface at temperatures of 170 - 190 K, or at the ice-vapour or ice-hydrophobicsurface interface at temperatures of 250 - 260 K (Kiselev et a1 ., 1973).
The differentcharacter of the Nn (1/T) curves (see Figure 2) for hydrophobic polyfluoroethylene and dispersedice particles on the one hand, and for hydrophilic systems on the other,evidences the importanceof the activesurface centres in the formation of theincipient mobilewater phase. We assessedthe quantity of mobile watermolecules per activecentre in different samples. In silica powderand Ca-kaolinite there are, for example, 4 and -7 mobile molecules,respectively, per active centre (OH-group) at T = 238 K. We did not takeinto account in thecalculations the most active primary adsorptioncentres, since their number is smaller by atleast an orderthan that of the OH-groups (Kiselev, 1970; Sklyankin,Kireev, 1972).
Similarresults were obtained from thestudies of frozenprotein solutions (Kurzaev etal. , 1975). Curve 5 in Figure 2 suggeststhat the qualitativecharacter of the N, (l/T) change in thissubstance is the same as in inorganicmaterials, Polar aminoacid residuesact as activecentres in proteins(Gaurovits, 1967). It has been establishedthat at 238 K the number of mobile watermolecules per polar aminoacid residue comes to -5, i.e. is closeto the magnitudes obtained forinorganic materials. The mobilewater phase in a biopolymer appears to have no specificcharacteristics different from those of inorganic systems.
The data obtained for Na-montmorillonite stand somewhat apart from this series. If exchange cationsare to be regarded as activecentres on the surface of montmorillonite,then there are 420 mobilewater molecules pe- exchange cationat T = 238 K. In ouropinion the difference is due tothe factthat exchange cationsare not the onlyadsorption centres in montmorillonites (Mooney et al, , 1952; Krasil’nikov,Skoblinskaya, 1972).
We nowWe wish to examine another extreme case, i.e,, the appearance of the mobilephase of water atthe ice-hydrophobic surfaceinterface of polyfluoroethylene. It hasbeen establishedthat the Nn (l/T) dependence for polyfluoroethylenepractically coincides with the corresponding dependence - 90 - forpolydispersed ice. Fletcher (1968) has demonstrated thatthe mobile waterphase arises on theice surface atnegative temperatures. This circumstance was believed to be related to thedisturbed structure of the regionadjacent to thesurface in icecrystallites. The factthat the Nn (1/T)curves of ice and polyfluoroethyleneare close suggests that the properties of thesurface inpure ice are similar to those of the ice-polyfluoroethyleneinterface. A hydrophobicsurface has virtually no effecton the formation of themobile phase of wateror on meltingof the total mass of ice. The roleof a hydrophobicmaterial appears to bemerely to form a surfacesimilar with respect to itsproperties to thefree surface ofice orwater. The so-calledhydrophobic interactions appear beto effected by the forces of thesurface tension of thatwater surface.
Proceeding from themagnitudes of the solid-ice interface andfrom therelative content of mobile water molecules, we canassess approximately thethickness, of thewater film nearthe solid-ice interface (Figure 4). In thesecalculations we assumed thethickness of thewater manolayer to be equal to 0.3 mv and thedensity of water outside the monolayer to be normal. As may be seen fromFigure 4, all the hydrophilic sol ids are characterized by theappearance of a water film at temperature of 170 - 190 K. The thickness of thewater films in the T 260 K region comes to 0.8 - 2 mmv, i"e., is of the Same order as thethickness of the films, where themobility of water moleculesaltered at room temperature(Olejnik, White, 1972; Morariu,Mills, 1972). It may thus be seenfrom the studies on melting of icein dispersed systems thatthe impact of a hydrophilicsurface on theproperties of adjacentwater horizons isrestricted to several molecule layers. None of thesedata corroborate the widespread hypothesis postulating the existence on thesurface of thickfilms of water with anomalous properties(Schufle et a1 . 1976).
The dataobtained from the experiments regarding temperature changes inthe NMR spectraand calorimetric measurements, arepresented above.These data suggestthat a phase transition of thetype of fusion actuallytakes place in the surface phase of waterand is not merelyan "apparent"effect inherent in the NMR method,as was assumed earlier (Resing, 1967, 1972; Pfeifer, 1972, 1976). Icebegins to melt at the phase interface. - 97 -
Figure 4
hFM 04 a a2 5 03 A4 a5 4 A6 x7 3
2
1
I
11 1 I 0 1 I 270 T,K 190 230
1) - thethickness of the mobile water layer as a function of temperature fordispersed ice; 2) - and frozen aqueous dispersions of: polyfluoroethylene; 3) - silica powder; 4) - Na-montmorillonite; 5) - Ca-kaolinite; 6) - silica powder samples; 7) - and silicagel with adsorbedwater.
In crystals with a largespecific surface the phase transition has a diffuse character,since an observablequantity of the liquid phase has been recorded within a certaintemperature interval below 273 K. Thisis due to the heterogeneousnature of the matter at the phase interface.
The problem of “diffuse” phase transitionsis examined indetail in B,N. Rolov’s monograph (1974), where it is shown thatthe major cause of thespread isthe non-homogeneous physicalstate theof matter. The heterogeneityshould be particularlyconspicuous in a system composed of smallentities varying in size and Shape, i.e.,in a dispersed medium. As may be deducedfrom theroeticalanalyses of phase transitions, in a system of finite dimensionspoint phase transitions do not occur at all ; consequently, - 92 -
thesmaller the sample, the moremarkedly diffuse ("washed out")the corresponding phase transition(Fisher, 1968; Hill 1963). Theoretical analyses of the resultsof our experiments are complicatedby the absence of a general theory concerning the fusion of solids (Ubbelode, 1969).
In a number of studies (see, for example, the survey in Kiselev's work, 1970) the drop in the temperature of the phase transition of water AT in porous bodies is attributed to the decrease in the elasticity of water vapours above the meniscus in capillaries with the radius r. V.A. Bakaev et a1 . (1 959) have demonstrated that the theory of capillary condensation cannot provide an unambiguous explanation of the experimental dependencies AT(r). As may be seen from Figure 5 borrowed from that work, the data obtainedfor non-porousdispersed bodies(silica powders) show a good agreement with the experimental dependency l/r (AT) of porous silica gels,
Figure 5
-1 L (HMj' -G ' I
1) - magnitudes of inverse radii of interstices (pores) as a function of the drop in the melting point of water according to the data obtained from dilatometric(Puri et a1 ., 1957); 2) - and calorimetric measurements (Bakaev et al. , 1959). 1, 2, 3 and 4 - silica gels, 3 - non-porous silica powder.
It has been demonstrated (Bakaev et a1 ., 1959, Kvlividze, Kiselev, 1967; Kiselev 1970) that a drop in the me1 ting point of an adsorbed phase can be interpreted more loosely, regardless of the shape of the meniscus, as - 93 - a generalproperty of thematter in dispersed state. The datafrom Figure 4 supportthis hypothesis. The thicknessof the films h on a porousadsorbent (i.e., silicagel) coincides with h of the non-porous silica powder. According to thetheories of Taman-Folman, themelting point of a dispersed surface phasedepends (allthe other conditions being equal ) on the characteristic size h of that phase. A number of size-dependent surface effectsare examined in Kiselev's work (1970).
The factthat the melting point AT of smallparticles is lower thanthat of a massive sample may be due tothe interphase energy being a function of thecurvature of r. For example, to assessthe law governing the change in AT/T OD N Ar" for sphericalmetallic particles (Gladkikh, Khodkevich,1971)". The constant A depends ontheparameters of the dispersed phase, which are usually unknown. The course of the dependence AT/Tm agrees qualitativelywith the data of Figure 5, but in termsof a phenomenologicalanalysis the lowering of themelting point of ice on the surface of hydrophilicsolids cannot be calculatedquantitatively without knowing thesurface tension coefficients theinterphaseat boundary (Chistotinov, 1973)
Infinite crystals andeven more so in dispersedbodies the process of meltingbegins at the interface between theparticles and the vapouror, inthe event of adsorption films and dispersion, of thesolid phase. Theoreticalcalculations indicate that the mean square of the amplitude of oscillationsin surface atoms i.e.,
In Debye's approximationthe initial melting of a crystal may be characterized by Lindeman' s temperature (Maradudin , 1968)
* Thissentence appears to be incomplete.(Translator). - 94 -
Tmel ti ng (ad) *mkeDv/3 hm2, where a -0.1 - 0.2; m is the mass of anatom, and d is theaverage distance between the atoms. Since ODs 5: eDV, Tmelting will be lower on thesurface. These effects can be expected to be particularly conspicuous in dispersed particl'es, where thesurface phenomena sharplyincrease in importance.
REFERENCES
1, ABRAGAM A. Yadernyimagnetism (Nuclear magnetism). Moscow,EL, 552 pages,1963.
2. BAKAEV V.A., KISELEVV.F. and KRASIL'NIKOV K.G. Poniahenietemperatury plavleniya vodyv kapillyarakhporistogo tele (Drop in the melting point of water in capillaries of a porousbody). - "Dokl . AN SSSR", VOI.125, pp. 831-843, 1959.
3. BEREZIN G.1.) KOZLOV A.A. and KUZNETSOVA L.V. Kalorimetricheskoeissle- fazovogoperekhoda kapi 1 lyarnogokondensata (Calorimetric study of phase transition of capillary condensate). - V. kn.: Poverkhnostnye Sily vtonkikh plenkakh i dispersnykhsistemakh. Moscow, "Nauka", pp. 202-209, 1972.
4. GAUROVITS R. Khimiya i funktsiyabelkov (Chemistry and function of proteins). Moscow, "Mir" , 530 pages , 1967, 5. GLADKIKH N .T. and KHODKEVICH V. I. Opredelenie poverkhnostnoi energi i tverdykh tel PO temperatureplavleniya dispersnykh chastits (Determination of the surface energy of solids from the melting point of dispersed particles). - "Ukr. fiz. zhurn.", Vol. 16, pp. 1429-1436,1971.
6. KVLIVIDZE V.I. and KISELEV V.F. Issledovaniefazovykh perekhodov vadsorbiro- vannoivode metodom YaMr (NMR studyof phase transitionsin adsorbed water). - Yhurnalstrukturnoi khimiilt, Vol. 8, pp. 221-226, 1967. 7. KVLIVIDZE V.I., KRASNUSHKIH A.V. and MOROZOV L.L. Issledovaniesistemy kaol init-voda metodom protonnogo magni tnogo retonansa (Study of the kaolinite-water system with the use of protonmagnetic resonance techniques). - V khn. : Svyazannayavoda vdispersnykh sistemakh, Issue 2, Izd-vo MGU (Moscow UniversityPublishing House) pp.97- 105, 1972.
8. KVLIVIDZE V.I., ANANYAN A.A., KRASNUSHKIN A.V. and KURZAEV A.B. Vliyanie mezfaznoigranitsy na plavleniellda v geterogennykhsistemakh. (The effect of the phase interface on melting of ice in heterogeneous systems). - V kh.: Svyazannayavoda v dispersnykhsistemakh, Issue 3, Itd-vo MGU (Moscow UniversityPublishing House), pp. 120-126,1974. 95 -
9. KISELEVV.F. Povekhnostnyeyavleniya v poluprovodnikakh i dielektrikakh (Surface phenomena in semiconductors and dielectrics). Moscow "Nauka" , 400pages, 1970.
10. KISELEV V.F. KVLIVIDZE V. I. and KURZAEV A.B. Poverkhnostnyeyavleniya na granitseled-gaz i led-tverdoetelo (Surface phenomena atthe ice-gas and ice-sol id boundaries). - V kn. : 11 Mezhdunar. konf. PO merzl oto- vedeniyu (Second InternationalConference on Permafrost) , Issue 4, Yakuts, pp. 199-202,1973.
11. KRASIL'NIKOV K.G. and SKOBLINSKAYA N.N. Sorbtsiya vody i nabukhaniemont- mori 1loni ta (Sorption of water and swell ing of montmorillonite) . - V kn. : Svyatannaya voda v dispersnykhsistemakh, Issue 2, Izd-vo MGU (Moscow UniversityPublishing House), pp. 66-85, 1972.
12. KURZAEV A.B.? KVLIVIDZE V.I. and PCHELIN V,A. Izuchenie metodom YaMR zamoro- zhennolpredel 'no-gidrofobnoi suspensii ftoroplast-voda (NMR study of a frozenextremely hydrophobic polyfluoroethylene-water suspension). - "DOkl AN SSSR" , Vola 108, pp. 391 -393 1973. 13. KURZAEV A.B., KVLIVIDZE V.I. and KISELEVV.F. Ob osobennostyakhfazovogo perekhoda vody v dispersnykhsistemakh (Distinctive aspects of the phase transition of water in dispersedsystems). - "Biofizika", VOI. 20, pp. 533-534, 1975. 14. PCHELIN V.A. 0 modelirovaniiidrofobnykh vzaimodeistvii (Modelling of hydrophobicinteractions 3 . - "Dokl. AN SSSR", Vol. 194, pp. 521-624,1970. 15. ROLOV B.N. Fizicheskiesvoistva rarmytykh fazovykh perekhodov (Physical properties of diffuse phase transitions). Riga,Izd-vo Latb. un-ta (LatvianUniversity Publishing House), 312 pages, 1974.
16. SKLYANKIN A.A. and KIREEV K.V. 0 mekhanizme vzaimodeistviya vody s pover- khnost'yukaolinita (Mechanism of interaction ofwater with the surface of kaolinite) . - V kn. : Svyazannayavoda v dispersnykh sistemakh,Issue 2, Izd-vo MGU (Moscow UniversityPublishing House), pp. 86-96, 1972.
17 CHISTOTINOV L.V. Migratsiyavlagi v promertayushchi khnevodonasy-schchennykh gruntakh(Migration of moisturein freezing soil materials unsaturated withwater). MOSCOW, "Nauka",144 pages, 1973.
18. UBBELODE U. Plavlenie i kristallicheskayastructura (Fusion and crystalline structure). Moscow, "Mir'', 420 pages,1969. 19. FISHER M. Prirodakriticheskogo sostoyaniya (Nature of the critical state). MOSCOW, "Mir", 222 pages,1968. 20. FLETCHER N.H. Surfacestructure of waterand ice. 11. A revised model. - "Phil. Mag.", Vol, 18, pp. 1287-1300, 1968. 21. HILL T.L. Thermodynamics of small systems, P.I. N.Y. - Amsterdam, XII, 171 pages, 1963. - 96 -
22. KVLIVIDZE V.I. Specificfeatures of phase transition of finely-divided sol ids from NMR data. - In:Magnetic resonance and related phenomena. Proc. XVI Congr. AMPERE, Bucharest, pp. 390-392,1971. 23. KVLIVIDZE V.I. et a1 ., The mobilewater phase on ice surfaces. - "Surface Science" , Vol . 44, pp. 60-68, 1974. 24. KFWSNUSHKIN A.V. and KVLIVIDZE V.I. NMR estimation of molecularmobility in systems with paramagnetic impurities. - In: Magnetic resonance and related phenomena. Proc. XVI Congr. AMPERE, Bucharest, pp. 694-697, 1971. 25. MOONEY R. W. et a1 . Adsorption ofwater vapour by montmorillonite.1. Heat of desorption and application of BET theory. 11. Effect of exchangeable ions and lattice swelling as measured by X-ray diffraction. - "J. Amer. Chem. SOC.'~,Vol. 74, pp. 1367-1371, 1371-1374,1952. 26 MORARIU V.V. and MILLS R. Self-diffusion of wateradsorpbed on silica. - "Z Phys. Chem." , Vol . 79, pp. 1-9, 1972. 27. OLEJNIK S. and WHITE J.W. Thin layers of water in vermiculites and mont- morillonites-modification of water diffusion. - "Nature. Phys. Sci .I' , Vol. 236, pp. 15-16,1972. 28. PEARSON P.T. and DERBYSHIRE W. NMR studies of water adsorbed on a number of silica surfaces. - "J. Colloid InterfaceScience", Vol. 46, pp. 232-248,1974. 29. PFEIFER H. Nuclear magnetic resonance and relaxation of molecules adsorbed on sol ids. - "NMR - Basic Principles and Progress", Vol. 7, pp. 53-153, 1972. 30. PFEIFER H. Surface phenomena investigated by nuclearmagnetic resonance. - "PhysicsReports (Section C of Physicsletters)", Vol. 27, pp. 293-338, 1976.
31 PLOOSTER M.N. and GITLIN S.N. Phase transition in water adsorbed on si1ica surfaces. - "J. Phys. Chem.", Vol. 75, pp. 3322-3326,1971. 32 PUR1 B.R. et al., Freezing points of liquidsadsorbed on porous solids. - "Trans.Farad. Soc.", Vol . 53, pp. 530-534,1957. 33 RESING H.A. Nuclear magnetic resonance relaxation of moleculesadsorbed on surfaces. - "Advan. Mol. Relax.Processes" , Vol . 1 , pp. 109-154 , 1967/68. 34. RESING H.A. NMR relaxation of adsorbed molecules with emphasis on adsorbed water. - "Advan. Mol. Relax. Processes", Vol. 3, pp. 199-226,1972. 35. SCHUFLE J.A. et al. Temperaturedependence of surfaceconductance and a model of vicinal(interfacial) water. - "J. Colloid Interface Science", Vole 54, pp. 184-202,1976. 36. MARADUDIN A. Defekty i kolebatel'nyispektra kristallov (Defects and oscillating spectrum of crystals). M., "Mirt8, 432 pages, 1968. - 97 -
INVESTIGATION OF THESTRUCTURE AND PROPERTIES OF BOUND WATER
B .A. Save1 lev Moscow StateUniversity, U.S.S.R.
The currentstate of knowledgeof such a complex geological body
~ as permafrost,from the position of physics and physicalchemistry, makes it possible to construct a model thatallows many of theproperties, components and processestransforming theearth materials to be satisfactorily explained; it alsoallows the forecasting of changes in thepermafrost under realconditions and theworking out of specific ways of influencingthe permafrost so as to achievethe characteristics desired.
Permafrost is a multicomponent,multiphase system found in subzero temperatures all components of whichare joined together by structural bonds. The peculiarity of permafrostlies in the fact that it containswater in threestates: gaseous, liquid and solid. The relationship between the various phases ofwater is determinedby the complex interaction of water moleculeswith the molecules of the mineral skeleton, and also with the ions, molecules and particles of thesubstances found inthe liquid phase. Therefore, it depends on thesubzero temperature, and thetype and concentration Gf substancesdissolved inthe liquid water;this includes adsorbedwater.
The physico-chemicalprocesses andstructural transformations takingplace in theearth materials, such as cation-exchange,migration, etc. brinyabout changes in theserelationships. The propertiesof permafrost (electrical,mechanical, seismic, ultrasonic, etc.) are, to a certain degree, determinedby the relationship between the phases of thewater, which appears as a liquidanisotropic layer between thesolid components.Depending cnthe above-mentionedconditions, the thickness of theliquid can varyfrom a monolayer of watermolecules retained on the surface of the foreign body by
ProceedingsThird International Conference on Permafrost, Vole 1, pp. 133 - 136,1978. - 98 -
Strongbonding forces, to a layerwhich ischaracteristically no different from freewater, and which does notstrengthen but rather, weakens it.
As stated above, a basicfactor determining the characteristics of permafrost isthe cohesive bond. The nature of these bonds canbe explained by a model reflecting the peculiaritiesof structure in thenear-boundary region of thepermafrost arising from the multiplicity of layers between the mineralpart of the skeleton and theice. The multilayeredsystem includes adsorbedwater which in turnconsists of a firmly bonded layer and a diffusion film, a mobile surface layer of ice and a contact layer of ice; all of these may undergoconsiderable transformation as a resultof changes in the thermodynamic conditions and thephysico-chemical processes.
The explanation of thisinteraction of water with the surface of thesol id body is connectedwith the study of thenature of thecentres of adsorption. Due to the number ofuncontrollable factors imposedon the phenomenon beingstudied, the task of revealing the essence of theprocesses of adsorption of water in suchcomplex heterogenic systems as unconsolidated materials meets with enormous difficulties. Consequently,researchers are attempting,with the help of a simple model system, toexplain the basic patterns of the phenomenon ofthe interaction of the adsorbent.According to V.F. Kiselev and hisco-workers (Ignat'ev et al., 1970) oxidesare the most convenientmodel. They are thebasic component of theoverwhelming majority ofsoils. We arerestricting ourselves to theview of mechanicsof adsorptionof water by oxidestaken by V.F. Kiselev, L,A. Ignat'ev and V.I. Kvalividze, and we will use theevidence of mobility of watermolecules as statedby O.Ya. Samoilov in 1957. The oxideshave a hydratesurface containinghydroxide groups linked by valency to the surface atoms of the watermolecules which, in a different way, interactwith the oxygenatoms. Inturn, the water molecules are linked together by hydrogen bonds. The bond between thehydrated surface of theoxides and the adsorbed water molecules is effected by thecoordination mechanism. An example of this is thejoining of two water molecules to the tetrahedrons Si (OH)4,
According to G.B. Bokie, thesurface of monocrystals of clayey mineralsis, as a rule,formed on the bases of hexagonalsilicon-oxygenous - 99 - tetrahedrons. Water molecules fill theholes of thehexagonal lattice of the minerals. At thelevel of thelower oxygen atoms thereare the depressions of the OH group of theoctahedron layer: these bond thetwo atoms of A1 and Mg. The proton of the OH group is transformedon the outside and can form hydrogen bonds withwater molecules entering the depressions. Since the distance between thecentres ofthe hexagonal comprise 5.5 8, and the distance between themolecules in the ice and thewater is approximately 3 8, theadsorption water molecules can not join together to form hydrogen bonds andform a film of waterwith a normal structure. Moreover, the water moleculesjoined to the OH groupby a hydrogenbond vacillatealong the axis of thedepression and jump from one depressionto another, reminiscent of the relay movements of molecules in a volume of liquid.Since there are no hydrogen bonds inthe compact monolayer due to thedistance between the adsorbedwater molecules, then their weakening influence on the bonding of watermolecules to a foreignsurface is considerably reduced. Consequently, the bond between theforeign surface and thewater molecules increases by severalorders ; thisis reflected in the intensity of therelay transfer of thewater molecules in this layer.
According to A.A. Sklyankinand K.V. Kireev(1972), the adsorption of waterby a kaolinsurface is conditioned by thecoordination bonds of the A1 and Si atoms for thefirst lot of water.Further adsorption can proceed on the OH groups by hydrogen bonds I
It followsthat the destination of water molecules during the formationof the monolayer depends on thecrystal chemistry of thesublayer. The questionarises: whatcan we consider to be themonolayer of water? Apparently,under normal thermodynamic conditions, when thereare no outside influences and when thereis stable composition and structure,the sublayer surface is saturated to a degreesuch thatthe indirect bonding of water mol ecul es cannot take place.
When consideringthe adsorption mechanism of the bond, it should be consideredthat the chemical processes onthe surface may exert an influence on theelectrochemical and ion-exchangeproperties. Innatural substances,cation-exchange takes place and this leads to complications in - 100 - theadsorption processes. By usingthemagnetic resonance method, a considerablereduction in the mobility of thewater molecules was achieved (Kvlividze,1970). By increasingthe quantity of water,the mobility of the moleculesincreases. On zeolite,for example, when there is only a little water,the water molecules are only bound withthe cation of theskeleton. An increase in the number of adsorption mol ecul es 1eads to an increase in the average number ofmolecular bonds. As a result, hydrogenbonds appear between thewater molecules, and theadsorption energy decreases. The mobi 1 ity ofthe adsorption molecules of thewater diminishes in a number of zeolitescontaining K, Na,Ca, Zi, and ice;this agrees with the view held by O.Ya. SamoilOvconcerning negative and positive hydrating ions. Thus, the strucutreof the layer of adsorptionwater near the surface of thesublayer is connectedwith the geometry of the distribution of active centres and will differsignificantly from the structureof ice and thestereometry of free water.
Incontrast to the spatial structure of the crystal lattice, which has saturated bonds sf differenttypes forming its structure coordination in the borderregions, for various reasons, uncompensated chargesappear. One reasonfor the appearance of sparecharges isthe dissociation of molecules fromthe hard surface of theclay particles onto the ions. Some of theions diffuseinto the dispersion medium andthose remaining, bonded withthe hard phase,serve as a sparesource of charge forthe particle surfaces. In some cases , thereiscompletion of thecrystal lattice, as a resultof the adsorptionof ions from solutions; this is due tothe occurrence of closer chemical bonds whichprevents them fromdissolving backagain. Cation exchange resultingfrom the substitution of the hydrogen in OH groupsby the metallic ions intensifies with a strengthening of the pH medium.
Thus, nearthe boundary ofthe unconsolidated materials and the solution,adsorption centres form which are qualitatively characterized by thediffering crystalline structure of theirsurface minerals; bythe differingcomposition and properties of thesolutions cantiguous to them, and bythe differing dynamics of thephysico-chemical processes inthe boundary 1ayers . - 101 -
Accordingto P.E. Zlochevskaya, P.S. Ziangirov, E.M. Sergeevand A.I. Rybachuk, (1970), the presence of a significantconcentration of exchange cations in the firmly bonded partof the adsorption water determines thereduced solvent action; this is due tothe screening of water molecules by the influence of boththe cation fields and thesurface particles. On the basisofcalculation ofthe distribution ofsurface potential and the electricalcapacitance of thedouble electric layer of clays between its diffused and firmly bonded ("boundaryn)parts, the above-mentioned authors came tothe conclusion that firmly-bonded water isnot involved inthe electrokineticprocesses. The opinionalso exists that adsorbed water has an increasedsolvent action comparisonin with unbound water, due to an increaseddipole moment and consequentlyto increased dissociation of water moleculesunder the epitaxial influence of thesublayer.
The remainder of theabsorbed water, the most mobile, iscalled "diffused1'.There isonly a slight change inthe specific unit capacitance of the firmly bound water inthe various fine-grained materials. As forthe capacitance of thediffused layer, its highest values is manifest in askanite gel *: its lowest - inkaolin; this is determined by the number oful trapores it containswhich have a radium of up to 100 1.
When studyingthe mobility of exchange cations (NA', K', Li') in bentonite, R. Low and D. Anderson (Low, Anderson,1958) determined the connectionbetween the structure of bound water and the type of cation.
Inunconsolidated materials, the ice crystals canbe formed from adsorbedwater, unbound water, or fromsolutions of watervapour, contained withinthe frozen body. Recrystallization may also takeplace. This is causedby the internal thermodynamics,thethermochemical and migration processes. The conditionnecessary for formation and growth of crystals from a 1 iquidenvironment isthe supercooling of theliquid environment, or a change theinconcentration theofdissolved substances it contains. Supercooling of theliquid environment of thesupersaturation of the vaporous
* Askanitegel - acidactivated clay, a montmorillonite-likeclay occurring as a decompositionproduct of volcanic ash. (TechnicalTranslator). - 102 - phase bringsabout a change of temperature,pressure, volume, concentration, etc. The formationand growth of crystals in a liquidis dependent upon the speed of accumulation of moleculesaround the centre of crystall ization, and theirordering in the ice lattice. The speed ofaccumulation is determined by therelay movement of thewater molecules in the liquid; and the speed of theirordering in the latticepoints is dependentboth on the energy of the watermolecules themselves andon thestrong field around the mineral sublayer, i .e. theepitaxial influence. The questionarises: where are the mostfavourable conditions for the occurrence of a centre of crystallization infree water, in diffused or firmly bonded layersin subzerotemperatures? Observation shows that,during changes of phasecomposition inpernafrost when the temperaturefalls, the adsorption layer of waterremains, even when thetemperatures are verylow. It has notyet been establishedat what temperatureadsorbed water transfers completely into ice The firmness of molecular bond inthe adsorption layer is many timesgreater than the bond between themolecules inthe ice lattice. On theother hand, theprobability ofoccurrence of centresof crystal 1ization in free water, a homogeneous environment, is considerablyless than condit in ionsheterogeneousof formation. It can therefore be assumed thatthe most probableoccurrence of centres of crystallizationis in the diffused layer , in whichthere is diminishedrelay movement, and that there is epitaxial ordering of molecules.
When centres of crystal1 ization haveformed, they spread laterally inthe free water and thusform a contactlayer of ice,the structure of which is determined by theepitaxial action of theadsorption layer. This is supported by Savel'ev's results (I.B. Savel'ev, 1971) from simulation of the freezing-overof water on severalpermafrost samples in a cold chamber, and bysubsequent study of the structures of iceformations in the contact layer and in the more distanthorizons of the ice coating. It was establishedthat there are contact layers with a specific structure that differs from the rest of theice which is further from the mineral surface. The thickness of the contactlayer depends on theinflow of moisture to theice which is forming atthe boundary of theliquid adsorption layer and whichvacillates within the 1 imits of fractions of a mill imetre to 5 mm. Due to orthotropicgrowth, thecrystals are considerably larger at 3 cm from thesublayer surface than theyare in the contact layer. The influenceof the surface of the base,and - 103 -
consequently, of theadsorption layer of water, isclearly visible in the dimensions and fomsof the crystals, and isscarcely discernable in the character of thedominant orienting optical axes. Under identical thermodynamicconditions of formation,thedimensions of thecrystals diminishprogressively as theinfluence of the base increases: glass; quartz layer,frozen sand, frozenkaolin; frozen askanite gel. When thetemperature of thefreezing over was -5' thesize of an average icecrystals on frozen sand was 7 timesgreater than that on frozenaskanite gel.
Crystalsire decreases with a 1oweri ng of thefreezing-over temperature, and theinfluence of thecharacter of thesublayer levels off. Apparently, in temperatureswhich are well below zero, when theintermediate, 1 iquidlayer betweenthe surface ofthe frozen earth materials and theice will be thick enough, thebonding forces between the water molecules that are furthest from themineral sublayer are reduced considerably and will approach thestrength of those between themolecules offree water. Underthese conditions,the influence of the adsorption layer on the formation of ice is notstrong enough toinfluence the structure of the ice that is forming, and contactice may or may notoccur. In this case, theice covering will be homogeneous in structure throughout its mass.
As a rule, when thereis little moisture and a lowtemperature, individualcrystals form (massivestructure); contact ice does notoccur.
When studyingthe distribution ofcations infreshwater ice 2+ 2+ coatings, I.B. Savellev (1973) discoveredthat the content of Ca , Mg Na', and K" increaseswith distance from contact with the adsorption layer ofwater. Thus, theinfluence of the adsorptionlayer is feltnot only on thestructure of thecontact layer, but also on the redistribution of their c hemi cal incl u sions ,
Studyof the NMR spectra of polycrystalline ice undertaken by V.F. Kisilev et a1 ., (1973) revealedthe presence of a mobilelayer (liquid) on thesurface of icebodies in temperatures below melting point. The mobile layeris found onan ice-gas surface or the surface of ice andany other hydrophobicbody. The mobility of theelements of thelattice of the - 104 - disorderedsurface layer was considerablyhigher than in the body of the crystal.Lowering theoftemperature was accompaniedby a diminished mobilityin the near-surface layers. It canbe assumed thatthe nature of high mobility of lattice elements at the surface of the ice is conditioned by thespecific mobility of hydrogenatoms; this was revealedearlier (Owston, Lonsdale, 1948). When thetemperature is below -78OC there is decrease in themobility of hydrogen atoms theinice; itssolidity increases spasmodically; and theice transforms from itsliquid state into a solid accordingto Rebinder, reaching its endurance limit. When thisoccurs, the crystalstransform from their hexagonal system into a cubicsystem. There is no sharp division between themobile surface layer and the rest of the ice.
The discoveryof a mobile layer on the surface of the ice provides an explanation for severalprocesses occurring innatural ice formations. It is known that when glaciersflow slowly, when thereis a stressfield a reorientation of crystalstakes place. It was notclear how thiscould happen. It can be supposed thatthepresence of differingreticular densitiesof molecules on thecleavage facets and faces of thecrystals causes thedifferences in mobil ity; this has not been proven by experiment. Resulting from thesepositions, the shifting of the mass ofmatter at the surface is conditionedby the stress gradient and thedifferent reticular density,i.e., by variousrelay movements it will leadto the formation of a more stable form and new orientation of the crystals.
I succeeded in finding an indirectaffirmation of the presence of a mobilelayer on theice surface. This concurs with the experiments carried out by Barnesand Vaipond (1909) to determinethe sublimation heat of pure ice: when thereis rapid sublimation, the heat value was closeto that of theevaporation of water and was onaverage, 608 cal/g, and701 cal/g for slowsublimation, i.e., closeto the energy of transition from indirect transformationfrom a solidto a vapour. This discrepancy,hitherto unexplained, can now be accounted forin the following manner: firstlythe mobilelayer of iceis quickly broken down, and thenthe deep layersare affected;this is causedby thediffusion of moleculeswithin the ice. It can be proventhat such a method for determiningthe energy ofphase transition from ice to vapourallows the possibility of establishingthe - 105 - mobility of watermolecules, and subsequently the strength of their bonds withthe ice surface,within the ice, and with thesurface of a foreign body (includingunconsolidated materials) - I can claimauthorship of this method.
On the basis of the above, it can be considered that the unusual structure on the near-boundary region of permafrostresults from its mu1 tiplicity of layersoccurring between the mineral part of theskeleton, and the ice. The multilayered system includesadsorbed water comprising a firmly-bonded layer and a diffusionfilm, a mobile surfacelayer of ice, a contact layer of ice adjoining the remaining mass of the ice body.
The strength of permafrost comes aboutnot as an additiveresult of the componentsand phases of thematerials, but due to a specific type of cohesive bond conditioned by the intermediatemultiplicity of layers. The adhesive bonds will be stronger than the cohesionstrength of the ice when thereis no diffusionlayer water.of This can occur in very low temperatures when theice will come in contact with the adsorption layer. Upon contact with thefirmly bonded layer of water on the icesurface, very strong bonding occurs. This leads to a sharpreduction of molecules on the surface of the ice, and a firm bonding of thesemolecules with theadsorption layer seems higher than thefirmness of the bonding between molecules within theice lattice. In this case,the adsorbed water and thesurface layer of the ice seem to be factorsstrengthening the permafrost.
As revealed by theexperiments of I.B. Savel 'ev (1972), in the presence of contactice, in every case, theseparation of ice from the permafrostbore a cohesive character and took placealong the boundary of the contact ice - icematrix separation. As a result of the breaking off on the sublayersurface a layer of ice 1 - 3 mm thick remained; this has the structure of a contact layer.
The firmnessofthe bond between the contactlayer and the remaining mass of ice strengthens with an increase in number of crystals in thetotal volume and with a drop in temperature.
The cohesive strength ofthe ice become greater than theadhesive bond when thereis considerably layer of adsorbedwater, i .e., thediffusior! - 106 -
layerwhich can occur either when temperaturesdrop further below zero, or as a result of an increasedconcentration of dissolved salts in the diffusion layer. An increase in thelayer of adsorbedwater leads to a weakening of its bond withthe ice, and this will increasethe mobility of themolecules of thesurface 1ayer. Consequently there is a decrease inthe firmness of the bonds withthe mineral layer. In this case, thefactors weakening the adhesion will be the diffusion layer and the mobile layer of ice.
Withinthe temperature interval from -1.5' to -5Oc, thebreaking away Of ice from thesurface of thesublayer had anadhesive-cohesive character. The relationship of thecohesion area to theadhesion area increases as thetemperature drops. Beginning with a temperature of -5OC and below, thebreaking awaywas of a cohesivecharacter in all experiments. In this case, the maximum strengthis that of finegrained materials; this is conditioned by the structure of the contact ice.
It is to be expectedthat the structure of thecontact ice stress field must change with time; without doubt this has an effect on the strength of the deforming and other properties of the permafrost
I feelthat future research into the near-border regions in permafrost will allow methods to beworked outfor controlling the action, with a view to obtaining the desired properties of permafrost.
Structuralparameters of congealed ice u on contact withfine-grained samples at -5B C (according to I.B. Save1 lev)
Sampl e Coefficient of Sectionalarea Volume of Surface of crystals tortuosity C of mean crystal mean crystalinunit volume 2 ssr x cm2 v,,x cm3 P, cm
As kani te gel 2.56 185 26 102 Sugl inok 2.61 295 48 82 Kaol in 2.37 452 77 68 Sand 2.37 884 177 57 - 107 -
REFERENCES
IGNAT'EVAL.A., KVLIVIDZE V.I. and KISELEV V.F. 0 mekhanizme elementarnogo aktavzaimodeistviya s poverkhnost'yuokislov, (Mechanics of theelementary event of interaction with the oxide surfaces). In the book:Svyazannaya voda v dispersnykhsistemakh, vyp 1. (Bound water infine-grained systems, No. 1).Izd-vo MGU, 1970.
ZLOCHEVSKAYA R.I., ZIANGIROV R.S., SERGEEV E.M. and RYBACHUK A.N. Issledovanie svoistv svyazannoi vody i dvoinogoelektrichesogo sloyasystemy "g1 ina-rastvor" . (Research intothe properties of bound water of the double electrical layer of the "C1 ay- Solution'' system. Ibid, 1970.
KVLIVIDZE V.I. Izuchenieadsorbirovannoi vody metodom Yaderno-magnitnogo resonanso.(Study of adsorbedwater by the nuclear magnetic resonancemethod). Ibid. 1970.
KISELEV V.F.s KVLIVIDZE V.I. and KURZAEV A.B. Poverkhnostnyeyavleniya na granitseled-gaz i led-tverdoetelo. (Surface phenomena at ice-gas and ice-solidboundaries). In the book: I1 Mezhdunar. konf. PO merzlovedeniyu,Doklad i sooloshch) (I1 InternationalConference on Permafrost.Proceedings and Reports, No. 4, Yakutsk, 1973.
SAVEL'EV I.B. Aktivnoevozdeistvie merrlogo dispersnogo osnovani a na strukturuprikontaktnogo sloya namorozhennogo 1 Ida.(Effect on the structure of the near-contact layer of theencrusted ice by the activity of thefrozen fine-grained base). "Dokl . AN SSSR", t. 201,No. 1, 1971.
SAVEL'EV I.B. Osobennostiledyanykh obrazovanii vblizikontakta s merzlymi gruntami.(Peculiarities of ice formationsclose to contact
withpermafrost). I1 Mezhdunar. konf. PO merzlotovedeniyu.Dokl I i soobshch.,vyp. 4. (I1International Conference on Permafrost. Proceedings and Reports. No. 4, Yakutsk,1973.
SAVEL'EV B.A., SAVEL'EV I.B. and GOLUBEV V.N. Strukturnyeosobennosti adgezii 1 Ida s tverdymitelami. (Structural peculiarities of adhesion ofice to solids). 1972.
SKLYANKIN A.A. and KIREEV K.V. 0 mekhanizme vzaimodeistviya vody s poverkhnost'yukaolina. (Mechanics of intcractionof water withkaolin surfaces) In the book:Svyazannaya voda v dispersnykh systemakh,vyp. 2. (Bound water infine-grained systems, No. 2). Izd-vo MGU, 1972.
LOW P .F. and ANDERSON D, Soi 1 Sci . SOC. her. Proc *, Vol . 22, 1958. OWSTON P.G. and LONDSDALE K. The crystallinestructure of ice. "J. Gloc."Vol. 1 1948. BARNES H.T. and VIPOND W.E. Phys. Rev., 27, 453, 1909.
- 109 -
CONDITIONS AND GEOTHERMAL CONSEQUENCES OF THE MOISTURE EXCHANGE BETWEEN THELITHOSPHERE AND THEATMOSPHERE IN PERMAFROST REGIONS
P.F. Shvetsov A1 1-UnionResearch Institute of Hydrogeologyand Geological Engineering Moscow, U.S.S.R.
As studies by leadingSoviet scientists have shown (Ignatovich, 1944; Kamenskii, 1947, etc.), one ofthe main processes involved in the formation(quality and resources) of deposits of subsoilwaters (aqueous solutions)theis exchange of water in the lithosphere-soiland 1 ithosphere-water-reservoir (watercourses) systems. The exchange of moistureinthe soil-atmosphere andwater (water courses) - atmosphere systems is beingstudied, of course, by meteorologists and hydrologists.
The exchange of water thelithospherein studiedas by hydrologistsis an irreversiblephysiogeological process of water(aqueous solutions)migration in the various rocks and theirocclusions - strata,rock masses andmassifs with varying pressure fields (heads), moisture contents (concentrations),temperatures and electrical potentials. It is a special case of the exchangethe ofcase of mass thein 1 ithosphere-soil and 1 ithosphere-water-reservoir systems.
The principalfactors underlying the exchange of water in these systems are the following:
1)tectono-orographic - thesituation of a givenarea in the geostructure and mesorelief, and also in relation to the marine basins, i .e. , the range of altitudes, angles and slope directions of the terrain surfaces;
ProceedingsThird International Conference on Permafrost, Val. 1 I pp.146 - 148,1978. - 110 -
2) lithologo-petrographic(corresponding to theunit of ¶eo-
structure) ¶ i.e. # the constitution, structure, composition and properties of the strata, rock masses and massifs of thegiven area;
3) meteorological , i,e. thezonal-regional water and heat balance of the active layer and the local weatherregime in this area.
Variouscombinations of thesethree independent heat-exchange and water-exchangefactors constitute individual internal subjects of hydrologicalinvestigation, designated according to kindsthe of heat-exchangeandwater-exchange geosystems involved. A water-exchange geosystem is the totality (complex) of thewater and aqueous solutions of the strata, rock masses, rockmassifs, soils and reservoir beds characteristic of a given geostructural form and li thologo-petrographic system.
It is obviousthat every water-exchange geosystem is at the same time a heat-exchangegeosystem. The idea of a complexhydrogeothermal approach to thestudy of the geothermal fieldin regions with layers of continuouslyfrozen soils stemfrom itsfirst investigator in northern Siberia. In a workdevoted tothe climate (andobviously therefore, riot previouslyfamiliar to hydrogeologists) Academician A.F. Middendorf(1962, p. 395) wrote:
"Inthe earth's strata, as in a huge filter, water of every temperature is descending to differentdepths and is risingfrom different depths todifferent altitudes and intermingling, as a result of whichthe temperatureof the ground strat are changed". This isnot consistent, of course, withthe belief that "permafrost is a productof climate" and with thecontradictory existence of a considerable number of springsmeeting the needs ofthe population and the economy innorthern regions. The creative idea,here, resembled the permafrost-climate concept which was widelyheld towardsthe middle of the nineteenth century and which had developedfrom the study of surface phenomena and thecomposition of the subsoils; the investigation of the processes intheir interior had notyet begun.The - 111 -
firststep in this promising, but difficult direction was takenbythe geologist N.M. Koz'min(1898).
Among the generally known characteristics of thewater exchange of thelithosphere with the soil and theatmosphere in the presence of a frazen geotoneare the following:
1 A continuouslyfrozen subsoi 1 "permafrost"or with a thickness, as a rule, of more than10 m constitutes a singular water-impermeable"gasket" between the soil and thecomparatively deep (subpermafrost)strata and massifs ofthe lithosphere; in hydromechanical terms (as a water-confininglayer), it is comparativelyuniform, notwithstandingthe variety of lithogenetic and petrographicforms and their complexes (strata, suites, series)entering into its constitution.
2. The interdependence of thesoil, subsoil (super-permafrost) and interstratawaters is possible and isactually realized owing to the discontinuouscharacter of thefrozen zone ofthe lithosphere, markedby "problems",according to A.V. Llvov(1916) inthe form of taliks of hydrologicalhydrogeological, geochemical and mixedorigin.
3. The cryogenichydrogeological boundaries between the water-bearing and water-repel1ing horizons, massifs andveins especially the upper and lateral ones,change positionin the course of annualand longer periodsof time; they are not always determined by, and indeedare often completelyindependent of the common lithogeneticregularities such as the alternation of clay andsand deposits or of monolithic and fissuredscaly rocks. The mobility of theseboundaries agrees completely with V .I. Vernadskii's(1933) most important idea concerning the pulsation ofthe cryosphere, andhas been confirmedby the investigations of students of permafrost who have demonstratedempirically that not only is "permafrost subjectto degradation" but that this degradation is also accompanied by deep freezingprocesses in the earth's crust (Sumgin et al.,1940).
4. The surfaces of frozenrock strata (FRS) arecold screens on whichwater vapours coming down (inspring and summer) fromthe warmer - 112 - atmosphereand soil andupfrom the deeper, unfrozen horizons theof lithosphere condense(L'vov, 1916; Sumgin, 1937; Koloskov, 1937, 1938). In view ofthe considerable gas permeability of soils androcks, their water exchange with the atmosphere is realized in large measureby diffusion andby turbulent(convective) transfer.
5. The replenishing of groundwatersprings and theincrease of riverflows in many regionspossessing icy frozen strata is due, apparently tothe thawing ofunderground ice(Yachevskii, 1899; Tolstikhin,1941). This phenomenon can be observedonly during the warming ha1 f period of the cyclicalalternation of heat exchange conditions of theearth's crust with the atmosphere; the opposite occurs during the cooling half cycle
A number of othercryogenic factors must now beadded to these generally known characteristics of the water exchange of the lithosphere with thesoil and the atmosphere in permafrostregions. One of these is due to thelow geothermal level of the heatexchange. The basis of this lies in the factthat the temperature of the soil, subsoil and interstratawaters that moistenthe FRS remain,over long periods (one warm season to many years), in theinterval between *4OC and thefreezing point of the aqueous solution, The anomalous variation of thedensity of freshwater in this interval plays anextremely important part in the energy and waterexchange of theearth's crust with the soil and the water reservoirs of high latitudes.
An entirelydifferent, .but no lessimportant hydrogeothermal effect is observed when fissures and other macrospaces fill up with aqueous electolyticsolutions whose concentrationsexceed 26 g/litre. The maximum densitytheseof solutions, which have lostthe character of water, corresponds tothe lowest temperature. Accordingly, anomalous temperature fields are created in the fissured rock strata - with negligeably positive or evennegative geotemperature gradients. To some extentthis constitutes a refinement of V.1. Vernadskii's (1933) beliefin the great importance of the cooling zone in the earth's crust for thedevelopment of certaingeophysical arrd geochemicalprocesses.
A second further condition of development of the water exchange of theearth's crust with theatmosphere and waterreservoirs in the Far North - 113 - liesin the increased importance of the "gas factor"in the movement of subsoilwaters across open taliks,since the total gas saturationof the interstrata waters here is greater than in areas devoid of frozen rock strata (Shvetsov,1951). Often the motion of groundand interstratawaters across an open tal ik under the influence of the gas factor wi 11 be a two way motion; the dense (cold)groundwater moves downwards, whilethe gaseous interstrata water moves upwards throughthe same relatively large talik occupied crack or seam; the downward motion of dense soil and groundwater will predominate in the warm season, theascending mixtures of water and gases inthe cold season.
A thirdsingular condition of the water exchangebetween the soil and theatmosphere in the presence of an FRS can be identified as increased temperaturegradients theinseasonally thawed layer(Principles of geocryology,1959). Reflecting the greatintensity of thetemperature field in the uppershell of theearth's crust, these enhanced temperaturegradients increasethe heat and moisturetransfer of thecapillary porous soils and rocks when the signs of thetemperature and moisture gradients of the rock or thesigns of thetemperature and densityof the waterare the same, which occurs in spring and atthe beginning of summer. The samemay be said of the diffusionof atmospheric humidity in coarse-grained and clastic formations.
The positiveenergy effect ofthe seepage (infiltration) of atmosphericwater into the soil and rocksmust be deemed anextremely importantcharacteristic of thewater exchange of thelithosphere with the soil and theatmosphere inthe FarNorth. A considerableaccess of heat in the subsoilthe attributable is infiltrationtheto of atmospheric precipitations. The periodic measurement ofrain water temperatures in Noril'sk has shown that it can be as much as 15' - 18OC there.Just the oppositeis observed in the extreme South, inthe sandy deserts of Central Asia,for example. Inthe Kara-Kums thefalling and infiltration of precipitations into the unsaturated sandy soils (zone ofaeration) lowers the s ubsoi 1 temperature,
It shouldbe emphasized that it is a questionhere of thethermal effect of infiltration, not of the amount of precipitation and the influx of - 114 - surfacewater from surroundingareas. The geothermal effect of the absorption of surfacemoisture by the unfrozen soil and its percolation downwards to thefrozen soil -subsoil layer with an annual heat reversal in a number ofplaces is not synonomous with theoverall thermal effect of the fa1 1 of atmosphericprecipitations or with any other form of moistening of theunderlying surface. Investigations in the UpperBureya basin have clearly shown that rain-drenchedhorizontal and gentlysloping (less that so) areas and tones in depressions and on flat interfluves with peaty boggy soils and clayeysubsoils arecharacterized by very low negativesubsoil temperatures (Bakakin et a1 ., 1954).
The infiltration of 150 - 300 mm precipitation and surface runoff waterover the spring and summer season into a coarse-grained,fissured layer of the earth'scrust with annual heatreversals is a principalcause of the formation of azonally warm massifs of the 1 ithosphere(year-round and frequently open taliks) in northern and northeasternregions where the mean annual atmospherictemperatures are -5' to -15OC. The infiltrationalso changes thestructure ofthe basic annual heatbalance equation by the introduction of an additional term and reduces its common componentwhich expressesthe loss of heat in theevaporation of moisture(Shvetsov, 1968). Taking this intoaccount, the following equation is obtained;
T =Ta+ R L (E V) + CVAT + B S - - a
Ta of R where T 5 - soil temperature; - temperature theair; - radiation balance; L - heat of evaporation of water; E - quantity of surfacewater remaining on thesurface and insidethe clayey soil; v - quantity of water seeping through thesoil to the subsoil in the warm season; AT - difference of temperature between thesubsoil and thewater that has penetrated into it from thesurface; c - thermal capacity; B - flow of heat from the interior of theearth or from thesoil into the lithosphere (totalled), and u - coefficient of heat exchange due to convection.
Thus, the veryimportant idea (Yachevskii, 1899) thatthe lithological composition of therocks of a given area"determine, so to speak,the extent to which the soil isreceptive to theexternal climatic - 115 - changes", requiresan essential supplement. Besides the quantitative extent, the differentdirection "of receptivity of thesoil" to theatmospheric precipitations and tosurface moisture of other origin must also be taken into account.
In the light of what has been saidabout the nature of thewater exchange conditionsof the 1ithosphere with the soi 1 (andatmosphere) the decisiveimportance of the lithologo-petrographical varieties of rockin the behaviour of groundwater in the Pechoracoal basin district becomes entirely clear.There are whole sectors in which an ancienteroded crust of Permian rocks is coveredby thick layers of practically water impermeable,and hence, as a rule,frozen clays. The behaviour of thesubpermafrost water in these sectorsreflects but faintly, if atall, the short term but radical changes in the conditions of water and heat exchange of the soil with the atmosphere. Justoppositethe observedis sectors in of the Yun'yaginskii, Verkhne-syr'yaginskiidiscontinuousthin,with type anthropogenic ( tlmorainic't) formations.
The discontinuouscharacter of the perennial cryolithozone, being aninevitable condition of the direct water exchange of theearth's crust withthe atmosphereand water reservoirs, isalso a consequence,as a rule, of thedevelopment ofthis complex physico-geol ogical process. Inorder to be a cause of considerablediscontinuity in the perennial cryolithozone the water exchange of thesoil-subsoil complex withthe atmospheremust be intense, i.e. , theremust be a sufficientquantity of surface water penetrating down tothe subsoil or of subsurfacewater rising to thesurface over a unitarea during a giveninterval of time (year or season). Hence, this is one of themain hydrogeothermal problems in geocryology. As far as theextensive factor is concerned,i.e., the total area of waterconducting open taliks, especially in relation to thetotal area of the perennial cryolithozone, it is considerable on its southernmargins, but small in its arctic sector.
It may be saidthat the water permeability of thesoil -subsoil complex isequivalent to itseffective heat conductivity, which is beginning to be determinedmore andmore by infiltration and influation,i.e. , by - 116 - convectiveheat transfer. The mean annualtemperature of thesoil-subsoil complex is rising in proportion to the square root of its conductivity, i.e. ,
AT = X vm where k - coefficientof filtration in m/day; m - thickness of layer exhibiting anannual heat exchange in m; x - a proportionalitycoefficient closeto 0.05, asproposed by the hydrogeologist I.A. Zuev on the basis of studies of a large number of areas in the Northeast of the U.S.S.R.
REFERENCES
BAKAKIN V.P., ZHUKOV V.F. and MEISTER L.A. Mnogoletnayamerzlota gornykh porod i usloviya stroitel 'stva v tsentral 'noi chasti Burenskoi vpadiny(Permafrost in soils and conditionsof construction in thecentral part of theBureya valley) Moscow, Itd-vo AN SSSR, 110pages, 1954.
BARANOV I .Ya. Yuzhnaya okrainaoblasti zemnoi poverkhnosti(Southern extreme of theearth's surface area) Leningrad,Gidrometeoizdat. 67 pages, 1956.
VERNADSKII V.I. Ob oblastyakhoxlazhdeniya v zemnoi kore (On regions of coolingin the earth's crust). - "Zap. Gos. gidrol.in-tal', Vol. 10, (2), 1933. IGNATOVICH N.K. 0 takonomernostyakhraspredeleniya i formirovaniya podzemnykh vod (On theregularities of distribution andformation of subsurface water). - Dokl . AN SSSR". Nov. seriya,Vol , 45, No. 3, pp, 133-136, 1947.
KAMENSKII G.N. Gidrogeologicheskieissledovaniya i razvedkaistochnikov vodosnabzheniya(metodicheskoe rukovodstvo) . (Hydrological investigations and therospecting of sources of watersupply (Methodological manual ) !, Gosgeol itdat. 79pages, 1947, KOZ'MIN N.M. 0 yavleniyakhvechnoi merzloty v nekotorykhmestnostyakh VostochnoiSibiri. (On permafrost phenomena in Eastern Siberia) "Izv.Vost.-Sib., otd. RGO", Vol. 23, Issue 45, pp. 58-71, 1892.
L'VOV A.V. Poiski i opisaniyaistochnikov vodosnabzheniya PO zapadnoichasti Amurskoizheleznoi dorogi v usloviyakhmerzloty pochvy (letnii i zimniirezhim rek, gryntovykh vod i usloviipitanii'ya glubokikh vodonosnykh tolshch v raionakhsploshnogo rasprostraneniya "vechnoi" merzloty). (The prospecting and descriptions of water supplysources along the western part of the Amur railroad in conditions of perennially frozen soil (summer and winterregimes of rivers,ground- water and conditions of feeding of the deep water-bearing strata in areasof dense distribution of permafrost)).Irkutsk, 882 pages, 1961. ~ - 117 -
MIDDENDORF A.F. Puteshestvie na sever i vostokSibiri. (Travel in the north and east of Siberia) , Part 1, Issue 3, St, Petersburgh, 270 pages, 1862. Osnovy geokryologii,(Principles of geocryology)ch. 1, M., Izd-vo AN SSSR, 1959. PONOMAREV V.M. Podtemnyevody territorii s moshchnoi tolshcheimnogoletnermerzlykh gornykhporod. (Groundwater ofregions with thick layers of perennially frozenground). Moscow, Ind-vo AN SSSR. 200 pages,1960.
SUMGIN M.I. Vechna a merzlotapochvy v predelakh SSSR. (Permafrost soilsin the U.S.S.R. 3 . Vladivostok. 372 pages,1927. SUMGIN M.I. Vechna a merzlotapochvy v predelakh SSSR. (Permafrost soils in the U .S.S .R. Y . 2nd ed., Moscow, 380 pages, 1937. SUMGIN M.I. KACHURIN S.P., TOLSTIKHIN N.I. and TUMEL' V.F. Obshchee merzlotovedenie [Generalpermafrost science). Moscow-Leningrad. Izd-vo AN SSSR, 340 pages, 1940.
TOLSTIKHIN N.I. Podzmnyevody merzloi tony 1 itosfery. (Groundwater inthe frozen tone of the 1ithosphere). Moscow, Gosgeolizdat. 201 pages, 1941
SHVETSOV P.F. Podtemnye vodyVerkhoyansko-kolymskoi gorno-skladchatoi oblasti i osobennosti ikh proyavleniya, svyazannye s nizkotemperaturnoi vechnoimerzlotoi . (Groundwater of the Verkhoyansk-Kolyma mining fold region and characteristics of their manifestation, associatedwith low temperature permafrost). Moscow, Izd-vo AN SSSR, 280 pages, 1951. SHVETSOV P .F. Zakonomernostigidrogeotermicheskikh protsessov na Krainem Severe i Severo-Vostoke SSSR. (Regularities of thehydrogeothermal processes in the Far North andNortheast of the U.S.S.R.). Moscow, "Nauka",112 pages, 1968.
YACHEVSKII L.A. 0 vechnomerzloi pochve v Sibiri. (On permanentlyfrozen soil inSiberia). - Izv. Russk. geogr. ob-va", Vol. 25, Issue 5, pp. 341 -352, 1899.
- 119 -
RESULTS OF EXPERIMENTAL STUDIES OF THE FREEZING PROCESS IN VERY FINE-GRAINED SOILS
T.N. Zhestkova Moscow State University, U .S .S.R.
Inrecent years the interest laboratoryin studies of the processes of freezing and ofthe cryogenic structures and textures of frozen earthmaterials has increasedsignificantly. This is due to thelargely hypotheticalnature of theextant theories regarding the genesis ofthe cryogenictextures studied innatural profiles. Laboratory studies make it possibleto model cryogenicstructures and texturesunder definite specified experimentalconditions, to revealthe congruence ofvarious parameters of the systemexamined and of thefactors affecting that system, withits controlledcryogenic structure and textureinstead of inferring from the cryogenicstructure and textureof a soilor rock its properties prior to freezing and duringfreezingthe process. Evidence obtained from experimentalstudies of cryogenicstructures and textures permits us to approachthe search for solutionsto the problems pertaining to the formation ofcryogenic structures and texturesof frozen soils or rocksdiffering in genesis,from more thoroughlysubstantiated positions. Inthis paper we outlineresults of investigationsinto the effect of theinitial water contentand density, rate of advance ofthe freezing front and distinctive features of primarytextures and structureson the formation of inherited (after A.I. Popov) cryogenicstructures and textures ir, fine-grained earth materials .
Laboratorystudies on theformation of cryogenicstructures and texturesinclude the following: 1) model1 ingof the freezing process in fine-grainedearth materials with concurrent observations on the dynamics of thedevelopment ofice lenses formation of cryogenic structures and their
ProceedingsThird International Conference on Permafrost, VOl. 1, pp. 157 - 162, 1978. - 120 - reorganization in thefrozen tone; 2) structural and textural-petrographic analysesof frozen earth materials and their constituents; 3) studies of the physico-mechanicalproperties of unfrozenearth materials and determination of theprincipal indices of frozen and thawingsoils and rocks; 4) juxtapositionof the results of laboratorymodelling with the data obtained innature (from large naturalprofiles).
The diagram of a laboratoryassembly, where freezing follows the pattern of a closed system,and thedescription of its major componentsand operatingprinciples are presented in the papers by Zhestkova et al., (1976) andZhestkova and Guzhov (1976). Due totransparent walls of the case we were ablephotographto the samples continuously,around the clock, throughout the duration of the experiment, and to conductobservations on the advance of thefreezing front, changes in thetexture of frozen andunfrozen earthmaterials, andon the growth of icelenses (Zhestkova, Guzhov, 1976)-
The groundsurface temperature was specifiedas constant for the durationof the freezing cycl-e or was variedaccording to the objectives of theexperiment. The sampleswere testedwithin the temperature range of -lo to -2OOC. The maximum durationof an experiment was 28 days , its minimum length was 5 hours. Inthe process of the research there were tested 269 soil samples measuring 60 x 60 300 mm, bothwith disturbed andundisturbed structures,with homogeneous orspecified primary textures (Zhestkova, 1976, 1977)
Polymineral and monomineral earthmaterials of diverse genesis werestudied. Monomineral soils were represented inthe tests by kaolinite and bentoniteclays, polymineral materials - byPaleogene clays, diluvial loams ("suglinok") sandsloamyand (ll~~pesll). The distinctive clayey-mineralogicalcharacteristics thesesoils of and their physico-chemicalproperties are outlined in the works by Zhestkova and Guzhov (1976)and Zhestkova et a1 , (1976). These earthmaterials differ sharply fromone another with respect for theircapacity to form ice. The maximum iceformation characteristicis of monomineralearth materials. In polymineralclays containing minerals of the montmorillonite,hydromica, etc., group,there was recorded a generally lower ice content thanthat of - 121 -
monomineralclays, development of small-scalecryogenic structures of the reticulateor layered type, and a reduction in themagnitude of heave of 1 .5 to 2 times.
The initialmoisture content W of the samplesexamined ranges H from thelower plastic limit W to themoisture content exceeding the upper P 1 iquid 1 imit WT. Water-saturatedearth materials were thoroughly frozen (degree of saturationwith water 0.87 - 0.95). The differentinitial moisturecontents and soil densities were ensured by preliminary compaction ofthe earth materials with the loads varying from 0.2to 60 kg/cm2. This research is conductedunder the supervision of Prof. V.A. Kudryavtsev.
THE EFFECT OF THE MOISTURE CONTENT AND DENSITY
The degree to whichearth materials varying in compositionand genesisare saturated with ice under the same type of freezing conditions, is determinedby theirinitial moisture content and density(Zhestkova, 1973). , A decrease inthe density or an increase in the moisturecontent leads to a more activeformation of ice lenses and intensifiesthe heaving of the ground.This was recorded inallthe samples studied at different temperatures of freezing. It hasbeen establishedexperimentally that the criticaldensity and moisturecontent of earthmaterials do notrepresent magnitudesconstant for a giventype of soil or rock, but are a function of the rate of freezingdetermined by thetemperature atthe freezing surface, heatflux in theunfrozen zoneand properties of theearth material For example, atthe surface temperature equal to -2OC, segregatedice formed at W HP= W a whereas atthe temperature of -6OC, WH = Wp + 7%. The effect of the initialdensity and moisturecontent was studiedwithin a largerange of variations in the rate of freezing with the temperature at the surface of the samples rangingfrom -2 to -1OOC. The existence of a thresholdin the formation of segregatedice permits us in many cases toavoid heaving by subjectingeither the soil or rock of thefoundation or the construction materialto preliminary processing.
The formation of a massivecryogenic structure at themoisture contentand density indices below the critical values is accompaniedby - 122 -
changes inthe moisture content within the confines ofthe frozen and unfrozen zones , bypartial heaving of theground, increased porosity of frozensoils or rocksversus that of unfrozenearth materials, andby uneven distribution of ice-cement in the frozen zone.
THE DYNAMICS OF THE MOISTURE CONTENT DURING THE FREEZING
In all the samples tested,excepting that of bentonite clay, there was recorded a change in the moisture profile during the cooling of the soil, but prior to thebeginning of freezing.During that phase themoisture content of the sampleincreases by 4 - 5% In theuppermost 2 - 3 cm thick 1 ayer .
As the frozenzone increases in thickness,the tone of unfrozen earth materials(or the zone of influence) grows and itsfield of the moisturecontent alters perceptibly. The size of the zone of influence depends on the rate of advance of thefreezing boundary, on the saturation of the frozen zone with ice.
The moisturecontent of the earth material at thefreezing boundary is unstable,being a functionof the freezing process (Zhestkova, Shur,1974) (Figure 1).
Figure 1
b
30 4
a) Changes in the moisturecontent at the freezing boundary as a function of the initial moisture content of the earth materials, b)freezing terrperature, and c) durationof the test. - 123 -
CRYOGENIC STRUCTURES AND TEXTURES
Inthe event of thesurface temperature remaining constant throughoutthe duration of thetest, there forms in the frozen zone of the samples a certainconjunction of horizonsdiffering with respect to their cryogenicstructures and succeeding one another inthe vertical sequence of earthmaterials. This order of succession of thecryogenic structures general ly corresponds(except forthe 1 ayeredcryogenic structure of the bottomhorizons) to the pattern of distribution of structuralhorizons in naturalprofiles of theepigenetic type (under conditions of a closedsystem with a homogeneous composition),where small -scale cryogenic structures become replacedin the ascending order along the section by reticulateor massivestructures (Zhestkova, 1966). A drop in the groundsurface temperature or a decrease inthe initial moisture content at a constant surfacetemperature leads to a reduction of the total moisture content of the earthmaterials within the frozen zone, to a shift of themoisture content maximum in depth, to the development of predominantlyreticulate cryogenic structures in the profile and to a generallylower level of saturation of the earthmaterials with ice. A definiteice content corresponds to each particulartype of thecryogenic structures confined tothe structural horizon. It hasbeen observedthat the structural horizons are saturated withice unevenly in thevertical section. Even thoughthe possible amount of ice formed withinthe soil or rock which freezes according to thepattern of a closed system, isinvariably restricted by theinitial moisture content of the sample, in isolatedtests the heaving of clays and loamattained 3.8 - 4.3 cm at thethickness of thefrozen zoneamounting to 10 - 13 cm.
It hasbeen establishedexperimentally that the formation of cryogenicstructures and theice content are not only functions of the absolutevalues of thesurface temperature, but also depend onthe magnitude of theheat flux from the bottom and, in a more general way, on therate of freezing of the earth material,
Graphs depicting changes withdepth in the rate of freezing and totalice content are presented in Figure 2. Concurrentexamination of these graphsreveals close relationship between them; moreover,the higher the rate - 124 - offreezing, the lower theice content, and viceversa. We did notcontrol therate of freezing in thetests. In the absence of themoisture redistribution by depth and of theformation of zones with increased accumulation of ice, the changes in therate of freezing should be roughly proportionateto &provided the surface temperature remains constant. The significant deviation from this law of freezing, the alternation of increases and drops in therate of freezing shows thatthe accumulation of ice is not determined by the rate of freezingalone. By modifying themoisture content field in the unfrozenzone, theaccumulation of icealso controls the migration of moistureto the freezing front and determinesthe character of the advance of the crystallization front.
Figure 2 t CM 2p 30 40 so ice, %
1
2
3
4
5
6 v, crnlday I 1 1 O,i)48 0,072 0,O 96" OJ2 4144
1) changes with depth in the rate of freezing, and 2) totalice content in the sample.
There has been observed an interdependence between therate of freezing and the character of cryogenicstructures and textures. With respect to therate of freez ing, theearth materials may be subdivided into thefollowing three groups: soils with I - compound, reticulate or layered, I1 - microstreaky or microret iculate, and I11 - massivecryogenic structures.
The rhythmical pattern of the advance of thefreezing front is ofteninterpreted as a combination of stops during theformation of ice 125 - layers andjumps duringthe freezing ofthin mineral interlayers. We ought to distinguish twocompletely dissim ilar cases of immobility of thefreezing boundary. The first case isthe stationary state arising in theevent of heatfluxes in the frozen and unfrozen zones beingequal. No crystallization of wateroccurs at thefreezing boundary. The migration of moisture in the unfrozentone on account of the gradient in the moisture content leads to its uneven distributionwithin the unfrozen zone.The flow of moistureat the boundary i?nil. Thesecond case is thegrowth of an ice lens. The rateof freezingis here not equal to zero and thereoccurs heaving, i.e. , a change in the volume of thefrozen zone. The analyticalexpression of thesetwo cases was examined in an earlier paper(Zhestkova, Shur, 1974), where the distinctiveaspects of specifying the conditions at the freezingboundary were a1so discussed,
Sincethe rate offreezing is a function of both theexternal conditions and thefreezing process, the rates of formation of cryogenic structureswithin the body arenot necessarily close in magnitude even when thesestructures are of the same type.For example, ice-cement forms in thin mineralinterlayers at different rates of advance of thefreezing front, which do not preclude the formation of segregated ice in other circumstances.
Experiments have shown (Zhestkova, 1977) thatthe rate of freezing of anearth material containing only ice-cement, may be even lowerthan the rate of freezing of a soi 1 or rock with segregated ice.
OBSERVATIONS ON FORMATION OF CRYOGENIC STRUCTURES
Observations on the dynamics of freezing through transparent walls ofthe case have shown thatin the course of theexperiments lasting for a period of up to 28 days, thereoccurs a veryslow, butcontinuous restructuring of icelenses and reorganizationof the cryogenic structure of thesoil or rock in the frozen zone (Zhestkova, Guzhov, 1976). Figure 3 shows severalphotographs of a freezingclay sample atdifferent points in timein the course of theexperiment. Studies on the dynamics of the freezingprocesses and formation of structural elementssuggest the following conclusions. The distinctive morphology(i.e., the design or the general - 126 -
Figure 3
410 hours
1 I
Dynamics of cryogenic structures in the process of the freezing of clays over a period of 560 hours. distributionpattern of icelenses in the frcren mass) is deterrriined in homogeneous earthmaterials with a uniform composition by: 1) the pre-freezingstructure of the unfrozen layer of earth material dehydrated by migration and adjoining the freezing boundary, i .e., the structure developing before theinitiation of freezing in thatlayer. This structure is determined by themoisture content and temperature (rate of cooling) of that - 127 - layerat the time when it begins tofreeze. The unfrozenearth material is brokenup by the cracks arising in the process of its desiccation as a result ofthe migration of moistureinto the superjacent horizons that arein the process of freezing, andbecause ofthe changes occurring in the volume of thatmaterial during its compaction and cooling; 2) thetexture of theearth materialdeveloping in theprocess of its freezing. In this casethe freezingearth material cracks up as a result of the splitting action of ice or fracturingaction of the water freezing in its interstices because of dehydration of thealready frozen earth material, onoraccount of physi co-chemical processes.
The types of crackslisted abovereveal the following distinctive featuresin the frozen andunfrozen zone respectively. The cracksrecorded in the unfrozen zone are:1) vertical , perpendicularto isothermal surfaces These cracks arise from within in moist unfrozen soil or rock in the event of a drasticdrop in the surface temperature. They may close up duringthe subsequent transitionof the unfrozen ground to thefrozen state. The ice, which verticalfillspartly,cracks only has a complex ablirnation*-segregation genesis; 2) horizontal , parallelisothermalto surfaces.Horizontal cracks arise inthe event ofthe dehydration of earth materialsunder conditions of a slow cooling of theunfrozen layer. During thetransition of theearth materials to thefrozen state some ofthese cracks fill withice (mainly of thesegregated type) forming layered cryogenicstructures, while others close up andcoalesce; 3) partings or sets of intersectingjoints producing hexagonalforms in theplan. These joints arise in theevent of desiccation or sharpcooling of theearth material. Duringthe freezing they fill with iceforming a thinice mesh bounding mineralpartings represented by aggregateswith the lateral surface measuring up to 1 cm.
In theprocess of theexperiment the complex cryogenic structure alters in the 3 - 5 cm interval(Figure 3). The increase in the thickness of horizontallenses and theaccumulation of icein the vertical cracks during the Slow advance of thecrystallization front lead to the disintegrationof thesystem of vertical blocks. - 128 -
Inthe freezing zone thereform diagonal cracks disposed an an angleto the freezing boundary,and cracksperpendicular to thefreezing boundary.
It has been establishedthat regardless of the type of the cryogenicstructures forming in the profile, the factor contributing to the development of largeice lenses is the deceleration of the advance of the freezingfront. The most favourableconditions for the growth of ice lenses arise when thetemperature of the sample surface changes in the course of the experiment,particularly thein event of a rise in thattemperature (Zhestkova, 1966; Zhestkova, Guzhov, 1976). The growth of ice lensesoccurs mainly in the zone of theearth material adjoining the freezing boundary on theside of the frozen soil or rock. The icelenses inside the frozen zone undergo significant alterations onaccount of the migration of unfrozen water in the event of a change in thermodynamic conditions.
A "chromaticzone" or a layer of desiccatedearth material has been recordedbelow the boundary of iceformation. Inthe process of freezingthis zone moves downwards togetherwith the boundary of ice formation. A drop inthe rate of advance of thefreezing front causes the chromatic zone toincrease in thickness.
In theprocess of formation and growthof an ice lens, mineral aggregatesbreak off the underlyingground and slowly become displaced or are forcedout by ice. The mean rateof displacement of mineralaggregates within an icelayer was 0.5 mm a day. A drop in temperatureleads to an increase inthe size of the aggregates broken off theunderlying ground by ice; to pollution of theice lens and to fragmentation of thecontact zones (ice-ground); and to anincrease in the rate of displacement of thesoil or rockaggregates. A rise in thetemperature of thesoil or rock (within the range of itsnegative values) leads to a decrease in the size of the aggregatesbroken off underlyingthe ground by ice, or even to discontinuation of thebreaking-off process and to accretion of pureice; to purificationof the ice layer, and to fragmentation and dispersal of the particles, in thecourse of which the aggregates broken off theunderlying groundonly partially, return to theplaces from which they were dislodged, - 129 - and "settle" there once again; lastly, it causes thedisplacenient of the soil or rock aggregates to slow down.
Whatever thetype of thecryogenic structure of an ice-saturated soilor rock 1ayer, its chances of becoming converted to an icelayer sustainedalong the strike are the greater, the higher its ice content during the period of its formation.
Observations on the changes inthe size of the sample duringthe tests have shown thatthe total increase in the volume ofthe earth material is a continuous process occurringthroughout the duration of the test. The absence of pauses in the heavingprocess during the freezing ofearth materialsvarying in composition, evidences simultaneous concurrent growth of severalice lenses.
THE EFFECT OF THE PRIMARY STRUCTURE AND TEXTURE
Cryogenicstructures and textures of theearth material from an undistrubed samplewere compared tothose of a sample withspecified primary cracks. The tests were conducted withthe view of elucidatingthe effect of thestructure and texture of a soilor rock prior to freezing on the formation of inheritedcryogenic structures (Popov,1967).
Soil columns withspecified primary textures were prepared from 1 ayers of earthmaterial characterized by a homogeneous composition,equal andconstant moisture content and density within each soil layer 3 - 4 cm in thickness,wellas as fromlayers of earthmaterials differing in composition. The soillayers inside the columnwere separated by closed, partlyclosed or open cracksvarying in site and in orientation(trend) relativeto the cooling surface of the sample. In some ofthe columns the cracks(cavities) between theadjacent layers were left vacant,while in othersthey were filled with washed quartz sand (Zhestkova, 1976). Samples of earthmaterials with layered, reticulate or composite primary textures wereprepared in this manner.
Inthe samples of homogeneous earthmaterials with closed cracks and in control samples thereform cryogenic structures of the same type. - 130 -
Closed cracks may not even fill with ice.Their presence in the soilor rock profiletherefore commonly is not reflected in its cryogenic structure and texture. On the other hand in the samples composed of layers of earth materialsvarying in moisture content and density, as well as in the columns consisting of loamand claylayers differing in composition,large ice veins form in theclosed primary cracks at the contact of thesoil or rock layers (Figure 4). Freezing of the samples of earthmaterial with partlyclosed vertical or horizontalcracks is accompanied by fillins of these cracks with segregatedice; partially closed cracks with a diagonaltrend havebeen observed in the profiles of frozenearth materials only in the form of dotted lines in isolated segments of thefrozen mass. After the sample has thawed out, the cracks fill with earthmaterial. Should the sample be refrozen,its cryogenicstructural pattern therefore commonly fails to reflect that primary structure.
Figure 4
Cryogenic structures in soil samples with different primary structures and textures.
Layered cryogenicstructure with ice veinssustained along the strike and measuring 0.3 - 0.5 cm in thickness, is the only type of structure forming in layered samples of soilmaterial with open hollow horizontal cracks measuring 0.1 cm (Figure 4). The ice is confined to the primary - 131 - cracks and appears tostraighten out the freezing boundary-line as a result of whichan "ideal"structure of thelayered type develops in theprofile. In the presence within a soil or rock sample of vertical and diagonalcracks measuring less than 0.1 cm, iceveins develop precisely inside these cracks, in view of which the cryogenicstructural pattern generally recapitulates the structure of theearth material prior to its freezing. Their presence in the frozen mass reduces the degree of jointing of theearth material below the freezingfront during thedesiccation. During thefreezing earthof materials with open horizontal or verticalcracks, these cracks not only fill with ice, but change in size and shape,as well as with regard to their disposition in thefrozen mass versustheir original position. In the samples with diagonalcracks freezing is accompanied by a thorough rearrangement of the initial texture of the sample with prevalent developNent in thefrozen mass of segregatedice lenses parallel to isothermal surfaces. These icelenses intersect the layersdeveloping in primarydiagonal cracks, which leads to theformation of mixed or disorderlycryogenic structures. The primary horizontallayering of the earthmaterial predetermines the development of layeredcryogenic structures within thefrozen mass andmakes the formation of cryogenicnets less probably. Primary texture of the earth materialpredetermines the morphology of dessicationcracks in the unfrozen layer below thefreezing boundary;primary cracksdenoting the areas of slackening in unfrozen soilor rock, reduce the possibilityof its cracking up during the dehydration.
The effect of the primary structure and texture on thestructure of a sample represented by an earthmaterial with specifieddiagonal and vertical cracks filled with ice, is considerablyless marked if that material was thawed out, then refrozen. When soil columns with horizontalcracks are refrozen,ice lenses develop inside the same cracks and may even be thicker than at the time of the initial freezing.
Small lenses of segregatedice develop in the frozen zone ofthe samples with open horizontalcracks measuring over 0.2 cm.The lenses form finely layered reticulate or incompletely reticulate cryogenic structures and largeice inclusiorls of a complicatedgenesis. They fill thepartings specified between the soillayers. Dynamics of the filling ofthese joints - 132 - with ice is described in Zhestkova's work (1976). Crystals of ablimation* ice which fillthe open cavitywhile the sample is in theprocess of freezing, "adgrow" to theunderlying ground. From that moment on thecracks fill with ice at a much fasterrate, a circumstanceattributable to changes in the mechanism of crystallization. Subsequent recharge and growth of the ice veins occur on account of pellicular moisture.
The mixed genesis of theice filling a crack is also reflected in its texture. Ablimation icepartly filling aspecified cavity, is a fragile, highly unstablesubstance; if left for 24 hours in a coldcloset, it sublimatesalmost completely.
Samples with specifiedcracks freeze more slowlythan homogeneous samples. For example, in one of thetests the freezing boundary in a homogeneous sample advanced by 4 cm whilethe cracks in the para1 le1 sample were being filled with ice.
The presence in the section of a layer ofdry sand is reflected in the cryogenic structure of thelayers of earth material separated by it. Within each layerthere develop finely layered, layered-reticulate and massivecryogenic structures. The degree of saturation of individualclay layers with icegradually decreases with depth. In the samples with interlayers of humid sand there forms an icecrust at the contact of sand with clay. In the caly samples interspaced by a 0.3 cm-thick vertical interlayer of water-saturatedsand, there also forms a thin (0.5 mm) ice crust at thecontact between the sand and theclay. The moisturecontent of the sand decreasesfollowing the freezing. The sand turns dry and loose and its moisturecontent changes from 16 to 3%.
Closed, partlyclosed andopen cracks (with a gap of less than 0.1 cm between thelayers of earth material) do not obstructthe transport of moisture from theunderlying horizons to the freezing front.
* Ablimation - from the Russian word ltablirnatsiya1l refers to theformation of ice crystals sublimated directly from water vapour in anopen cavity or crack in the ground. This is similarto hoarfrost. (Technical Editor) - 133 -
The columns,where thelayers of earthmaterial are separated by horizontalcracks with the cavity measuring Over 0.2 cm, reveal a break in the moisturecontent profile. An open fissurelimits the access of the moisturefrom theunderlying horizons to the freezingfront. Sand interlayersmeasuring 0.2 cm in thickness, also impede themigration of moisturefrom the subjacent horizons tothe freezing front. Water is transportedthrough the sand interlayerin the form of vapour,but on a negligiblescale as compared tothe magnitude of thepellicular moisture transportin the homogeneous control column of earthmaterials. This is preciselythe reason for the moisture content ofthe earth material underneaththe sand interlayerin the unfrozen zone beingclose in magnitude to theintial moisture content (with a differenceof 2 - 3%). A similar phenomenon, I.e. , restricted movement of waterthrough sand interlayersin layeredsoils freezing under the open-systemregime, has been established experimental ly by N .F. Pol tev (1 967).
TEXTURES OF FROZEN EARTH MATERIAL
Studiesof distinctive textural-petrographic features of frozen earth materials were carried out by usingintegrated techniques and method of lenses in sections with anarea of 2 x 2 cm (Zhestkova et a1 ., 1976a) The studies havedemonstrated thatin a frozen mass withfinely reticulate, reticulateincompletelyor reticulate cryogenic structures, theearth materialis composed of unequalsized aggregates, ice-cement and inclusions of segregatedice. Large aggregates form withinthe mass partialborders delineating concentrations of smallerclay aggregates. This type of annular differentiation of theearth material is often interpreted as a result of multiplerepeated freezing and thawcycles. The dataavailable evidence that annulardifferentiation of the earth material may be produced notonly by particles,but also by soil or rockaggregates; it may alsoarise under the effect and as a consequence of one single freezing.
It has been observed thatin frozen earth materials with layered cryogenic structures the orientation of segregated ice crystals alters in the zone of their contact with the soil or rock. - 134 -
In horizontalice lenses measuring over 0.1 cm, thecontent of soilparticles decreases, there appears a multitude of intersticesat the contact with ice,ice crystals increase in size and change in shape.
In large interstices offine-grained earth materials which are not completely filled with water by thetime, when thefreezing begins, ice crystals become disposedalong the radius. This circumstance, as well as the saturation of the upper part of theinterstices with icecrystals and their gradualre1 ease downwards suggest that ice crystals grow in ice 1 enses around theinterstices along the line of theheat flux. A similarstructure (probably the same typeof growth, too) is also characteristics of ice from aggregates of earth materials.
In horizontallenses ice crystals are oriented for the most part with their major axisperpendicular tothe trend of theice lens. No distinctlydefined pattern has, however,been established in theorientation ofthe crystals forming ice layers varying in trend.
The texture of ice-cement has been observed to a1 ter with depth in the samples with layeredcryogenic structures. In the upper layersthe crystals of ice-cement are acicular in shape and appear to be intergrown with theaggregates of earthmaterial. In thecentral part of the frozen zone the crystals ofice-cement coalesce atisolated points forming an ice lens discontinuousalong its strike.
NO differences in texture havebeen revealed between theice of the cement type,ice of inclusions and that from the framework ("skeleton") of the soilor rock either in homogeneous samples or in the samples with specifiedclosed cracks.
Ice lenses from the samples with partlyclosed cracks are distinguished by a more orderlyorientation and largersegregated ice crystals composing thelenses.
The ice filling open horizontalcracks consists of minute acicular crystals of theablimated type and of large columnar icecrystals of the - 135 - segregatedtype, which areoriented withtheir major optical axis perpendicular to the freezing boundary.
Open verticalcracks become filledwith ice only partly, We recordedhere ice of two types (i .e. segregated andab1 imated) , as was also the case in open horizontalcracks. Acicular crystals of ablimatedice develop on thelateral walls ofthe cracks and grow in the direction perpendicular to theirtrend. Crystals of segregated iceinvade vertical cracksthrough their lateral walls from the horizontalice lenses occurring in the frozen mass.
REFERENCES
1 ZHESTKOVAT.N. Kriogennyetekstury i 1 'doobrazovanie v rykhlykh otlozheniyakh(Cryogenic structures and ice formation in loose deposits) . MOSCOW, "Nau ka" , 165 pages, 1966. 2. ZHESTKOVAT.N. Zavisimost' 1 'donasyshcheniya ot nachal'noi vlazhnosti i plotnostitonkodispersnykh gruntov (Saturation with ice as a function of the initial moisture content offine-grained soils). V kn.: Merzlotnyeissledovaniya. Issue 13,Izd-vo MGU, Moscow StateUniversity Publishing House, pp. 67-78, 1973.
3. ZHESTKOVAT.N. Vliyaniepervichnogo slozheniya grunta na ego kriogennoe stroenie (The effect of theprimary texture of frozenearth materials on theircryogenic structure and texture). - "Westn. Mosk, un-ta", Ser. geol ., No. 5, pp. 102-115,1976. 4. ZHESTKOVA T .N. K voprosuob usloviyakh obrazovaniya 1 Ida-tsementa (Contributionto the problems related to the conditions of formation of ice-cement), V kn.: Mertlotnyeissledovaniya. Issue 16, Izd-vo MGU, Moscow State University Publishing House, pp. 47-54, 1977. 5. ZHESTKOVA T.N. and GUZHOV V.G. Eksperimental'nye dannye o dinamike kriogennykhtekstur v promerzayushchem grunte(Experimental evidence on dynamics of cryogenicstructures in freezing earth materials). V kn.: Merzlotnyeissledovaniya. Issue 15, Izd-vo MGU, Moscow StateUniversity Publishing House, pp. 209-215, 1976.
6. ZHESTKOVA T.N,, ZABOLOTSKAYA M.I., ROGOV V.V. and GUZHOV V.G. K metodike izucheniya struktury 1 Ida-tsementa i 1 Ida-vklyuchenii v merzlykhgruntakh (Methods of studyingthe texture of ice- cement and iceinclusions in frozen earth materials). V kn.: Merzlotnyeissledovaniya. Issue 16, Itd-vo MGU, Moscow State UniversityPublishing House, pp.145-152, 1977. - 136 -
7. ZHESTKOVA T.N.) MEDVEDEV A.V. and MELAMED V.G. Rezul'tatysopostavleniya 1aboratornogo i matematicheskogo model irovaniya 1 'donakopleniya v promerzayushchikh tonkodispersnykh gruntakh (Results of thejuxta- position of laboratory and mathematicalmodelling of theprocess of ice accumulation in freezing fine-grained earth materials). V kn.:Merzlotnye issledovaniya. Issue 15, Izd-vo MU, Moscow StateUniversity Publishing Houses pp.37-45, 1976.
8. ZHESTKOVA T.N. and SHUR Yu.L. 0 vlazhnosti talogo grunta na granitse promerzaniya (Moisture content of unfrozenearth materials at thefreezing boundary). - "Vestn. Mosk. un-tal',Ser. geol., No. 4, pp. 69-73, 1974. 9. POLTEV N.F. Vliyaniepervichnogo slozheniya gornoi porody na ee teksturu v merzlomsostoyanii (Effect of primarytextures and structures of earth materials on their structure in the frozen state). V kn: Merzlotnyeissledovaniya, Issue 6, Izd-vo MGU, Moscow State University Publishing House, pp. 246-251, 1967.
10. POPOV A.1 . Merzlotnyeyavleniya v zemnoi korekriol itologiya (Permafrost phenomena in the earth crust Icryolithology) Izd-vo MGU, Moscow State University Publishing House, 302 pages, 1967. - 137 -
THE ROLE OF HIGHLYMINERALIZED GROUNDWATER IN THE COOLING OF THE LITHOSPHERE AT DEPTH
A.B. Chizhov Moscow State University, U.S.S.R.
The phenomenon ofthe widedistribution of highly mineralized groundwaterwith subzero temperatures (subsurface kriopegs according to N I Tolstikhin'sterminology) and theirinfluence on theformation of geotemperature fieldscontinues to attractthe attention of researchers. The currentrelevancy of this problem is determined by the rapidly increasing volume of prospecting and recovery of oil, gas and hardminerals inthe arctic and northern Siberia, and by thestudy of both the water resources and the geothermalthe resources of theseregions. Soviet scientists N.I. Tolstikhin, P.F. Shvetsov, N.I. Obidin, V.M. Ponomarev, A.I. Efimov, P.I. Mel'nikov, Ya.V. Neizvestnov, V.T. Balobaev and others have made a great contributionto its development. The materialaccumulated to date permits a quantitative assessment of individual aspects of the formation of underground kriopegs and their influence on geocryological andgeothermal conditions.
P.F. Shvetsov(1941) was one of the first to draw attention to the role of highlymineralized groundwater in the cooling of thelithosphere inpolar regions. This role is confirmed by thefollowing data on the depth of occurrenceof the 1ower 1 imit ofthe kriopeg boundary (0'. geoisotherm) . Thus, if within the MarkhinskayaTrough, thedepth of occurrence of the Oo geoisothermreaches 1500 m (Mel'nikov, 1967), then inthe very same latitude in the Vi lyui sync1 ine and the PredverkhoyanskTrough, where thepermafrost isunderlain by weaklymineralized waters, the thickness of thepermafrost zone does not exceed 600-700 m on average. Withinthe Botuobinsk Uplift (areaaround the town ofMirnyi), the thickness of thepermafrost zone includingthe kriopegs is 500-600 m (Efimov, 1964, Chizhov,1968), and within theneighbouring Yakutsk artesian basin containing weakly mineralized subpermafrostwater it is 200-300 m.
ProceedingsThird International Conference on Permafrost, VOl. 1, pp.166 - 167, 1978. - 138 -
The mechanics of the coolinginfluence of thekriopegs can be explained as fol lows:
1)by free convection under the effect of a density gradient(Klimovskii, Ustinova, 1962);
2) by forcedconvection during movement of cold,highly mineralized water of thenear surface horizons when there is subsidence of strata deep within the earth
materi a1 s (Me1 I nikov , 1967) ;
3) by reduction of heatloss during phase transformation in materials saturated with highly mineralized water.
Freeconvection. According to we1 1 known concepts(Tolsti khin, 1941),there are two subrones inthe vertical section of thepermafrost: permafrostformed during the freezing of fresh and salinegroundwater; and highlymineralized subzero groundwater(kriopegs) . By directobservation and generalizationof data on temperaturesand mineralization of kriopegs,the authorestablished the presence, incertain circumstances, of a third intermediate zone, which is comprised of bothice inclusions and kriopegs (Chizhov,1968). Ice formationin the horizon with highly mineralized water is accompaniedby anincrease inconcentration and density of thelatter. Thus, theconvective cooling of materials is indirectlyassociated with the formationof an intermediate subzone, in whichthere isfreezing out and cryogenic concentrating of subsurface solutions.
Forthe purposes of analyticalresearch on the role of free convectionin the formation of the permafrost zoneand thecooling of the lithosphere, we will depict a rock mass inthe fowl of monolithicblocks, divided by verticalfissures containing highly mineralized water. Convection currentscould only occur inthe fissures; they would not be present in the weaklymineralized blocks. An indicator of thethermal effect of convection is the change in effective conductivity of a liquid h3 and the coefficient of 3 convection = X /X, where h theis true coefficient of thermal conductivity of the liquid. - 139 -
From thetheory of heat exchange(Lykov, 1972), it followsthat 'k = f (GrPr) , where Qr = g6at13/v2(Grashof's criteria), Pr = V/a (Prandtl'scriteria) , where g is theacceleration due togravity, 1 is the distance between thewalls ofthe fissures, At isthe difference in temperaturesbetween the lower and upper 1 imi ts ofthe 1ayer being researched, v isthe kinematic viscosity, a isthe coefficient of thermal diffusity, and 13 is thecoefficient of volume expansion of theliquid. In connectionwith the freezing solutions of electrolytes, a value is determined according to therelationship between thetemperature ofthe freezing solution and itsdensity (the latter is a functionof the concentration). For a sodium chloridesolution in the diapazone of subzero temperatures (actualtemperatures for underground kriopegs), the value f3 is equal to 9.7 x
Freeconvection in a fissure takes place when GrPr > 1000and when lo3 < GrPr < IO6 Ek = 0.105(GrPr)0'3(Lykov, 1972). AS indicated by the calculations,for a fissure 0.5 cm wide,the effective thermal conductivity of the highly mineralized waters in the fissure will beapproximately 4 times greater than the molecular thermal conductivity (ck s;5 4).
The root mean squarevalue of thethermal conductivity of the rock mass can be found from theexpression: heM = heN + X (1 - N) , where X is P P thethermal conductivity of therock, N is thevoid coefficient of the fissure,which is equal to therelationship of thearea of the fissure and thearea of therock mass. Obviously,the cooling influence of free convection will increasewith the size of the fissure, the void coefficient of thefissure, and the ratio of he to h The most favourablyconditions P' arefound in carbonaceous rock masses where the fissures havebeen widenedby karstprocesses.
Calculations show thatconvection currents which form during freezing out ofhighly mineralized water further appreciably the cooling of thelithosphere for a fissurewidth of 0.8 to 1 or more centimetresand a coefficient of thefissured state of no lessthan 5%. Under fieldconditions of freezing, due toperiodic changes in surfacetemperatures, the thickness ofthe permafrost zone withregard to thisfactor canexceed the"normal" - 140 - value by1.3 to 1.5,and inthe thick areas of faults with a fissure gap of 1 .5 to 2 cm, it canbe twice as much. There isvirtually no possibility of freeconvection currents occurring in fissuredrocks saturated with highly mineralizedwater due to temperature gradient only, without the participation of cryogenicconcentration.
Reduction of heat loss during the freezing of water in rocks saturatedwith highly mineralized water. The influence of heatfrom the formation of ice at the depth where rock freezes under conditions of periodic fluctuationsin surface temperatures hasbeen researchedby V.A. Kudryavtsev and V.G. Melamed (1966). It was shown that a reductionin the latent heat of phase transitionduring the freezing of 1 m 3 of rock Q, leadsto an increase in thedepth of perennialfreezing; this will, more orless, be thevalue of thegeothermal gradient. A fourfoldreduction Q, in rock with highly mineral ized water leads to an approximate twofold increase in depth of the Oo geoisotherm when thegecthermal gradient is zero and at most 30, and10% when thegeothermal gradient is 0.01 and 0.02 deg/m.
There is a complex relationship between theinfluence of free convectionand the reduction Q, on thedepth of thepermafrost zone. When there is no iceformation, which happens when thetemperature of therocks is higherthan the freezing point of thesolution, free convection does not occurand the geothermic gradient isclose to normal: 0.2 deg/m for the sedimentarycover of the RussianPlatform and 0.034 deg/m in the Epihercinian folds. When there is freezing of kriopegs,development offree convection involves a decrease in the geothermalgradient and consequently an increase in the effect of the reduction Q, at the depth of cooling in the lithosphere. Abnormally low values for thegeothermal gradient inthe zone ofkriopeg development (0.01 to 0.005 dge/m and less) is supportedby observation in the field. When bothfactors are active, this can lead to the permafrost depth increasing 2 to 2.5 times, and, in veryfavourabl e conditions, 3 times.
Forcedconvection. The coolinginfluence brought about by the movement of kriopegs when strata deep inthe 1 ithospheresink is relatively negligible.This is due tothe extremely slow filtration and thedip of the strata which, inthe sedimentarycover of theplatform, are measured in - 141- fractions of a degree. Rough estimates of thehydrothemic effect of kriopeg filtration in a homogeneous stratumunder the conditions of the platform, by the method of G.A. Cheremenskii(1972), show that a change in the geothermal gradientsubject to this factor is less than 10%.
As withtheperennial freezing of rockscontaining fresh groundwater,the formation of kriopegs is mainly associated with the periodic fluctuationsof temperatures at theearth's surface, and, lessfrequently, withsporadic changes, as for example, inthe case of marineregression. A locationclose to the occurrence of highly mineralized groundwater furthers deep cooling of thelithosphere. In this case, if onaccount ofspecific thermodynamic conditions no intermediate subzoneforms, the cooling effect is reducedconsiderably. When an intermediatesubrone is present,the temperature fluctuations within it intensify the convective heat exchangeand this leads to kriopegspenetrating deep into the rock.
The formation of a thickkriopeg zonecan impede the upward movement of subsurfacebrines towards the surface from the deep, warmed horizons. Thus, at theboundary of thesouthern slope theof Anabar anticlinewith the Angara-Lena Depression, a sharpincrease in depth of occurrenceof the base of thekriopegs of from 500-600 m to 100-150 m canbe observed; thisis associated with the upward movement ofthe groundwater through the fissure zones deep belowthe Angara-Lena Depression. A reduction in thethickness of the kriopegs also results from theactivation of water exchange underthe effect of positiveneotectonic movements whichare accompanied by a deepening of thetrench. In the basin of theRiver Vilyui (Botuobinskoe Uplift) the filtration speeds ofthe kriopegs, according to the data of V.E. Afanasenkoand theauthor, attain 30-60 cm/yr.There is a noticeablereduction in the depth of occurrence of thelower limit nearthe drainagepoints at 100-200 m. The influence of theneotectonic uplifts withinthe water area of theArctic Ocean is of a differentcharacter: the sharpreduction in surfacetemperature as water emerges frombelow sea 1 eve1 cause intense freezing of rocks and formation of kriopegs.
Greatnegative geothermal anomalies of the earth'scrust, the study of whichpresents an importantgeophysical, geological and geothermic problem,are associated with kriopegs. Some aspects of theproblem havebeen - 142 - dealtwith in this paper. It must be emphasized thatdischarge and hot springscaused by specificreactions (including formation and destruction of crystallinehydrates ofunderground gases), can also display this same influence on thethickness and the temperature regime of the zone of highly mineral izwl gv*cundwater.
REFERENCES
1. EFIMOV, A.I. Temperaturamnogoletnemerzlykh porod v okrestnostyakh g. Mirnogo. (Temperature of permafrost in the vicinity of the town of Mirnyi). In the book: Sovremennye voprosy regional'noi geokriologii (merzloto- vedeniya).(Current questions on regional and engineeringgeocryology (Permafrost)). M., "Nauka", pp. 63-83, 1964.
2. KUDRYAVTSEV, V.I. and MELAMED, V.G. Formularascheta glubin mno oletnego promerzaniya i ottaivaniyatolshch gornykh porod. (Fornlu 9 a fcr calculatingdepths of perennialfreezing andthawin of permafrost). - In the book: Mertlotnyeissledovaniya, vyp. 6. 7 Permafrost Research, No. 6). Izd-vo MGU, pp. 10-14, 1966. 3. KLIMOVSKII, I.V. and USTINOVA, Z.G. Ob osobennostyakhtemperaturnogo rezhima mnogoletnemerzlykh porod raiona kimberl itovoi trubki Udachnaya. (Peculiarities of the temperature reglon of the permafrost in the Udachnaya Kimberl ite Pipe). In the book: Mnogoletnemerzlyeporody i soputstvuyushchie im yavleniya na territorii Yakutskoi ASSR. (Permafrost and its accompanying phenomena in theYakut A.S.S.R.). M., Izd-vo AN SSSR pp. 96-106,1962.
4. LYKOV, A.V. Teplomassoobrnen. (HeatmassExchange). "Energiya", p. 560, 1972.
5. MEL'NIKOV, P.I. Vliyanie podzemnykh vodna glubokoe okhlazhdenie zonyzemnoi kory.(Influence of groundwateron the deep coolingof the upper zone of theEarth's crust). - Inthe book: Merzlotno-gidrologicheskie i gidrogeotermicheskieissledovaniya na Vostoke SSSR. (Permafrost- hydrogeologicaland hydrogeothermal Research in the East of the U.S.S.R.). "Nau ka"pp. 24-29, 1967
6. CHEREMENSKII, G.A. Geotemiya.(Geothermal studies). I. , "Nedra",p. 271 , 1972. 7. CHIZHOV, A.B. Orolivzaimodeistviya mnogoletnemerzlykh porod i podzemnykh vod v formirovanii merzlotno-gidrologicheskikh uslovii (naprimere Zapadnoi Yakutii).Role of theinteraction of permafrostand groundwater in theformation of permafrost-hydrogeologicalconditions (using the example of Western Yakutia). - Inthe book:Merzlotnye issledivaniya, vyp. 8. (PermafrostResearch, No. 8). Izd-vo MGU pp. 11 1-122,1968. 8. SHVETSOV, P.F. K voprosu o svyazitemperatury i moshchnostivechnoi merzloty s geologicheskimi i gidrogeologicheskirnifaktorami. (The connectionbetween temperatureand thickness of permafrostand the geological and hydro- geologicalfactors). Izv. AN SSSR. Ser.geolog., No. 2, pp. 114-124,1941.
9. TOLSTIKHIN, N.I. Podzmnyevody merzloi zony 1 itosfery. (Groundwater of the permafrost zone of the 1 ithosphere) M. -L. Gosgeol izdat.p. 201 , 1941. - 143 -
EXPERIMENTAL INVESTIGATION OF HEAT ANDMOISTURE TRANSFER DURING SUBLIMATION- DESUBLIMATION OF WATER IN FINE-GRAINED SOILS
E.D. Ershov, V.V. Gurov, I.A. Komarov and E.Z. Kuchukov Moscow State University, U.S.S.R.
The problem of the sublimation of ice in fine-grained soils and the desublimation of water vapour on subsoil surfaces involvesa complex set of processes and phenomena such as the phase transformation of moisture and its transfer to frozen subsoils, the heat and moisture exchange of the subsoil with the surrounding vapour-gas medium, the structural-mechanical and rheologicaltransformation of thesubsoils in thecourse of their freeze-drying and wetting, etc. On the one hand this results in a definite scientific and practical interest in the study of the problem; on the other hand it produces familiar methodological and technical difficulties in the setting-up and conducting of experimental investigations.
On the scientific plane, a study of the processes of sublimation and desublimation of the moisture in fine-grained soils is neededin order to explain the mechanismof the phase conversions from iceto vapour to ice, the characteristics of the external and internal heat exchangesin frozen soi Is, and in order to develop a methodologyfor investigating the processesof heat and moisture transfer that complicate the phase transformations of water, etc. The process of sub1irnation of ice is notonly a subject of investigation, but constitutes a universal method of studying the structure and properties of ice, frozen soils and capillary-porous bodies. ' The processes of freeze-drying of subsoils and the crystallization of water vapour on subsoil surfaces acquire considerable current importance also for practicaltasks in connectionwith the planning, construction and exploitation of large underground engineering worksfor various purposes, the walls of which are madeup of frozen, fine-grained soils. An account of the
Proceedings Third International Conference on Permafrost, Vol. 1, pp. 169 - 173, 1978. - 144 - processesof heat and moisturetransfer during thesublimation and desublimation of moisture infine-grained soils isalso needed for the quantitativeappraisal and prognostication of thethicknesses and extents of glaciers and of annual fields of icing,the sealed-in humidity regime of soils,subsoi 1s and roadsurfaces, and forsolving a number of problems in permafrostscience, climatology, etc.
APPARATUS AND METHODOLOGY OF INVESTIGATION
In 1970,complex experimentalinvestigations of the processes of sublimation and desublimation of moisture in fine-grained soils were begun in thePermafrost Studies Department of Closcow StateUniversity under the guidanceof Professor V.A. Kudryavtsev,and have continuedinto the present year.
Forstudying the processes of heat and moisturetransfer in fine-grainedsoils on thesublimation of ice two laboratoryset-ups were designed. The mainparts of these are an airthermostat operating in the negativerange of temperatures, a sublimation chamber with specimens ofthe soilsunder investigation, an electricfan, and a blockunit for registering and controlling the operatingregime of the apparatus. The novelty of the apparatusesconsists inthe fact that in one of them thesublimation of the ice is realizedin the atmospheric medium at atmosphericpressure, while the secondone permitsinvestigation of theinfluence of highpressure and high molecularweight of gaseson the process of icesublimation in fine-grained soils. The sublimation chamber of thelatter equipmentconsists of a thick-walled,cylindrical vessel fitted with a system forfeeding in cold-compressedgases.
The soil specimenswere either cy1 indricalrectangularor parallelepipeds 8 to 10 cm highwith cross-sectional areas of 12 - 15 cmZ. The temperatureprofile at the soil sampling level was measured withthe aid of copper-constantanthermocouples, the working junctlons of whichwere placed at regularintervals of 1 cm alongthe vertical axis of symmetry of thecontrol specimens. The lateralsurface and lower base of each subsoil specimen was sealedoff hermetically by means of transparentcassettes - 145 -
(polyethyleneor organic glass), and evaporation of thesubsoil moisture took placethrough the open upperbases. Inthis way uniforni measurementand visualization of theprocess of freeze-drying of the subsoils wereachieved.
Investigation of the mechanismand regularitiesofthe water vapourdesublimation process at subsoilsurfaces was carriedout in a third apparatus,the basic difference from those described above consisting in the Creating of a controlledgradient of negativetemperatures between the upper and lowersurfaces of soil specimens. The temperatureon the lower base of the specimen was producedand kept constant with the aid of a metallic stamp connected to a supplementary liquidthermostat. The crystallization of water vapours was realizedin the atmospheric medium at atmosphericpressure. The height of thesoil specimen was 3 cm.
Each apparatusconstituted a closed,thermally insulated system permittingthe conducting of prolongedtests at temperatures T = 253 - 273'K, at air (gas)flow velocities over the soil specimens of V = 0 - 20 m/sec,and atrelative humidities of 4 = 50 - 95%. The creation of a uniform T, V, 9 profilein specimensimmersed flowingin air was realizedtheby hydrodynamicair-flow stabilization section. The T, V, $ controlaccuracies of theequipment were O.l°K; 0.1m/sec and 1%, respectively.
The main unknown characteristics of theprocesses being studied arethe intensity of sublimation and desublimation(density of flow of water vapourevaporating condensingor onthe open surfaces of thesubsoil specimens) , therate of descent of the drying zoneand thegrowth of the crystallizing snow layer,the temperature and moisture profile in the subsoil specimensand their measurement as a function of timeand ofthe constitution,structure and properties of thesubsoils. The methodology of preparingsubsoil specimens, and of conductingexperiments and processing the experimentaldata, the description and diagrams of apparatus, as well as the composition,structure and properties of thefine-grained soils under investigationare given elsewhere (Ershov, Gurov,1972; Ershov et a1 ., 1975). - 146 -
HEAT AND MOISTURE TRANSFER DURING SUBLIMATION OF ICE IN FINE-GRAINED SOILS
The mechanism offreeze-drying of fine-grainedsoils is directly associatedwith the phase transformationsof moisture assuch and withthe transfer of heat and moisture in subsoils.According tothe hypothesis formulatedelsewhere (Ershov, Gurov,1972; Ershov et a1 .* 1973), the sublimationofice infine-grained soils isnot only and notjust a transformationof moisture from the solid to the gaseous state,but also involvesthe evaporation of unfrozen water with continuous replenishing of its supplies at the expense ofthe ice, with which unfrozen water in the soil pores is present in a state of dynamic equilibriumin the soil pores at a giventemperature and pressure. theIn works referredto, it was demonstratedthat inthe generalcase the sublimation intensity of ice (Is) in dispersedsoils is determined by two components - themoisture flows in the gaseous (Iv)and in the 1 iquid phase (I,) :
In coarse-grainedsoils however, the secondcomponent practicallyis non-existent.Inequation (1) Kv and $ arevapour diffusion and liquid waterdiffusion coefficients, respectively, R isthe gas constant, P the watervapour pressure, W thesubsoil moisture per unit weight, yo theweight of the SUbsQil skeletoq per unit volume.
The mechanism ofmigration ofunfrozen water and vapourof transferis determined by the thermodynamic conditions of interaction between thesoil and surrounding medium, thecharacter and energy of thebonding of moisturewith the mineralskeleton of thesubsoil and thecharacteristics of itsstructure. It must be emphasized that a transfer of water inthe liquid phase in the zone ofdrying of very fine-grained subsoils is greater in the region of intensive phase transformations,i.e., atrelatively high negative temperatures. At lowtemperatures (T < 260°K) and in coarse-grainedsubsoils the amount of unfrozenwater is negligible and thesublimation intensity of theice is determined by diffusevapour transfer, to whichthere isless - 147 -
resistencein coarse-grained (aranaceous) than in fine-grained (clayey) ones. According to our figures, at T = 268'K and at atmosphericpressure in gravels of variousfractions Kv = (7 - 11) lom6m2 s and inthe clays of 2 2 Kv = (2 - 4) lom6m /s and inthe clays of K, = (2 - 4) lom6m /s,
I$ = (2 - 4.5) 4 10-1 m2/s. When thetemperature increases and the external pressuredecreases, Kv increases, and $ increaseswith increasing T and W of thesubsoils. Ey virtue of therelatively small moisture andheat transfer coefficientswith the subsoil compared withthe corresponding external exchange coefficients,theintensity of thefreeze-drying process is restricted by theinternal heat and moisturetransfer. Here the transfer of moistureplays a determining and limitingrole in the transfer processes, sincewith the inputof heat by conduction and convectionto the zone of phasetransformations, the diffusionresistance to moisture transfer in both phases is considerablygreather than the equivalent thermal resistance. Sincethefreeze-drying notis intense (Ershov, Gurov,1972) and the temperaturegradient occurring in the subsoil is small (&5OK/m), it may be assumed infirst approximationthat the process of icesublimation in fine-grainedsubsoils takes place under quasi-isometric conditions. This greatlysimplifies the solution to the problem of heat and moisturetransfer duringthe freeze-drying of rocks, since the moisture transfer problem can be formulated and solvedindependently of theheat transfer problem.
Regularitiesheatof transfer in subsoils.Since both the absolutevalues andgradientsthe temperatureof involved in the freeze-drying of subsoilsare negligible, we neglectthe exchange of heat in thesubsoil pores byradiation and convection, in comparisonwith heat transferbythermal conduction. Experimental data from the study ofthe dynamics of the temperature field in subsoils have shown that the profiles of temperaturesof dried and frozenlayers (unaffected by the process of ice sublimation)are almost linear. At themobile boundary separating the subsoillayers (in the zone ofmoisture phase transformations)they lose the salientpoint producedby thedifference of thernlophysicalcharacteristics of the subsoil , and also by thepresence here of the flow of heat. Inthis case theheat balance equation at the mobileboundary can be writtenin the followingform: where X hf arecoefficients of heatconductivity of the subsoil in dry and dr a frozenlayersS respectively, and r is thelatent heat of sublimationof ice.
Analysis of theexperimental data has shown thatthe intensity of theflow of heat inthe frozen layer qfdecreases inthe course of time, whilein the dried layer qdr it remainspractically constant. The constant character of qdr leadstothe conclusion that inthe process of ice sublimation, it followsfrom equation (2) thatthe value of qf is determined and limited by the intensity of icesublimation (the change of r(T) inthe temperatureinterval under consideration can be neglected).
When therate of flow of air was increased,the values of qf and qdr increasedat a fasterrate (1.5 - 2 times) in therange 2 - 10 m/s, but thedifference betweenthem continuedto correspond to the expenditureof heat in phasetransformations. Lowering the temperature decreases the value ofqf, but the value qdr remains practically constant. For specimens of polymineralclay andloam thedecrease of qf if 10 - 15watts/m when T decreasesfrom 271 to 260°K. The absence of a marked air temperatureeffect on thevalue of qdr and thecoefficient of heat exchange, is apparently associatedwith the negligible change in thermalconductivity and with the viscosity and otherphysical characteristics of the air in the temperature intervalunder investigation. The rateof flow of theair has a substantial effecton the thickness of the boundary layer, leading to a change in the resistenceto heat transfer in it.
Regularities of moisture transfer during the freeze-drying of soils. The characteristics of themoisture profile in fine-grained soils and its dynamicsduring freeze-drying, and also theinfluence of thevelocity, temperature and relativehumidity of the air flowon the intensity of the sublimationof ice in subsoils and themobility of the sublimation zone in themwere reported on atthe I1 InternationalConference onPermafrost (Ershov et a1 ., 1973). In particular, it was shown therethat an increase in the velocity of the air flow of 5 m/s and a reduction in the temperature from 273 to 261°Kshow the greatest effect onthe value of I. In thewetness profileof specimers of moisture-saturatedfine-grained soils of undisturbed and disturbedstructure of massivecryogenic texture, three characteristic - 149 - moisturepoints are noted, Further study of thephysical character of the first twoof these, carriedout on theinitiative of V.A. Kudryavtsev, enabled us to propose a new method of determiningthe quantity of unfrozen water inthe ice of frozen fine-grained soils, basedon the regularities of distribution of thetotal moisture content during sublimation of theice (Kudryavtsev et a1 , 1976). At thepresent time this method, possessing a number of technical andeconomic advantages compared, for example, withthe widelypractised calorimetric method, is beingintroduced into practice in constructionengineering explorations in areaspermafrostof soil distribution,including the Baikal-Amurmainline track.
The investigationof the process of freeze-dryingof rocks and llpurell ice under conditions of high pressure in a gaseous medium of different molecularcomposition was of definiteinterest. Experimental investigations were carriedout with the following iner gases:helium (P = 4) andargon (p = 40)and with air (p = 29). The choiceof these as working gases was due firstto the fact that the studied range of variations of theirmolecular weights embraced themost widespread natural gases: methane (P = 16),ethane (p = 30) andpropane (11 = 44), and secondlythat they are safe to handle underlaboratory conditions. A study of theeffect of pressure of a gaseous medium on theintensity of sublimation of ice in subsoils was carriedout over a range of pressures from atmospheric to 12 1052 N/m (Figure 1 ) .
Figure 1
Intensity of icesublimation in fine-grained soils as a functionof themolecular composition and pressure of the gaseous medium. 1 - ice; 2 - polymineral clay; 3 - kaoliniteclay; 4 - loam. - 150 -
Analysis of equation(1) shows thatwith increasing pressure the freepath length of the vapour molecules decreases with increasing pressure and hinderstheir diffusion, leading to a decrease inthe value of I,. The effect of u isalso associated with a change in thecoefficient of vapour diffusion D, thevalue of which is 9.4 . loh5 in a heliumatmosphere, -5 2 2.2 1 lom5inair and 2.1 - 10 rn /s in argon. The molecularcomposition of the gas does notappear to have ar?y effect on moisturetransfer in the liquid phase.This isconfirmed indirectly bythe disproportionate change in the relationship between thevalues K, and Is inthe helium andargon atmospheres for the finer-grainedsubsoils - clays(Figure l),in whichthe share of the migrationof unfrozen water attains considerable values.
The effectof the granulometric composition on the value of Is becomes apparent intheir specific active surface area, the amount of unfrozenwater, the mean effectiveradius ofthe pores and theactive porosity, and in the case of the arenaceous soils, mainly in the porosity and theeffective radius of the pores. The influence of themineral composition is determined by thenature ofthe crystallochemical structure of the argillaceous minerals,
The microaggregatecornpositicn ofrocks in the process of their freeze-drying becomes evident in thenature and extentof the influence of theconstitution of alteredcations and the concentrationof water-dissolved salts in the pore solution on the mobility and quantity of unfrozen water and on thestructure of the pore space.
Withincreasing valency of thealtered cations saturating the montmorilloniteclays, the thickness of the films of unfrozenwater increases as demonstrated inthe work of A. Ananyan (1972), and thisresults in their greatermobility and a highercoefficient of diffusion. On theother hand, owing tovery strong coagulation, there is a sharpdecrease in the fineness of theclays, resulting in an increase of the mean effectiveradius of the pores and of thevapour transfer coefficient. Owing to the exchange of monovalentcations (Na') fordivalent and trivalent ones(Ca2* andFe3*) in montmorilloniteClays, an increase is produced inthe value of I, (Figure2) at the expenseboth of 1" and I,. An investigation of thesublimation of ice - 151 - inkaolinite clays saturatedwith the same cationsas the montmorillonite claysdid not show any regularinfluence of the valency of cations on the value of I,. The intensityofice sublimation insoils with different concentrationsof pore solution bears an extreme character. With increasing concentrationof the poresolution up to thethreshold ofaggregation (coagulation) it decreases,reaches a minimum and after the aggregation thresholdincreases again (Figure 2), which is due to thecorresponding change in thecoefficient \ (Ershov et al., 1975).
Figure 2
lo 01 1 " 2bo 4b0 6th 800 T,ll Effect of the composition of exchange cations and concentration of pore solution on the intensity of icesublimation in fine-grained soils. 1 - 3 - montmorilloniteclays saturated with different exchangecations; 4 - 6 - kaoliniteclays saturated with different exchange cations; 7 - 10 - polymineral clay prepared in CaCl solutions of variousconcentrations.
The sublimationof ice insoils with a differentdegree of occupation of pores by moisture (q < 1, q = 1) leads to a specificdifference inthe character of themoisture profile during freeze-drying. The above contemplatedregularities of mo7stl;rc transferduring the freeze-drying of fine-grainedsoils were obtained for c1 = 1, whichguarantees practically frontaldrying of thesoil strata. For q c 1 theprocess of freeze-drying has a spatialcharacter, i.e., the moisture profile possesses a dryingzone - 152 - of substantialsize and (this is sharplyexpresses for q = 1) thereare no areas of large and small moisturegradients on it, while for q < 0.7 the boundary separatingthe dried layers of subsoil from thoseunaffected by the process of sublimation of ice is generallyabsent. This difference in the nature of the development of theprocess of freeze-drying causes a decrease in thevalue Of Is inmoisture-unsaturated frozen soils compared with moisture-saturatedones. This is confirmed by data on thesublimation of ice in specimens of clay and sand with differentlevels of poreoccupation by unfrozenwater and ice.
A study of theinfluence of the inhomogeneity of fine-grained soilsresulting from thealternation of layersofsoil differing in granulometry and mineralogicalcomposition, density and moisturecontent on the development of theprocess of theirfreeze-drying has shown that, firstly,the value Of Is in these is determined and restricted by the intensity of sublimation in thelayer characterized by a decreasedcontent of unfrozenwater and, secondly, the distribution of the moisture in thedried tone of thestratified subsoil has a spasmodic character.
The study of regularities of sublimationice in the above-considered specimens of disturbedtexture, structure and properties permittedthe formulation of a satisfactoryexplanation of the process of freeze-drying of fine-grainedsoils of undisturbed texture and of various origin and age. The study of the processes ofheat and moisturetransfer was carriedout on monoliths of fivegenetic complexes, namely alluvial,scree, lacustrine-alluvial , glacial-marine and marine, the description and characteristics of which were ~ivenelsewhere (Ershov etal. 9 1975). From the analysis of theexperimental data it was established that theeffect of the age of soilsis expressedin their sclidity, while the effect of their origir: is expressed in the concentration cf pore solution. In younger soils (Upper Quaternary)the intensity of ice sub1 imation, owing togreater porosity , appeared greater than in ancientsoils (Neogene) e The process of ice sublimation in a givengranulometric variety of soils proceeds less intensively in mrinedeposits than incontinental deposits; the more fine-grainedthe subsoil, the greater this difference. - 153 -
HEAT AND MOISTURETRANSFER IN THE COURSE OF VAPOUR DESUBLIMATION IN SOILS
Unlikethe process of icesublimation, the kinetics of which are determined by theresistance to thetransfer of moisture,the intensity of desublimation Idof watervapours on the surface of Soilsis determined by the exchange ofheat between thevapour-air medium and thesoil, i,e., it is limitedby the thermal-physical properties of theinteracting mediaand the 1 ayer of snow that forms. The crystal1ization of watervapour molecules on thesurface of frozen soils takes place when saturationvapour pressure is reached at theair-subsoil interface at a giventemperature, PSat(T). PSat(T) decreases withdecreasing temperature, and thisfavours the initiationof water vapour crystal 1 ization.In the laboratory apparatus PSat(T) isattained byincreasing the controlled gradient ofnegative tmperatures between thevapour-air medium and the lowersurface of the Subsoil, the latterbeing the colder.
As investigationscarried out by the replica method*have shown, thesurfaces of veryfine-grained andcoarsely fragmented soils are nonuniformfrom the energy standpoint. The processof desublimation ofthe first ice crystals(in the form of snow) proceedsselectively, becoming localized on thesurfaces of active centres of crystallization, In very fine-grainedsoils these centres,evidently, are complexwater molecules adsorbed on thesoil surface, whereas in coarse-grainedsoils they are variousmacrc- and micro-defects of thesurface (splits, protuberances, etc.). The influenceofthe mineralogical composition of thesoil is revealedin the form, size and orientation of thefirst ice crystals. Thus, on clays of polymineral,kaolinite and montmorillonitecomposition they had theidioformal appearance of hexagonalflakes 0.02 - 0.03 mm insize placed withtheir base surfacesflat against or at a slightangle to the surface. Inquartz, most of the ice crystals are isometricflakes of C.01 - 0.02 mm in Size, while in calcitethey are long "needles" sometimes growingtogether. The smallestice crystals (1 urn) areattached to surfacesof sericite, while the largest (0.1 - 0.2 mm) are foundon labradorite.
* The investigationsby the replica nlethodwere conducted by V.V. Rogov. - 154 -
After the first crystals of ice had formed, the desublimation of the vapour continued to take place on the ice crystals themsel ves , which united into a dense, flat layer at distancesof 0.2 - 0.4 rnm from the surface of the subsoil, whilethe flat shape of the layerremained constant throughout theentire process. A5 the mass of snow accumulated,a differentiated consolidation of the snow took place in the direction of lower temperatures (on the subsoil side), caused by the action of the vapour pressure gradient in the layer and the intense recrystallization of the snow. Now the large star-shaped and dendritic crystals disintegrated, acquiring a round granular shape. During the initial period the process of thermal metamorphism also proceeded more intensively (Figure 3) on specimens of ice and metal compared with the soi 1 specimens.
Figure 3
Intensity Id of desublimation of vapours, thickness of crystalled layer, Ed) and its density pC in various specimens, as functions of the processing time. 1 - metal , 2 - ice; 3 - sand saturated with water; 4, 5, 6 - polymineral, kaolinite and montmorillonite clays respectively; 7 - sand not saturated with water.
The Valua wf . Id decreases- wtth time and with decreasing temperature gradient between the "core" of the vapour-air current and the lower surface of the sail specimens, and with increasing relative humidity of - 155 -
this current. Given constant parameters of the current (T, V, 9, P) the difference in absolute values of Id for different soils (Figure 3) is due mainly to the difference in the thermal conductivity coefficients of the subsoils, since redistribution of moisture in the moisture-saturated subsoils at the expense of its transfer from the snow layer in the course of the experiments was negligible (about 1% of the overall moisture balance). The value of Id in moisture-saturated soils was considerably higher than in unsaturated ones, and has a tendency to increase with decreasing fineness of the soils. The difference in thickness td of the layer of snow forming in the soils under investigation (Figure 3) was due to a different intensity both of the vapourdesublimation process in soils and of the thermal metamorphism processes of the snow.
The kinetics of the vapour desublimation process in coarse scree (the investigations were carried out on small and medium gravel and small rubble in accordance with V.V. Okhotin's classification) is determined not only by the thermal conductivity of these fragmentary rocks and their contactile thermal conductivity but also by the intensity of the heat transfer processes in the rock stratum. The experimental data show that Id increases with increasing block size for various packings of the fragments in coarse screes.
FORECASTING AND MANAGEMENTOF THE PROCESSES OF SUBLIMATION AND DESUBLIMATION OF MOISTURE
The forecasting and management of the processes of sublimation and desublimation of moisture in fine-grained soils are based on the main methodological ideas on the forecasting of ground freezing and the principles of controllingfreezing processes in the ground (Kudryavtsev, 1961; Kudryavtsev , Ers hov , 1969). In thecourse of this a varied permafrost-engineering-geological survey of the construction area is being carried out side by side with the operation of engineering installations; a forecast of the development of moisturesublimation and desublimation processes is made on the basis of a structural model that takes the geological and thermal-physical situation into account in actual natural conditions;for the optimumfunctioning of an installationunder the - 156 - projectedconditions the measures required to controlthe processes of external and internalheat andmoisture transfer frozenin subsoils, accompaniedby moisture subl imation and desubl imation, are indicated.
Forthe process of icesubl imation infine-grained soils a structuralforecast model is now beingconstruction (Ershov et a1 ., 1974). With itshelp a roughestimate is being made ofthe thickness of the zone that will be driedout in soils of various composition during the period of operationof an engineeringinstallation, which can be as much as 1 m. In theevent of removal of a freeze-driedsoil, the subsoil mass canregress by severalmetres.
The methodology of controllingtheprocesses moistureof sublimation and desublimation subsoilsin hasbeen worked out from investigationsof the partial and generalregularities of theseprocesses, a knowledgeof which enables us tofind the neededmeasures to improveand alterthe fundamentalparameters ofthe processesthat are studied. In this connectionthe current set of methodsbreakdown into twogroups. One of theseinvolves measures fordirecting the change inthe parameters ofthe gaseous medium (T, V, +, p, etc.) and thesurface character of thesubsoil formation. When thesubsoils are covered with coatings of asphalt,latex and hydroparafin,the sublimation iceofthein subsoils practicallyis eliminated. The secondgroup of methods involvesthe various means of controllingthe processes of sublimation and desublimation of moistureby varioustechnological and frozen-soilimprovement measures. For example, previouscompaction and drainage ofsubsoils and theapplication of methods of lubrication,silication, resinification, etc., greatly retard the process ofsublimation and desublimation of themoisture in the subsoil. The process of sublimationcan be intensifiedby the method of saltstabilization of subsoils. The intensity of icesublimation in subsoils can be promotedby applyingpermafrost improvement, creating some type of cryogenictexture, or covering the subsoi 1 surface with a 1ayer of ice.
Obviously, a solutionto the problem of controllingthe processes ofmoisture subl imation and desublimation innatural conditions constitutes part of a coordinated application of bothgroups of methods, promoting a more I - 157 -
effective control of the processes of external and internal heat and-mass transfer in frozen subsoils interacting with the gaseous medium.
In conclusion, we note that a major programne of investigations into the processes of moisture sublimation and desublimation in fine-grained soils, up to and including their forecasting and control, is being carried out in the Permafrost Studies Department of Moscow State University. The results so far obtained are already being applied in the practice of construction-engineering exploration and may be utilized in future for the purpose of forecasting and controlling the investigated processes.
REFERENCES
ANANYAN A.A. Otsenka srednei tolshchiny plenok vody v talykh i merzlykh tonkodispersnykh gornykh porodakh. (Estimate of the mean thickness of water films in unfrozen and frozen, very fine- grained soils). In the book: Svyazannaya voda v dispersnykh sistemakh (Bound water in fine-grained systems), No. 2, Izd-vo MGU, pp. 106-114, 1972. ERSHOV E.D. and GUROV V.V. Massoperenos v protsesse sublimatsii l'da v dispersnykh gruntakh pri vzaimodeistvii ikh s vozdushnym potokorn. (Mass transfer during the process of ice sublimation in fine-grained soils when they interact with a flow of air). In the book: Teplo- i massoperenos (Heat and mass transfer). Vol. 2, Part 2, Minsk, pp. 212-224, 1972. ERSHOV E.D. , GUROV V .V. and DOSTOVALOV B.N. Sub1 imatsiya 1 Ida v dispersnykh gruntakh razl ichnogo kriogennogo stroeniya pri i kh vzaimodeistvii s vozdushnym potokom. (The sublimation of ice in fine-grained subsoils of various cryogenic structurewhile interacting with a flow cf air). I1 International Conference on Permafrost. Reports and communications, No, 4, Yakt. Kh. Izd-vo, pp. 185-188, 1973. ERSHOV E .D. , GUROV V.V., KOMAROV I .A., AKIMOV Yu .P. and KUCHUKOV E.Z. K raschetnoi skheme prognoza morotnogo i ssusheniya dispersnykh gornykh porod. (On a structural model to forecast the freeze-drying of fine-grained soils), In the book: Mertlotnye issledovaniya (Permafrost studies), No. 4, Izd-vo MGU, pp. 222-229, 1974.
ERSHOV E.D. I KUCHKOV E.Z. and KOMAROV I .A. Sublimatsiya 1 Ida v dispersnykh porodakh. (Sublimation of ice in fine-grained soils). Izd-vo MGU, 223 pages 1975. - 158 -
KUDRYAVTSEV V.A. Merzlotnaya s'emba kakosnovnoi vid merzlotnykhissledovannii. (Permafrostsurveying as a basic form of permafrost investigations). Inthe book:Merzlotnye issledovaniya (Permafrost studies), No. 1 Izd-vo MGU, 1961.
KUDRYAVTSEVV.A. and ERSHOV E.D. Klassifikatsionnaya skhema priemov PO naPra- vlennomu itmeneniyumerzlotnykh uslovii . (Classification scheme of methods for controlledchanging of permafrost conditions).In the book: Merzlotnyeissledovaniya (Permafrost studies), No. 9, Izd- VO, MGU, pp. 155-1579 1969.
KUDRYAVTSEV V.A., ERSHOV E.D., GUROV V.V., AKIMOV Yu.P., KOMAROV I.A. and KUCHUKOV E .Z. Sposob opredeleniya kol ichestvaneramerzshei vody i l'da v gornykhporodakh. (Methods of determiningthe amount of unfrozer; water and Ice scNs , fluthorsi statement no, 532044, - ''Eyulleten tzobretentt", No. 38, 1976, - 159 -
WATER MIGRATION,FORMATION OF TEXTURE AND ICE SEGREGATION IN FREEZING AND THAWING CLAYEY SOILS
E.D. Ershov, V.G. Cheverev, Yu.P. Lebedenkoand L.V. Shevchenko Moscow StateUniversity, Faculty of Geology, U.S.S.R.
The problem ofmoisture migration and segregated ice formatiori in Soilsis constantly attracting the attention of large numbers of specialists. Itssolution is of greatpractical and scientificimportance in terms of the refinement of existing systems or alternatively, the orgination of new systems forpredicting the development of heaving and theformation of the cryogenic structuresof both the seasonally frozen layer and the permafrost. In view of thehighly complexnature of this problem, a wholeseries of questionsremain to beanswered. This calls forfurther study. They include, in particular, the mechanism and thelaws governing the transferofmoisture and ice segregation in frozen,freezing and thawingsoils, the distinctive features of thecoagulation, dispersion and textureformation processes, the role of shrinkage,swelling and distension and also thedisjoining action of thin films of water in the formationof cryogenic structures.
Experimentalstudies of these inadequately understood facts of the problemwere conducted in an integrated manner, thatis, in determing the characterof the change in the basicparameters of heat- and mass transfer and theprocess of ground iceformation infreezing orthawing soils. The following weremeasured: thetemperature t, the moisturecontent W, the volumetric mass ofthe soil skeleton ysk, theexternal and internalflows of migratingmoisture, its thermodynamic potention pw and thestressed and strainedstate of thesoil Further,the process leading to segregatedlensed iceformation was continuouslyobserved by means of microscopy,photography and time-lapsecinematography.
ProceedingsThird International Conference on Permafrost, Vol. 1, pp. 175 - 180,1978. - 160 -
AS thesubject of theresearch, saturated soils of varying mineralogical and grain-sizecompositions usedwere (kaolinitic, montmorillonitic and hydromicaceous-montmorillonitic clays,clayey silts and sandy si1ts) theproperties of which had previously been described in sufficientdetail (Ershov et al. 1975).
The experimentsinvolving unidirectional freezing and thawing of finelydispersed soil sampleswere conducted on a specialexperimental unit, usingthe procedure described in papersby Kudryavtsev et a1 ., 1976and Lebedenko, 1976. It is especiallyimportant to note that the freezing of the thawed or the thawing of the frozen samples was only partly accomplished, that is, by not more thanhalf of theirlength, which ranged from 12 to 30 cm in thevarious experiments.
Analysis of theresults of theexperiments, using for this purpose microscopy,photography and cinematrography,conclusively corroborates earlier evidence (Puzakov, 1960; Orlov , 1962) thatthe formation of segregated layers ofice occurs for the most partin the freezing zone of thesoil in the below-freezingtemperature range. The growth of thinice layers at the freezingfront, that is, at the boundarybetween the thawedand thefrozen zones, canhere be regarded as merely a particular coase of icesegregation.
This was used as a basisfor further experimental research directed towards a study of thephysical mechanism, theparameters and the laws governingthe development of themoisture migration process, not only in the thawedzone but more particularlyin the frozen and freezing zones. Of specialinterest here is the character of development of themotive force of the moisture migration in freezing soils.
Inthe initial period of cooling, when allof the soil is still in the thawed (unfrozen)state, potential gradients of themoisture grad vW and a migrationalflow directed towards the coldside of the sample are absent. In some cases an oppositelydirected flow of water is observed,which is indicative of theinconsequential role of thepurely thermal diffusion mechanism of moisturemigration towards the cooling (freezing) front in saturatedsoil. With the appearanceof thefirst ice crystals and the - 161 - originationof below-freezing temperature gradients in the soil, the motive forcesof the moisture migration (grad vw) associatedwith the increase in the unexpended surfaceenergy of themineral skeleton of thesoil during transition of partof the bound waterinto ice begin to be clearlyexhibited. Simultaneously,the occurrence of a stable migrational flow of moisture in the freezing zone is recorded in the experiments(Figure 1). The presence ofgrad vw and themigration of moisture in the freezing zone thusensure the developmentof the potential gradients of themoisture and itsmigration in the thawedzone. This was alsorecorded in theexperiments.
Figure 1 Pws Jlkg
Development with time anddepth of the moisture potentialsin freezing soils. Timefrom beginning of freezing,hours: 1-0; 2-1 ; 3-2; 4-3; 5-5; 6-7; 7-kaoliniticclay; 8-polymineral (hydro- minaceous-montmorillonitic) clay; 9-clayey si1 t; 10-sandy silt; 11-position of freezingfront.
Duringvisual observation of further freezing and segregated ice formation it provedpossible to distinguishclearly three typical zones: I - a thawed zone, I1 - a freezing zone (in whichrapid phasetransformations of moistureoccur, forming crystals and thinlenses of ice), and I11 - a frozen zone (forthe most part with a lensedcryogenic structure, the segregated ice formation in which isrelatively slow). Zones I1 and I11 have a lighter hue thantone I, which is due to thepresence in the latter of a largequantity of liquidmoisture and the absence of ice. The boundarybetween zones I and I1 is thefreezing front, and betweenzones I1 and I11 is the visible boundary of segregatedice formation. - 162 -
The experimentsindicate that in the initial period of freezing the visible boundary of segregatedice formation lags behind the freezing front. Subsequently, as thefreezing process slows and eventually ceases thevisible boundary of lensedice formation is seen to draw closerto the freezing front and ultimatelythe two fronts merge, Here, at thebeginning of freezing the temperatures of thefreezing front t and atthe front of the segregated ice Efr formation t have lowervalues and ttfr > tEsi. &si With further freezing the soiltemperature atthese fronts rises (Figure 2), and segregated ice formation accordingly occurs in a range ofhigher below-freezing temperatures, which on thewhole isin agreement withthe findings of otherauthors (Puzakov, 1960; Orlov, 1962).
Also closelyassociated with the development of thefreezing zone isthe formation (of the experimentallydetermined) motive forces of moisture migrationgrad uw. Thus, duringthe first period of freezing anabrupt increaseoccurs inthe potential gradients in the unfrozen zone of thesoil whichthereafter decrease and atthe final instant offreezing, when degeneration of zone I1 occurs,they drop toalmost zero (Figure 2).
Thus, potentialgradients of moisture originating in the freezing zone arethe cause of moisturemigrating from the unfrozen zone intothe freezing zone. In thegeneral case themigrational flow developing can be separatedinto two components. One of them is causedby the internalmoisture exchangeand dewatering of theunfrozen zone of theground itself, the other byan influxof water from outside, for example, from an aquiferouslayer. The study of the time-related change that occurs in the density of the overall migrationalflow 1, underthe conditions obtaining in both t'openll and llclosedtt systems ofsoils, showed that 1, decreasesasfreezing progresses, in accordancewith the drop in grad uw and grad t (Figure 2). The internal migrational flow of themoisture depends notonly on the freezing regime but also on theshrinkage properties of the soil. It followsfrom the experiments that in accordance withthe higher values of themoisture potentials here the regionsadjacent to the freezing zone dewatermost rapidly. As thedistance fromthe freezing front increases the rate of dewatering (Y, = -%),a1 like I,, decreases in accordance withthe decrease in grad pw (Figure 3). As a result of thedewatering ofthe soil, consolidated regions formed in advance of the - 163 -
Figure 2
2
12
1 6
I
0 1
1
3 2
5 t0C Variation with time in the position of the freezing front; the visible boundary of segregated ice formation; 3) the temperature at the freezingfront t 4) thetemperature of segreated ice fonnatf&'t * 5) themoisture potential gradients in the thawkBi9 zone of the freezing soi 1 ; 6) the density of theinterior migrational flow at the freezing front; 7) thedensity of theexterior migrational flow at the freezing front; 8) the density of the summated migrationalflow at the freezing front. freezingfront. Essentially, these were merely a region of transit moisture migration from deeper layers in which thedensity of the migrationalflow remained constant. Here, althoughthroughout the freezingprocess as a whole thedegree of infilling of the poresof theoriginally saturated soil samples had not changed and was close to unity, thetotal porosity had decreased on account of the consolidation of the ground during its dewatering. - 164 -
Figure 3
I A I
AI llA
The variation in relation to the depthof the freezing saturatedclay of: themoisture potentials LI , the m- efficients of moisture conductivity X , the d8nsity of themigrational flowof moisture I akl the rate of de- watering and ice accumulation aI/ay. - 165 -
increase in the ice content and thickness of the ice lenses in the lower temperature range.
Parallel with this it should be noted that the presence of the aquiferous layer increases pW in the regions of soil adjoining it and, in steepening the potential gradients of the moisture, leads to a growth of the total migrational flow on account of the intensification of the external mass transfer, that is, the increase in the migrational flow entering the freezing ground from the aquiferous layer. The character of the time-related variation in the external, internal and total migrational flows of moisture in the clay is illustrated in Figure 2, from which it follows that after the attainment of maximum values at the end of freezing, the migrational flows of moisture drop to almostzero.
The study of the laws governing the change in the parameters of the moisture migration process in freezing soils in relation to their particle sizes and mineralogical composition showed thatas their particle sizes become smaller the moisture potentials and their gradients increase, while the coefficients of moisture conductivity hw decrease. Thus, in the actual experiments, from clays to sandy silts hw increased from 1.05 x loc8 to 4.1 x lom8 cm/sec. The significant decrease in the gradients in the series clay-clayey silt-sandy silt leads to a decrease in the magnitudes of the 2 moisture flows and ice formation (in clay Iw = 7.3 x lom6 g/cm sec, in clayey 2 2 silt it is 7.0 x lom7 g/cm sec, and in sandy silt it is 3.0 x g/cm sec). Further, in the clays and the clayey silts the major role in the moisture transfer process is played by internal moisture exchange on account of the greater capacity for shrinkage; in the sandy silts, external moisture exchange -6 2 has themajor role (in clay Iext = 3.0 x 10 g/cm secand 2 2 = 5.3 x g/cm sec; in clayey silt IeXt = 0.08 x lom6 g/cm sec and Ii nt 2 Iint = 1.8 x lom6 g/cm sec; in sandysilt Iext = 0.07 x g/cm2 and Iint 0.01 x g/crn2sec). In soils that vary in their mineralogical composition the total migrational flow of moisture has lower values (in an montmorillonitic clays, however, the internal migrational flow of moisture usually predominates (by one to two orders) on account of the lower - 166 - coefficients of permeability and the greater capacity for shrinkage during dewatering of the unfrozen tone. Conversely, in kaolinitic clay, the external migrational flow is substantially greater than the internal (Iext = 9.1 x 10-6 2 and Ii nt = 2.9 x g/cm sec) .
The above discussed results of the experimental study of the freezing process were concerned for the most part merely with the necessary conditionfor ice lens formation, that is, heat- and mass exchange. Nevertheless, as Indicated by the analysis of the experimental results, there still exists an adequate physical-mechanical condition for the fomation of thin layers of ice (Kudryavtsev et al., 1974, 1976). Accordingly it is necessary to dwell in greater detail on the texture formation process, on shrinkage, swelling and the stressed-strained state offreezing soils.
Each of the three zones distinguished in the freezing soils, as indicated by their study with the scanning electronmicroscope, is characterised by a specific pattern of development with respectto the texture formation process. Due to the transfer of moisture into the freezing zone, shrinkage of the thawed zone (I) is accompanied by an orientation of the particles along the migrational flow, their convergence and the fornation of microaggregates,which is confirmed by a change in themicroaggregate composition (Ershov et al., 1977). The mass by volume of the soil skeleton of the thawed zone usual ly increases by 0,l to 0.3 x l O3 kg/m3 and thereby reaches the shrinkage 1 imit, which was also noted previously (Fedosov, 1935, Ershov et al., 1976). The study of soils of differing composition and structure showed that shrinkage strafn builds up with an increase in the particle sizes and porosity of the soil, and also with an increase in the relative content of minerals of the montmorillonitegroup. It was established experimentally that the rate of freezing also influences the value of the shrinkage strains. The lower therate of freezingthe greater the dessication, the consolidation and the shrinkage strain (Figure 4).
The magnitude of the shrinkage h shr in freezing soils can be very considerable and in some cases even comparable to the thickness of the thin layers of ice undergoing formation. When calculating the heaving magnitude he it is therefore necessary to take into consideration the shrinkage strain. - 167 -
Inthe general form this can be written:
where h isthe total thickness of the thinlayers icein the strained tsi of state (Kudryavtsev et a1 ., 1974).
Figure 4
I I h*lO:M
Variation in (a) themoisture content and (b) thedensity of kaolinitic clay according to (c)the depth and nature of displacement of the strain gauges placed in it. 1 and 2 - rat of freezing of the clay 2.1 x 10 m/sec and 0.57 x 105 m/sec respectively; 3 - freezing front; 4 - position of the strain gauge.
It isin the freezing zone (11), where theprincipal role in textureformation is playedby migrating moisture and thecrystals of ice forming in largepores, that the swelling and distensionprocesses take place. The action of the swelling and distension forces results in a rearrangement of thetexture of themineral skeleton that beenhas forming at the above-freezingtemperature. In this zone a partialfragmentation of the previouslydeveloped microaggregates occurs. The microblocks are turned - 168 - around, disturbingthe established orientation. As a rule the smallest of the particles form a "jacket" around the microblocks.
In the frozen zone (111) of the soil a further rearrangement of the texture occurs. The crystals of ice forming in the minutepores apparently cause splitting of the microblocks and microaggregatesobserved in the freezing zone. The orientation of the microaggregates which is typical of the unfrozenzone disappears. According to the results of the microaggregate analysis, in the frozen zone of thesoil there is an increase in thecontent of particles and microaggregates of the very finefraction (Ershov et a1 ., 1977).
The migration of moisture from the thawed into the frozen zone, the dewatering of the sail below the freezing front and the ice segregation in the freezing zone 1 ead to the development of a field of volume- and gradient stresses in the finelyparticulate freezing soils. Furthermore, in the freezing zone, non-uniform swelling and distensionstrains develop and corresponding to them, swelling stresses Psw and distensionstresses Pd, and in the thawedzone - non-uniform shrinkage strains and stresses PShr. The interaction between the forces acting in differentdirections in freezing soils results in the origination of the following shear stresses Psh:
and the following normal (perpendicular to thefreetlng front) tensile stresses Pt:
Pt = 's 's hr + Pd)
As is we1 1 known, the presence of stresses leads to the formation in the soil of zones of stress "concentrations1' at places where thetexture bonds are weakened. In freezingsoils the boundaries of the microaggregates that had developed as a result of texture formation during shrinkage will be zones of stress "concentrations". Furthermore, the shear stresses will favour the development of horizontal (or near horizontal) stress concentration tones and - 169 - thetensile stresses wi11 favour the development of vertical zones. It is towardthese zones (horizontal , verticalor inclined), the water in which is subject to tensilestress, that the migrational flow ofmoisture will be directedunder the influence of the Pt and PSh gradients. If themagnitude of thestresses developing inthe freezing soil is sufficient to overcome the localtextural cohesiveness of the soil PCoheI?, thenucleation mustthen occur
of horizontalice lenses in accordance with the condition: +
'shr 'sw ' 'coh-a + 'tr and of vertical ice lenses in accordance withthe condition:
Pn = P shr - 'sw ' 'c0h.a ' 'tr where Ptr is the externalpressure (including the true pressure according to thealtitude of the freezing soil). The findings of D.S. Goryacheva indicate that theswelling pressure is associated by a rectilinear dependence withthe weightbyvolume ofthe soil and itsmoisture content and rangesfrom 0.2 x 105H/m2 at a soildensity of 1.2 x lo3 kg/m3 to 1 .lo5 H/m2 at a soil density of 1.45 x lo3 kg/m3.
Experimentalstudies have shown thatin freezing soils, depending on theircomposition, structure and properties, and alsoon the conditions of freezing, the magnitude of thenormal tensile stresses Pt canrange from 0 to 0.2 x 1O5 H/m2 to 2 x lo5 H/m2. Based on themagnitude of therecorded values Of Pt, freezingsoils canbe arranged inthe following series: clay > clayey silt > sandy silt. Thus, for example, duringfreezing under identical conditionsthe following Pt magnitudeswere recorded: inkaolinitic clay, 2 0.80 x 1052 H/m in polymineralclay, 0.60 x lo5 H/m , and in finely particulateclayey silt, 0.56 x IO5 H/m2. Duringthe development of normal tensilestresses the original microstructure and mineralogicalcomposition of thesoils ha5 a highervalues. If thesoil structure consists of microblocks then, as a rule,the instrument readings of Pt are of smallermagnitude as shrinkagestrain occurs along theblocks. Samples of bentoniticand polymineralclays afford a vivid example of this, - 170 -
Fiqure 5
I
strain
Variation (a) with time and (b) with depth, of the volume and gradient stresses (1,2,3,4) and the moisture content (1 '# 3' , 4'); (c) character of tge cryogenic structuges. Time, secs; l,l' - 33 x 3.6 x 10 ; 2 - 45 ~~3.6x 10 ; 3,3' - 60 x 3.6 x 10 ; 4,4' - 80 x 3.6 x 10 ; 5 - visible boundary of segregated ice formation; 6 - freezing front; 7 - rate of freezing, cm/hr, - 171 -
Inthe same soil a regularincrease in the normal tensilestresses is observedwith a decrease in therate of freezing andan increase in the degree of dewatering. Inkaolinitic clay, for example, with a decrease in the rate of freezingfrom 0.3 to 0.03 cm/hr the normal tensilestresses increased from 0.4 x IO5 to 1.5 x lo5 H/m2. Here themoisture content of thesoil had alteredby 20% (Figure 5). Inthe frozen and freezingtones of the sample horizontalice lenses had formed, sincethe Pt magnitudesthat had caused them to develop were insufficient to overcome thelocal structural cohesiveness of thesoil inthe vertical direction. Thus, with a freezingrate inthe kaoliniticclay of 0.2 cm/hr (W init = 50%, Ysh = 1.20 X lo3kg/m3) in the temperaturerange corresponding toice lens segregation, normal tensile 2 stresses of Pt = 0.7 x lo5 H/m were recorded. At thisinstant the swelling stresscorresponding to thesoil density (ysh = 1.32 x lo3 kg/m3) is 0.65 x 105 H/m2, and thelocal structural cohesiveness of the soil (according to laboratory determinations of these conditions) Pcohma = 1.5 x 1052 H/m . In accordancewith condition (2) Pshr = 0.7 x + 0.65 x 105 = 1.35 x IO52 H/m . In accordance withcondition (1) theshear stresses can then be written as 2 's h = 1.35 x lo5 + 0.6 x lo5 = 2.0 x IO H/m . Consequently, inthe experimentwhich hasbeen discussedthe formation of onlyhorizontal ice lensesshould havebeen and was infact observed. The formation of vertical 2 lensescould not haveoccured, as Pt = 0.7 x lo5 H/m and would havebeen unable to overcome thelocal structural cohesiveness (P,oh.a = 1.5 x IO5 H/m2) . The frequency of theice lenses in the freezing zone is predetermined by thegradient of thestresses developing inthe soils. As the experimental studies showed, as therate of freezingdecreases the volume-and gradient stressesincrease although their gradients decrease (Figure 6) , whichalso predeterminesthe more sparsearrangement ofthe ice lenses in the developing cryogenicstructure.
The exampleprovides striking evidence that the formation of a particulartype of cryogenicstructure when thethermal condtion is met is predeterminedby the physico-mechanicalprocesses developing during freezing of the soils.
Theabove discussed mechanismand laws governing moisture migration and icelense segration in the frozen zone of freezing soils in many ways - 172 -
Figure 6
Dependence of volume and gradient stresses and their gradients on the rate of freezing. closely resemble the same processes during their thawing, although thereare definitedifferences between them. The migration of the unfrozen water and the formation of thin icelayers during thawing occurs in thetotally unthawed, frozen zone of the soil under theinfluence of theprevailing temperature gradientthere, which leads to themanifestation of a grad Wfraz and correspondingly, a grad vW. With thawing as opposed to freezing however, the process of segregated ice formation takes place against a background of an overallincrease (rather than a decrease) in the temperature of the frozen zone. Accordingly, the thin layers of segregated iceoriginating at low temperatures(corresponding to a region transitional to N.A. Tsytovich's tone in which thesoil is in an almost frozen state) grow under conditions of an overallincrease in the temperature and a zero isotherm closelyadjacent to them. After merging with the latter the thin layers of ice cease to grow and begin to melt. When the thawing front is advancing sufficiently slowly, ice layers of considerablethickness succeed in growing in thefrozen tone and havebeen found to have a high content of ground inclusions. Here, a specific cryogenic structure develops which in the literature is frequentlyrefered to as "ataxi tic" (Vtyurina and Vtyurin, 1970) or llzonular'l (Katasonov, 1960). - 173 -
The rate of growth of the thin layers of ice in the frozen tone of thawingsoil when thereis nochange in its composition orstructure depends onthe temperature gradient. For example, when grad t rangedfrom 0.2 to 0.5 deg/cm inthe frozen zone of thawingkaolinitic clay, the density of the migrationalflow forming the thin layers of iceincreased from 3 x loc6 to 7 x g/cm 2 sec. The values of thecoefficients of diffusion of unfrozen water in the 0’ to -2OC rangevaried between 1.5 x lo-’ and 6 x 10’’ mz/sec. Furthermore, inthe same tone a layeredcryogenic structure formed after severaldays, the thickness of thethin layers of iceranging from 2 cm close to OOC to fractions of a mm at -2’~.
The effect of thecomposition of thawingsoils on the migration of moisture and the formation of segregated ice in their frozen zone is analogous tothe general law that prevails in freezing soils, i.e.,with an increase in thecontent of minerals of themontmorilloni te group or a decrease inthe fineness of the soil, when other conditions are equal the rate of the moisture migration and iceformation process decreases.
Inorder to ensurethat the experimentsapproximated tonatural conditions,both a singlepartial thawing and also a repeatedcyclical thawing and freezing of thefrozen soils were carriedout. An analysis of such experiments showed that as theboundaries of the maximum depth of thaw become higher from cycle to cycle theice lenses that haveformed in the frozen zone become buried.For example, in an experimentwith kaolinitic clay involving its repeatedfreezing and thawing and a simultaneousdecrease in the depth of thaw, fouricy layers were recorded in whichthe type of cryogenicstructure depended on therate of thawingand the distance between theicy layers dependedon thedepth of thethawing layer. If thedepth of thaw didnot increase but decreased,then simultaneously with a lowering of thefreezing front a transformation and,downward mixingof the icy layer occurred. In this case theblock cryogenic structure that had previouslydeveloped was transformedinto thick horizontal ice lens.
Inconclusion it shouldbenoted that the large complex of experimentalstudies that has been conductedwith respect to moisture migration,texture formation and icesegregation in freezing and thawingsoils - 174 - has indicated the need for embarking upon a serious and special study of a wholeseries of thermophysical , physicochemical and physicomechanical processes in freezing and thawing soils. Only on the basis of a combined examination of the geological-geographic, thermophysical and physicomechanical condjtions in freezing and thawing soils will it be possible in the future to discover the particular and the general laws governing the cryogenic structure formation process and to work out a system for classifying the various kinds and types of cryogenic structures in relation to the conditions under which they were formed.
REFERENCES
VTYURINA, E.A. and VTYURIN, B.I. Ice formation in soils. Moscow, "Nau ka" press, 1970. ERSHOV, E.D., KUCHUKOV, E.A. and KOMAROV, I.A. Ice sublimation in finely dispersed soils. Izd-vo Moscow State University (MGU) , p. 223 , 1975. ERSHOV, E.D., CHEVEREV, V.G.I SHEVCHENKO, L.V. and SOKOLOV, V.N. Texture formation in finely dispersed soils during freezing complicated by moisture migration. Moscow University. Geol. series (at the printer's), 1977. ERSHOV, E.D., SHEVCHENKO, L.V. and LEBEDENKO, Yu.P. Distinctive features of the shrinkage and heaving process in freezing soils of differtng composition and properties. In: Permafrost Studies , 15th edition, Izd-vo MGU, pp. 226-227, 1976. KATASONOV, E.M. Preliminary classification of the cryogenic structures of permafrost talus deposits. - "Trudy Sev-Vost. otd. In-ta merzlotovedeniya na territoriya Yakutskoi ASSR". (Transactions of the Northeastern Division of the Institute of Permafrost in the Yakut ASSR). Yakutsk, pp. 12-14, 1960. KUDRYAVTSEV, V.A., ERSHOV, E.D. and SHEVCHENKO, L.V. Role of the shrinkage process in ice formation and the heaving of freezing soils. "Vestnik MGU. Ser. geol .'I No. 3. pp. 80-91 1974. KUDRYAVTSEV, V.A., ERSHCV, E.D., CHEVEREV, V.G., LEBEDENKO, Yu.P. and SHEVCHENKO, L.V. Moisture migration and segregated ice formation in freezing and thawing finely dispersed soils. "Papers given at the 5th All-Union Conference on Heat and Nass Exchange." Minsk, pp. 115-125, 1976. ORLOV, V.V. Cryogenic heaving of finely dispersed soils. Moscow, Itd-vo AN SSSR, p. 187, 1962. - 175 -
PUZAKOV, N.A. Ther thermal and aqueous regime of roadbeds of highways. Moscow Avtotransizdat, p. 168, 1960. FEDOSOV, A.E. Physicomechanical processes in Soil5 during their freezing and thawing. Moscow. Transzheldorizdat, p. 47, 1935. CHEVEREV, V.G. and LEBEDENKO, Yu.P. Methodology of laboratory studies of the moisture migration, heaving and ice formation process in freezing and thawing soils. "Results of the 3rd Scientific Conference of Post-graduate Students and Young Scientists of Moscow State University, Hydrogeological series." (VINITI, Dep. No. 247-76), 1975.
- 177 -
EFFECT OF LONG-TERMtRYOMETAMORPHISM OF EARTH MATERIALS ON THE FORMATION OF GROUNDWATER
S .M. Fotiev Industrial andResearch Institutefor Engineering Surveys in Construction Moscow, U.S.S.R.
The conditionsof groundwater formation a1 teredradically in the course Of theQuaternary period over the immense territoryof Eurasia and NorthAmerica under the effect of cryometamorphism of earthmaterials. Cryometamorphismcombines powerful mu1 tiannual physical , physico-chemical and physico-mechanicalprocesses occurring inearth materials as a result of changes intheir temperaturewithin the range of negativevalues. In the event of therock or soil temperature dropping below O°C, thereare formed, underthe impact of cryometamorphism, beds of cryogenic earth materials.
In assessingthe effect of cryometamorphicprocesses inearth materials on conditions,under which groundwater forms, we shouldfocus primarily on thespatial variability analysis of the main characteristicsof cryogenic beds thatare of primary importance from the hydrogeological viewpoint. We shalldefine more specificallytheir rolethein transfornation of hydrogeologicalconditions on theterritory markedby the distribution of cryogenicearth materials, i.e., inthe cryogenic region.
The temperature ofearth materials is a zonalfactor determining theintensity of theprocesses of cryogenic metamorphism inearth materials and groundwaterand characterizing the changes occurringin their physical physico-chemical and physico-mechanicalproperties. The degree of cooling of earthmaterials within the negative temperature range and itsstability in timedetermine: a) theoverall thickness of thebelt of cryogenic
ProceedingsThird International Conference on Permafrost, Vol. 1, pp. 182 - 187,1978. - 178 - metamorphism of earthmaterials and groundwater; b) thethickness of the cryogenicaquiclude in earthmaterials saturated with freshwater; c) the possibility of a cryogenicaquiclude developing and its thickness in earth materialssaturated with salt water; d) distinctiveaspects of the changes occurring in the chemicalcomposition and mineral content of water in the process of its crystallization; e) temperature regime of descending and ascending groundwater flows; and f) thepresence or absence of groundwater recharge and runoffareas and their size.
Repeated freezing ofwater increases the degree of jointing, hence thepermeability of the earth materials containing water.
The thickness of cryogenic beds is a zonal and regional characteristics of thepresent-day hydrocryological environment reflecting the conditions, under which theprocess of long-term cryometamorphism evolved and its stability in time and space. The thicknessofcryogenic beds characterizes the presentthickness of the belt ofcryogenic metamorphism in earth materials and groundwater within the structures.
The structure and texture of cryogenic beds areintrazonal characteristics of thepresent-day hydrogeocryological environment reflecting thespecific aspects of cryometamorphic processes in earthmaterials as depending on the presence of gravitationalwater in cracks and interstices I as well as on its composition and mineral content. The structure and texture of cryogenic beds characterizethe correlation within thevertical section of different horizons of cryogenic earth materials varying markedly with respect totheir hydrogeologicalproperties (Figure 1).
Under specific hydrogeocryologicalconditions there form cryogenic beds with distinctivetextures and structures (KT-1 - KT-9)*. Cryogenic beds of each type have their own designationderived from the names of their constituenthorizons of cryogenic soilsrocks,or The textures and structures of cryogenic beds reflect the possibility of fresh or saline water being present within the structures.
~ ".. . . . * KT stands for "cryogenicbeds". (Trans1 .). - 179 -
Figure 1
Textures and structures of different types of cryogenic beds I - horizonof frozen earth material (cracks and intersticesare filled with ice) - a cryogenicaquiclude; I1 - horizonof cooled* earth materials (cracks and intersticesare filled with salt water) - water-permeableearth mterials; 111 - horizon of frost*earth materials (with cracks and intersticescontaining neither water, nor ice, or homogeneous rock) - air-dry earthmaterials; IV - earthmaterials with positive temperatures, where cracksand interstices may containfresh water (1) , salinewater (2) or no water (3).
The thickness and discontinuity of thecryogenic aquiclude a re zonaland regional characteristics of cryogenic beds determiningthe major distinctiveaspects of cryogenic changes inthe conditions of formation of groundwater withinthe structures. The thicknessof the cryogenic aquiclude may be equal to thetotal thickness of thecryogenic beds orto a fraction thereof ( Figure 1 ) .
The thickness of thecryogenic aquiclude differentiates the feasibility of thegroundwater recharge and runoff as a functionof the water, soil and rocktemperature, as we1 1 as of the discharge of ascending or descending flows; it separates in space the once integral hydrodynamic systems or weakens thelinks between theirconstituent parts; it changes the direction,velocity of motion and regimen of groundwater; it determinesthe distinctiveaspects of thehydrodynamic and hydrochemicalzoning of groundwater and thecapacity of the given structure; it altershydraulic propertiesof individual aquifers or systems ofaquifers and determinesthe temperature conditions of ascending and descendinggroundwater flows.
* The terms "cooled" and "frost" arethe Russian terms used (okhlathdennyi and morotnyi,respectively) translated literally. These termsappear to referto new conceptsintrcduced by the author in this paperand have therefore no equivalentsin English (Trans1 .). - 180 -
The discontinuityof the cryogenic aquiclude characterizes the size of groundwaterrecharge and runoffregions and determinesthe specific aspects and activity of water exchange.
The principalcharacteristics of cryogenic beds repeatedly and fundamentallyaltered in thecourse ofthe Quaternary period. In studying specificaspects ofthe cryogenic changes in hydrogeologicalconditions within the structures of the present-day cryogenic region or even outside its boundaries, it is thereforeimperative to find answers to a number ofhighly importantquestions. When didthe long-term freezing of earth materials begin? What is the lengthof continuous existence of cryogenic aquicludes? How did their thickness and intermittent pattern of existence, as well as the temperature of theirconstituent earth materials change in time? We can answer these questionsonly proceeding from a thoroughstudy of the developmental history of cryogenic beds.
The evolutionaryhistory ofthe cryogenic beds found on the arritory of the U.S.S.R. has been studiedmainly in isolated regions, and so farthere are very fewworks pertaining to theterritory as a whole (Velichko, 1973). Analyses of the new datamaterial accumulatedby Soviet researchers inthe last 10 - 15 years,evidenced that the process of long-term cryometamorphism of soils and rocksdeveloped during the Pleistocene and Holocene virtuallythroughout the territory of the U .S.S.R. and was a 1ati tudi nal , as we1 1 as an a1 ti tudinal zonal phenomenon. The numerousand variedtraces of long-term cryometamorphism in earthmaterials aregenerally arranged in the form of zones differingwith respect to the duration and intensity of thecryogenic metamorphicprocesses ofearth materials,which took place within their boundaries.This circumstance is naturally reflected in the thickness of the cryogenic beds of earth materials and in the length of theircontinuous existence.
Proceedingfrom an analysis of thehistory of evolution of cryogenic bedsand fromthe belief that the warm Holocene epoch was an importantclimatic boundary, theauthor established on theterritory of the U.S.S.R. threegeocryological zones: theNorthern and Southern zones of long-term cryornetamorphisrn ofsoils and rocks, the boundary between which - 181 - - 182 -
Figure 2 Map of hydrogeocryological regionation of the territory of the U.S.S .R. 1 - Fresh-waterprovince: a) - theroof of thecry0 enic aquiclude at ttw dept of 5 m orless; b) - asynchronous cryogenic aqu 9 cludesseparated by a horizon of thawed earthmaterials; c) - theroof of thecryogenic aquiclude at thedepth of 100 - 200 m; 2 - Subaerialsalt-water province: a) - the roofof the cryogenic aquiclude at thedepth ofthe 5 m or les;;b) - the roof of the cryogenic aquiclude at the depth of 100 - 200 m; 3 - The province of air-dry earth materials; 4 - The province of fresh water and air-dry earth materials; 5 - The provinceof salt water and air-dryearth materials; 6 - The submarine sal t-waterprovince; 7 - Isolinesof the thickness (m) of cryogenic beds (after I.Ya. Baranov, V.V. Baulin and S.M. Fotiev); 8 - The location of thehydrogeocryological profile and its number in Figure 3. Boundaries: 9 - of firm land in the Upper Pleistocene(after N.N. Nikolaev and V.V. Shul Its); 10 - Of thecryogenic region during the Pleistocene climatic minimum (after A.A. Velichko as supplemented by S.M. Fotiev); 11 - Of thecryogenic region during the Recent period(after I.Ya. Baranov, V.V. Baul in and S .M. Fotiev);12 - Between theNorthern and Southern zones;13 - Of the areawith cry0 enic beds which didnot undergo surfacedegradation duringthe Holocene (BY ); 14 - Of thearea with discontinuous (Bf) and sporadic (B;) cryogehicaquicludes; 15 - Of the area marked by the distribution of Upper Holocene cryogenic beds (after V.V. Baulin and N.G. Oberman) ; 16 - Of the area with different types of cryogenic beds;17 - same, established tentatively.
Explanation of the index letters is provided in the text.
coincideswith the line of junctionof the Pleistocene and Upper Holocene cryogenic beds; and the zone of seasonalcryometamorphism of earthmaterials (Figures 2A, B and C). Withinthe confines of theNorthern zone (A) the freezingof earth materials continued for tens and hundreds of thousands of yearswithout interruptions, whereas on theterritory of theSouthern tone (B) thisperiod of timerepresents a repeatedalternation of the epochs marked by long-termfreezing of earthmaterials with epochs of multiannual thaw. Withinthe zone of seasonalcryometamorphism (C) the process of freezing of soil s and rocks annually gave way to thaw processes.
The differences inthe development of long-termcryometamorphic processes inearth materials are naturally reflected in the formation of the characteristicsobserved in cryogenic beds atthe present time. Whereas in theterritory of the Northern zone thetemperature of theearth materials varies between -2' and -16'and thethickness of continuouscryogenic beds is 500 - 1500 m or more, thesoil and rocktemperature on theterritory of the - 183 -
Southern zone varies between O°C and 2 - 3' below O°C and thethickness of discontinuouscryogenic beds and permafrostislands does not exceed 100 - 150 m. This evidences that the effect of cryometamorphism of earth materials on theconditions of formation of ground water was highly non-uniform in differentgeocryological zones.
The Northern zone of long-term cryometarnorphism of earth materials is locatednorth of theline of junction of Pleistocene andUpper Holocene cryogenic beds. The zone covers most of the area (61%) of thepresent-day subaerialcryogenic region (Figure 2A). In the courseof the Quaternary period, during the epoch of thePleistocene thermal minimum in particular (after A.A. Velichko),the earth materials were cooled to low (-20°C or even lower) negativetemperatures ensuring high intensity of theprocesses of cryometamorphism in the soils and rocks. The low temperature of thefreezing earthmaterials combined with the lengthy duration and greatstability of theircooling period are the factors responsible for the considerable (up to I 1500 m andmore) thicknessof the cryogenicbeds. This is why the hydrogeologicalenvironments formed within differentstructures prior to the beginning of theQuaternary period underwent the most thorough cryogenic metamorphism on the territory of the Northern zone.
The intensity of cooling of earth materials and the stabi 1 i ty in time of the processes of long-term cryometarnorphism of soils and rocks were uneven within theboundaries of that immense territory. The distinctive regional developmental patterns of this process were determined in a number of waysby the climate growing generally more continental and harsher, as well as by itsstability in time in the easterndirection throughout the Quaternaryperiod. This is reflected in the drop in temperature of theearth materials, in the increasedthickness and age of thecryogenic beds, and in theeastward expansion of the Northern zone along the nleridian. The development of long-term cryometamorphism of earthmaterials within the boundariesof the Russian andWest SiberianPlatforms andChukchi peninsula became increasingly non-uniform as a result of repeated and lengthy advances of the sea, during which largeportions of firm land were flooded in the Pleistocene. Under submarine conditionsthe cryogenic beds formed earlier became completely orpartially degraded, whereas in subaerial environments - 184 - the process of cryometamorphism of earthmaterials continued without interruptions. The intrazonal spatial non-uniformity of the thickness of cryogenic beds from various regions located in different parts of the zone, is shown in Figure 2.
Distinctive aspects of cryometamorphism of earth materials within individual regions were determined by the specifl’c correlation inside each structure of the thickness of cryogenic beds on the one hand, that of the fresh-water zone, of the zone of regional jointing of soils and rocks of air-dry earth materials on the other. The structures and textures of cryogenic beds formed under different hydrogeocryogenic conditions are shown in Figure 3.
Figure 3
Hydrogeocryological sections of cryogenic beds (the location of the profiles is shown in Figure 2).
The paleohydrogeocryogenic conditions, underwhich different types of cryogenic beds formed, were analyzed by the author earlier (Fotiev, 1975). This analysis permits us to differentiate the territory of the Northern zone into hydrogeocryological provinces marked by the occurrence within their structures of soils or rocks containing fresh or salt waters, or of air-dry earth materials. Each province is characterized by a definite combination of different types of cryogenic beds. The fresh-water province is characterized - 185 - by the predominantdevelopment of frozen soils or rocks (KT-1 ) , whereasbeds Of cooled or frozen earthmaterials (KT-6) occur at localized sites in the shelf, and while beds of frozen or frost soils or rocks (KT-8) are found only in mountainous regions. The salt-water province is characterized by a predominantdevelopment of bedscomposed of earthmaterials frozen or cooled (KT-2) under subaerialconditions or of beds with soils or rockscooled (KT-4) in subaqueous (submarine)environment, while beds of frost and cooled earthmaterials (KT-9) develop at local sites under subaerialconditions. The province of air-dry earthmaterials is characterized by a predominant development of beds with frozen and frost (KT-3) or only frost (KT-7) earth materials, while beds of cooled or frostsoil or rock (KT-5) develop at localized sites in the shelf.
The most significant cryogenic changes in theconditions of groundwater formation occurred in thestructures, where, as a result of the crystallization of waterin interstices and cracks of soils and rocks, there formed low-temperature cryogenic aquicludes. They persisted continuously for tens and hundreds of thousands of years and coveredover 95% of the area. Even during the epochs of climatic warming their degradation was partly possible only from the bottom up on account of the heat flux from the Earth's interior. Under these harsh and stable geocryological conditionsthe groundwater recharge and runoff regions confined to open water-absorbing or water-tapping tali ks, concentrate in all thestructures exclusively in river-valley floors. Because of the concentrated heat and moisture transfer, they exist only at localized sites. The association of the recharge and runoff regions with rejuvenated tectonicfractures has unequivocally determined the dependence of water-exchange activities upon the mobility of the regions during the Neogene-Quaternaryphase of tectogenesis.Differences in the activity of water exchange are naturally reflected in the thickness of the fresh-water zone, and in the thickness,texture and structure of cryogenic beds, hence in the distribution of hydrogeocryological provinces. On the territory of the Northernzone fresh-water provinces are confined for the most part to the mountainous region of Eastern Siberia, whereas salt-water provinces occupy here the shelf, theislands and most of the northern territory in Western and Eastern Siberia. - 186 -
The mountainous-folded region of Eastern Si beria is characterized by the most recentactivity tectonic movements with an amplitude of 500 to 2000 m or more.The specificaspects of cryogenic metamorphism of earth materials within individual structures havebeen determined by the hydrogeological environments formed therein prior to the beginning of the Quaternaryperiod.
In most structures the thickness of frozen beds was smaller than that of the fresh-water zonedue to the active water exchange throughout the Quaternaryperiod. In isolatedstructures with less favourable conditions with regard to water exchange the thickness of the fresh-water zoneproved to be comensurable with that of frozen bedswhich resulted in the occurrence of brackish water directly underneath thefrozen so41 or rock. In the mountain massifs marked by highly contrasting most recent movements of a considerable amplitude, by abundant tectonicfaults and a deeply eroded relief, the water-bearing assoclations of earth materials occurring above the base level, were drained to a fairlygreat depth, while in the rocks occurring below the base levelthere formed a thickfresh-water zonedue to theactive water exchange.These differences in the hydrogeological environment predetermined the development of different types of cryogenic beds. Thick (500 - 900 m) cryogenic beds represented maSnly by frozen earth materials (KT-3, KT-7 and KT-8), formed above the base level, while beds of frozenearth materials formed in thesestructures and in depressions below the base levels. Due to theactive movement of groundwater, theirthickness is atonal (200 - 300 m). Fresh water persistsin these structures even under theharshest geocryological conditions(Figure 2).
Platform regions arecharacterized byweak manifestations of the most recenttectonic movements with predominance of lengthysubsidences or stable upheavals ranging between -100 and +300 m in amplitude. The newest tectonicfaults are not characteristic of theplatform. Because of the negligible degree of erosionthe relief is here only slightly rugged and the earthmaterials have not beenwashed through percolation. In basins of this kind thethickness of cryogenic beds surpassed that of thefresh-water tone. This circumstance has resulted in extensivedistribution of the second type of cryogenic beds over the territory of the platform(Figure 2). - 187 -
Present-day characteristics of cryogenic beds from different basinssuggest that they formed under differentconditions. In the West Siberianbasin, the territory of which was repeatedlyflooded by desalinated seawater, saline water is found in the circum-Eniseiarea below thehorizon offrozen soils and rocks, at the depth of theorder of 200 m. The 1 ow content of mineral matter(10 - 15 g/1) and the high (-l0C) negative temperature of the water in the upper part of the layer of cooled soilsor rocksevidenced that they were littleaffected by cryogenic metamorphism. The totalthickness of cryogenic beds is here of theorder of 400 m. In the north-easternpart of theSiberian Platform the circumstances of cryogenic metamorphism of earthmaterials and groundwater were different.Stable, harsh,acutely continental climatic conditions predetermined a considerable cooling of soils and rocks and continuousaggradation of cryogenic beds throughout the Pleistocene. This may be the reason for the unique present-daygeocryological environment in the Olenek basin, an environment unlikeanything knownon Earth. Cryogenic beds attain here a thickness of 1500 m, whereas the thickness of the layer of frozen earth materials does not exceed 200 m (Mel'nikov, 1966; Balobae et a1 ., 1973). The magnesium-calcium chloridecomposition of brines,their high (up to 100 g/1)mineral content andlow (-S0C) temperature in the upper part of cooled soilor rock horizon evidencethe significant development ofcryogenic metamorphism therein. The abundance of mirabilitecrystals within thecracks in earthmaterials suggeststhat during the Pleistocenesoils and rocks were cooled to considerably lower temperature (below -8OC) atthat depth (Kononova, 1974). Hydrogeocryologicalprovinces with saline water are found virtually everywhere on islands and in isolatedareas on theArctic coast, where groundwater is linkedhydraulically to the sea (Neitvestnov et al., 1971).
Within the boundaries of the Anabar massifcryogenic beds also measure over 1000 m in thickness, but theirtextures and structuresare entirelydifferent. Cryogenic beds of the third type formed here as a result of cryogenic metamorphism of crystallinerocks. The featurescharacteristic of this province of air-dryearth materials are the negligible (up to 50 - 100 m) thickness of thefrozen soil or rock layercoinciding with the thickness of the ancientwater-laden weathering crust, and theunparalleled thickness of the layer of "frosty"soil materials. The massif contains no - 188 - underground waters other than the groundwater found in the seasonally thawing layer or in closed taliks from river Val 1eys (Underground water. .. . ., 1967).
Fresh water escaped freezing on theterritory of theplatform only insidethe structures, where thethickness of cryogenic bedsproved to be smaller than that of thefresh-water zone. The Yakutian basin is the most representative example in this respect. The thickness of frozen rock or soil beds in second- or third-order topographic lows attains here 600 m, while the thickness of thefresh-water tone is in excess of 1000 m. This is the greatestthickness determined with confidence for a cryogenic aquiclude. The detailed hydrochemical investigationscarried out by R.S. Kononova,made it possible to identify within thebasin horizons marked by cryogenic concentration or cryogenic desalination of underground water. The chemical composition of the groundwater, thesignificant deficit of formational pressure, as well asresults from detailed geothermal studies evidence that the degradation of frozen beds proceeds from the bottom up (Balobaev et a1 .) 1973).
In the northern part of the zone there has been segregateda territory(a subzone), within theconfines of which cryogenic beds (dating back 1argely to the Upper Pleistocene) occur below the sea level(Figure 2, A*). These beds occupy a portion of the firm 1 and vacated by. the sea in the latter half of the Upper Pleistocene. During that epoch, as thesea retreatedthere formedunder subaerialconditions cryogenicaquicludes and an active process of cryometamorphism took place in the sea water entrapped in cracks and interstices of soil and rock. As a result of the advance of the sea, whichbegan 18 - 17 thousand years ago, the long-term process of freezingdlscontinued in the soil materialsas the land gradually subsided below the sea level, and theice filling thecracks and interstices in the soil and rock,gradually became replaced by sea water at below-zero temperatures.
At thepresent time the cryogenic beds developed on theterritory of that subzone are predominantly of the second, fourth and sixthtype. So far theirdistribution hasbeen studiedinadequately. Cryogenic Pleistocene beds of the second type, which recently subsided beneath thesea, persist - 189 - alongsidethe above beds in shallowcoastal areas of the East-Siberiansea. According to the data of N.F. Grigor'ev,the overlying frozen earth materials have a low temperature (as low as -12OC). The difference in the texture and structure of the cryogenic beds within the confines of theshelf reflect different stages ofthe metamorphism occurring under theeffect of seawater in thecryogenic beds formed under subaerialconditions.
The southerntone oflong-term cryometamorphism in soils and rocks is locatedsouth of the line of junction of thePleistocene andUpper Holocene cryogenic beds (Figure 2, 6). Inside this tone geothermal and hydrogeological regimes underwent repeated and substantial changes in the course of the Quaternary period.
Cryogenic aquicludesdeveloped within its structures during the cold epochs and persistedfor longperiods of time. These aquicludes cardinallyaltered the hydrogeological nature of groundwater basins:the conditionsof groundwater recharge,flow and runoff changed; the depth at which groundwater occurred,increased as depending on thethickness of frozen soilsor rocks; and fresh-waterresources diminished. In the process of freezing of water-bearingsoiTs-and rocks a portion of freshwater was fixed in the form of iceinclusions. The bulk of fresh water was, however, squeezed outinto the underlying aquifers. Havingadded to thethickness of the fresh- and brackish-waterzone, it then outflowed on the surface through tali ks providing an outletfor water. As a result of this not onlythe chemical composition of the groundwater, but even the pattern of hydrochemical zoning altered in some of the structures.
In the course of the warm epochs thecryogenic aquicludes degraded partlyor completely, hut the formerhydrogeological environmentnever became completelyreestablished in thesebasins, since the water-bearing soils and rocks,as well as the composition of the groundwater itself had undergone qualitative transformations as a result of cryometamorphism.
The effect of cryometamorphism of earthmaterials on the conditions of formation of underground water in the Southern zone was highly non-uniform, but generallyless significant than that in the Northern tone. - 190 -
The intrazonal non-uniformity of cryogenic changes in the hydrogeological environment was determinedmainly by theconditions underwhich this process developed: the Upper Pleistocene was the epoch of the most extensive distribution of low-temperature cryogenic aquicludes;the earlyhalf of the Holocenewas the epochmarked by the maximum degradation of cryogenic aquicludes; while the latter half of the Holocenewas the epoch, during which there developed new high-temperature cryogenic aquicludes. With regard to the conditions of development )of long-term cryometamorphism of soils and rocks in the Upper Holocene and at present,the Southern tone breaks up fairlydistinctly into two parts with the boundary-line extending along the southern boundary of the modern cryogenic region. In the northern part of the zone, within theconfines of the present-day cryogenic region (Figure 2, B1 ) , the processes of long-term cryometamorphism of soils and rocks developed throughout thePleistocene and Holocene, in its southern part (B2) - only during the Pleistocene.
Within the boundaries of the modern cryogenic region, on the territory of the Southernzone, there have now been found cryogenic aquicludes differing in age. This is due to the fact that after the partial degradation of thePleistocene cryogenic beds represented by the first or second type, during the latter half of the Holocene there formed here once again cryogenic beds of the first type.
High-temperature (up to -0.5OC) cryogenic aquicludes of the P1 eistocene age have so far been detected only in the Pechora and West Siberian basins". In the northern part of the zonethey are separated from the base of the UpperHolocene cryogenic aquicludes by a horizon of thawed out rocks. Along the southern periphery of the cryogenic region the roof of relic cryogenic aquicludes lies at the depth of 100 - 200 m from the surface (Figure 2, BY). The part played by cryogenic aquicludes of thePleistocene age inthe formation of groundwaterremains virtually obscure, sincethe information available on their distribution and thickness is limited.
* In the southern part of the Tunguska basin they havebeen established tentatively proceeding from analyses of the history of development of cryogenic beds (Fotiev et a1 . , 1974). - 191 -
In the Upper Holocene the processesof long-term cryometamorphism of earthmaterials developed over fairlylarge areas of the Southern zone under relatively mild climaticconditions. These conditionsare primarily responsiblefor the zonal increase in thethickness of the cryogenic beds from a few metres in thesouth to 100 m (rarely more) in the north. Cryometamorphism of soils and rocks was not an all-embracingprocess, since in thecourse ofthermal interaction of naturalwater with freezingsoils or rocksthere formedopen taliks of the hydrogeneticclass in allthe elements of the relief. N.N. Romanovskiiand A.B. Chizhov established in their works the vitally importantrole played by rainwater as the agentdetermining the degree of discontinuitycryogenicof beds. These researchersalso demonstrated a certain dependence of the conditions under which the processes of long-termfreezing of rocksdevelop, on thepresence or absenceof conditionsfavourable for infiltration of rainwater, particularly in interfluves. Depending on theconditions of infiltration of rainwater, there became segregated territories, where long-term cryometamorphism developed practically everywhere, and those, where it developed in isolated massifs or only at localized sites thus giving rise to the continuous, discontinuousor sporadic (islands) distribution of cryogenic beds.
The territory marked by the presence of continuouscryogenic beds (Figure 2, E;), is confinedexclusively to the mountainous regions of the Southern zone (the mountains ofthe Trans-Baikal region, Southern Siberia, etc.). This is the only territory, where, due to the specific altitudinal-zonal pattern of heat exchange between theearth materials and the atmosphere, the Upper Pleistocenegeocryological environment did not undergo significant changes at the time of the thermal maximum in the Holocene. As a result of this cryogenicaquicludes have persisted here for tens or hundred of thousandsof years,as is also the case on theterritory of the Northern zone. They coverover 95% of thearea and have a tremendous impact on the formation and distribution of groundwater within the basins.
The territory marked by a discontinuousoccurrence of cryogenic beds, occupiesclose to 27% of thesurface area in thepresent-day subaerial 2 cryogenicregion (Figure 2, Bl). Relatively mild climatic and geocryological conditions in conjunction with large amounts (300 - 400 mm) of rain water and - 192 - with the increased jointing arising in water-containing soils and rocks as a result of their repeated cryogenic disintegration, have predetermined the development of numerous water-absorbing of water-releasing taliks. The modern cryogenic aquicludes have been in continuous existence for tens, hundrends less often even thousands of years and cover 95 to 5% of the surface area, as depending on the water-permeability of the soil or rock Sn question and on conditions of infiltration of rain waters. This is the factor explaining the spatial (territorial) non-uniformity of the effect of long-term cryometamorphism on the conditions of groundwater formation in different structures. The significant degree of discontinuity and the small thickness of cryogenic aquicludes in on all the elements of the relief induce an activewater exchange and make it possible for fresh water to occur inside the structures.
The territory marked by the distribution of cryogenic beds in the form of islands, occupies approximately 12% of the surface area of the modern subaerial cryogenic region (Figure 2,, Bi). Cryogenic beds measuring 10 - 25 m in thickness, occur here in the form of isolated islands which are confined to shaded sites and consist of poor filtering deposits. Cryogenic aquicludes generally coincide in this territory with lithological aquicludes. The modern long-term cryometamorphism of soils and rocks therefore plays here a negligible part in groundwater formation.
On the territory south of the boundary of the present-day cryogenic region, located mainly in the Russian and West Siberian Platforms, the process of long-term cryometamorphism of earth materials developed only during the Pleistocene (Figure 2, B2). For the time being the nearly total lack of specific information on the main characteristics of cryogenic beds during the different Pleistocene epochs of climatic warming or cooling, makes 5 t impossi ble to assess the role ofthe processes of long-term cryometamorphism of soils and rocks in the formation of today's hydrogeological environment inside different structures. It can be merely assumed that the thickness and stability in time of cryogenic aquicludes increased on the territory of the platform in the northern direction. It may be inferred from the extensive development of pseudomorphs in wedge ice that in the central part of the Russian Platform and in the south of Western - 193 -
Siberiathe temperature of earthmaterials during the Upper Pleistocene may have been as high as -3OC and the thickness of cryogenic beds was of the order of 100 - 300 m. It may therefore be assertedthat cryogenic metamorphism of earthmaterials and groundwater did not passwithout leaving any traces.Inside the structures there may have or, indeed, have perhaps persisted local zones with increasedcontents of water in soils and rocks due to thecryogenic jointing of theseearth materials, or azonalhorizons of cryometamorphosed water(horizons of cryogenicconcentration or desalination), but the cryogenicorigin of these anomalies has simply been ignored. These symptoms of cryogenic metamorphismhavebeen found increasingly more often in earthmaterials and in groundwater from the territory of the present-daycryogenic region, particularly in the structures, where the beds of frozen soi 1 s or rocks have been degraded f rorn the bottom up.
The tone of seasonal cryometamorphism of earth materials is located southof the boundary of the Upper Pleistocenecryogenic region* (Figure 2, 6). During thePleistocene and Holocene seasonalcryogenic metamorphism prevailed on the territory of that zone penetrating to the depth of 5 - 10 m. Long-termcryometamorphism of earth materials was characteristic only of high mountains. Itsintensity varied with altitude during thecold andwarn epochs of the Quaternaryperiod, At the presenttime the processes of long-term cryometamorphism of earthmaterials are in progress within the Glavnyi (Principal)range in the Caucasus at absolutealtitudes of over 3 - 3.5 thousand metres.
To assess more fully the effect of cryogenic metamorphism of soils and rocks on conditions of groundwater formation, we are thus proposing a new scheme for sequentialhydrogeocryological regionation of the territory of the U .S .S.R., with new taxonometric units, i .e., hydrogeocryological zones and subzones,and, within the confines of the latter, of hydrogeocryological provinces.
* Once the territory of this zone has been studied in greater detail from paleogeocryologicalpositions, we may find here, too, signs oflong-term cryometamorphism of soils and rocks. REFERENCES
1. BELOBAEV V .T. , DEVYATKIN V .N. and KUTASOV I.M. Sovremennye geotermi - cheskie usloviya sushchestvovaniya i razvi tiya mnogoletnemerzlykh gornykhporod. (Modern geothermal conditions of occurrence and development of permafrost). - V kn. : II Methdunar . konf. PO Merzlotovedeniyu (IN: 11 International Conference on Permafrost). Dokl. i soobshch., Issue 1, Yakutsk, pp. 11-19, 1973.
2. VELICHKO A.A. Prirodn i protsess v pleistotsene(Natural processes in the P1ei stocene J . Moscow, "NBU ka" , 256 pages , 1973. 3. KONONOVA R.S. Kriogennayametamorfizatsiya podmerzlotnykh vodVostochno- Sibirskoiartezianskoi oblasti (Cryogenic metamorphism of sub- permafrostwater in the East Siberian artesian region). "Sov. geologiya", No. 3, pp. 103-115, 1974.
4. MEL'NIKOV P.I. 0 glubinepromerzaniya verkhnei zony zemnoi kory na territorii Ya ASSR (The depth of freezing in the upper zone of the earth's crust on the territory of the Yakutian ASSR) . V kn.: Geotermicheskieissledovaniya i ispol'zovanie tepla Zeml i. Moscow, "Nauka", pp. 110-1 18, 1966. 5. NEIZVESTNOV Ya.V., OBIDIN N.I!, TOLSTIKHIN N.I. and TOLSTIKHIN O.N. Gidrogeologicheskoeralonirovanie i gidrogeologicheskieuslovfya sovetskogosektora Arktiki (Hydrogeological regionation and hydrogeologicalconditions in the Soviet section of the Actic regions). V kn : Geologiya i pol eznyeiskopaemye severa Sibirskoiplatformy. Leningrad, pp. 92-105, 1971. 6.
7. FOTIEV S.M. Usfoviya formirovaniya i rakonomernostirasprostraneniya razlichnykhtipov kriogennoi tolshchi na territorii SSSR. (Conditions of formation and distribution patterns of different types of cryogenic beds on the territory of the U.S.S.R.). Trudy PNIIIS, vyp. 36, MOSCOW, Stroiizdat, pp. 135-146, 1975. a. FOTIEV S.M., DANILOVA N.S. and SHEVELEVA N.S. Geokriologicheskie usloviyaSrednei Sibiri (Geocryological conditions in Central Si beria). Moscow, "Nauka" , 146 pages, 1974. - 195 -
LONG TERM DYNAMICS OF GROUNDWATER ICINGS
N.N. Romanovskii and V.E. Afanasenko Moscow State University M.M. Koreisha Industrial and Research Institutefor Engineering Surveys in Construction Moscow, U.S.S.R.
In recentIn years, as a result of complex, permafrost and hydrogeologicalsurveys and specialresearch projects, a large amount of material has been obtainedwhich bears evidence of theintense perennial and centuries old dynamics of groundwater icings,especially of deep subpermafrostdrainage. Individual occurrences of icingsappearing and disappearing,shifting up or down alongvalleys, changing in form,dimension and volumeof constituentice (ice comprisingthe icing) were known earlier. However, the scale of theperennial dynamics of icings and thegeological effects of theiractivity turned out to be immense and surpassed even the boldestexpectations. Vastterritories, restricted to thetectonic intermontanebasins of the Verkhoyana-Kolyma foldmountain region, the north ofthe Baikal mountain region, and theriver valleys in the mountain massifs of theCherskii , Selennyakh,Suntar-Kayata ranges, the Buordakhskii Massif, the StanovoeUpland, etc., have been fashioned by icings. The surface of the tectonicdepressions are systems of flatsites of annualappearance of icings,frequently not associated with the rivervalleys. A number ofsites arecovered by icingsevery year, others are re1 ic forms. Rivervalleys havinggroundwater icings in the valley floor are of a distinct shape, where wideningcorresponds to sites of icings.
Geologicalactivity of icingsleads, on the one hand, to erosion of thesides and a widening of thevalley floor: on theother hand, to the
ProceedingsThird International Conference on Permafrost, Vol. 1, pp.213 - 218, 1978. - 196 - erosion andremoval of fine-grained,supes-suglinok* floodplain deposits beneath theicings. In addition,deposits of sand,gravel , and pebbles form streams,glaciers and me1 twater, and slopedeposits of gravelly rock debris are exposed at the surface. The mechanics of theaction of icings havebeen investigated by P.F. Shvetsov and V.P. Sedov, S.M. Fotiev, N.M. Romanovskii and others, and therefore wit 1 not beexamined in this paper. We wi 11 concentrate on the factthat the product of icing activity, the so-called "icing is a high qualitymaterial for roadbeds and a good foundationfor buildings, and that the drysurfaces of ancient icing sites are very suitablefor various types ofconstruction. However, conditionsfor any kind of economic activity imediately in the zone of icingformation are extremelyunfavourable. Therefore, the studyof the causes and patternsof migration of icings is ofgreat theoretical and practicalinterest.
Research intovarious types of hydrologic textures, which have, to varyingdegrees, beenchanged by deep perennialfreezing andhave differing distributions of waterbearingtaliks, showed thatthe special features of their formation, regime and perennial variability of their icingsare, on the one hand, associated with the type of waterforming the icings, and on the other hand, with the nature of the taliks, their genetic features,their dimensions, form, and the interrelationship of the variouscategories of tali ks in plan and in section. We will reveal this situation through the example of groundwater icings of deep subpermafrost drainage which discharges through open taliks (Figure 1). The most complete analysis of thepatterns of the dynamics was achieved for verylarge icings of a given origin (Romanovskii et a1 ., 1973).
An extreme example of theinterrelationship between talik and icing is the development of thelatter above groundwater springsthat discharge through hydrogeogenous open taliks. The conditionfor this is the development of low temperaturepermafrost and a severeclimate. The spring issues from thecentre of the icing forming a dome above the outlet, in the centre of which is a hydrolaccolith(Figure 1-1) Suchan icing was
* Supes - si 1ty sand with some clay, sandy si1 ty loam. Suglinok - clayey silt with some sand, clayey silty loam - Trans1 .) - 197 -
Figure 1
Diagram of the relationship between groundwater icings and water-beari ng tal iks . 1 - permafrost; 2 - layer of seasonalthawing; 3 - layer of seasonal freezing; 4 - open tali k in fissured bedrock; 5 - seepage tal ik; 6 - direction of groundwater movement; 7 - icing: A) channels in the body of the icing through which water issues; B) waterlenses; C) fissures in the hydrolaccol i ths; 8 - permafrost boundary (a) and layer of seasonal freezing - thawi ng (b) . discovered under theso-called "Lake Gusinoe" in the Selennyakh depression and was studied (Romanovskii et al., 1974) in conditions of thick low temperaturepermafrost (tav -5, -7OC). The diameter of thetali k is only a few metres at the surface. Themaximum summer discharge was 66 l/sec when the surfacewater temperature at theoutlet was +0.2OC. At the end of the winter, it had apparentlydecreased to from 10 to 12 l/sec. In the winter months, these icings protect the earth materials of the tali k from freezing. The water emerges ontothe surface of the icing through the fissures in the hydrolaccolith. When springs areceasing to function at the end of winter and starting up again in spring, theicings covering them facilitate a speedy - 198 - upward breakthrough of water, because of the melting from top to bottom of the ice constituting the icing, erosion, seepage through the fissures, etc.
When the regimeof the groundwater springpersists year after year,the quantity of ice forming theicing in winter remains virtually constant. Changes in the volume of theicing are dependent only on the amount of ice that does not melt in the summer. On the whole, thereis little change in the form of the icing.
Usually, in severe permafrost conditions, a seepage tali k of earth materialsexists belowhydrogeogenous or underwater taliks(infrabed, flood plain,etc.). Before issuing at the surface to form an icing, some of the water from the deep discharge passes through the seepage tali k of unfrozen ground. Therefore, it is as if thelatter distributes the groundwater over thearea of icing formation. The specialfeatures of theicing and the nature of change in its parameters in theperennial system aredecisively dependent on the position, dimensions, and extent of the seepage tali k.
There are two basic types of occurrence: - when the seepage tali k is closed and extends into theseasonally thawed layer which freezes completely in winter(Figure 1-1) , and when an open or closed seepage tali k extends as an uninterrupted strip increasing downwards through thesection (Figure1-IV). There is a transitional occurrence: this is when a seepage talikseparates inwinter into a system of isolatedtaliks where thereare limitedstatic reserves of water and a stagnant regime. Because of these, onlysmall icings can form (Figure1-111).
If thereare uninterrupted seepage tali ks, open or closed, then the dimensions and form of theicing body and the volume of constituentice will vary considerably from year to year, and arestrongly dependent on the climaticconditions of thewinter. In a severewinter with little snow, when the seasonal freezing reaches its perennial maximum and the flow in the seepage tali k becomes very 1 ittle, much of the groundwater issues at the surface and forms largeicings in winter. In contrast, in a mild winter with a largesnowfall, the seasonal freezing of theearth materials is not great, consequently,the sections of the tali ks are not greatly reduced and a small - 199 - amount of thewater goes into the formation of icings. In such years, either the dimensions of the tali ks are minimal or tali ks do not form at all .
In the occurrence being studied,all the parameters of theicings change everyyear and there is a clearconnection between these changes and fluctuations in climate.
In anotheroccurrence, where water from the deep subpermafrost discharges from the "blind" seepage talik and is present below theoutlet to the surface, virtually the sameamount of groundwater is used in the formation of icings. The differences from year to yearare not usually greaterthan the errors in measurements of the volume of ice comprising the icings. They are mainlyconnected with the factthat in autumn, some of the water below theseepage talik manages to flow out along the layer of seasonal thawing . Dependingon thelength of time from the beginning to the end of the thawing of this layer, the amount ofwater issuing from the volume of ice can also be associated with changes in ,theperiods when theicings cease growing in spring.
In theoccurrence being analysedthere can be veryconsiderable changes in formand location;these changes are of a periodicnature. This is mainly associated with two conditions. First, with displacement,the sideways migration of seepage tal iks, and theirfragmentation; secondly with a change in theirlength. The latter process is, to a considerabledegree, long-term cyclic(self-fluctuating) in character.
Figure 2 is a diagram of theperennial dynamics of the Oisordookh icing in the Selennyakbasin in the Northeast U.S.S.R. It was first investigated in 1939 by P.F. Shvetsov and V.P. Sedov (1941), and again by them jointly in May-June 1972. The supplementaryuse of aerial photographs over a number ofyears made it possible to establish that there areconstant changes in the location of the body of theicing, the point of thickestice in different years, and the position of channels in the ice above the seepage talik. We must add that,according to the data of A.S. Simakovand Z.G. Shil'nikovskaya, on the 1951 photographs,there wasno ice at the icing site. Considering the fact that from 2.5 - 3 to 3.5 - 4 m of icemelts during the - 200 - sumner in thisregion, it can be taken that in 1951, thethickness of the icing did not exceed 4 m. In 1972, theice at thecentral part of theicing reached a thickness of 6 - 8 m, i.e. , an icing of this thickness canthaw in 2 - 3 years,if there is no further growth of ice in thewinter. The area of theicing was 5.85 km 2 in 1939, and in 1972 it was 8.55 km2, i.e.,there was an increase of approximately 30%. Periodically, a so-called"icing tongue" appears under the main body of the icing and disappear again ; i t extends for up to 10 - 12 km along the Oisordookh valley. All indicationsare, that a massivegroundwater icing of deep subpermafrost dischargeexisting in very severe permafrost and climaticconditions is very dynamic in character; it alsoindicates that perennialicings can periodically turn into annual icings .
Fiqure 2
Schema of the Oisordookh icing. 1 - Upland slopes composed of bedrock 2 - high terrace above floodplain; composed of supes-suglinok deposits with syngeneticice wedges; 3 - alluvial surface of a very high ancienticing site; 4 - alluvlalsurface of a lower, young icingsite; 5 - high "islands" on thesurface of a present day icing sitefilled with depressed vegetation; 6 - surface of present day site, no vegetation, composed of sandy-gravelly-pebbly deposits; 7 - scarps eroded by icing; a - bedrock slope; b - "ancient"icing sites; c - high terraces above thefloodplain; 8 - thermally eroded depressions; 9 - rising groundwater springs ; 10 - boundary of hydrogeogenousopen tal i ks; 11 - boundary of infrabed seepage talik; 12-16 - boundaries of icingice; 12 - in 1951 (date unknown); 13 - mid-June 1939; 14 - 9 July 1965; 15 - 11 July 1964; 16 - 20 July 1972. - 201 -
Direct and indirect(according to growth) observations of many massivegroundwater icings inthe Northeast U.S.S.R. show thatthe lower parts of the icings periodically shift up and down the valley floor, and that "icingtongues" appear and disappear.This is associatedwith changes in lengthof the seepage talikduring interaction with the icing. This process isessentially as follows. Under the body of an icing 5 - 8 m thick,both surface and groundwaterare considerably protected from frost action. Due to theretarded action of heat loss, themoving water is able to issue from the dischargelocation over a considerabledistance. In summer, when thereis fragmentationand thawing of the seepage talik underthe water course, the flow increases in length.In the perennial ice of an icing, above thetalik, a tunneldevelops, followed by a "canal". In autumn, thellcanal" isthe firstto fill withice, protecting the water flow from frostaction. A series of hydrolaccolithsform along the llcanalll through which there is an outpouring of wateronto the surface (Figure 3-1). Secondary canalsand tunnelsbranch off from the main canal, distributing the water from the icing - formingsurface. Just as the talik increased inlength during the summer, so theicing correspondingly starts to extendalong the valley (Figure 3-11). In subsequentyears, sustained direction of this advanceleads tothe development of an "icing tongue"below the main body of the icing , and to a decrease inintensity of icingformation in the latter. This, in turn, determinesthe general increase in area and the decrease in thi,ckness of the icing(Figure 3-111). Finally,the thickness of theice becomes such that it thaws eithercompletely, or to a considerabledegree. Consequently, the protectiveinfluence of the "canals" in the icing disappears. When thereis a flat icing site devoid of ice,the surface water flow andthen the seepage talik itself fragment intoseveral branches. As a result,in autumn, the water inthe shallow braided water courses and in theshallow closed seepage taliks belowthe numerous streams, quicklychill andfreeze, forming a concentrated,often dome shaped icingnear the groundwater surface outlet (Figure 3-IV). The seepage talik below themain body ofthe icing is no longerfed with groundwater. It now falls into the system of isolated taliks and thenfreezes. Icings no longerform where thetalik once existed.After theformation of the dome shaped icingthe fragmented water courses and the shallow seepage talik become concentratedinto a singlecourse and a single talik.Associated with this is thefact that in winter, in "blind" water - 202 - courses and taliks,the flow ceases when the icing is sufficientlythick. Due to their small volume, the water pressure is not great enough to break through the very strong ice and form a hydrolaccolith through which water would issue to the surface. Consequently, the stagnant water in thetali k and canals in theice freeze, and the water flow is directed to the main stream. A series of large hydrolaccoliths form along the stream and, in winter,especially in the second half, ice formation startsagain. Later, the main stream and the talik beneath it increase in length, and the cycle is repeated.
Figure 3
Diagram of perennial changes in length of a seepage talik and a groundwater icing in severepermafrost and climateconditions. Legend as in Figure 1 .
Such cyclic(self-fluctuating) . changes in dimension and form of large groundwater icings lead to theirperiodic transition from perennial to annual icings and viceversa. A distinction must be madebetween perennial and annual icings, and theintermediate type, that is, the Surmer icings and corresponding stages of development of the very same groundwater icing for the specific character of its relationship with the waterbearing taliks. - 203 -
Naturally, even such a renowned icing as the "Moms", one of the largestin the world, undergoes considerableperennial changes; thisis probablyreflected in the observable discrepancies in estimates of its area in thevarious sources: from 76 to 112 km2. In anycase, it is known that in some years a largearea of this icing remains all sumer, in otheryears, it has virtuallymelted completely byAugust (Yakovlev, Koreisha, 1973). The selffluctuating nature of the changes in form and area of theicing in a Severe climateis in itself not connected with its perennial fluctuations. Withoutdoubt, perennial fluctuations of the mean annualtemperatures , amplitudes of changes in temperature during the year, the thicknesses of snow cover,etc., have an influence on the continuity of the development cycles of icings,the continuity of stages withinthe cycles, etc. They can deformthe cyclic(self fluctuating) nature of the development, butthey cannot change it in essence.For radical changes , there would have to be a profound change in the permafrost conditions.
The periodic changes of location of thedistributing taliks finally leads to an increase in thedimensions of the icing sites compared to thedimensions of the icings themselves.
As wellas the periodic changes, there are in nature, well known, induced changes. In our case, theseinclude both the appearance and the disappearanceof taliks which discharge water ontothe surface, and also directedshifts in location of taliks. The factthat open taliks and the icingsassociated with them can cease toexists has been known for a long time(Springis, 1961). It was alsorevealed by the authors when they were researchingthe junction of the bra and Nekharanskie icingsinthe Selennyakh basin(Figure 4). Thus, in 1972, the "Upper" groundwater spring, which had issuedthrough the hydrogeogenous open talik beneath theriverside bedrockscarp of the Qra above Mt. At-Khayaand that fedthe Upper Kyra icing, was no longer in existence(Shvetsov, Sedov, 1941). Inthe past, the spring had a dischargerate of 340 l/hr. At thepresent time, allthat remainsare shingle filled depressions where thewater used to emerge, and a dry stream bed - 204 -
Reformation of open tali ks hasonly been ascertained in recent years. Thus, the talik that formed the "Lake Gusinoe" icing(cf. Figure 4), appearedvery recently at the location of the small lake "Eusinoe" described by P.F. Shvetsov and V.P. Sedov in 1939.
Figure 4
Diagram of the Kyra-Nekharanskii icing junction. Upper Quaternary and present day alluvialsurfaces whichwere exposed to the action of icings at various times; 2 - lower terraces with fresh traces of icing action, but not now covered with ice; 3 - terraces with distinct traces of the icing forming processes within which secondaryprocesses areactively developed; 4 - surfacestransitional between 2 & 3 in character; 5 - surfaces with traces of shaping by icings,sharply attenuated secondary processes; 6 - surfacestransitional between 3 & 5; 7 - high surfaces with weak traces of former icing forming processes; 8 - Upper Quaternarydepositions of an "ancient"alluvial plain with syngenetic wedge ice; 9 - surfaces composed of Jurassic bedrock.Boundarfes oficings in various years; 10 - December 1868 (according to Maidel'); 11 - May 1939 (according to Shvetsov & Sedov); 12 - 11 July 1964;13 - 5 July 1970; 14 - 18 May 1972. Groundwater springs from deepdischarge, and their yield;15 - those no longerextant; 16 - existing icings.
Recently, no longerthan 100 years ago, a hydrogeogenous open talik appeared on thevalley slope of the rivulet IlVeshchegolI, the r4ght tributary of the Ulakhan-Kyuegyulyuyur, in thenorthern part of the Kular - 205 -
Range (Afanasenko et a1 . , 1973). The talik, which has theform of a truncated cone, appeared at thepoint of intersection of two largefaults whichrun in a northwesterly and northeasterlydirection. The thicknessof thepermafrost surrounding the talik reaches 380 I 400 m, decreasing to 150 - 200 m withinthe icing site. The volume of water from thesprings is 12 - 15 l/hr and the volume of ice attains 340 m3, The icing site below the spring is covered with the remains of trees which were growing there prior to theformation of the talik and theicings. Both of the above mentioned regions have highseismicity (up to 8 degrees).Apparently, the groundwater brokethrough as a result of an earthquake shock, causing a hydraulic thrust. Reformation of open taliks has also been confirmed inthe region of the StanovoeUpland, where there are known to be earthquakes of up to 10 degrees.
Induced changes of location of taliks has been established in many regions of theNortheast U.S.S.R., especiallywithin the superimposed Cenozoic tectonicdepressions suchas the Uyandinskaya,Mom-Selennyakh depressions,etc. Underwater andhydrogeogenous open taliks restrictedto thefracturing tectonic disturbances bounding the depressions and dissecting itsfolded cover,are constantly shifting, mainly along the faults. Recent tectonic movement seems to be the cause of thisshifting; it apparently bringsabout changes in thepermeability to water of theearth materials in variousparts of thetalik. As a result,the rising water in the permafrost thawsone of the walls of the talik and there is a correspondingfreezing of thatpart of thetalik where movement of water has ceased. When an icing shifts,then so does thetalik, leaving behind it a stretch of terraced icing sites
Several of the mountainous regions of theNortheast and of Zabaikal'eserve as examples of individualdirected developments and shifts of icings. Here, duringdegradation in the Upper Pleistocene Ice Age, icings occupiedthe I'Utl shaped valleyswhich were beingfreed of glaciers.Directed evolution of icings is veryclosely connected with the evolution of glaciation.
Glacialtroughs in regions of recent Upper Pleistoceneglaciation undergo strong and highlyindividual shaping by icings. Very frequently, - 206 -
icings and icing sites are found in glaciated areas of valleys situated above the moraine and rockbar complexes and arefilled with layers of coarse granulardeposits from glaciers and meltwater. Along the periphery of mountainous structures,icing sites areeither relic or have present day icingscovering a verysmall part of them. On the other hand, in the middle and upper regions of the glacial troughs, icings are forming at the present time, many of which completely fill the valleyfloor and lead to their widening (Nekrasov et a1 ., 1976).
The scales of icing migration, under the influence of both induced and cyclic changes, arerepresented in Figure 4. Here, notonly are present day perennial shifts of icing sites apparent, but so is a whole series of various more andent sites.
Research into theperennial dynamics of groundwater icingshas convinced us that the theory of long term forecasting of icing formations for variouspractical engineering problems is verynecessary for concrete estimates of correspondingprocesses phenomena:and primarily the pecul lari ties of i ts cyclicnature (self-fl uctuation) and the induced evolution of icings. Also, paleographicreconstruction of the nature of regions with icing development cannot be sufficiently complete and reliable withoutconsideration of the dynamics oficings, and theirgeological and 1andscape-formi ng action.
REFERENCES
AFANASENKO V.E. , BULDOVICH S.N. and ROMANOVSKII N .N. 0 proyavleniyakh mineral'nykh vod v severnoichasti Kularskogo khrebta. (Occurence of mineralwaters in the southern part of the Kul arski i Range). - Byull . MOIP, otd. geol . Vol . X/XI (6) pp. 91-102, 1973. NEKRASOV I .A. , ROMANOVSKII N .N. , KLIMOVSKII I .V. and SHEINKMAN V .S. Rol 'naledei v mofologii lednikovykh dolin khrebta Cherskogo. (Role of icings in the morphology of glacial valleys in the Cherskii Range). - In the book: Gidrogeologicheskie issle- dovaniya kriolitozony (Hydrogeologicalresearch of the permafrostzone). Yakutsk, pp. 83-92, 1976. - 207 -
ROMANOVSKII N .N., AFANASENKO V .E. and KOREISHA M.M. Dinamika i geolo- gicheskaya deyatel 'nost' igantskikh naledei Selennyakhskoi tektonicheskoi vpadiny. !Dynamics and geological activity Of the icings in the Selennyakh Depression). - Vestn. MGU. Ser. geol. No. 6, pp. 52-74, 1973. ROMANOVSKII N.N., AFANASENKO V.E. and KOREISHA M.M. Naled' Ozero Gusinoe". (The Lake Gusinoe" icing). In the book: Merzlotnoe issledovaniya vyp. 14. (Permafrost Research, No. 14), Izd-vo MGU, pp. 105-108, 1974. SPRINGIS K.Ya. Nekotorye priznaki proyavleniya tektonicheski kh dvithenii v Verkhoyano-Kolyskoi skladchatoi oblasti . (Some indications of tectonic activity in the Verkhoyana-Kolyma folded region). - In the book: Neotktonika SSSR. (Neotectonics of the U.S.S "R.) Riga, Izd-vo AN Latv. SSR, pp. 223-229, 1961. SHVETSOV P.F. and SEDOV V.P. Gigantskie naledi i podtemnye vody khrebta Tas-Khayakhtakh. (Massive icings and groundwater of the Tas- Khayatakh Range). M. , Izd-vo AN SSSR , 81 pages , 1941 . YAKOVLEV O.N. and KOREISHA M.M. Merzlotno-gidrogeologicheske issledovaniya v raione Momo-Zyryanskoi nalozhennoi vpadiny. (Permafrost- hydrogeological research in the Moma-Zyryanka superimposed basin). In the book: Inzhenernye izyskaniya v stroitel 'stve, Ser. 11. Geokriologicheskie issledovaniya, vyp. 7 (25). (Engineering surveys in civil engineering, ser. I1 Geocryological Research, NO. 7 (25), pp. 34-37, 1973.
- 209 -
THE ROLE OF TECTONICS IN THEFORMATION OF PERMAFROST ON LOW PLAINS
V.V. Baulin, E.B. Belopukhova, N.S. Danilova, G.I. Dubikovand A.Ya. Stremyakov Industrial andResearch Institute of EngineeringSurveys in Contruction, Moscow, U.S.S.R.
Inrecent years, the effect of tectonicson permafrost, permafrost processes,and frozen ground features has attractedthe attention of many Sovietresearchers. This effect is examined in many studiesdevoted to the problems of engineeringgeology as a who1 e, and to the study of permafrost in particular. The mostclearly defined position concerning the intereaction of tectonicswith the earth's surface was formulatedby I.V. Popov (1961): "All exogenicprocesses are, to one degree of another,controlled by endogenic processes".This is one ofthe basic positions in morphostructural analysis (Gerasimov,1970). The effect of tectonics on permafrost was first observed by P.F. Shvetsov, A.I. Kalabin and N.I. Tolstikhinwith regard to mountainous regions, where it is exhibited most clearly and is reflected in the landscape.
Almosteveryone engaged in researchinto permafrost on low plains has also notedthe important significance of tectonics in the formation of Permafrost as a whole, in thedevelopment ofthe cryogenic processes and of theirindividual characteristics (Kudryavtsev, 1954;D'yakonov, 1958; A.I. POPOV, 1967; Baulin, 1966, 1970; Baulinet al., 1970; Belopukhova,1971; Belapukhova,Danilova, 1974).
As a result of thisresearch, it has been shown thatthe tectonic developmentof a territory, especially in its very recent stage, is a decisive regional factor determiningthespatial differentiation permafrostof conditions. It is justthis regional effect that determined the type of - 210 - permafrost and the complex offrozen ground features on thevast low plains (WesternSiberian, Central Yakutia and Kolyma-Indigirka). In thisregion, the effectof tectonics is of such a magnitude that it greatlydisturbs the zonal manifestationof the environmental processes.
When examiningthe effect of tectonics on the permafrost of low plains,the fluctuating movement ofthe surface, and the differentiated structuralformation and thedisturbance of the sedimentary cover should be borne in mind. The effect of tectonics on thepermafrost of the region is not exhibiteddirectly but throughother factors, including a who1 e complexof landscapeconditions; this sometimes creates certain difficulties for research intothis process. Thus, the dependence of thediscontinuous nature of permafrost on thetectonics near the southern boundary of their distribution isexhibited through the composition of theearth materials, the moisture at thesurface, and thevegetation cover. The effectof each factor on the permafrost is different and depends notonly on themanifestation but also on theamplitude of thetectonic movements. Thus, for example, swamping ofthe surface, inthe caseof subsidence, and initial growth of a moss cover,can bringabout the re-formation of permafrost, and later, when thereis excess water,can cause the thawing of permafrost.
A furthercomplication to thestudy of the problems examined in this paper is the fact thatthe formation of permafrost took place inthe Quaternaryand embraced a periodof almost a millionyears. At the same time, even the most recenttectonic stage covers 10 million years. In this case, analysisof the general system ofthe region's tectonic development isvery important. In Western Siberia,for example, thebasic features of the tectonicstructure lasted throughout the Mesocenozoic; thisgives reason for assuming inherited development of a significantpart of thelocal textures (Chochia,1968) and theirone-directional effect onthe permafrost. Inherited development of texture has also been established in severalregions of the MaritimeArctic Lowland (Velikotskii, 1974).
To date, no sufficientlyaccurate methodshave been workedout for analysis of the tectonic life of the earth's crust for the period of perennial freezingof deposits. Repeated precisionlevelling of theEarth's surface - 211 -
(Map of Contemporary Vertical Movements.. . , 1973)* is a great he1 p ir analyzingthe effect of tectonics on permafrost. However, theyonly take in theregions in the European part of the U.S.S.K. In thepast few years, a method has beenworked out forrevealing the movements of the earth's crust on thebasis of comparison of repeatedaerial photography at an interval cf 10 - 15 years(Orlov, 1975). These data show thestrong effect of contemporary movements on permafrost,particularly on high temperaturetypes of permafrostnear the southern boundary. In individualcases, it is possible to judgetectonic movements of theearth's surface by thecondition of the permafrost and thefrozen ground features.
The uneven and inadequatecoverage of the problem of interaction c;f the tectonics and permafrost partlyexplains a certain degree of schematism in thefollowing presentation of material.
DISTRIBUTION AND MEAN ANNUAL TEMPERATURE OF PERMAFROST
The tectonicstructure of theterritory, and the groundwater associated with it, is one of thestrongest factors determining the discontinuousnature of permafrost. Groundwater in zones of tectonicfaults determinesthe existence of taliks, even in thethick, low temperature pern:afrost of thearctic plains. Within theconfines of the inherited Tazovskoe uplift, where the mean zonal temperature of the ground is below -4OC, thereare many closed tali ks caused by thedissected re1 ief of this uplift. In the depressions, which arecharacterized by the evenness of their surface,permafrost is continuous, even when there are high temperatures.
In thesouthern regions, where high temperaturepermafrost is developed, thetectonics can predetermine the existence of permafrostover considerable areas.
Thus, in thesouthern forest zone and theforest-tcndra of the European part of the U.S.S.R. and in Western Siberia, thepercentage of occurrences of permafrost in regions of tectmic submergetices is considerably
.. - " * Karta sovremennykh verti kal 'nykh dvizhenii.. . , 1973 - 212 - higher than in regions of uplifts.This phenomenon is associatedwith the fact that in regions of submergence, there isconsiderable peat content at the surface,favouring the existence of permafrost; whereas upliftingis characterized by an increase in forests, and by theexistence of thawed ground, typical of forests. In the middlereaches of the Nyd River, in the regionof the Fledvezh' uplift (West Siberia), owing to the absence of peatland dissectedrelief, the zone of discontinuouspermafrost is shifted no less than 30 - 50 km inthe north in comparison with thesurrounding terrain.
The mean annual temperature of permafrost is ccntrol!ed try the tectonics throughlandscape conditions at the surface(relief, water content, vegetationcover, redistribution of snow).
It is characteristic of tectonicuplifts to have variationsin ground temperatures by areathat are related to thedissected character of the surface. Thus, inthe north of the Tazovskii Peninsula (Yamburgskae uplift), thedifference in temperature throughout thearea is approximately 8'. On the whole, the mean annual temperature is higher than in the depressions,although inindividual areas the ground temperature may be lower.
CRYOGENIC STRUCTURE OF PERMAFROST
It is thespecial features of thetectonic reyinle and its accompanyiEg sedimentation and denudationprocesses onlow plainsthat gave riseto the formation of permafrost of variouscompositions ar,d structures. Marine transgressions, caused by recent movements and fluctuations cf the glob21 ocean level, covered the northernextremes of Eurasia for the larger part ofthe Pleistocene. The variousintensities and directivities ofthe neotectonic movements determined thechangeability of the composition and thickness of theunconsolidated deposits, and also their levels of freezins. Thisfurnished a reason fordividing and arrangingFerrnafrost intoarch type and depression type.
Arch typepermafrost of the low plainsis inherent in tectonic structures(arches, uplifts, etc.) of the Mesozoic cover. Changes in the lithologicalfacies inthe sections of Pleistocenedeposits on positive - 213 - structuresare associated with lag, which Gccurs when thereis a general lowering of terrain: and advance, where thereis doming, (Matveeva,Perugi n, 1971). In such sections even insignificantfluctuations of sealevelare registered. The sedimentationcycles of polartransgression on positive structures were exhibitedin the lithological variety of sediments (facies non-recurrentlayers of sands,clayey sediments with intercalations and lenses of coarsegravels). In sections of thearch type, the sands and gravels correspond to theregressive stage of the polarbasin. For Pleistocene deposits of the archtype, thefollowing arecharacteristic: erosion, interruptions in sedimentation, and rapid facies variatiGns thecf lithological compositionover a shortdistance. Tectonic structures that are composed of Paleogene and Cretaceousmaterials downwards from thesurface, and which were either stable or dominated by denudationprocesses for most of the Quaternary,should be regarded as an extreme example ofarch type permafrost.
Observations show that in thestructure of thepermafrost in the niost recentpositive structures, great variations can be observed in tt,e dependence on thebasic directions of development, i.e., denudation or accumulation of sediments.
1. Within theconfines of the most recent positive structures of denudationdevelopment, epigeneticpermafrost with indisputablesigns of inur!dation prior to, and during freezing,is widespread. The upper horiz0r.s of theCretaceous and the Paleogene clayeymaterials, forming the numerous positivestructures of the second and third orders in the north of Westerr1 Siberia and the KhatanyaLowland, covtar’n differingquantities of ice and are characterized by a complex crJogenic structure. Since all positivestructures in these regionsreflect vast disjunctive disturbances in thePaleozoic base and the Mesocenozoic cover, a certain dependence of high icecontent of the materials within thestructure on thetectonic disturbance and high degree of water encroachment during the period of freezing can be traced. The materials arefractured by a system of fissures in two intersectingdirections, through which groundwater would circulate,i.e., along the bedding plane and at at? angle to it. The bearing of the fissbres in thematerials of the Mesocenozoic covercorresponds to thebearings of thetectonic disturbances of the base (Geologicheskoestroenie/Geological Structure/. . . ., 1968). Through these - 214 - fissures, which served as collectors,artesian discharge water would rise to thesurface; this water would bring about high icesaturation in the upper horizons of thefrozen clayey layers andwould form enormous hydrolaccoliths (the sulphate-sodiumccmpositim of the ice core points to deep seated water). For as far as the systems of tectonicfissures can be traced within the positivestructures over vast areas andhave definiteorientation, so can a high ice saturation of thematerials be traced within positive structures over vast areas with the same orientation. Areas of Pre-Quaternaryclayey materials with high icecontent appear in the locality as linearridge landscapeforms. Features characteristic of the structure ofpermafrost clays withinthe confines of thepositive structures of denudation development are: fissuredtype of cryogenic structures, deformations of ice streaks (faulted or dislocated along thevertical by severalcentimetres), and extremely high ice content (40 - 60%) above the 40 metre layer, which decreases with depth, althoughindividual thick layers of ice czn be traced to 100 ITI and below.
Within the youngestblock structures, which rise rapidly, and among which the Tamansk uplift or1 the Gydanskii Peninsula can be included,the upper 40 - 50 metre pertrafrost horizon is composed of fissured sandy clays with a small icecontent, and dates to theCretaceous. It extends as ice saturated (30 - 40%), fissured silica clay and sandy clays with an apparentthickness of 30 m. Icefilled the bedding, fissures,diagenetic fissures and also those at an angleto the bedding. Such a distribution of icecontent in thepermafrost sectionis associated with a stronglydissected surface of an up1 ift, with drainage and desiccation of the lipper, wost fissured, weatheredhorizon of materials at the time of freezins, From the surface,to the depth of ancient dissecting of relief by erosion, which, at the moment of freezing, did not exceed 40 - 50 m (owing to thedistribution of the icecontent), sandy clays were dehydrated. Their freezingled to theformation of an upper horizon witb littleice content. Below the depth of erosion,fissured sandy and silica clays froze if thefissures were filled withwater. This is how the icyclays were formed, the covering of which is exposed in naturalsections 20 - 30 ni above thepresent-day depth of dissection.
2. Within theconfines of the positive structures, characterized inthe period of Boreal transgression by an accumulation of sediments - 215 - variegatedin the 1 ithologicalsection, epigenetic and polygeneticperaafrost formed. Theirstructure is variable; in the permafrost sections, n:aterials with high and low icecontent alternate. The relationship of these horizorls in thesection is determined by the presence of clayey and sandy (water bearing,prior to freezing)horizons. Large (thickriess to 20 m) layers of stratifiedice are inherent in this type of permafrost and are restricted in, the overwhelming majority of cases, tocontact with clayey and sandy materials. No kind of pattern of distribution by depth of eitherclayey, ice horizons or large beds of ice has been established. In Western Siberia, (Bol'shekhetskoeuplift) ice, clayey horizons are exposed by boreholes zt variousdepths from several tw,s of metres to 100 I 150 m. This is also the case with beds of ground ice that are exposed at depths of from severalmetres to l@O- 120 rn.
Of great interest are permafrostsections of positive structures in thesections of which, a change in the processes of sedinlentation and denudation in thePleistocene lias heen established. Under theseccnditicns, the upper layer of theperrrafrost section is exhibited as a polygenetic featureconsisting of alternatingepi- and syngenetichorizons of materials (west limb of the Nurminskii arch on the Yam1 Peninsula).
Depression typepermafrost on low plains is inherentin recent negative structures of the Mesocenozoic cover, in which neither any noticeable advance during the subnergence of theregion, nor lag during doming, was reflected in the change of thelithofacies - or else they were less contrasting.
It is characteristic of this type of section to be very uniform and clayeyin the composition of thedeposits. Even theconsiderable fluctuations insealevel, which in the archtype section are recorded in a change in the 1 ithofacies and discontinuities of thedeposits, are notrevealed by the con:position inthe basin typesection. When thesedeposits haveemerged from below sealevel,there is a pattern of diminishingice content with depth through thesection. Increased ice content is characteristic uf the upper most horizon of materials measurableinmetres. Eelow this, it decreases uniformly to moisture values untilthe moisture value brings it to theplastic - 216 - limit*. When there was syngeneticfreezing of sediments in basins, in subaerialconditions (periodically submerged riverflood plains of rivers, deltas, and swamps) syngeneticpermafrost was formed, thethickness of which can be measuredcanbe in tens of metres(Yana-Indigarka, Kolyma Lowlands). Syngeneticfreezing of accumulatedsediments was accompanied in polar and subpolarregions of the U.S.S.R. by the development of wedge ice and icy soil 5.
THICKNESS OF PERMAFROST
The thickness of permafrostwithin the permafrost zone is determinedby a complex of naturalfactors caused by thetectonics These factorsaffect the permafrost, by way of theheatflow, to its lower limit.
Inthe regional framework, themost important are those processes takingplace in the base,and, in the firstinstance, at the time of its consolidation (Provodnikov, 1963). The effect of thisfactor hasbeen best studied in WesternSiberia, where the rate ofthe heat flow increases approximately1.5 times froc: the regionsof ancient folding to theregions of youngfolding; this is noticeablyreflected theinthickness of the permafrost. The generalirrcrease in depth of perennialfreezing of materials from west to east (withinthe permafrost zone) coincideswith the increase in age ofthe base and, consequently,with the decrease ir: heatflow to the permafrostbase (Figure 1). An abnormallySreat thickness (to 500 m), in the Yenisei area of theplair:, is restrictedto regions of the oldest folding of the base(Baikal 'skaya and Rannesalairskaya). In the westernpart of the plain, the thickness of thepermafrost rarely exceeds 200 - 300 m, i.~., namely in tb.eseregions, the materialsof the base have been transformed by youngerHercynian folding. A considerablfincrease in the density of heat flowtowards the permafrost base takes place above thepositive structures of highsystems. A similar phenomenon, as is known, is associatedwith the heat anisotropy of stratifiedmaterials (D'yakonov, 1954) and withthe effect of groundwater(Kudryavtsev, 1954). A1 1 ofthis leads to a reduction uf
* Literally"to the limit of being able to be rolledinto a string". A standard use in soil mechanics in the SovietUnion with regard to clay. (Trans1 ) . - 217 -
100 - 200 m in thethickness of permafrost(Figure 2); thisis borne out in practiceby all anticlinal structures of WesternSiberia and Yakutianct containing Gas deposits(Baulin, 1966; Ostryi,Cherkashin, 7960). In the earth materials above a gas deposit, a low temperature can result from the shielding of the heat flow, and the potentialadiabatic expansion of the gas. This is borne out by materialsfrom boreholes in certain gas deposits of WesternSiberia.
L aJL Figure 1 L w V L L aJ e, w
Hercinian K"! L.
Dependence of thickness of permafrost (1 ) on the landscape and age of the base (2) West Siberia, 66 - 67's.
Fisure 2
Profile of the Central Vilyui Uplift. 1 - sand; 2 - clay; 3 - aleuri te; 4 - sandstcne; 5 - permafrost boundary - 218 -
CRYOGENIC PROCESSES AND FROZEN GROUND FEATURES
The tectonics of a regiondetermine the development and spatial localization of thecryogenic processes and frozenground features, and the direction and intensity of their development.
The maindevelopment withinthe confines of tectonic uplifts is in thermalerosion, small thertnokarst forms, epigenetic wedge ice,ice soil and iceveins, and frost mounds (restricted to thedrained thermokarst lakes) circleformation, slope processes (solifluction, dells, arable slopes) , etc,
In tectonicdepressions, the main development is in syngenetic wedge ice,lake thermokarst and frast heave.
Frost fracturing, wedge icefeatures and polygonalterrain are, to a considerabledegree, controlled by thetectonics. The tectonicfissured state of thematerials can exert an influenceon the formation of a mesh of frost fissures and can determine the direction of thedevelopnlent of polygonal systems, especiallyin the arches of tectonicuplifts, where tensilestresses developand make weakened zones. Possible, it is forthis very reason that a connectioncan be seen between the frostfissures and thelinear ridge relief on the tectonic uplifts of Western Siberia.
The formation of onetype of wedge icefeature or another depends onthe tectonic conditions of theregion. Thus, thicksyngenetic wedge ice is formed onlyin conditions of accumulation of sediments, i .e., in regions of considerablewbsidence. Such arethe ice wedges of the lowlands of the Northeast U.S.S.R., andCentral Yakutia. Under the same conditions, the rate at whichsubsidence takes place affects thedimensions ofthe wedge ice features:the faster the subsidence, the smaller the width of ice wedge and thegreater their vertical thickness. In conditions of uplift, it ismainly epigenetic wedge icefeatures that form; they are mainly wedge shaped, and theirvertical thickness usually does notexceed 3 - 5 m and rarely increases to E - 8 rc. In addition to wedge ice,soil ice and veinsalso develop; this is connectedwith the peculiarities of f1oodir;g and drainagE atthe surface and the materials of theseasonally thawed layer. - 219 -
The tectonicpeculiarities of theterritory also affect the formation of humnmky permafrost terrain. It is most clearly marked at the surface of theuplifts, having a great effect on theconditim of the permafrost. In hukmocky terrain, the zones of discontinuous and sporadic permafrost move northwards,insofar as the trenchdepressions are usually restricted to tali ks
Thawing of ice wedges, and permafrostdeforn~ation at the surface of polygonal relicpeatlands, also proceed in a different manner in depressions and on uplifts. When there is lowering of terrain, a relativelyfast melting of wedge ice and disintegration of peatlands is observed; this is due to the excessive wetting of thesurface. On uplifts,the nlonolithic character of the polygonal peatlands is retainedlonger, even near the southern boundary.
Heaving. Perennial heaving depends on the composition of the surfacedeposits and thepresence of groundwater that ensuresice formaticr;, i .e., on the factors which are closely connected with the tectonic peculiarities of the territory. In the north of Western Siberia, within the tectonic uplands (Orlinoe, Samburgskoe), are the renowned frost mounds (hydrolaccol iths) , whichformed as a result of deep seateddischarge water. The height of these mounds reaches 30 m. Analogous heave features have been described in northern Canada,where theycomprise a system of mounds 13 - 17 m high, forming two parallelridges stretching for 50 km, These mounds are "planted" on theline of the tectonicfault and were fomied during the freezing of the deep seatedwaters that discharged along it.
Perennial heaving during freezing of variegated, nwine, P1 eistocene deposits on positivestructures in Western Siberialed to the formation of mounds af 1 esser dimensions (to 10 m) without an icecore. They havebeen examined in detail on the Urengoiskoe, the Pur-Peiskoe and ather up1 ifts .
TO heave formations developed exclusively cjn positivestructures belong the 1 i near ridge 1 andscape (Bo1 'shekhetskoe, Samburgskoe I Tab-Yakhinskoe and otheruplifts in West Siberia). It is a system of ridyes and depressions,regularly oriented in the direction cf the basictectonic disturbance, - 220 -
In tectonicdepressions, perennial frost mounds have a more limited distribution.Their growth is brought about by ice formationinclayey deposits of the floodplain facies of alluvium or lake-swamp deposits. These arethicker in territoriesthat underwent submergence during the Pleistocene and the Holocene. This type of mound has been studied in West Siberia (Yaginetskaya and Nadymskaya depressions) and in the European part of the U.S.S.R.
Thermokarst. The high icecontent in the upper permafrost horizon, and also the low degree of dissection of the surface in tectonicdepressions, furthersthe development of thermokarstlakes within them. Thus, on the Nadym-Pur interfluve of Western Siberia, lakes can occupy 50% of the surface, while in thearch region of theuplifts, it decreases by 2.5 to 10% (Lastochkin,1969).
At the same time, deep thermokarst lakes whichformed as a result of the melting of thickice lenses of injectedorigin, are encounterd within the confines of uplifts.
Upliftscharacteristically have orientedlakes and basins, as describedfor the maritime plains (Stremyakov,1963; Velikotskii, 1972) and Western Siberia , where they are found in thedepressions (Andreev, 1960). The orientation of lakes is caused by their confinement to lines of tectonic disturbances.
On up1 ifts, thermokarst combines with the processes of thermal erosion; this leads to the development of an erosional network of gullies , to thedissection of thesurface, to the loweringof lakes and to theformation of khasyrei (West Si beria) and alas (East Siberia). Alas and khasyrei are widely distributed even within theconfines of uplifts, but thepercentage is much higher in relation to the generalfrequency of lakes on uplifts,
Reformation of permafrost, which is taking place at present on the western region cfthe perrnafrcst zone, and which, on the whole, is caused by thecooling'of the climate that began in the Fifties,is also controlled by thetectonic regime cfthe territory. In tectonicdepressions of the taiga - 221 - zoneofWestern Siberia, the most intensive reformation of permafrost is takingplace in the relatively dry areas, the gradual submergence of which leads to theaccumulation of moss cover. An increase in the amount of water inthe damp areas,under these conditions, can give rise to anothereffect, i.e., it can lead to thethawing of existing permafrost. On thetectonic uplifts of this zone, reformationof permafrost is characteristic for the extremeareas of bog which are inthe process of draining and whichborder on theforest, where there is intensegrowth of mosses. Thistype of phenomenon is observedon the Vyngapurovskoe uplift of the Siberian Uvalas.
REFERENCES
ANDREEV Yu.F. Mnogoletnyayamerzlota i ee znacheniedlya poiskov strtiktur na severeZapadnoi Sibiri.(Permafrost and its importance in the investigation of textures in the north of Western Siberia). In thebook: Ocherki PO geologiisevera Zapadno-Sibirskoi nizmennosti(Studies on thegeology of the north of the West SiberianPlain). Trudy VNIGRI, No. 158, L., pp.191-218, 1960. BAULIN V.V. Moshchnost'merzlykh tolshch kak odin izpokazatelie tekto- nicheskogostroeniya raiona. (Thickness of permafrost as an indicator of thetectonic structure of theregion) Geolagiya i geofizika, No. 1, pp. 53-61, 1966.
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BELOPUKHOVA E.B. and DANILOVA N.S. @sobennostiformirovaniya mncgolet- nemerzlykhporod doliny rek Pravoi Khetty i Fladyma. (Pecul iari ties in the formationof permafrost in She Val 1eys of thePravaya Khetta and Nadynl Rivers) . Trudy PNJI IS, No. 29, M., Stroizdat, pp. 103-110, 1974. - 222 -
VELIKOTSKII M.A. Svyaz'termokarstovykh protsessov c neostrukturami i intensivnost'yu noveishi kh tektonicheskikh dvizhenii na territorii Yano-Omoloiskogo mezhdurech'ya. (Connection of thermokarstprocesses with the neostructures and intensity of recent tectonic movements in the territory of the Yana- Omoloi Interfluve). Problerny kriolitologii (Problems of Cryol i thology) , No. I I Izd-vo MGU, pp. 54-64, 1972. VELIKOTSKII M.A. 0 rolitektonicheskoi treshchinovatosti v razvitii tennokarsta na severe Yano-Omoloisogo mezhdurech'ya. (The roleof the tectonic fissured state in the north of the Yana-Omoloi interfluve) Problemy kriolitologii (Problems of Cryolithology), No. IV. Izd-vo FPIGU, pp. 244-251 1974. Geologicheskoestroenie i prognoz neftegazonosnosti severa Zapadnoi Sibiri. (Geologicalstructure and the prediction of the presence of oil and gas in the north of Western Siberia). Trudy VNIGRI , no. 263 , L. t'Nedratl, 246 pages, 1966.
GERASIMOV I.P. Osnovnye printsipy i zadachi morfostrukturnago analiza. (Basic principles and problems of morphostructural analysis) In the book: Primenenie geomorfologicheskikh nletodov v strukturno-geologicheskich issledovaniyakh.(Implementation of geomorphologicalstructural methods in structural geology research) , M. "Nedra" 1970. D'YAKONOV D.I.Geotermiya v neftyanoigeologii. (Geothermy in petroleum geology) . M. , Gostoptekhizdat, 277 pages, 1958. Karta sovremennykh vertikal 'nykh dvizhenii zemnoi koryVostochnoi Evropy. (Map of contem orary vertical movements of the earth's crust in Eastern Europe P Scale 1 : 2,500,000. Edi tor-in-chief - Yu.A. Meshcheryakov,1973. KUDRYAVTSEV V.A. Temperaturaverkhnykh gorizontov vechnonwzloi tolshchi v predelakh SSSR. (Temperature of the upper horizons of permafrost in the U.S.S.R.). M., Itd-vo AN SSSR, 184 pages, 1954. LASTOCHKIN A.N. Rol 'neotektoniki v raspredelenii i morphologii ozer severa Zapadno-Sibirskoiravniny. . (Role of neotectonics in the distribution and morphology of the lakes of the West Siberia Plain).Izv AN SSSR, Ser. geogr. No. 5, ppi 79-86, 1969. MATVEEVA T.A. and PERUGIN N .N. Nekotoryeosobennosti stratifikatsii neogenovykh (miotsen-antropogenovykh) otlozhenii severa Zapadnoi Sibiri . (Some peculiarities of the stratification of neogenic(Miocene-Quaternary) deposits of the north of Western Siberia). Trudy VNIGRI No. 293, "Nedra" , pp. 57-74, 1971 , - 223 -
ORLOV V.I. Analizdinamiki prirodnykh uslovii i resursov.(Analysis of the dynamics of environmentalconditions and resources). M., "Nauka" , 275 pages, 1975. OSTRY G .B. and CHERKASHIN A. F, Povedeni e nizhnei grani tsy vechnomerzlykh porodkak odin iz kriteriev pri poiskakh struktur na severo-vostoke Zapadno-Sibirskoinizmennosti . (Behaviour of thelower permafrost boundaryas one of the criteria during research into the texture an theNortheast of the West SiberianLowland) "geologiya i geofizika" NO. 10,pp. 62-68, 1960.
POPOV A.I. Mertlotnyeyavleniya v zemnoi kore(krioli tologiya). (Permafrost phenomena inthe earth's crust (cryolithology)). Izd-vo MGU, 304 pages,1967.
POPOV I.V. Inzhenernayageologiya SSSR. (Engineeringgeology of the U.S.S.R.). Pt. 1 Izd-vo MGU, 178pages, 1961 . PROVODNIKOV D.Ya. Karta tektonicheskogoraionirovaniya Zapadno-Sibirskoi plity. (Map of tectonicregionalization of the Western Siberian platform).Novosibirsk, Izd-vo AN SSSR, 1963. STREMYAKOV A.Ya. K voprosy o proiskhothdeniiorientirovannykh ozer. (Probler of theorigin of orientedlakes). Ir, the book: Mnogoletnenlerzlye gornyeporody razlichnykh raionov SSSR, (Permafrost in varicus regions of the U.S.S.R.). M., Izd-vo AN SSSR, pp.75-107, 1963. CHOCHIA N.G. Lokal'nye (struktyroobrazuyushchie) neotektonicheskicdvizheniya severanizmennosti i ikhvyrazhennost' v rel'efe. (Local (structure- forming)neotectonic movements in the north of thelowland and their manifestationin the landscape). Trudy VNIGRI, No. 263, L., "Nedra", pp.166-173, 1968.
225 -
CRYOLITHOGENESIS AS AN INDEPENDENT HYDROTHERMAL TYPE OF SEDIMENTARY PROCESS
Sh .Sh . Gasanov Pacific Institute of Geography, Vladivostok, U.S.S.R.
The theory of cryolithogenesls is a promising comprehensive trend in permafrost studies allowing us to elucidate more thoroughly the structural and texturalpatterns of frozen earth materials, to assess theirproperties and to work out scientificallysubstantiated forecasts of their short- and 1ong-term development.
The position of cryolithogenesis thein system of physico-geographicalvariants of soil and rockformation on Earth is del ineated by hydrothermal factors predetermining and modifying geoenergyand stresslevels of thetotal conjunction of simplesedimentary and diagenetic processes and mineraltransformations (Popov 9 1967 , 1976; Shilo, 1971 ; Gasanov, 1973, 1976; Danilov, 1973; Katasonov, 1973, etc.).
As was demonstrated earlier, cryol ithogenesis as a zonal hydro-thermotype of thesedimentary process develops in areas with a positive balance of theatmospheric moisture and withnegative temperatures atthe base of the activelayer; futhermore, the outer boundary of thecryogenic zone coincidesapproximately with the boundary of thephreatic belt in the humid zone (Gasanov , 1976).
Innature humid rock-formingprocesses are replaced by cryogenic processes gradually and thelevel of stress, 1 ithogenetic effect and diversity of thelatter increases in the directlon of high latitudes as the air temperaturesdrop. The extent of thephysico-chemical alteration of the
Proceedings ThirdInternational Conference on Permafrost, Vol. 1 $ pp.271 - 276, 1978 - 226 - mter involvedin lithogenesis is a function of thelength of time during which itis subjected to the given dynamic and hydrothermal conditions, a circumstancedetermined in its turn by thepotential energy of thematerials transported into the zone of hypergenesis.This energy depends on the altitude, at which thematerial in question is found in the given terrain, on thelatitude of the locality and on thedistance from the catchment basin.
Unparalleled distinctive physico-chemical 1 ithogeneticprocesses occurwithin the cryogenic zone during the main stages of sedimentation (weathering,migration, accumulation and diagenesis), as a resultof which there develop typomorphic paragenesesof earthmaterials differing radically in allthe characteristics pertaining to their Composition, structure and texture, from theproducts of lithogenesis in otherzones,
The physical and mineralogicalstabilization of the reactive components of the newly depositedsediment (i .e., mineral matter,water, solutions and gases) and thetransformation of the sediment into a sedimentaryformation occurs in thecryogenic tone below the base of the seasonally thawing layer (SThL) under thermodynamic conditions which arenot characteristic of otherzones. With respect to theirlithogenetic effect the sum total of theprocesses occurring below the SThL may be referred to the category of diagenetic processes (Popov, 1967;Danilov, 1973; Katasonov, 1973), with the foot of the SThL acting as thephreatic surface of the groundwater outsidethe cryogenic zone, kdhich forms the boundarybetween two media differingin regimenand physico-chemical state.
As is well known, the main distinctive features in the composition,structure and texture of the products of Cryogenic diagenesis (both subaerial and subaqueous) are determined by the temporal relationship between theprocesses of accumulation and those of long-term freezing. Correspondingparageneses of frozenrocks are established in conformity with the above. The parageneses are amalgamated into types and subtypes, the systematicposition of which may be representedin the following form (a point on which most cryol itho1 ogists agree). - 227 -
Cryogenicdiagenesis subaerial andsubaqueous)
_I Syngenetictype Epigenetictype 1 1 J + Subt es Subtypes es Subt northern southern synchronous- asynchronous-synchronous- southern northern (freezi ng epigeneticepigenetic(freezing the from the fromfrom the bottom up)bottom" top down) The specificaspects physicalof andchemico-mineralogical transformationsin the cryogenic zone at the stage of the mobilization matter aredescribed in I.A. Tyutyunov'sworks (1960). The most effective processesarethose of thephysico-chemical weathering constituting a succession of severalinterrelated elementary processes, as is illustrated in the fol lowing diagram:
Disc harge joints Zone of preliminary disintegration h '> C1 eaving
L Zonecryogenesis of
As a result of this, a fraction of the internalenergy of primary silicates andalurnosilicates istransferred tothe surface of clastic materialsthus increasing their physico-chemical activity and stimulatingthe developmentof the intricate cryogenetic complex of processes.Cryogenesis, which commonly develops inneutral, weakly alkaline or weaklyacidic media, is accompaniedby leaching, as well as by verticalredistribution and removal in a definite sequence of themobile products of decay (Tyutyunov,1960). At the same timethere takes place a synthesis of low-temperatureminerals with a predominantlyhydromica-montmorillonite composition (Konishchev, 1973; Uskov, 1973). Duringthe weathering, the processes of iceformation fulfill a dualfunction being both an effectiveweathering agent and a component of theresultant earth materials, where they act as an authigenicmineral. At - 228 - theinitial state of themobilization of matter,the ice forming in themophysicalweathering joints causes cleaving which exceedsthe resistance of earth materials to rupture;furthermore, the formation and melting of ice in theinterstitial spaceensure the displacement of theresultant fragments and theirshift in the horizontal direction.
In the event of completecolmatage of the pore space with products ofphysico-chemical weathering, the ice formation in the seasonally thawing layeracts in yet another capacity contributing to theseparation of the polydispersed system with evacuation of coarserfractions to thesurface. As this type of sortingprogresses, while weathering of thematerial transported to thesurface continues, the lower layers of theprofile invariably change to permafrost under conditions of reducedwashout. Moreover, the i ce (segregated and cement ice), as well as crystallohydrates become then incorporated into the sequence of frozenearth materials as new typomorphic mineralformations.
As a result of the joint effect of the processes examined and their development inenvironments with reducedwashout, there forms in flat water-dividingareas of thecryogenic zone a distinctlydifferentiated weathering-crustprofile of the cryogenictype (Gasanov, 1973). Taking into account the specificnature of theweathering processes (cryogenesis) and the distinctive composition and structure of their products,this type of weathering crust maybe referred to ascryogenic-siallitic.
During theslope stage of cryolithogenesisthe migration of the materialmobilized by weathering isrealized under theeffect of a series of successive typomorphic physicalprocesses based on periodicformation and melting of ice. We can distinguishseveral belts on theslopes of a complete profile of thecryogenic zone. These beltsdiffer in the dominant. of the cryogenic 1 ithogeneticprocess and arecontrolled by thesteepness of the slope and by thecomposition of mobile weathering products.
In theapical portion of the slope the movement of the rock-block, material iseffected through separation and expulsion of frozenwater fragments in micro-lows of theslope and inthe porespace of the parts of - 229 -
Continuingphysical and physico-chemicalweathering processes pave the way for other forms of denudation, first of all for subsurface washout of sar,d and landwaste by thaw and rain water. The products of the washdown gradually fill the porespace and often form debriscones, which may coalesce here and there, alongthe periphery of thebelt of rock-streams.
Below the second beltthere occurs separation of the polydispersed wedium once the interstitial space has been filled with silt, in which ice formation under theeffe?ct of theseasonal freezing and thawins ispossible. The separationis accompanied by theevacuation to the surface of coarsely fragmentarymaterial (residual freezing out). The magnitude of thefreeziny out offragment H inthe course of thecorresponding freezing-thawing cycles n is determined by the verticalarea of contact of thefragment with the freezingsoil or rock sh on the onehand and by the mean nsgni tude of heave ah on the other:
H = Shf (Ah)n
As soon as a definite amount of fine-grainedfractions accumulates in theincryogenic talus and thecoarsely fragmentary material beconies uncohesivebecause of separation,the washdown of thetalus gives way to solifluction, a qualitatively new processplaying a major part in morpholithoyenesis of theslopes in the cryogenic zone. As a result of the work carried out by L.A. Zhigarev, V.S. Savel'eva and otherresearchers, it has been established that solifluctionis a viscous-plasticlaminar flowage of thawing or freezing humid dispersedearth materials, The epures of their velocity and tangentialstresses are roughlydescribed by the Shvedov-Bingham's rheologicalstability law forthe case of tangential - 230 -
stresses r exceedingthe long-term shearing strength of thesoil or rock by rL-t*:
r = yhsin+; r = r dV L-t + aT' where y is the volume weight of theearth material ; h is the depth from the surface ; I-, stands forviscosity of unfrozen earthmaterials; dV is the verticalgradient of velocity; and @ isthe angle of theslope.
We may thus distinguishfour lithodynamic belts with nlobile and diffuse boundaries on theslopes of the complete profile in thecryogenic zone. In tectonicallystable regions with a fairly srnooth relief and stable climaticconditions the belts examined gradually move up theslope and become superimposed one upon another.
In an environment marked by theascending development of cryogenic lithodynamicbelts, various types of subterraneanice change to thefossil stateas new diageneticformations. Down theslope theprocesses of underground ice formation become increasingly more complex with formation of progressivelylarger agglomerates in the followingsequence: cement-ice, segregatedice, wedge ice. The above complex of different types of ice formation ischaracteristic of theslopes in complete profiles and in the event of the lower belts becoming reduced as a result of intensified denudation(washout) processes, the concurrent types of ice formation drop out.
In the areas, where thestructures and textures of thecryosphere are of thecontinental type, fluvial processes play the leading part in the evacuation of thematerial transported to the foot of theslopes, as well as in its mechanical and faciesdifferentiation. The formation of alluvium in thecryogenic zone is accompanied by a number of typomorphic, ccncurrent or overprintcryogenic processes. These processes have a marked lithogenetic effectparticularly clearly perceptible during the"constrative"** phase.
* L-t. = long-term.(Transl .).
** Unable to findthe meaning of the term "constrative".(Transl .I, - 231 -
Because of this, a5 well a5 due to cryogenicdiagenesis, the products of the fluvial accumulationacquire distinctivefeatures ofcomposition, texture and structure, which are not characteristic of otherzones. Their specific nature is preciselythe evidence, on thebasis of which A.M. Katasonov, A.I. Popov and Yu .A. Lavrushi n set apart a1 1 uvium as an independentgeographical variant.
AI luviumfrom mauntain streamsof the cryogenic zone isaltered but slightly and revealsall the distinctive features of composition, structure,texture and faciesratio characteristics of alluvium from the humid zone (Shantser, 1966). The distinctive dynamics of theprocesses shaping river beds, as well as of erosion and accumulationprocesses in the mountain belt result in a significant preponderance of beds exhibitingthe synchronous-epigenetictype of freezing. Because of this and in conformity with the composition of the predominant earth materials,the ice formed here is mainly of the ice-cement type.Ice-rich sediments with streaky cryostructuresare therefore found at localizedsites in the rock-sequences of terraces and flood-plains cf mountain streamsin the form of lenses of a small extent. In conformity with thedistinctive nature of cryolithological structures and texturesdescribed above, thermokarstprocesses have a limited development inalluvium from the mountains and play a minor role in the morpholithogenesis of thevalleys. The alluvialdeposits examined thus form one singleinter-related complex with deposits of the slope series and with those of mountain or valleyglaciers. This complexcan probably be treated as having the rank of a cryolithologicalformation from mountainous countries,
Alluvium of therivers from the plainsin the cryogenic zone in an environment, where erosion and accumulation areperceptibly affected by cryogenicfactors at every stage of the hydrographicsystem.
Fluvialdeposits building river beds or found in suspended state, are largelysilty in composition and representthefinal product of weathering (Konishchev 1973). Because of this,as well as due to the continuous exchange between the fluvialdrift (building the river bed or suspended) on the one hand and deposits from river banks on theother, the - 232 - differentiation of theprincipal alluvial facies by grain size is rcla-Lively small. The differencesin the structures and texturesof the sudinient are more pronounced.
The most clearlyperceptible signs of the effect of cryogenic factors on erosion and accumulation havebeen recorded in theflood-plain horizon. The growth of syngenetic wedge ice (WI) is of primaryimportance among thesefactprs. Wedge icealters the morphology of thefluvial plain, its hydrologicalreginen and sedimentation dynamics, as well as the composition and structure of thesediments.
As is well known, the fornlation of WI is accompanied by the development on thesurface of a distinct relief with low-centrepolygons, As a result of thisthe hydrological regimen of the flood plain changes:flood water does not invade it frontally in a continuous layer, but slowlyseeps through thevegetation and fills polygonal depressions, whereupon only the ridges of the polygons projectpartly or complet.ely above the water. The presence of polygons in therelief markedly increasesthe degree of surface roughness.Direct erosion of theflood-plain surface commonly observedir; the temperature belt, therefore does not occur here. Flood waters do not vacate the fluvial plain with thedecline of theflood in the stream channel, as isthe case in the humid zonel but remain therefor a lengthyperiod of time, up until the winter, Suspended matter becomes deposited in still water, as a resultcf which flood-plainsedimects of thecryogenic zone are devoid of theflowing-water type of bedding. Morever, with respect to their envi ronnlents of deposition, texture and structure, these sedimects are closer to the lacustrine than to theflood-plain type. In thecontinental part of the permafrost reg’on, in the event of a certainclimatic structure prevai 1 ing , not only a1 1 of the suspended and colloidal ratter, but also the saltsdissolved in the water precipitate, as a result of which the salt contentin the sedinlents of thepresent-day flood-plain horizon increases. Under conditions of theshortage of atmosphericmoisture during the summer leading to the evaporation cf water frorrt the depressions of the polygons,the salinity of flood-plain sediments is determinedaccording to (Gasanov, 1976) - 233 - where S is thesalt content of the earthmaterials; SB standsfor the salinity of theflood water; h is theheight of the evaporating water column; y is the volume weightof the soil and istands for the mean annual thickness of the alluviation.
Wedge ice (WI) isthe most characteristicstructural and textural feature of alluvium in rivers from theplains. Under syngeneticconditions of growth WI attains significant dimensions.
In the areas governed by geothernlal conditions,the morphology, texture and structure of WI are (as has been demonstrated by B.N. Dostovalov) closelyrelated to the sedimentation dynamics. Taking into account thisfact and othervariables, we can distinguish threetheoretically possible growth patterns of WI, which determinethe main parameters of their rrlode of occurrence.
1. Lmax = a at mkh - 5,
2. -I LMX h - E,
3. L = at m-+ ma x 2m 0, where Lmax is the maximum width of an ice vein, a is the width of a rudimentary year-oldvein, m is therate of sedimentation, h stands for the depth of penetration of an open frost fissure, and 5 is the depthof seasonal thaw.
The firstpattern is possibleonly theoretically, since steady accumulation of sedimentswith the thickness specified as an unrealistic proposition. The second patternreflects the growth of syngenetic WI, and the third pattern - that of epigenetic WI
In conformity with thecondition of the second pattern at m << a wedge ice should expand in width toseveral tens of metres, and according to the conditions of thethird pattern - to infinity, i .e.$ up until it coalesceswith the next parallel vein. However, this does not occur, since - 234 -
thegrowth of WI in widthis limited by the decrease inthe width of the frostfissure with the growth of theice vein in conformitywith the well-known ratio of thethermal expansion coefficients of ice and frozen ground (Grec his hchev 1970).
The syngenetic k1I developingunder the flood-plain regime (pattern 2) , may evolveaccording tothree main patterns, asdepending on the correlation between m and a:
= 0.5 (h E) at m = a 2. Lmax -
3. L > 0.5 (h E) at < c1 max - m
The syngenetic WI formedaccording tothe first twopatterns, fails to attain its maximum size because thereserve of thethermoelastic deformationofthe block is utilizedhere incompletely: due to thehigh rates of sedimentation and correspondingdisplacement of the permafrost roof, the number of cycles of iceformation at a fixedlevel falls short of the maximum figure.Reduction of the number of cyclesat each level of ice formationis compounded bythe fact that the rudimentaryyear-old vein decreases in lengthwith expansion of theice wedge in width. The WI growing underthe flood-plain conditions according to the first two patterns has a smallwidth (Lmax+ 0.5 (h - t)), straightlateral contacts, andminimal flexuralstrain in the cores of thepolygons,
Expansionof WI inwidth in conformity with the third variant outstripsthe rate of the upwardaggradation of permafrost.Consequently at a certainstage, having exhausted the reserve of thermoelasticity of the block, the icevein attains its maximum width andceases to grow. In an environmentwith Sedimentation continuing steadily in the floodplain and a correspondingrise of thepermafrost roof, the magnitude of thermoeleastic strain of theblock increases (conversion of a two-componentsystem to a single-componentsystem with maximum values of the thernalstrain coefficient) and the icevein starts growing onceagain. As a resultof - 235 -
mu1 tip1 e recurrences of such cycles there arises a system of "1inii tll* ice veins which are insertedinside one another andhave flexuose or scalariform lateralcontacts at the level of each cycle of renewed growth. A vein of this kind attains the maximum width all along its height (Lmax > 0.5 (h - E)). The cyclic growth pattern of WI has also been recorded in the structure and texture of polygon cores These coresare represented by series of steeply bent horizontalor ice-soil layers. Each series corresponding to a fullcycle is associated with a portion of the"limit" vein bounded along thevertical by two neighbouring contiguousshoulderings I and reflectsthe gradualreplacement of theconditions prevailing in a low centered polygon filled with water, by those of a flat polygon, as the growth of the relevantportion of the "linlit"vein discontinues.
As is well known, the growth of WI is accompanied by the evacuationto the foot of the SThL of theenclosing earth material equal in volume to the newly formed ice. In terms of the dynamic effect this type of iceformation is therefore equivalent to the accumulation on theflood-plain surface of theyearly accretion of fluvialdrift of a corresponding thickness, In conformity with therule dictating that sedimentation a.nd WI formation must be in a state of equilibrium,the rates of growth ofthe SThL vary in the transversesection of theflood-plain. In the inner flood-plain**the veins grow annually, at maximum rates and to maxinlum dimensions, whereas towards the stream channel syngenetic WI gradually decreasesin size becauseof the more intensivealluviation. The innerflood plain in thecryogenic zone thus aggrades at the same rate as theare2 adjoiningthe waterchannel or even faster, as a result of which the transversesection of theflood-plain acquires a gradient oriented towards theriver-bed rather thantowards its rear boundary, asis the case in the humid zone.Syngenetic aggradation of frozen flood-plainsediments with the parallel growth of syngenetic WI may continuefor a lengthy period of time without being interrupted by thermokarst or by lateraldrift of thestream channel . As hasbeen demonstrated by V .L. Sukhodrovskii , thelatter is restricted to a narrow belt of nleandering with possibleformation of a mass
_____~ ~ ~ ~~~ . ~~~ .. "~ * i.e. with the maximum possible width. (Transl .).
** May refer to the river bed itself. (Transl .). - 236 -
of superposed flood-plains. The iceveins overlain by a migrating watercourse,cannot thaw out completely, because on theterritory of a plain thermal settling of the stream-channel floor would lead to a reduction in the gradient or (in the event of WI having a significantthickness) may even result in formation of reversedslopes (gradients). Therefore, should a water channel finditself migrating above syngeneticice veins, theirpartial thawing from thetop will invariably be accompanied by intensifiedaccretion of stream-channelalluvium, whichwould first 1 inlit, then arrestthe degradation of permafrost. Tke hypothesispostulating that WI invariably thaws out into the "constrative" phase as a result of theintensive migration of the stream channel overthe valley, thus contradicts the dynamics of watercourseprocesses. This is one of the main reasons for the limited content of stream-channel facies in the profiles of "constrative"alluvium from the cryogenic zone versus the alluvium found in the temperature zone.
Following theestablishment on thesurface of high flood-plain conditions, thereupon of theterrace regime,overprint processes of lacustrine thermokarst begin intensivelydeveloping in wedge ice under the effect of increased surface humidificaticn, and wedge ice grows to a considerablesize by following the epigenetic growth pattern 3. In contrast tc the conditionsprevailing underneath a river bed, sublacustrine thawing way penetrate to considerabledepths, since therestraining condition mentioned earlier with reference to rivers, does not applyhere.
In theevent of thermokarst lakes beingdrained or drying outl the tali ks underlyingthe lakes freeze in a synchronous-epigenetic manner. Under certainlithological and hydrogeologicalconditions this ir,duces redistribution of free water under theeffect of pressure with stibseyuent localization and freezing of that water inconformity with the laws governiFg the formation of injection ice. In the systerc of processesrepresenting cryogenicdiagenesis, injection is thefinal stage of icefamation giving rise to the 1 argest concentrations of ground ice.
In environments of this kind ice forms in several stages. The formation of iceis triggered off by the draining of the lake, whereupon one or severalsedimentary lakes remain at the bottom of the young alas. The - 237 -
second stage is associated with freezing of the alas overburden during the first winter. The freezing is accompanied by forwation of segregated ice and by corresponding kaving of the surfaceoutside the residual lake, beneath which there rmain unfrozen earthmaterials. DGriny thefreezing of the basallayers of the: overburder? interstitial waters of theunderlyirq sand may also become involvedin theformation of segregated ice to thelevel of the maximum capillaryrise of water, i.e., to the depth of the first few tensof centimetres. Once the water contentattains the level of capillaryrupture, thehydraulic unity of the water columnbecomes disturbed and the process discontinues. In the balance of ice formation within the overburder, this category of water is therefore of secondaryimportance even with regard to the maxi mum magnitudes i nvol ved
The subsequentfreezip5 and theinclusion into this process ofthe coarse-grainedwater-saturated soil raterials fronl thetalik mark the beginning of the third developmental stage in the system. This stage is accompanied by water being expelled from thefreezing front in amour,ts exceeding the volume of the interstitial space in conformity with the fornlula (Tsytovich, 1973)
v = BnS -Ah At where V is the volume of the waterexpelled, isthe volume expansior, coefficient of water during freezing, n stands for theporosity, S is the freezingarea and Ah is the thickness of thelayer freezing during the time interval At.
In these circumstances the kinetic energyof heaving will be attenuated by the resistance of the most markedly weakened part in the roof of the system underlying the residuallakes. Consequently, t.he maximum pressurein the roof of the water-bearinglayer will be equal to the natural pressure of the layer undergoing deformation, provided we lake into account the resistance to shear along itsrear glide planes: - 238 - where p is thepressure in the closedsystem; yw and y standfor the volume 9 weight of waterin the residuallake and of theunderlying earth materials (ground), respectively; hk, and h standfor the thickness of the water and g earthmaterial layers, respectively; rs is the resistance of the layer undergoing deformation to shearalong its glidingperimeter; and t4 is the piezometriclevel (surface) of water in theclosed system. Under conditions of continuingfreezing of thesystem, the equilibrium at the roof of the aquiferwill become disturbed inducing discharge,hydrostatic suspensim and heaving ofthe roof deformed until thereestablishment of the state of equilibrium. In theevent of thetali k becoming completelyfrozen, the vol ume of the frost mound Vh wi 11 be
Vh = f3v
Starting at some initial point in the freezing of thetalik, the system begins to functionaccording to the same principle as a hydraulic press;therefore, the smaller the diameter of theresidual lake relative to that ofthe alas, the greater the resistance of thelake floor tc deformation. This suggests thatdifferential heaving is possibleonly at: a definite diameter of the residuallake. If it is below a certaincriticnl size,there will either form a flatice layer, or interpermafrostpressure waterwill persist beneath thefrozen crust, In the presence at the bottonl of the alas of severalresidual lakes with differentdiameters, all larger thanthe critical size, the site, at which kinetic energy of pressurewater becomes attenuated,will gradually shift from thelarge to the small residual lakes as the hydrochemical situation changes. Themaximum heaving willoccur beneath the few large, though shallowresidual lakes found inthe alas, where all thepressed out waterconcentrates. The lake may increase in diameter as a result of theresidual lake water retreating (in the form of a ring or half-ring) from the heaving site, and thealas deposits frozen earlier may partly thaw out and grow warmer underneath that water. In the event of an asymmetrical retreat of the lake,the heaving plane tilts in such a manner that its high face is oriented towards thedeeper part of thelake.
Heaving deformations in thelake begin at the weakest point cf the bottom rather than all over thelake floor, which is due to the uneven bottom - 239 - topography and unequal thickness of theoverburden. Up until a certainlevel the heaving occurs exclusively cn account of the infiltration of water intc the weakened zone. Thereupon (after the summit of the mount emerges above thewater level) the infiltrated waterbegins to freezecausing the mound to increasein volume accordingly and producing additionalhydrostatic pressure withinthe system. As theice core of heaving grows, the radius of the freezing frontincreases, as a result of which theice core acquires a lerticular shape.Migration of water from theresidual lake underneath the mound and theice core is precluded under thesecircumstances by the filtration pressure head in the unfrozen part of the closed system and by the correspondingtemperature stratification in the frozen zone.
Viewed from positionsof cryogenic diagenesis, the major impact. of injected ice formation in alases lies in assembling the initially disseminated and disjointed ice into a larger homogeneousmass Kith art appropriate morphologicalexpression of that block on thesurface.
The finalevent in iceformation at theconclusive stage of continentallithogenesis in the cryogenic zone is repeatedinjection, the products of which are known under the name of "icesheets" or "massive ice". Views on the mechanism governing their formation vary. These views were analyzedin B.I. Vtyurin's work (1975).
Judging from the sum total of the evidenceavailable, the ice sheets discussedcorrespond most fully, in our opinion, to the mechanism cf injection.
The position of repeatedlyinjected ice (RII) in tt-e senel al pattern of cryogeniclithogenesis is quite clear and differs from that: of tlx injectedice proper discussed earlier. Repeatedly injectedice fornls urder conditions of synchronous-epigeneticfreezing of lithologically non-homogeneous media over large areas vacated by seawater under +:he regressive regime, or of ice sheetsin foothills. bo repeatedlyirjccted ;(-E forms in the territories, where conditions of thesyngenetic formatiar, of loose overburden prevail for a long time. This is the point, wherc - 240 - repeatedlyinjected ice differs radically from injectedice proper, andwhich may serve as a key to predictingthe main distributionpatterns of the f orrner .
Loose mu1 tilayereddeposits from such territories contain differentcategories of underground waters,including gravitational water. In porous sandy or sandy-pebblymedia, within one singlehydraulic system, freewater steadily moves with laminarflow (Darcy's law). The total energy at any point in thefluid in the cross-sectionalareas of the flow, which are being compared, is defined according to the conservation Gf energy or constant head principle(Bernoulli's law) as the sum of theelevation head, nressure head and velocity head
PI ri zl+"+~=zp1 VL t-t-thp2 v; y 2g 2 y 29 1-2 where Z1 and Z2 representthe elevation of thepoints in the flow above the levelselected for ConIParison; pl, Pp and V1, VqL. arehydrostatic pressures and velocities of motion,respectively, ir! the cross-sectionalareas compared; y is the volume weight of water; g is the accelerationcf gravity; and hl ... is theloss of head in thecross-sectional areas compared.
Darcy's and Bernoulli'slaws, considered in conjunction with crle another,explain the principal mechanism Soverning the move~entc c;f groundwater in an anisotropic medium, as we1 1 as the re1 ations hip between the morphological conditions of the flow on the one hand, thehydrostatic head, velocity of theflow, and hydraulicgradient on the other.
In theevent of synchronous-epigeneticfreezing of the earth materialscontaining such waters, there occur directed changes in the boundary conditions and the motion ofthe flow becomes unstable. The flow regimen becomes disturbed as a result of permafrostbarriers arising in filtration paths and blockingthe flow partly or completely. Emergence of a permafrost barrier leads to a partial or complete attenuation of kinetic energy and to its conversion to potential energy in the forn~of adc'iticnal backwater Ah and corresponding heaving of thesurface above the obstacle, which is equal,according to Bernoulli'sequation (Utkin, 1972), to - 241 -
v; + v; Ch =
Since the water-bearingstratum within ow singlehydraulic system covers a fairly large area,the backwater may spreadever tens or hundreds of retres above the point of interception. P.5 a result OS: this there occur: areal heaving with neyligibly small gradients.Freezing of earth materials at the head of the water-bearinghorizon is accompanied by squeezing (pressing) out of excessive(relative to theextent of porosity)quantities of water. This produces additionalhydrostatic pressure in the systerri with a corresponding rise of the hydraulicgradient and heaving above the pair!. of interception, In theevent of a loss of velocity of the flct:, -increased hydrostaticpressure and continuing drop of temperatures of the earth materials, free waterfreezes beginning at the roof of the horizon. Git-letl blocking of the flow from the water-bearinglayer occurs, thelaminar flov! above the point of interception may change to a turbulent flow wi-th suspension of hard mineraladmixtures, a processintensified by the presence of frazilice in the aggregates ofearth rraterials. Curing the bulk freezirg of thistype of mixture without any sign cf the orthotropic mcchar!ish-, t.hr;re arises a layer of ice with suspended n:ineral admixturessinjilar to authogenic gas inclusions, Once theviater-bearing stratum has been completely blocked off (beingconfined within its natural boundaries and boundaries superposed by freezing),there emerges a closed system with a subsequent redistribution of water and quicksand towards its weakened sectorclony the water-impermeable layers, and with variablevelocities due to annual temperaturevariations, At this stage of theprocess there Kay form areas isolatedhydraulically from the rest of thesystem, where ice fornlaticn may proceed independently. Repeated injections of this kind are accompanied by exfoliation of thelayers of earthmaterials adfrozen to the foot of theice formed earlier, and their subsequent inclusion into the ice in the form of xenoliths. This phenomenon is particularlycharacteristic crf theperipheral parts of the sheet. J.R. RacKay's data (1972, pp. 17) on 200 wells from sheetdeposits showgood agreement with therelationship examined above between ice and enclosingsoils or rocks:in 95% of cases the ice was underlain by sand or gravelin 5% by clay; on the ather hand, in 75% ice was superposed by clay or boulder loam and only it) 20% by sand or gravel . The relationship between sheetdeposits and subterraneanpressure waters is thus obvious. - 242 -
The products of cryogenic diagenesis examined above at the stage of long-distance transport, inalhde diverse types of ground ice (segregated ice, wedge ice and injected ice) and can probably be classified as an independent cryolithological complex equivalentto the complex of mountainous countries.
The above survey of the main processes of consolidation and Subaerial diagenesis of reactive components in the cryogenic zone suggests the following conclusions:
1. The main processes of mobilization, migration, accumulation and diagenesis in the cryogeniczone are typomorphic in character because of the distinctive natureof the hydrothermal factors governing these processes.
2. At the continental stagesof cryolithogenesis in the direction from the water-dividing areas towards the terminal runoff basin, there have been distinctly observed two interrelated,yet opposite (with respect to their lithodynamic effect) tendencies. These trends are apparent in the matter tendingto assume a state of equilibrium relative to the thermodynamic conditionsin the Cryogenic zone. The first tendency lies in the disintegration, dispersion and dissipation of mineral matter accompaniedby endothermal effects and developing mainly accordingto the sandy- silty pattern. Synthesis of clay minerals in the.cryogenic zone may be 1 irnited to thegroup of hydromicas and montomorillonite. The second tendency liesin the steadily increasing contentsof ice in the products of cryogenic diagenesis,in the concentration of ice in progressively largermasses, and in the superposition (with concurrent exothermaleffects) of increasingly more complex types of ice formation in the sequence: cement-ice segregated ice, wedge ice, injected ice. These distinctive individual features of the diagenesis of matter ir: the cryogenic zone are precisely the factors, on the basisof which cryolithcgenesis has been set apartas an independent hydrothermotypeof the sedimentary process. - 243 -
REFERENCES
1. VTYURIN B.I. Podzernnye l'dy SSSR (Ground ice in the U.S.S.R.). Moscow, "Nauka", 212 pages, 1975.
2. GASANOV Sh.Sh. Geograficheskayalokalizatsiya i osnovnye cherty tip0r;ior- f i znlz kriogennogo 1 i togeneza (Geographic 1 oca1 ization and the rnai n features of typomorphism in cryogenic 1 ithcgenesis). V kn.: Novye dannye PO geoloyiiSevero-Vostoka SSSR Magadan, pp. 96-105, 1973. 3. GASANOV Sh .She Kriolitoyenet - fiziko-geograficheskii variant osadochnogo protsessa(Cryoli thogenesis - a physico-geographicvariant of the sedimentary process). V kn. : Probl emy kriol i tologii , Izd-vo MGU (Moscow StateUniversity Publishing House), Issue 5, pp. 23-37, 1976.
4. GRECHISHCHEV S .E. K osnovam metodi ki prognoza temperaturnykhnapryazhenii i deformatsii v merzlykh gruntakh (Fundamental techniques for predictingtemperature stresses and strains ir, frozenearth materials). MOSCOW, 52 pages, 1970. 5. OANILOV I.D. 0 polozheniikriolitogeneza v obshchei skheme polyarnoga 1 i togeneze (The position of cryol i thogenesis i r! the general patternof arctic lithogenesis). I1 Mezhdunar. conf. PO. merzlo- tavedeniyu (I1 International ConferencE on Permafrost). Dokl . i soobshch. Issue 3, Yakutsk, pp. 23-28, 1973.
E. WTASONOV E.N. Printsipy istoriznla i aktualiznla v geckriologii (The principlesof "historism" and "actual ism" in geocryology) . V kn .: Problenyyeokriologii. "Nauka", Novosibirsk, pp. 19-25, 1973. 7. KONISHCHEV V.N. Kriogennoe vyvetrivanie (Cry0 micweathering). - II Mezhdunar. konf. PO merzlotovedeniyu I1 International Conference on Permafrost). Dokl. i soobshch.9 Issue 4, Yakutsk, pp. 38-45, 1973.
8. POPOV A.1. Merzlotnyeyavleniya v zemnoi korelkriolitclogiya. (Phenomena caused by freezing in theearth's crust/ cryolithology). Izd-vo MGU (Moscow State URiversity Publishing House), 304 pages, 1967.
9. POPOV A.I. Kriolitogenez, sostav i stroenie rrierzlykh Forad i podzemr.ye 1 'dy /sovremennoe sostoyanie problemy) (Cryolithogenesis,compcsition, structure and textureof frozen earth materials lrd ground ice (present-day status of the problem)). V kn.: Prublmykrioiitclogii. Izd-vo KGU (Floscow State UniversityPublishing t,ouse) pp. 7-3€, 1976.
10. TYUTYUNOV A.1 . Prctsessyizmeneniya i preabrazovaniya pochv i gornykh porod pri otritsatel'noi temperature (kriogenet; (Processes of alteration and transformation of soils androcks at negative temperatures(cryogenesis)). Izd-vo AN SSSR (U.5 .S .R. Acadeci:, of Sciences Pub1 ishing touse), Noscow, 144 pages, 1960. - 244 -
11. USKOV M.N. Clinistye mirleraly nlrloyoletner'merzlylch pleistotsenovykh i sovremennykh donnykh utlozheni i Tsentral 'nci Yakuti i (C1 ay n!ineraI s ir! perenniallyfrozen Pleistocene and Recent bwtkonic deposits Gf CentralYakutia). I1 Mezhdunar. konf. po trerzlotovedeniyu (TI InternationalConference or, Permafrcst). Uckl . i soobshch.Issue 3, Yakutsk, pp. 88-92, 1973.
12. UTKIN 8 .V. Nekhanizm formirovaniyalinzovidnoyo tela v vcdotokakh i yruntakh (The mechamism governing the formatior of lenticular bodies in streams and earthmaterlals). - same as above, pp. 93-95, 1973. 13. TSYTOVICH N.A. Mekhanika nlerzlykhgruntov (Mechanics of frozenearth materials). Moscow, "Vysshaya Shkola", 445 pages, 1973.
14. SHANTSER E.V. Ocherki o gcneticheskikhtipakh kontinental 'nykhosadochnykh obrazovani i (Sketches of genetic types of contitmtalsedimentary forniations) MOSCOW, "Nauka", 239 pages. 15. 5HILO N .A. Periglyatsial'nyi litogenez v obshcheiskherlie protsessa kontinental'noyo porodoobrazovaniya (Periglacial 1 ithcgenesis in the general pattern of the process Gf continwtal ice formation). V kn. : Periglyatsional'nye protsessy , Ragaclap, pp. 3-56, 1971. 16. P'ACKAY J.R. The world of underground ice. - Anr;. Assoc. Am. Geogr. 62, pp. 1-22, 1972. - 245 -
CYCLIC NATURE OF THERMOKARST GFl THE MARITIME PLAIN IN THE UPPER PLEISTOCENE AND HOLOCENE
G.F. Gravis All-Union Research Institute of Hydrologyand Engineering Geology, Moscow, U.S.S.R.
In permafrostareas, thermokarst is one of the main factorsin the formation of aggradationplains. N.A. Shilo (1964), emphasizing itsgreat importancein the formation of thelandscape and deposits of theplains of
Northeast Asia I suggested that thennokarstlacustrine sedimentation should be regarded as a specialtype of periglaciallithogenesis. However, the history of this process has received little study, and existing views on the way in which thermokarstprocesses act on thesedimentary materials at different stages of developnlent of aggredationplains is only weakly corroborated by relevantpaleographic material,
At thepresent time, there are two basicpoints of view concernjny thehistory of thermokarst. According to the first opinion,therrnokarst and earthmaterials containing ice develop synchronically, and the age cf thermokarstformations is derived in the same way asis the age of the permafrost(Kachurin, 1961). This opinion is shared by most researchers. Recently,the first data on some datingsfor alas* sediments (Konishchev, 1974) have appeared ; these ref1 ect the long and complex devel opnlent of thermokarst.
According to the second view, thereis no temporal connection between the formationof sediment containing ice, and thermokarst (Liaranova, Biske, 1964; Tomirdiaron, 1975): duringthe Upper Pleistocene,materials with a high icecontent fornled , completing thesection of unconsolidated
" * Alas - depressionwith gentle slopes and flat bottom (Trans1 .). - Proceedings Third International Conference on Permafrost, Vol. 1, pp. 283 - 287, 1978. - 246 - sediments on theplains of NortheastAsia; in the Holocene, there was thawing cf ground ice, and formation of lacustrinelaridscapes.
In the summer of 1973, while working on the Claritime Plain and the NovosibirskIslands as a member of theexpedition from the Permafrost 1r;stitute of the Siberian Branch of the Academy of Sciences of the U.S.S.R., the author studied a number of outcrops of sediment of the alas complex, and synchronic alluvial and maritime materials. Samples of wood and peat were taken;these were datedin tt-z Institute's Kadiocarbon Laboratory, The materialsobtained allowed certainconclusions to be drawn concerningthe pecul iari ties of thermokarst development in this region.
The diagram depicts the section of the Oyagosskii Yar* an the southern shore of the Laptev Straits, 18 km south of the nmth of .the Kondrat'evayaRiver. At this pcintthe sea erodes the small nlonadnock of the ancientsurface of the Maritime Plain (the so-called edotny**) and tl-re adjoining area of the thermokarstdepression (alas).
The base of thesection consists of coastalsediments containing an abundance of driftwood (cf. Fig. , Va) . Sedimentation took place under severeclimatic conditions; this is apparent from the finesyngenetic ice veins and theprimordial, arenaceous veins which formed within the tidal zone. Accumulation cf rcarine sedimerits was acconpanied by partial,local erosion, but thawing of the perrrlafrost was not deep: the lower part of many fineice veins was unaffected. \!here ice wedges thawed eitherpartially or fully, enveloppingtextures would form; these were first described by N.N. Romanovskii (1958) The age of the specimen of driftwood (IM-232) was given as more that 42,000 years.
There is a transition upwards through the sect-ion froni coastal sediments to shallowwater sediments - lagoon or laastrine (IV) Shallow water isindicated by the rootstock of water plant:, and I;y the absence of traces of any significanttaliks. It did not affect the ice-veinsenclcsed in the coastalsedinmts lying klow.
* Yar - steep sandy bar;/: (Trsnsl.). ** Edorny (sing. - edorria) - type uf tew-airi ir Yakutia; eroded terraces, or ridges and low nlour,tair!s (Trans1 .). 247 -
Lacustrine seditrlents in turn give way very gradually to fluvial sediments (III a, b; layer 7). Theirsubaerial origin is shown by the roots of herbs,buried inthe very place where they had grown. There is an indistincthorizontal, and in places,horizontal, phacoidal bedding: the more arenaceouslayers, or supes* lenses up to 0.5 cm in thickness,alternate withthe more siltylayers, up to 0.3 cm thick. The closestpresent day ar.alog of these sediments arethe floodplain alluvia of the small rivers of the Maritime Plain, and on thisbasis, they are related to the fluvial deposits, without any inquiry into thefacies conditions of their accumulation.
The spore-pollenspectra of thesesediments contain 70 - 80% spores(mainly of green mosses), 10 - 20% pollens from shrubs and woody plants (birch, willow, alders,etc.), 10 - 15% herbpollens (mainly sedges and grasses)(analysis by A.M. Lisun).Their distribution is very similar to thesubfossil distribution of the specimens taken from thearctic wasteland on Kotel’niiIsland, with one difference; in thesubfossil spectra of Kotcl’niiIsland there is, almostwithout exception, a predominance of grass pol 1 en.
Above this, 1 ies a complex of depositsassociated with the complete cycle offorniation of thermokarstdepressions and theirersuiny degradation,right up to the stage where they beconle completely filled by fluvialsedimentation. The earlieststages of the development of thermokarst are recorded by the thermodelapsing of sediments(accorairry to M.S. Ivanov, 1972) ; these wereformed when there was thawing and subsidence of seuitnents containingice (IId; bed 6). Their upper limitis undulating and is clearly recorded as a thinlayer of denselydistributed individual pockets of peat. Above theselies a bed of thermokarst lacustrinedeposits. Some ofthe deposits thawed from the top downwards (IIc; lower part of bed 5); some of them from the bottonl upwards, away frcnl thefrozen substratunl (IIb; upper part of bed 5). The section of the alas complex is completed by lake-swmp sediKentscontaining lenses and pockets of peat; and there is alsothick wedge ice (IIa; bed 4). They accumulated and froze on the swampy bottonl after the disappearance of thelake.
* Supes - silty sand with some clay, sandy silty loam (Trans1 .). - 248 -
The absolute age of thepeat from the upper part of the bed of lake-swamp sediments is 33,720 ? 1500. According to N.V. Kind (1974), tbis date is that of the Karginian Interglacialperiod and correspoKdswith the finalstage of the Malokhetskoe warming period.Therefore, the hholecycle of developnlent of thethernlokarst depression took placeconsiderably earlier.
The spore-pollenspectra of lacustrine sediments does not differ from those of fluvial accumulations. Frorn thepalynological data, it has been assigned,with some certainty to the Karginian Interglacial:in the top layer of the lacustrinesediments the poller; content for woody plants and shrubs(alnlost invariably birch and alders)increases to 54%. Lacustrine and swamp sedirnwtsare clearly distinguished by an increase of up to 21 - 66% in thecontent of herb pollens(mainly due to grasses). The sporecontent varies within the range of 27 - 78%, thepollen content from woody plants and shrubs is from 1 to 7%. Spectra whichhave a similar composition are found insurface samples from water-logged habitats:the edges of alasses,the centralareas of concave polygons,hollows, etc,
Afterdepressionthis,the becane filled with fluvial accumulations of the same type as the underlyingceposits, which a1 ternate with lacustrine, swamp accumulations (IIa; bed 2), thegreater part of which were removed by slope processes. The spore-pollenspectra in bed 3 do not differ from those of thelacustrine and fluvial sedimnts lyins below.
The thernlokarstdepression situated next to the edomanlanodnclck fornled 'prior to the Karginian Interglacial: its age, determined, by the peat frortl the therrnodelapsing of sediments at the base of the alas complex (119; bed 14), turned out to be more than 42,000 years (IN-235).
The peatylacustrine-swamp sediments (IIa; bed 11, 121, at the top of thesection of the alas complexbegan to form afterthe lake had disappeared;this occurred 5,750 -t. 200 years (IN-230). In an outcropin the upper part of the slope of thealas monadnock, cemetery mounds are exposed, buriedbeneath a layer of solifluctiondeposits. In thethermally eroded ravine between the cemetery mounds, there is an abundance of buriedtrunks and branches of shrubs, and also of herbaceous rmains (VI). The age of the .. 249 -
remains of theshrubs was determined by theradiocarbon method as 8,570 i 210 years (IM-231) . Obviously, at that time, the thermokarstdepression was still occupied by a lake,along the shores of which, there was intensive erosion of the edoma,
The spore-pol len spectra of thestrata containing remains of shrubs arecharacterized by their high content of pollen from the woody plant and shrub groLp (74 - 94%), mainly alders. In the younger lacustrine-swamp strata,the pollen content from the woody plant- shrub group is 6 to 7.5%; in the dominant group are herbaceous pol lens (66 - 72X), mainly sedges, with some grasses,etc.
The data obtained show thatthe thermokarst depression examined, formed and developed considerablyearlier than the Holocene. During the Holocene, the lake degraded and thermokarst development virtuallyceased.
Thisconclusion can be reached from the analysis of radiocarbon datings of samples taken from thermokarstdepressions typical of the various regions of the Maritime Plain and the Novosibirsk Islands. In allcases, the formation of peatlands which complete the section of the alas complexand encroach OF the lacustrine-swamp or lacustrinesediments, began in theearly Holocene (samples IM-215, 225) or even at thevery end of the Upper P1 ei stocene (sampl e IM-227) (Tab1 e)
In Holocene depositsthere is typically, at most, only ane horizon containing remains of woody plants and shrubs. In thermokarstdepressions containing no lake at thepresent time, it isrestricted to the uppermost lacustrine sediments or to the ower part of thepeatlands covering them around the bottom. The absolute ages of the woody remains are very close: 8,570 L 210 to 9,320 k 200 years (Im-215, 225, 231). Itis to this verytime interval that thethin layer of peatin the solifluction accumulation cn the 12 to 14 metre bench of the mar ne terrace on Kotel 'nyi Islandbelongs; this indicates that solifluction ceased temporarily.Therefore, on the Mari%inle Plain,as in Alaska, on Kamchatka and SakhaliE (Kind, 1964., p. 229), the cl ivatic optimum falls at the beginning of the Holocene. Hcwever, the fomatior, of thelarge thermokarst depressions was already conlpleted by this tire. - 250 -
The yradualdisappearance of thermokarstinthe Holocene was paralleled by a lowering of the sea levelafter the maximum transgression at the beginning of the Holocene (date IM-218 to 9,660 * 220 years from the upper horizon of the 8 metre marine terrace in thesouth of Bol'shoi Lyakhov Island), and by thecarving of rivervalleys. From the upper horizonof the alluvium forming terrace 1 above theflood-plain of the Saan-Yurekh River (theterrace is relatively uniform in height and is level with thehighest point of thethermokarst depression) the date 8,270 -t. 200 years (IM-222) was obtained;the high floodplain has a date 3,460 f. 200 years (IM-221). The process of reduction of thelakes and formation of swamp sediment containiris ice at the bottom of alasses is still continuing (IN-219 and 223). Of course, the high stand of thesea level caused inundation of negative landforms and intensivethermokarst developnlent. With thefall in the sea level and the lowering of lakelevels, the intensity of permafrost degradationdininished,
The data examined above allows us to conclude that on the Maritime Plain and the Novosibirsk Islands,thermokarst develops without interruption, simultaneously wit.h theformation of depositscontaining ice; however, its intensityfluctuates. At least,for the period embracing the second half of the Upper Pleistocene and the Holocene, thermokarst development is mainly characteristic cf coldglaciation epochs (the Zyrian and theSartan epochs). A decreasein intensity of thermokarstcoincides with the relatively warmer periods(Karginian, Interglacial , Holocene).
It appears that changes in the degree of surfaceinundation, associatedfluctuations in climate, and fluctuationin sea level (the main base level of erosion) form thebasic, most cornon factorin determining the fluctuating rate of thermokarst. Marine transgressionfurthers increased inundation of theplain and consequently intensification of thermokarst.
Thus thermokarstdevelops cyclicallyand, hypothetically, it takes place as follows. Each cycle of thermokarst embraces tw relatedperiods of cooling andwarming cf theclimate, namely glaciation-interglaciation, and is dividedinto four parts. - 251 -
Stage I - time of thecold, moist climate of the first half of the Ice Age. In this period,cryogenic weathering of rocks,activity of snows and glaciers, and slopeprocesses are active in transportation. There is a sharpincrease inthe quantity of unconsolidatedmaterial reaching the rivers. As a result,despite the lowering of thesea level, there is increasedaccunlulation in thevalleys, especially at the heads of streams and in places where thereis a decrease in gradient j.e., in deltas; at points where riversleave the mountains;in places where they cross negative 1 andforms (includingthermokarst basins). There is a tendency to a wearing down of theplair,, to thefilling of thermokarstdepressions with fluvial (ardpartly slope) accumulation. Having possiblyintensified theat beginning of this stage,thermokarst development later gave way to sedimentation,
Stage 11 - time of the cold,dry climate of the second half of the Ice Age. The intensity of disintegration of earthmaterials and clf transportation of coarse materials decreases and, as a result, under the cocditions of low sea level,eriosion-denudation begins, It impedes accumulation of water on the plain and thus inhibits the development of t hermo kars t .
Stage I11 - the end of glaciationepochs, The rise insea level intensifiedinundation of negativelandscape features which existedearlier and had not been completely filled with sedimentsduring the first stage, or which had appearedagain during the second stage. As a result of this, intense developnlent of therrnokarst takes place.
Stage IV - interglacial,postglacial age. As a result of a certaindegree of lowering of the sea level under conditions of relatively little slopeprocess activity, there is erosion apd thermal erosion cf the plain; a lowering of lakelevels; and a consequent reduction inir,tensit] 6f thermokarst development. - 252 - - 253 -
Cryol ithological Section of theQuarternary Deposits inthe Outcrop on the Oyagosskii Yzr.
Left - li thologicalsection; Right - column of permafrost structure. 1 - heavy supes; 2 - lightsupes; 3 - obliqe, phacoidal crossbedding of supes arid fine sand; 4 - intercalations,lenses and pockets of peat; 5 - roots of herbs, and rootstock of waterplants; 6 - remains of shrubs; 7 - driftwood; 8 - wedges of peat in frostfissures between seasonal frost mounds ; Cr - prirxordialarenaceous veins; 10 - ice wedges; 11 - enveloppingtextures formed during total subaqueous thawing of ice wedges; 12 - as 11, but only partial thawing;13 - lenses of injectedice, cryogenic textures formed by freezing from below; 14 - concave-laminar, reticulate; 15 - concave-sporadic-laminar, phacoidal; 16 - crass bedded, cryogenic structures, formed by freezing from above; 17 -- cross-bedded; 18 - horizontal-sporadic-phacoidal "postcryogenic structure"*; 19 - horizontal-laminar; 20 - phacoidal ; 21 - upper surface of permafrost.
Genesis of deposits (columns with Roman r!uclerals .indicate cryogenicstructure); I - solifluctiondeposits formed duringdisintegration of the edcma. Alas complex: I1 a - lake-swatxp deposits,frozen from below; I1 b - thermokarst lake depositsfrozen from below; I1 c - the same, but frozen from above; I1 d - thermodelapsing deposits(frozen from above), fluvialdeposits; I11 a - frozen from below; 111 b - thawed in a sublacustrinetali k and refrozen from above; IV - sediments of shallow lagoons or lakes,off-shore marine deposits; V a - frozen from above, partially thawed during accumulation and againfrozen from above; V b - thawed under thermokarst lakes and then frozen from above; VI - talus at the bottom of a thermally eroded ravine. Composition and structuralpecularities of deposits.(Arabic ntirnerals indicatelithological section): 1 - heavy-supes, brown patterns on a bluish,dark gray ground, non-laminar; 2 - heavy supes, non-laminar, bluish, dark gray,non-laminar, with pockets of autochthenouspeat and rootstock of herbs; 3 - heavy supes,gray with brownish hues, non-lminar, denselypenetrated by roots of herbs; 4 - heavy supes, bluishdark-gray to gray non-laminar , hi th pockets and lensesof authochthonous peat, with roots of herbs; 5 - lightsupes, light grayin colour; in the upper partof the layerthere is clearlyobservable fine (1-2 mm) phacoidal bedding due to the variedcontent of arenaceousRaterials and allochthonousvegetal detritus ccntainicg a largequantity of roots ofherbs, twigs from shrubs; below this, the supes becomes more homogeneous, the bedding and roots of herbs disappear, penetratingonly rarely and indistinctly, shallowpockets of peat; 6 - licht. supes,gray, bith traces of buckling;in places, there are blocks, in the nucleus of which, theoriginal horizontal bedding is preserved; tcwar*ds the Feriphery of theblocks, the layers curve upwards or downwards; in the lower part of thelayer, there is an undulatingintercalation of individual crumblingclods of decomposing peat; 7 - lightsupes, gray, with ill defined horizontal bedding: layers which are more arenaceous and are about 0.5 crn - 254 - thickalternate withthe more siltylayers (0.3 cm), occasionalpenetration by vegetal detritus, a 1 arge amount of roots of herbs; 8 - 1 ight supes, gray, with brown patches, and with distincthorizontal bedding (thickness of layer 0.5 to 1 .O cm); thereis vegetal detritus and rootstock of water plants,all vegetal remains are encrusted with supes cemented with iron oxides; 9 - 1 ight supes, bluishdark-gray to gray,horizontally bedded with individual lenticules of fine-grainedsand, with frequentintercalatiors of vegetal detritus, with lenses of allochthenouspeat and driftwood; 10 - oblique, phacoidalcross-bedding of supes and fine-grainedsand; also contains renlains of grasses, sedges, etc.; 11 - heavy supes,bluish dark-gray to gray,peaty, with lenses and intercalations of autochthonouspeat with a thickness of up to 18 cm; 12 - lightsupes, bluish dark-gray to gray,peaty, with lenses and pockets of peat, the quantity and dimensions of which decrease with depth; 13 - lightsupes, bluish dark-gray to gray,cryptolamipar, in the upper part of the layerare rootstocks and other remains of water plants; 14 - lightsupes, bluishdark-gray to gray with shallow and crumbing 1 enses of autochthonous peat.
The smallerthe thermokarst depression, under similarconditions, the more apparent is the cyclicnature of thethermokarst + As the dimevsions of thethermokarst forms increase,the stronger is the tenciency for the processes to be repeated. Local adjustments of thecyclic processes are introduced by coincidenttectonic nwements of the Earth's crust. In morphostructures which are undergoing intense development, the cyclicnature of the thermokarst can be completelyinhibited; on positivefeatures - on account of constantsevere denudation of the surface: on the negative features -- because of constant inundation. - 255 -
RadiocarbonDating of a number of sections of Quarternary Deposits of the Claritinle Flain and the blovosibirsk Islanc!s
- """ Sampl e No. Occurrence Cepth of Conlpcsition of sample, hdiocarban extractior!layer whichfrom tiates
IM-228 Kotel'nyi Island, 0.50 - 0.60 Peat from the 10 cn 8,440 t 200 east cost of intercalation in soli- Stekhanovsk Eay in fluction deposits cover- the Arctic, bench in5 marinesediments I1 of the marine terrace (height 12-14 nl) IM-217 Bo1 'shoi Lyakhovsk 5.00 Encrustedciriftwocd >42 000 Island , south shore fror.1 the 1ower hor-izcn in theregion of in offshore deposits the mouth of the Dymnaya River, out- crop I1 of the marine terrace (height 8 n)
IM-218 as above 0.75 Encrusted driftwood 9,660 2 200 from the upper horizon iK offshore deposits
111-21 5 As above, rear of 0.70 - 0.80 Driftwood f ran; the 9,220 i 200 the same terrace, base of thepeat peat mound mound
IN-21 4 as abGve 0.005 - 0.15 Peat from the cpper 8,340 9. 2oL7 layer of the peat mound
IM-219 Fari time P1ai n, 0 .oo Peat from thesurface 2,510 1: 175 hear Uryung-Khastakh of the rim. (height lrn) Mt. , bottom of the bordering c polygon with thermo karst depres - en1 argi ng ice Kedges sior: , polygonal peat mound
IF:-220 AS above, outcrop 0.60 Wood from the upper 9,120 i 220 of the alas complex horizon of 1acus tri ne on the banks of sediKents fi11 i ng the mal 1 rivers inter- thermokarst depression secting the themo- karst depression - 256 -
IM-221 MaritimePlain 1.10 Intercalation of alloch- 3,460 -r 200 upper reaches of thonous peat in fluvial the Saan-Yurekh R., a1 1uvi UK high floodplain (relative height 1.5 m)
IM-222 As above, 1st ter- 0.75 Intercalation of autoch- 8,270 i 200 race(relative thonous peat in flood height 6 m) plain alluvium
IM-22 5 MaritimePlain, 1.80 - 1.90 Wood from the base of 9,320 k 20@ region of the peat mound Khamnaann 'a Mt . , side of thermo- karst depression, peat mound
IM-224 As above 0.20 Peat from the upper 7,670 ? 200 layer of the peat mound
111-223 As above,central 0.00 Peat 715 k 160 part of the same t hermo karst depres- sion, top of the perenni a1 frost mound
IF-227 As above,side of 4.40 Peat from base of 11,870 L 250 anotherthermokarst peat mound depression, peat mound
IM-226 As above 0.20 Peat from upper of 4,59@ t 250 peat mound - 257 -
REFERENCES
BARANOVA, Yu.P. and BISKE, S.F. Severo-Vostok SSSR (Istoriya razvitiya rel'efa Sibiri i Dal'nego Vostoka).(North-East U.S.S.R. (Historical Developnlent of the Relief of Siberia and the Far East)). M., "Nauka", p. 29@, 1964.
IVANOV, M.S. Tipy i fatsii termokarstovykhctlozhenii Tsentral'nci Yakutii. (Types and Facies of the Deposits cf CentralYakutiya). -In the book: Problerny izucheniyachetvertichnogo periodz.. (Problems of theQuarternary) . M, , "Nauka" , pp. 83-89, 1972.
KACHURIN, S.P. Ternlokarst na territorii SSSR. (Thermokarst in the L.S.S.R.). M., Izd-VO AN SSSR, p. 290, 1961.
KIND, N .V. Geokhronologiya pozdnego antropogera PO i zotopnyrndannym. (Geochronology of the Late Quarternaryaccording tc Isotopic Data),(Trudy Geologich. in-ta AN SSSR, vyp. 257). M., "Nauka", p. 255, 1974.
ROMANOVSKII, N.N. Merzlotnyestruktury obleksniya v chetvertichrykh
otlozheniyakh I (PermafrostEnveloppi ng Textures in Qmrterrlary Deposits). -h'auch. dokl.vysh. shkoly. Geologc-geo. nauki, NO. 3, pp. 185-189, 1958.
TOMIRDIARO, S.V. Kriogennaya evolutsiyaravnin Severc-Vcstoka Asii v pozdnem ledni kov 'e i yolotsene.(Cryogmic EvolLtiorI of the Plains of Northeast Asia in the Ice Age and the tioloccne) -1zv. Vsesoyuz. yecyraf.ob-va, Val. 107 vyp. 2, 1975.
SHILOV, N.A. K istoriirazvitiya nizrnennostei suhrkticheskogo pcyasa Severo-Vostoka Asii. (Ristcricalkveioprnent of the F?;;-ir.s of the Subarctic F,eI;ion of' Mrtheast Asia). -Inthe book: Tektoni ka i glubinnoestroenie Severc-Yostoka SSSR, (TEctor~im and Deep Structure of I!orthcast l:.S.Z.R.) Trudy Sw. -Vat. kompl. n. -i. in-ta SO API SSSR, vyp. 11, Flagadan, pp. 154-1159, 1964.
- 259 -
SOME ASPECTS OF THE MECHANICS OF FROST FRPtCTURING OF SOILS IN THE PERFiAFRCST ZONE
S.E. Grechishchev All-Union Research Institute of Hydrogeology and Engineering Geology Moscow, U.S.S.P..
For theresolution of some scientific and practicalgeocryological problems it is necessary to predictthe geometricparameters of frost fractures. The latterare formed in soilsin permafrostregions as a result ofthe freezing of thesurface during thewinter. These fractures, emerging onto thesurface of the soil, form a periodic,generally rectangular or close-to-rectangular system, termed fracture polygons, on theplane surface. Among the geometric parameters of frostfractures are the width of the opening,their depth and thedistance between neighbouringfractures (length of polygons). The determinationof these values nay be carried out by methods of the mechanics of continuousdeformable media.
During thewinter in thepermafrost regions the soil is frozen to a depthgreater than the depth of thefrost fracturing, for purposes of calculationthe frost fractures may be schernatized as equilibriumfractures of a normal rupture,merging onto thesurface perpendicular to the boundary of a continuous senlispace withprescribed mechanical properties. In this case,for the calculation of the depth of theequilibriurr, fractures one may utilise Irwin and Barenblatt'scondition of strengthatthe apex of a fracture(Barenblatt, 1950; Cherepanov, 1974; Razrushenie, 1975).
where k coefficient of the intensityof normal stressesin the apex of the 1 - fracture, Klc - a physicalconstant - theviscosity coefficient of failurein the apex of a fracture of a normal rupture.
__I ProceedingsThird International Conference on Permafrost, Vol. 1, pp. 289 - 294, 1978. - 260 -
TO determinethe coefficient of theintensity of stresses, kl, it; is necessary to have a solutionconcerning the distribution of stresses around thefracture. Since around thefracture there is formed a zone of re1 ief (Lachenbruch, 1962), within which thestresses are found to bc below the iimit of thelong-term strength (Grechishchev, 1962), thedetermination ofthe stresses may be carried out if one makes thesimplifying assumption that the frozerl soil works as an elastic medium.
Let us consider the solution to the problem of the thermoelastic statein the vicinity of two marginal fracturesin a half-space, The boundary conditions of this problemhave the form (Figure 1):
where CIO depth of and 8x' y' roxy - stress components; hl and h2 - first second fractures; 21 - distance between fractures.
Figure 1
""""
X
Schematic diagram fGr the calculation of thethermal-stress state of a block with fractures: a) - for a singlefracture, b) - for two fractures; 1 - schematiccurve of the thermal stresses ux close to the surface of the soil y = 0. - 261 -
Let us represent 0 ik (i,k = x9y) inthe form of the SUK of the known stresses p ik in a continuous(without fractures) half-space with the same temperaturefield and certainadditional stresses oik, i.e.,
Then thefield of theadditional stresses should be determinedon thebasis of (2) withthe following boundary conditions:
where p xl’ px2 - stressesin the continuous (without fractures) half-space on the linescoinciding with the contours of the first and second fractures.
For the case, which isimportant in practice, of fractures that arelocated at a distancefrom one another(h1/21 < 1 h2/21 < 1 ) we will presentequations, which we obtainedby Kolosov andMuskhelishvili ‘s method (Muskhelishvili , 1966), for deternliningthe coefficients of theintensity of stressesin the apexes of thefractures, the width of the opening of the fractures and thenormal additional stresses tangential to the surface y = 0.
Theequations for thecoefficients of intensity of thestresses are: - 262 -
The equationsfor determining the width of the opening of the fractures are:
where St I S2 - width of opening of thefirst and second fractures respectively ; EL.-tP - limiting long-term modulus of deformation with tension; v - Po1'sson's coefficient:
The equation fordetermining the normal additionalstresses tangential to the surface y = 0 is:
With X1 = A = 0 expressions coincide with thesolutions 2 (5) - (7) for a single fracture, obtained in previousstudies (Karpenko, 1965; Savruk,
1975) * - 263 -
Below we willconsider the most frequentlyencountered case of fractures that are of the same depth,i.e., in equations (5) - (7) we will assume hl = h2.
For frost fracturesthe load p,(y) , includedequationsin (5) - (7) and representing the stresses theundisturbedin (without fractures)half-space, is the sum of the temperaturestresses pt (y) and of X thestresses of the intrinsic weight of the soil pl(y), i.e.,
Let US considerthe effect of each of the components of these stressesseparately.
The thermal tensilestresses pi(y) in an elastichalf-space with a load-free boundary may be calculatedaccording to the well-known equation:
where a (t) - coefficient of a stabilizedtemperature ckfornlationwith a OD lowering of the temperature from -2G to t; t - absolutevalue of thenesativc temperature in up OC; L.-t - 1imi t of the long-term strength with stretchicy of the frozen soi 1.
The characteristics of frozendispersed soils ~1 m and E[.-t a re dependent on thetemperature.. At a temperature below -2OC their relatimship to thetemperature may be represented by thefollowing empirical expressiurs, which are insatisfactory agreement with the experimentaldata that were citedin a previousstudy (Grechishchev, 1971):
where Eo, BE, a0, B~ - empiricalvalues . - 264 -
Let us assume that the temperature of thesoil surface during the winter t changesaccording to the periodicprinciple: TI
where t mean minimal temperatureof the soilsurface during the coldest 01 - month; w1 = 0.2~10-~ l/c - frequency of temperaturefluctuations, corresponding to a periodequal to theduration of the winter; r - time.
Then for approximatecomputations the temperature of thesoil may be calculated according to the we1 1-known equation:
where u1 = m;aM - coefficient of thermal diffusivity of the frozen soi 1.
Expression (12) will be the more accurate the furthernorth the region is located from the southern boundary of the permafrostzone.
We may presentexpression (9) with the help of the empirical relationships (10) in the following form:
In practice we have established, on the basis of data thatare availableto us, that fcr a wide range of frozensandy-clay and peat soils the followingconditions are alwaysobserved: - 265 -
These conditionsallow us to introducethe approximation
theerror of which inthe range of -2O+ t < tO1 does not exceed 10%. Thus equation(13) may be given thefollowing form
Let us takeinto consideration also the following circumstance. The occurrence of fractures is possible onlyin the case when thetenlperature stressesclose to the surface of thecontinuous block of soil exceed the limit of the long-term tensilestrength. Calculations show that such exceeding, as a consequence of theviscous and plasticproperties of the soil,turns out to be one or two ordersof magnitude smaller than thelimit of the long-term strength. At thesurface of thesoil, therefore, with y = 0 and t = tO1 thetemperature stresses may be taken as being equal to the limit of the long-term tensile strength, i .e.,
where 8 (to,) - limit of the long-term tensile strength ofthe frozen soil at a temperature of t 01 -
Taking thisinto consideration, expression (15) may be writtenin the form of thefollowing definitive approximation:
where t is determined by equation (12).
The stresses from theintrinsic weight of the sGil ir; a continuous ha1 f-space are determined by the well-known expressions: - 266 -
Sincethese stresses, incontrast to thetemperature stresses, are compressive and with compression of frozen soils v =: @.5, then it may be assumed inapproximation that:
By substitutingexpressions (19), (17) and (12) into (8) and then into (5) - (7) and by employing numerical methods for calculatingthe integrals,it is possible to calculatethe unknown parameters of thefrost fractures. Onlitting the details of thecalculation, we willpresent some results for the case of fractures of the same depth, assuming in equations (5) - (7) that hl = h2 = h, X, = X - h = h/21. 2-
Figure 2
of x2 n3 125 1 I
-t,"C 24 6 8 io 12
Relationship between the viscosity coefficient of failure Klc and thetemperature of frozen soils 1 - sand with W = 10 - 17%; 2 - supeswith W = 20 - 25%; 3 - peat with W = 300% (W - total moisture content by weight). - 267 -
Calculation of the depth of frost fractures
Experimentaldata available to us (Figure 2) allow us to establish thatthe viscosity coefficient of failure KlC, included in expression (]I), is approximatelyproportional to the square root of the absolute value of the negativetemperature in 'C. Thus we may approximately assume:
The values of functions -t kc' kl q, Kc and i$ arepresented in Table I and 11. InTable I thelast column refers to a singlefracture.
The deternlination of thedepth of the fracture from equations (21) arc (22) may be carried cut, for example, by a graphical method making use of Table I and 11. As an example we will present the results of calculations based on this equation with = 10 and t = 6.1 (Figure 3). As is cp/t 01 evider.t in Figure 3, the calculatedrelationships between plh and 0 have two tjranches: a descending and an ascendingbranch with paints of inflection at - 268 - - 269 -
vlh = 0.7 to 0.9. It is interesting to notethat this value of ulh at the points of inflection is preserved for any r, A and t /tal, which was ascertained by us by means of directcalculations. CP
TABLE I1
Function R, 0,05 0,28 0,24 0,15 0,07 0,06 0,1 0,29 0,25 0,17 0,lO 0,09 0,2 0,31 0,27 0,20 0, 14.. 0, 13 0,s 0,35 0,32 -0,26 0,23 0,22 Function K~ 0,19 0,19 0,14 0,07 0,20 0,20 0,16 0,lO 0,23 0,22 0,18 0,14 0,28 0,29 0,26 0,23
Figure 3
-a "-6
The relationship between the depth of frost fractures u h arid the dimensionless stresses 13 with iT = 113 arid t /t = 6.1: 1 - for a single fracture (A = 0); 2 - in thebk?s&e of a neighbouring fracture at a distance of 2.5 p h from the first fracture (A = 0.4); a - in the middle of winter; t: - at the end of winter. - 270 -
The descending branch iscaracterized by the condition
which corresponds to thecondition of instability sf an equilibriumfracture. For theascending branch dh/dF > 0, i.e.,the fractures defined by this branch should be stable. If one takes into consideration that practicallyfor any soils pl = 0.33 to 0.40 l/m, then this means that the depth of the fractures growing in wintercannot be less than -1.7 m. From this it also followsthat for determiningthe depth of fractures one should utilize onlythe upper ascendingbranches of thecurves.
An examination of the graphs in Figure 3 also shows that the frost fracturesclose up partially or even completely towards the end of the winter, For example, if physicalthe properties soiltheof are characterized by thevalues K = 10 and (r = 30, thenaccording t.o Figure 3 the depthof a single fracture in the middle of wintercomprises plh = 2.7, while at the end of winter this value is p,h = 2.0, If however, for example, t,he physicalconstants of thesoil would be iT = 10 and = 15, then a single fracture in the middle of winter wouldhave a depth ulh = 2.1, while at the end of winterthis fracture would close up corrpletely (the linefor E = 15 lies to the left of the curve p1 h - (s forthe end of thewinter). Theoretically,therefore, fractures that exist only durin9 thewinter are Rot excluded. In this case, naturally, they cannot serve as a basis for the growth of vein ice,since it is assumed thatthe growth of thelatter occurs at the expense of meltwater during the spring.
An examination of the graphs inFigure 3 allows one also to reach certainconclusions concerning the influence of a neighbouring fracture on thedepth of the fracture under consideration. A comparison of the curves with X = 0 (singlefractures) and X = 0.4 (neighbourinyfracture located at a distance of 2.5 v1 h) shows that neighbouring fractures have a lesser depth than singlefractures. This means that, for example, if thereinitially existed a single(primary) fracture and laterthere appeared a neighbouriny secondary fractwe, then the primary fracturepartially closes up. - 271 -
Calculation of the opening profile of frost fractures.
and at the end of winter - beginning of spring
where y, S - dimensionless and actual value of the opening of the fracture at depth y ; (r - dimensionless stress according to equation (23).
-t The values of functions 4, Sk and !? arepresented in Tables 1I1 and IV. In Table IV the last line (A = 0) corresponds to a single fracture.
TABLE 111
Y /h 0 0,2 0,3 0,7 I1,O 111 I 0,5 1 Function 3; 1,O 0,92 0,"s 0,67 0,53 0,37 0 2,O 1, 62 0,95 0,80 0,57 0,31 0 3,O 1,38 0,97 0,80 0,50 0,20 0 Function 3; 0,5 0,04 0,040,04 0,04 0,03 0 1,o 0,12 0,12 0,Il 0,11 0,09 0 2,0 0,28 0,27 0,25 0,23 0,220 0 3,O 0, 37 0,38 0,28 0,27 0,24 0 - 272 -
TABLE IV
Y /h x 0 1 0,2 0,3 0,5 1 0,7 1.0
Function Sy 0,40 0,26 0,29 0,30 0,32 0,31 0 0,35 0,29 0,32 0,33 0,34 0,32 0 0, 25 0,35 0,37 0,38 0,39 0,36 0 0,15 0,40 0,41 0,42 0,42 0,39 0 0,lO 0,43 0,43 0, 44 0,44 0,40 0 0,07 0,43 0,44 0,44 0,44 0,41 0 0,05 0,44 0,44 0,45 0,45 0,41 0 0,oo 0,41 0,45 0,45 0,45 0,41 0
As an example in Figure 4 there are presented the profiles of single (A = 0) fractures,calculated on the basis of equations (25) and (26) with ;f = 20. As is evident from this Figure, at the end of the winter the width of the opening of the fractures on the surface is 6 - 9 times less than during the middle of the winter.
Figure 4 0.2 0,4 0.6 0,
-Calculated profiles of opening 's of single frost fractures at u = 20 and various depthsplh: 1 - with qh= 1; 2 - with plh = 2; 3 - with qh= 3; a - in the middle of winter; b - at the end of winter. - 273 -
Also ofinterest is the fact that during the middle of thewinter thefractures have clear-cut wedge-shaped out-lines,while at the end of the winterthe width of thefractures changes little withdepth, which is in accordancewith the actual observations presented inthe study byNackay (1974). Withfractures of greatdepth (for plh > 1.5) theirterminal zones are drastically narrowed,which isexplained by the increasingeffect with depth of the intrinsic weight of the soil itself.
Calculation of the equilibrium distance betweenneighbourinq fractures (width of fracturepolygons).
The formation of a second fracture,neighbouring a first fracture, obviously depends on the size of the temperaturestresses in the vicinity of the firstfracture. The character of the change of thetemperature stresses in thevicinity of the fractures is shown schematicallyin Figure 1. As follows fromthis figure and equation (7) thetemperature stresses caused by a smooth winterdecrease inthe surface temperature (long-period temperature oscillations)increase with increasing distance from a singlefracture, asymptoticallyapproaching the limit of thelong-term tensile strength at a temperature equal to to,. In this case one may explainthe appearance of a second fracture at a finitedistance from the first fracture bytwo causes: 1) the static non-homogeneity of theproperties of thesoil - fluctuation in thetensile strength (Lachenbruch, 1962), and 2) secondaryshort-period temperaturefluctuations, creating additional stresses in excess of the limit of thelong-term strength (Grechishchev, 1975). The second cause seems to US to be bettersubstantiated, since inthe case of very slow changes in temperature in a block cf soil there shouldoccur a redistributionof the stressesin such a way thatat any pointwithin the block these stresses do not exceed the 1 inlit of the long-termstrength.
Takinginto consideration that which has been presented above, for thedetermination of thedistance between neighbouringfractures we will assume the following condition of strength: - 274 - where (ox)I - stresses caused by long-period changes in thetemperature of the soi 1 surface with an amp1 i tude of tO1; ( uX) - additional stresses caused by short-period changes in the tmperature of thesoil surface with ari arr,pl itude of tO2and frequency w2.
We may note immediately that in equation (28) there is not inoluded the component of the stresses from the intrinsic weight of the soil, sincethis is substantially smaller than the thermal components.
Substituting in expression (28) the values of the included components accordfng to equations (7), (17) and (15) , and carrying out a numerical integration, we obtain:
where Q II - anlpl itude of additional stresses,
r - time of relaxation with stretching of the frozen soil; G‘ - function, determinedaccording to Table V; p2 = m.
TABLE V
(rt in the centre of a polygon 0,5 0 0,20 0,62 0,79 0,87 0,92 0,97 I,O 1,0 0 0,04 0,08 0,74 0,81 0,87 0,912 1,O 2,o 0 -0 -0 0, 12 0,83 0,91 0,94 1,O 3,O 0 -0 -0 0,03 0, 15 0,93 ‘0,98 1,O -t 4 for a single fracture 1, 0 0 0,06 0,181 0,85 0,901 0,92 0,96 1,O 2,0 0 0,03 0,05 0,26 0,900,95 0,97 1,0 3,0 0 0,Ol 0,03 0,lO 0,440,96 0,98 1,0 - 275 -
The values of u2 are 6 - 8 times larger than y . Therefore yh = 6 to 8 yh and 91 6 to 8 yl Since in practicalcalculations there are observed theconditions vl h >l , and LI, 1 > 1 , then accordir,g tc Tab1 e V it maybe assumed that
If, inaddition, one takes into considerationcondition (17) togetherwith expression (30), then equation (23) may be given thefollowing form: Ft pp= 1 - f, (32)
where
Graphs ofthe relative temperature stresses d are presentedin Figure 5. From an examination of thesegraphs and condition (32), fcr example, it follows that with f = 0.1 alongside a singlefracture with 2 depth of plh = 1 .O there may be formed a neighbouring fracture at a distatxe not closer than pll =: 3.0. This will be the minimal equilibriumdistance between fractures. Moreover, after the formation of the neighbouriny fracture the stressin the center of the polygon, between the fractures, falls to thevalue Tt r* 0.64 (in Figure 5 thecurve u1 h = 1 for two fractures at ull = 1.5). For these same conditions it is possible tu estimatethe maximum width of an equilibriumpolygon, since only those polygons will be stable for which the stresses between thefractures, 8' according to condition (32), will be smallerthan 1 - f = 0.9. Otherwise, the stresses afterthe formation of the secand fracturestill remain high and there will occur theformation of one more fracture, between thefirst two.In the givencase such a maximum equilibriumdistance between thefractures is p1 (21) = 10, sincethe stresses inthe centre of such a polygon (with vll = 5) are somewhat smaller than 0.9. Thus the graphs in Figure 5 allow one to establish the minimum and maximum width of equilibrium polygons.Fcr - 276 -
Figure 5
2 9 4 5 6 7 0 9 ' 10 "- U 6
Stresses Tt = u /crp (t ) at the surface of thesoil at distante ttfr8k a fracture ofdepth h: a - for a singlefracture; b - inthe presence of a neighbouring fracture at a distance of 21 from the first fracture.
An examination of the graphs in Figure 5 and a consideration cf the circunlstance that under naturalconditions the value of f inequatiorl (32) ranges from 0.07 to C.18 allows one to reachthe more genera! conclusior! thatin undisturbed conditions the width of the polygons, evider,tly, may range approximately within thelimits of 2 < p 21 < 12, i ,e., from 6 tc 4@ 1 nl (with p, 0.35 l/m).Therefore the descriptions, encountered in ttle literature, of polygons up to 100 m in width (see, for example,Lachenbruch, 1962) force us to propose that in the center of such pclygor,s there also existedfrost fractures which, for some reason or other, were not mar,ifestec! in thelocal stress relief. - 277 -
In conclusion wemay notethat the proposed method of calculation of the parameters of frost fracturespermits the resolution of several other interestingquestions. In particular, this concernsthe determination of the conditionsnecessary for the formation of secondgeneration fractures,
REFERENCES
BARENBLATT ti. I. 0 ravnovesnykh treshchinakh,obrazuyushchi khsya pri khrupkolri razrushenii . (Equilibrium fractures formed by brittlerupture) - "Doklady AN SSSR" (Report of the Academy of Sciences of the U.S.S.R.), Vol.127, No. 1 I pp. 47-50, 1959.
GRECHISHCHEV S.E. K raschetuglubiny kriogennykh treshchin i razmerov pol i gonov rastreskivaniya v gruntakh. (A contribution to the calculation of the depth of frost fractures and of the dimensions of thefracture polygons in soils). In the book:
Geokriologicheskieissledovaniya ' (Geocryological studies). Trudy VSEGIEGEO - Transactions of the All-Union Scientific Research Institute of Hydrogeology and EngineeringGeology, rjo. 87, MOSCOW, pp. 4-13,1975. GRECHISHCHEV S. E. K osnovam metodi ki prognozatemperaturnykh napryazheni i i deforrcatsii v nlerzlykh gruntakh. (A contribution to the method for the prediction of temperature stresses and defornlation in frozen soils). MOSCOW, VSEGINGEO, 53 pages, 1971.
KARPENKO L .N. 0 rnetade rascheta napryazhennogo sostoyaniya v okrestnosti neglubokoivyrabotki, proidenFoi PO vertikal 'nonw ugol 'nomu plash. (A method for the calculation of the stress state in thevicinity c;f a shallow working, traversed along a vertical coalseam). Fiz . -tekhn . problerny razrabotki poleznykh iskopaetcykh (Physical and technicalproblem in the develap- rnent of usefulminerals), No. 4, Publ. "F!auka", pp. 3-9, 1965. MUSKHELISHVILI K*I, hlekotoryeosnovnye zadachi matematicheskoi teorii uprugosti . (Some fundamentalquestions of themathematical theory of elasticity). Moscow, Publ. tlI\Iaukall, 706 pages,1966.
PANASYUK V.V. Predel 'noe ravnovesie khrupkikb tel s treshchinami. (Limi ti ny eqLi librium of brittle bodies with fractures). Kiev, Publ "Nzu k. dumka" , 382 pages, 1968. Razrushenie(Rupture). Volume 2. Matematicheskieosnovy teorii razrusheniya.(Mathematical principles of the theory of rupture). Editor G, Libovits, Moscow Publ, IIMirtl, 763 pages, 1975. - 278 -
SAVRUK M.P. Napryazheniya okolo treshchiny v uprugoi poluploskosti, (Stresses around fractures in an elastichalf-space). - Fiz.-khim, mekhani ka niaterialov (Physico-chemical mechanics of materials), 11 , No. 5, pp. 59-64, 1975.
CHEREPANOV G.P. Mckhanika khrupkogo razrusheniya. (Mechanics of brittle rupture). Moscow, Pub1 . "Nauka", 640 pages 1974. MACKAY J .Ross Ice-wedge cracks, Garry Is1 and Ncrthwest Territories. - Canadian Journal of EarthSciences Vol . 11 , No. 10, pp. 1366-1383, 1974. LACHENBRUCH A.H. Mechanics of thermal contraction cracks and ice-wedge polygons in permafrost, New York, 69 pages , 1962. - 279 -
MINERAL STABILITY IN THE ZONE OF CRYOLITHOGENESIS
V.N. Konishchev Moscow StateUniversity, U.S.S.R.
The essential rock forming character of cryogenicerosion is studied mainly inrelation to particlesize distribution. The stability of particles of coarsealeuritic size (0.05 - 0.01 rnm) and theinstability of both larger and smallergranulometric elements when related to factorsof cryoeluviogenesis,lead to a number fundamentalof geological and paleogeographicconclusions. In theopinion of many investigators,this particularaspect of supergenesis,in the conditions of the cryosphere, is an underlyingcause of theformation of the loess depositsthat are so widely found in permafrostregions and Pleistoceneperiglacial areas.
Another position bases itself OK the very real possibility of aleuriticdeposits with similargranulometric parameters being formed inthe course of the sedimentogenic differentiation of mineralsubstance in both aqueous and atmospheric media.
The problem is further complicated when, applying theprinciples of thetheory of lithogenesis to thesedimentary deposits formed inthe courseof redeposi tion, we are forced to recognizethe existence of both cryogenic (inherited from erosionthe stages) and sedimentogenic characteristics in their make-up.
Thus the currentlyaccepted lithological criteria fcr products of the cryogenictransformation of differenttypes of rocks are reduced to granulometricindications that are of an equivocalcharacter and open to variousinterpretations as far as their origins are concerned.
ProceedingsThird International Conference on Permafrost, Val. 1, pp. 306 - 311, 1978. - 280 -
Hence thepresent need to develop more definite criteria which, it may be hoped, wi 11 enable us to identifythecryogenic eluvium of fine-grained rocks and theproducts of its redeposition, and todistinguish these from sedimentary rocks of similargranulometric composition, but which arelaid down under differentclimatic conditions at thevarious stages of 1 i thogenesis,conditions that do not involve any cryogenicfactors. At this point,obviously, it is expedient to consideranother important lithological characteristic of sedimentaryformations, namely their mineral constitution,
Analysis of the mineral compositions of formatiorx which can almost certainly be regarded as either true cryogenic eluvium or asthe products of its directredeposition (e.g., theloess-like mantleformations of the Bo1 'shezemel 'skayatundra of Northwestern Siberia) shows that their most characteristicconstituent, i.e,, thecoarse aleurite fraction, is made up principally of primarymineral debris,testifying to the leadingrole played by thefine grinding of various types of primary mineralsin their formation. Secondary aleuriticparticles in cryogenic eluvium play a subordinate role.
Ir. order to determine the mainmechanisms invclvedthein disintegration of variousminerals as a result of cryogenicdisintegration factors we must find answers to thefollowing questions: (1) do all minerals have the same crushing 1 imi t; (2) what determinesthe actual crushinglimit of a given mineral and to what extent is it connectedwith the specific structure of the mineral and thenature of the external effects of thecryogenic erosion factors; (3) how must one explair?the fact that, notwithstandingthe existence of a fragmentationlimit of primary minerals considerablyexceeding the size of the argillaceousminerals, the latter are subject to a powerful effect in the course of cryogenicerosion (Konishchev et a1 , , 1974).
As we know, the phase transformations between water and icein fine-grainedsubsoils take place in thenegative temperature range, owing to the inhomogeneity withrespect to energy and structure of the watercontained in them. - 281 -
The pub1 ishedformulae regarding the unfrozen water contents of varioustypes of fine-grained rocks as a function of thetemperature (Nersesova, 1958) are widely known. It hasbeen shown experimentally, that the more strongly groundwater is subjected to theinfluence of mineral particlesurfaces or of dissolvedions, the lower thetemperature at which it crystallizes. A certain amount of bound water does not turn intoice at all, but remains in the unfrozen state. It may therefore be assunled thatduring crystallization of groundwater individualmineral particles of thesubsoil system contain adsorbed bound water which surrounds them on theirsurfaces and thethickness of which decreasesasthe temperature changes. It is important to emphasize that howeverlow the temperature, a distinctlayer of unfrozen bound waterremains around individualparticles of thesubsoil mass. The film of unfrozenwater remains notonly on thesurfaces of argillaceous and other very fine-grained mineral particles, but also on those of the coarser aleuritic and arenaceousones.
Themain elementaryprocesses involved in the disintegration of mineralsduring the freeze-thaw cycle are as follows:
1) the expansionpressure of iceresulting from thefreezins of waterin relativelylarge cracks in rocks and minerals;
2) closelyassociated with thisprocess, the cryohydrogenic disintegration of grains, which is caused by therepeated fluctuation of expansion pressures from thinfilms of waterin the microfissures of minerals owing to their hydration-dehydration in thecourse of ice formation in comparativelylarge pores and fissures of thesubsoil;
3) temperaturefluctuations which resultin volume-gradient stresses that areintensified owing to the heterogeneous structure of thefragments and grains;
4) thepressure of thecoating of ice on the mineral particles arising because of the more intensetemperature comprcssioK of ice compared withrocks and minerals as thetemperature - 282 -
of thefrozen subsoil decreases (Konishchev, 1973; Mazurov, Tokhonova,1964).
The effects of thesefactors on theindividual particles are exertedindirectly, through the layer of unfrozenwater bound tothe surfaces ofthe particles. Hence thecharacter of thedisintegration of mineral grains depends notonly, but also on the thickness and properties of the 1 ayer of unfrozenwater. Here we mustregard the particle and thelayer of adsorbedunfrozen water surrounding it more or lessas a unit.
As far as theprocesses of particledisintegration in the course ofcryogenic erosion are concerned, all the water contained in the subsoil canbe dividedinto two categorieswhich have contrary effects onthe stability of theparticles, namelythe stable layer of unfrozen water and the thermally active water,
Underactual giver. conditions, the stable bound layer does not freeze.This determines its different thickness under different conditions. At verylow temperatures the stable layer of watercorresponds to a layerof strongly bound waterl as identified by E.M. Sergeev et a1 .I (1971), to 2 1 ayer of adsorbedwater (Lomtadze, 1972) and to a boundaryphase ofwater (Tyutyunov, 1961 ) .
Under conditionscharacterized by higher temperature values the stablelayer can include some of t,he loosely bound layer of water(Sergeev et a1 . , 1971 ) orthe near boundary phase(Tyutyunov, 1961). Such properties of thestrongly boundwater that appears to constitute a largepart of the stablelayer as greaterdensity, viscosity, elasticity andconsiderable shearingstrength, enhance thestability of theparticles in the presence Gf variousexternal effects.
The reinforcement of frozensubsoi 1s with thin f ilms of adsorbed, unfrozenwater is a factorwhich, at sufficiently low temperatures, increases their strength(Tyutyunov, 1973; Save1 lev,1975).
The thermallyactive water is ttx maindisintegrating agent. From thestandpoint of its disintegrating action it may bedivided into two kinds, - 283 - namely free water and thelayer of metastablewater to which thesurface layers of bound waterbelong. The layer of metastablewater is generally similar in its propertiesto loosely bound water(Sergeev et a1 ., 197’1). The main characteristic of thethermally active water is its mobility, i .e., its zbility to migrate in thecourse of thefreezing and thawing of the subsoil and in thecourse of phase transformationsinto ice, Depending on thecourse and speed of theprocess, the thermally active water affects the mineral skeletondifferently. During thefreezing of subsoilsthermally active water undergoingtransformation to the solidstate producesexpansion pressures in comparativelylarge particle fissures.
In contrast to thefree water, the water of themetastable layer ischaracterized by high viscosity and a high modulus of elasticity. These properties, combined with its mobil i tyin the freezing and thawing cycle, result in the cryohydrogenic disintegration of subsoilparticles. During the freezingstage metastable waterpresent in themicrofissures of the particles emerges frcmthem, moves into the inter-particle poresof the subsoil towards growing crystals of ice,thereby somewhat reducingthe expansion pressure of thefilms of waterin the microfissures. During the thawing stage, because of the melting of theice in microfissures whose widthexceeds twice the thickness of thestable layer of water, the former thickness of adsorbed water isrestored. This once more increases the expansion pressures of the films of water inthe microfissures, which reach maximum values at O°C, when thefilm of adsorbedwater is thin. The fluctuation of the exparsion pressurein the microfissures resulting from the migration of the metastable layers of bound wateralso promotes disintegration of the particles.
The disintegration of mineral particles reaches it5 limit when the thickness of thestable layer of water becomes conimensurate with the dimensions of thestructural cracks and defectsthat mar thesurface structure of thelayer of particles(Figure 1). From this we draw an important conclusion, namely that thecrushing limit of minerals is a direct function of thethickness and protectiveproperties of thestable layer of water (Figure 2) .
The magnitude and thestrength properties of thestable layer are determined firstly by thesurface properties of the mineral particles, and - 284 -
Figure 1
Manifestation of the factors of cryogenic distntegration in fissures of different size. 1 - mineral; 2 - stablelayer of water (a); 3 - metastable layer of water (M) ; 4 - free water. bl - largefissures in whichwedging effects of ice and water occur; b2 - microfissures in which thereare fluctuating wedge pressures from films of bound water; bj - ultramicrofissures in which there are no wedging effects of ice Lor fluctuating wedge pressures from films of water. secondly by theproperties of the groundwater solution (pH value,quantities and kindsof dissolved substances). The surfaceproperties of the mineral particles, which determinethe sorption capacity, are expressed intheir specific surface energy. The la,tteris determinedprimarily by the crystallochemicalstructure of the surfaces of the differentminerals, and also,in the opinion of a number cjf investigators, by theirfineness of grain .
A very reliable way of estimat.ing the magnitude of the stable 1 ayer in differentminerals is to employ the data on their maximum hygroscopicity. According to the figures of E .N. Sergeev et a1 ., , (1 971 ) , the maximum hygroscopicities of particlessmaller than O.GO1 mm are 0.9% for quartz, 8 - 17% for feldspars(albite, microcl inu, orthoclase) and 36 - 48% for nlicas (nluscovite, biotite). - 285 -
Figure 2
Wedging action of ice in a crack at differentthicknesses of the stable layer of water (arrow lengths correspond to wedge pressures of ice). 1 - mineral; 2 - stablelayer of water (a); 3 - ice.
If the ratios of adsorptioncapacities of these ninerals also hold forlarger particles, it may be concluded that thethickness of the statle layer of waterin a polymineral mass in the process of freezing will be a maximum for the micas,smaller for the feldspars and a minimum for the quartz.
Available figures on the free surface energy of nluscovite crystals (4.5 joules/m2) and quartz crystals (0.5 joules/m2)(Pol', 1971) confirm this relationship. Thus, if we accept the given ratios, the crushinsliniit for quartz mineral grainswill be thehighest, that for micas thelowest, while that forfeldspar grains will occupy an intermediateposition. A more accurate idea of thevalues of thestable layer can be obtained by analysing - 286 - thecurves of unfrozen water in subsoils of variousmineralogical composition. However, themajority of publishedcurves of unfrozenwater content as a function of thetemperature describe the phase state of the waterin absolute weight units relative to the weightof the dry mineral part of thesubsoil, and thereforecannot give an accuraterepresentation of the influenceof the skeletal surface energy on the unfrozenwater content.
A recalculation of the unfrozenwater content, not per unit weight of subsoi 1, but per total surfacearea, which was carried out elsewhere (Anderson, Tice, 1972; Anderson, Morgenstern,1973), enables us to estimate the magnitude of thestable layer of water at varioustemperatures for varioustypes of subsoils and minerals, From an analysis of thesecurves it may be concluded that thespecific surface energies in primary minerals is higher than incertain clays.
Among the latter,kaolinite has a stablelarger layer of water than bentonite. Confirnlationof this is obtained from a studyof the NMR spectra of the adsorbed waterprotons in montmorillonite and kaolinite. According to thefigures of A.A. Ananyan et a1 ., (1973),for approximately the same quantity of adsorbed layers of waterthe transverse relaxation time T, is shorter than would correspond to Ts .M. Raitburd and M .V. Slonimskji Is (1 968) conclusionconcerning the strong bonding of adsorbed waterin kaol ini te. According to R.1 . Zlochevskii Is figures (1969) I thesurface conductivity of montmorillonite is 4 - 5 times greater than that of kaolinite. From allthis it may be concluded thatthe specific free surface energyof kaol ini te is greater than that of nlontmoril loni te, a1 though the absolutequantity of unfrozen haterinmontmorillonite clays is always greater owing tothe greater finess of their grain. Hydromicas, of course, occupy an intermediateposition.
Very importantfor an understanding of the wholemechanism cf cryogenicerosion isthe assumption thatthe specific surface er,ergy (SSE), which determinesthe thickness and properties of thestable layer of water, depends on thefineness of grain.This assumption is based on a.number of publications by V.F. Kiselev and hisco-workers. Fronl studies of the character of thedehydration and the adsorptioncapacity of very fine-grained - 287 -
quartzsoils (particle sizes from 960 to 3.8 mm) it was established that the water content per unit surfacearea decreased with increasing fineness. One of is of Si0 the reasonsfor this relationship associated with the packing 2 tetrahedrons on the surfaces of small quartz particles owing to the arnorphization of theirsurface layers. However, the paraboliccharacter of the SSE curvesas a function of the fineness, as indicated by V.F. Kiselev’s investigations, can be consideredapplicable only to the very fine-grained part of the granulometricspectrum of quartz particles.
When the lessfine-grained part of the spectrum is taken into considerationthe relationship becomes more complex.
One of the methods of studying bound water in fine-grained systems is to investigatethe electrokinetic characteristics, especially the charges on subsoilparticles. The formation of an electric charge on thesurface of a mineral particle depends an its crystallochemicalstructure and on the composition and properties of the medium interacting with it. It follows from this that the charges on subsoilparticles are an index of theirsurface energy.
TABLE Variation of thecharges on mineral particlesas a function of fineness(Savel’ev 1971)
,”. N I E Fraction, 0.5- 0.25- 0.05- 0.01 0 ” uv 7-Q.5 0,l-0.05 - CG5- a” mm 0.25 0.1 0.01 0.005 G. 003 I -01 3 o Quartz -0,372 -2,172 -2,590 -4,632 -1 ,@14 -0,220 +r- -4,342 VI Microcline C,302 4,@20 2,71312,903 1,974 1,621 * W s- Calcite 5,1824,493 11,875 6,292 1,481 0,509 - 0 I V) Gypsum 7,858 11,524 20,533 14,666 - - rn? cu ~FI Hornblende -0,135 -0,549 -1,543-3 968 -24,397 -0,617 I mnL , L w Muscovite 79,030 134,275 89,521 42 ,273 0,527 I 0,246 5s L .r Biotite C -4,481 -20,316 -25,250 -10,013-1,088 -0,178 VE
The structural-sorpticnaldifferences of mineralsof differwt fineness of grainare well illustrated by a table taken from the work of B.A. Savel ‘ev (1971 ) in which the data of E.R. Sergeev and his co-worker5 are cited. It isclear from thetable that the maxin;um chargecorresponds to a - 288 - certainfineness of grain. In thecase of quartz,the main rock-forming mineral of sedimentaryrocks, the charge density is a maxinlum for the fraction 0.05 - 0.01 mrn. The higherthe charge of themineral, the coarser the fraction that carriesthe maxinlum charge.
The tablein question pertains to theair-dry state ofthe mineral particles. It can be assumed, however, that theprincipal relationships between the chargevalues, and hence also between the SSE’s of different minerals and of particles of differentfineness, will continue to hold when theyare interacting withwater. The valuesin the table do not conflict, for example, with the above cited maximum hygroscopicities of therespective minerals.
Using theexisting relationships of the SSE to mineralcomposition and fineness, as stated above, firstly an explanation is found for the already known characteristics of cryogenicerosion. Secondly, it becomes possible to propose, in general out1 ines, a theoretical model of the minerologicalcomposition of thecryogenic eluvium, showing, inparticular, how the commoner individualminerals are distributedover the granulometric spectrunl
The most general mechanism, obviously, is the accunlulation, in the course of cryogeniccrushing, ofmineral particles with maximm SSE as the particles most resistant to thecryogenic erosion factors.
Let us introduceas a criticalsize (CS) , theparticle size of a givenmineral which has maximum SSE. For quartz the CS is equivalent to the size range of thecoarse aleurite fraction (0.05 - 0.01 mm). Particles of thissize are very stable,since the correlationofthe dimensions of microfissures and defects of variouskinds and thethickness of the stable 1 ayer of waterprevent the occurrence of any spl i tting action by ice or thin films or water.
Quartz particles whose dimensions exceed the critical must be ground up intensivelyin the course of theirregular freezing and thawing in the wet state. This is due, on the one hand, to a lower SSE, and, on the - 289 -
Quartz particles ma1 ler thanthe CS are characterized bylow SSE values and this,it would appear, must lead to theirintensive crushing. Evidently, however, this does not occur,for along with a reduction of the SSE in the small particlesthere is also a reduction in the size of the microfissures and defects and this, of course,limits the possibility of theirdisintegration, without, however, preventing itentirely. Lowering of the SSE of the small particlescauses their aggregation in thecourse of freezing. Thus the granulometricspectrum of quartzrelative to the factors ofcryogenic erosion isdivided into three parts: 1) particleslarger than the CS - unstable; 2) particles cf CS - very stable; 3) particles below CS - comparativelystable and tending to form aggregates.
For otherminerals, cbviously, the same regularities must be observed,except, of course,for the critical size of the particles. For feldspars, judging from the figures, the CS is larger than that of quartz, whilefor stratified silicates (biotite, muscovite, chlorite) it is larger still. The CS's of amphiboles and pyroxenes are the same as thatof quartz. If we postulate an initial mixturecomprising particles of quartz, feldspars, amphiboles, pyroxenes and micas whose dimensions exceed the corresponding CS values,then theoretically, under the action of the cryogenicerosion factors, a transformation of themixture must occur whose granulotxetric spectrum is determined by the maximum contents of theseparate minerals it-; the givenyranulometric fractions,corresponding to their maximum SSE. Thus the coarsealeurite fraction must be characterized by a rnaxin;um content of quartz, amphiboles and pyroxenes; the maximum contentof feldspars must be observedin thecoarser fine-sand and small arenaceous fractions, The maximum mica contentwill be found in a stillcoarser granulometric fraction. - 290 -
Under naturalconditions rocks of differentfineness (sands, boulderclays, etc.) are found inthe region of Cryogenic erosion, and in these theminerals are distributed over the granulometric spectrum in other ratios and theirvalues maybe very differentrelative to thecritical size. Under theaction of cryogenicerosion the original mineralogical spectrum must change inaccordance with the mechanisms described above. This imposes specialrequirements with respect to the nlethodology of studyingthe mineralogicalcomposition of thecryogenic eluvium and the primary rocks. These requirementsconsist in the necessity of studying thedistribution of individual rock-formingminerals on the basis of narrow granulometric fractionswithin the limits of theentire granulometric spectrumof both the primary and the secondaryrocks.
Some of the above considerationsconcerning the behavious of a number ofminerals in the course of cryogenicerosion havebeen confi rnled experimentally. A study of the changes ingranulometric composition of variousminerals after fiftycycles of freezing (-20°C) and thawing (+3OoC) has shown that particles of quartz, hornblende and diopside 0.05 - 0.1 mm in sizeexperience marked disintegration, the intensity of which increases with increasingnloisture levels. This suggests that thecritical size of these mineralslies in the smallerfraction. On theother hand thegranulornetric composition of a primary specimen of albite made up of grains of theSam dimensions remained practicallyunaltered, evidently because thissize of albitegrain corresponds to the criticalsite. The behaviour of micas and chlorite, i ,e,, minerals with high charges, is interesting. These minerals disintegrate with great intensity in theair-dry state. When they are saturated withwater to thelimit of fluiditythere is practically no crushingofbiotite and chlorite (0.05 - 0.1 mm grains) but nluscovite decreases markedly insize, Very probably this is associated with the protectionafforded by films of water. A detailedanalysis of this experimerit has been made in a special paper (Koni tsev et a1 . , 1976). The same experiment alsoestablished the disintegration cf particles of various minerals whose sizes were smaller than thecritical (electron-microscopic investigations).
In a work by G.P. Mazurov and E.$. Tikhonov (1964) theresults of changes in the fineness of quartz and feldspar sands due to theirrepeated - 291 - freezing and thawing were given. On thebasis of theirfigures, using an index of relativestability of particles* we estimated the stability of quartz and feldspar grains 1 to 2 mm in size. Under otherwiseidentical conditions it was found to be greaterfor the grains of feldspar. That is to say, for coarsegrains the ratio of surfaceenergies of quartz and feldspar remains the same as for thefiner ones. This determinesthe ratio of crushing intensities, which was higher for thequartz grains.
The idealpattern of particlestability may be complicated by the presence of adsorbed substances,various kinds of films, etc. on their surfaces, a1 t eringthe SSE. For example, the particles of quartz in primary rocks were often covered wi th films of iron hydroxide, aluminium, and organomi neral compounds and this can substantiallyaffect the character and intensity of theircrushing. The same applies to eroded and partially eroded grains of fel dspars and other mineral s .
The properties of the stablelayer of the bound water also depend on thequantity and composition of theions adsorbed on thesurfaces of subsoilparticles. The rrlaximuni hygroscopicityfor example, depends on the valency of the cations adsorbed by the particle surface (Sergeev et a1 ., 1971). The size of the:,table layer of water, obviously, also increases with increasing valency of the adsorbed cations. Hence theresistance of the particles to the action of the cryogenicerosion factors corresponds to the s erri es:
cation'3 r cation" > cation+1
This rule is very we1 1 i 1 lustrated by theresults of experiments on the freezing: of quartzsands saturated with solutions of various salts (Pol tev, 1966). The freezingstability of a quartz particleincreases with increasing salt concentrationin the pore solution; sand containing a CaCI2 solution is more resistant to freeziny than one saturated with sodiunl salts (NaCl , fia2S04). The effect of the pH of a subsoilsolution on the character of the
of size fraction in % before freezing; b - quantity of same fractionre- maining after thefreezing cycles; n - number of freezing and thawing cycles. - 292 - cryogenicdisintegration mineralsof has not been studied,Currently availabledata indicate that the value and sign of theelectrostatically activecentres on argillaceaous mineral crystalfragnients, and hence the properties of the bound water, depend on the pH value (Osipov, Sergeev, 1972).
In an acid medium thesurfaces of theargillaceous particle fragmentsreceive a positivecharge, and in an alkaline medium theyreceive a negative one, The positivecharge in an acid medium is higher forminerals of the kaolinitetype than for niinerals of the montmorillonite type. In an alkaline medium the difference is negligible. In theacid medium thetotal charge on argillaceousminerals is lower than in thealkaline medium. This agrees closely with theabrupt increase in viscosity of an argillaceous suspension on transition of the medium from acid to alkaline.This phenomenon is bestexpressed in kaolinitepastes (Osipov, Sergeev, 1972).
Since the magnitude of the particle charge is a factor involved in itsresistance to cryogenicaction, it maybe assumed that as the pH of the medium decreasesthe stability of an argillaceous mineral in thepresence of cryogenicerosion factors will also decrease, With respect to the primary mineralsthis assumption alsoappears very probable. However, thequestions callsfor a specialinvestigation.
The effect of externalfactors on cryogenic erosion can also be estimated on thebasis of theideas expressed above. Among theconcrete factorsleading to a given set of physical-geographicconditions, the principal ones are:the number of transitions through O°C, the amplitude of thetemperature fluctuations, the rate of freezing, the continuous duration cfthe frozen state and the number oftemperature fluctuations in the negativeranse of values, characterized more or less by the mean annual temperature of the soil.
The effect of thesefactors on the nature and intensity of cryogenicdisintegration is determined above all by theireffect on the correlation of the stable and metastablelayers of bound water and their dynamics in the freeze-thawcycle. Thenumber of transitions through O°C, * 293 - the main factorinvolved in cryogenicdisintegration in theopinion of many investigators,cannot unequivocally accouRt for the variousaspects. of the transformation of fine-grainedsubsoils. This follows from the well-known rule thatthe finer the subsoil, the broaderwill be therange of temperatures in which phasetransformations of waterare observed. Kence to appraise the intensityof the disintegration of fine-grainedminerals a more accurate indicator would be the number of temperaturefluctuations within the entire range of phas-e transitionsof water. Since the phase transitions of the bound water take place in a negativerange of temperatures,an important index of the intensity of cryogenicdisintegration is the continuousduration of thefrozen state of therocks, characterized by their mean annual tenlperature. The extent of coolingof the rocks determinesthe magnitude of the stablelayer of water which, as shown above,plays a protectiverole in the process of cryogenic disintegration. We know thatthe lower the temperature,the less unfrozen water there will be in fine-grainedsubsoils, and hence thethinner the stablelayer of water. From this it followsthat. theintensity of fine-grain disintegration increases with increasingdegree ofcooling in thefreeze-thaw cycle, as is partlyconfirmed by Tricart's experiments(1956) in which he simulatederosion under maritime and continentalclimatic conditions.
REFERENCES
ANANYAN A.A., VOLKOVA E.V. znd FEOKTISTOVA O.B. Otsenkazavisimosti vremen relaksatsii protonov vody v tonkodispersnykhgornykh porodakh ot vlazhnostiporody. (Estimate of the variation of relaxationtime of waterprotons in veryfine-grained rocks as a functionof the wetness of the rock). In the book: Merzlotnyeissledovaniya (Permafroststudies), No. 13, Izd-vo MGU, pp. 158-161,1973.
ZLOCHEVSKAYA G.I. Svyazannaya voda v glinistykhgruntakh. (Bound water in argillaceoussubsoils), Izd-vo NGU, 174 pages, 1969. KISELEV V.F. Poverkhnostnyeyavleniya v poluprovodnikakh i dielektrikakh, (Surface phenomena in semi-conductors and dielectrics) , Moscow, "Nauka" , 295 pages, 1970, KONISHCHEV B.N. Kriogennoe vyvetrivanie.(Cryogenic erasion). I1 InternationalConference on Permafrost. Reports and Communications, No. 3, Yakutsk, pp. 38-44, 1973. - 294 -
KONISHCHEV V .N. , ROGOV V.V. and SHCHURINA G ,h. v1iyanie kriogennykh protsessov na glinistyenlineraly. (Effect of cryogenicprocesses on argi!laCeousminerals). "Vestn. MGU, Ser.Geograf.", No. 4 pp. 40-46, 1974.
LOMTADZE V.N., ROGOV V.V. and SHCHURINA G.N. Vliyaniekriogennykh faktorov na pervichnye mineraly (rezul 'taty eksperirnental 'nykh issledovanii). (Effect of cryogenicfactors on primary minerals - results of experimentalinvestigations). In the book:Problemy kriolitologii (Problems of cry01 itholow), No. 5, Izd-vo HGU, pp. 50-60 , 1976. MAZUROV G.P. and TIKHONOVA E,$. Preobrazovaniesostava i svoistv gruntovpri mnogokratnonlzamorazhivanii. (Transformation of thecomposition and properties of subsoilsin the course of recurrentfreezing). - "Vestn. LGU", No. 18, Issue 13, Ser. Geol. i Geograf., pp. 35-44, 1964.
NERSESOVA Z.A. Fazovyisostav vody v gruntakhpri zamerzanii i ottaivanii. (Phase constitution of the water in subsoils during freezing and thawing).In the book: Materia7y PO laboratornymissledovaniyam merzlykhgruntov (Materials on laboratory studies of frozen subsoils) No. 1 Moscow, Izd-vo AN SSSR, pp.31-35, 1958.
OSIPOV V.1. and SERGEEV E.M. Kristallokhirciyaglinistykh rnineralov i ikh svoistva.(Crystal chemistry of arglllaceousminerals and their properties)."1nzh.-geol svoistvaylinistykh porod i protsessov v nikh".Trudy Mezhdunar.sirnpoz., No, 1, Izd-vo NGU, pp.151-153, 1972,
POL' R.V. Mekhanika,akustika i uchenie o teplote.(Mechanics, accoustics and theory of heat), Per. s Nem. Moscow, "Nauka", 479 pages1971 . POLTEV N .F. Iznleneniegranulometricheskoyo sostava peschanykh gruntov pri vozdeistvii na nikh rastvorov elektroli tov i protsessazarnerzaniya- ottaivaniya. (Change inthe granulornetric constitution of arenaceoussubsoils when acted upon byelectrolyte solutions and processes of freezing andthawing). In thebook: Merzlotnye issledovaniya(Permafrost studies), No. 6, Izd-vo MGU, pp.199-206, 1966.
RAITBURD Ts .M. and SLONIMSKAYA M.V. Kristallokhirriyapoverkhnosti glinistykh mineralov i mikrostrukturaglin. (Crystal chemistry of the surface of argillaceousminerals and themicrostructure of clays). In the book: Fizicheskie i khirnicheskieprotsessy i fatsii(Physical and chemicalprocesses and facies). MOSCOW, "Nauka",pp. 42-50, 1968.
SAVEL'EV B.A. Fizika, khimiya i strocnieprirodnykh 1 'dov i merzlykhgornykh Forcd. (Physics,chemistry and structure of nativeice and frozen rocks).Izd-vo f4GU, 506 pages I 1971
SAVEL'EV B.A. Fiziko-chirnicheskieosnovy formirovaniya stroeniya, sostava i svoistvmerzlykh gornykh porod. (Physical -chemical basis of the structure,composition and properties of frozen rccks). I1 InternationalConference on Permafrost, Reports and Comnunications, No. 8, Yakutsk, pp. 92-108,1975. - 295 -
SERGEEV E.bl.* GOLODKOVSKAYA G.A. and ZIANGIROV R.S. et a1 ., Gruntovedenie. (Soi 1 science). Izd-vo MGU, 595 pages, 1971. TYUTYUNOV I .A. Vvedenie v teoriyufomirovaniya merzlykh porod. (Introduction to the theoryof the formation of frozenrocks), MOSCOW, Izd-vo AN SSSR, 108 pages, 1961 .
TYUTYUNOV I .A. Novye predstavleniya o prirodeprochnosti merzlykh gruntov. (New ideas on the nature of frozensoil strength). I1 International Conference on Permafrost, Reports andCommunications, No. 4, Yakutsk, pp. 142-147, 1973.
ARDERSON D.M. and TICE A.R. Predicting unfrozen watercontents in frozen soils from surfacearea measurements. Highw. Res. Record No. 393. pp. 12-18, 1972.
ANDERSON D.M. and MORGENSTERN .N,R. Physics,chemistry and mechanics of frozen ground: A review. I1 InternationalConference on Permafrost. National Academy of Sciences,Washington, D.C. pp. 257-288, 1973. TRICART I. Etude expikimental du problhede la gglivation. Bull, periglac. NO. 3, pp, 41-45, 1956.
- 297 -
PRINCIPLES OF CLASSIFICATION OF POLYGONAL-VEIN STRUCTURES
N.N. Romanovskii Moscow StateUniversity, Department of Geology, U.S.S.R.
Polygonal-vein structures (PVS), whichform as a result of the frostfracturing of the upper level of the ground, encompassnumerous form of soil(earth) veins, composed of materialsof varying composition, ice veins(called wedge ice and polygonal wedge ice by differentauthors), ice-soil , soil-ice, and othertypes and varieties of veins The dimensions of the polygonal lattice vary in plan,as does the morphology, and theheight and width in crosssecti on. There is much in the 1 i terature devoted to their description.
Polygonal -vei n structures are veryimportant inthe evaluation of geocryologicalconditions in permafrostregions, in the permafrost facies analysis of Quaternarydeposits, in paleogeographic reconstruction, etc. A1 1 of the above makes it necessarythat they be systematized on a geneticbasis, with mandatory consideration of thenatural conditions under which theyform, and of theprocesses occurring during theirformation. In doing this it appearsnecessary to us that 1) theclassification schemebe based on fundamental geologicalprocesses, separating them from secondary and associatedprocesses, and 2) thatthe rangeof conditions under which the respective PVS categories form be established.
The study of modern structures which arecurrently in the process of development, and of old structures whichhave often been subjected to profound secondarychanges, reveals that a number of forms whichformed under differentconditions aremorphologically very similar. PVS develop in deposits of differentorigin and properties. These depositsconstitute the
ProceedingsThird International Conference on Permafrost, Vol. 1 I pp. 319 - 324, 1978. - 298 - environmentwithin which these structures are found. This environment is not inert; it acts upon the PVS, alteringtheir morphology,dimensions, and composition. It often happens thatstructures which form under similar conditionsacquire pronounced morphological differences invarious types enclosingground. For this reason, the external similarity or difference of veinscannot be used as thebasis for their genetic classification.
The classification scheme proposedbel ow for polygonal-vein-structuresis based on thefollowing principles:
1. All of thestructures are subdivided into twomain groups: primary and secondary.Primary structures form as theresult of repeated frostfracturing, infilling of thecracks with mineral deposits or ice, and subsequentannual reconstitution of the material inthe fractures. Secondary structuresappear as the result of thedegradation of primarystructures when theythaw as a result of increaseddepth of theannual layer of thawing,and also as the result of degradationof permafrost.
2. Primary PVS classifiedare according to two main characteristics:firstly, on thebasis of theposition of the frost fracturesin the seasonallyfrozen layer (SFL) or seasonally-thawinglayer (STL) andpermafrost system; secondly, according to thenature of the materialwith which the fractures are filled. Successive reconstitutions of thematerial filling the fractures are essentially predetermined by whether they liewithin the SFL (STL) or whetherthey penetrate the permafrost, Fer this reason,theprocesses of transformationtheofmaterial inthe fractures,which affect the morphology of the developing structures, are secondary(concomitant) although highly important. They aredirectly related to variousdeformations and other changes inthe enclosing rocks, whichare also concomitant.
3. Polygonal-veinstructures form over a geologicallylong period of time,during the course of which the conditions of theirformation do not remain unchanged. In some cases theconditlons aresuch that the characteristic,distinctive traits ofthe vein structures change only quantitatively, while in other cases the changes are of a qualitative nature. - 299 -
Inthe former case theposition ofthe fractures inthe STL-permafrost system,and thematerial filling the fractures, remain constant, with the resultthat certain categories of PVS areessentially basic. In theother casethe position of the fractures in the STL-permafrost system changes with time.This occurs chiefly as theresult of changes inthe temperature regime of therocks and thedepth of the STL. In some yearsthe frost fractures are locatedentirely within the STL, othersin they penetrate into the permafrost. The depth of thaw periodicallyincreases to suchan extentthat it reachesthe maxinlum depthtowhich these fractures penetrate, which results in the me1 ting of thematerial which filIs the veins. As a result of this,there are formed primarystructures of a transitional,intermediate characterbetween the basic categories.
Themanner in whichthe frost fractures fill up as the PVS develop remainsthe same in some caseswhile differing inothers. Thus, when conditionsare such that there is enough moisture at the surface of the earth duringthe period when thefractures are open ("gaping"),they fill upwith waterevery year, forming veins of congelation ice as theyfreeze. The fracturesdo not fill up withice when thereis insufficient moisture at the surface.In the presence of eolianprocesses the cracks may be filledwith air-dry eo1 ian sand. But thesurface moisture conditions may change periodicallyeither as theresult of changes inthe climate or inthe local faciesconditions. In view of this,there may be periodic changes inthe nature of thematerial which fills the fractures, and the resulting structure reflectsthese variations,
Whilethe first principle onwhich the classification scheme for polygonal-veinstructures is based may be consideredto be generally accepted andquite. well understood, the remaining two principles require explanation and substantiation.
Classification of PVS according to theposition of thefrost fracturesin the STL (SFL)-permafrostsystem is determinedby the factthat, instructures which are entirely within the STL (SFL),ground icecannot accumulate. The icewhich forms in the frost fractures melts every year.In structures(or, more precisely,in the lower parts of structures) which form 300 - in Permafrostbelow the STL, on theother hand, ground ice may accumulateand remain for many years. Such PVS categories as wedge iceare represented almostwholly by congelationground ice. The author has shown in a number of papers(Romanovskii, 1970,1973 and others)that the penetration of frost fracturesfrom the STL intothe permafrost depends on the mean annual temperature atthe foot of the STL or inthe layer of their annual temperaturefluctuation - tmean.These temperaturesare the boundary between thestructures which form entirelywithin the STL (SFL),and thetwo-level structures whose lowerportion forms within the permafrost and may contain groundice, and whose upperportion is located within the STL. The former may provisionally be called"high-temperature" inirsmuch as theydevelop at hig her tmea,,values than the latter "low-temperature" structures. During suchforniation of low-temperature PVS with a decrease in tmean,and with otherconditions being equal, the thickness of the STL decreasesand the depthof penetration of the fractures below the STL intothe permafrost increases. As a result,there is a localdecrease in thedimensions ofthe upperportion of thevein structures, andan increase in thelower portion. Thus, there is a naturaltemperature control over the penetration of frost fractures fromthe STL intothe permafrost andover the development ofthe resultingvein structures, It must be notedthat the temperature of the rock at whichthese qualitatfve structural changes occur variesfor soils of differentcomposition and icecontent, i.e., thereis a relationship between thesetemperatures, the lithological characteristics of therocks, and their moisturecontent (permafrost-facies) (Romanovskii, 1972) This relationship is nottaken into account in the classificationofthe polygonal-vein structures,but its existence should be borne in mind when carryingout geocryologicalresearch and when reestablishingpaleological permafrost conditionsfor vein structures in rocks of variouscomposition and origin.
Frost fractureswhich form in thefall andwSnter arefilled mainly by theentry of 1) me1 twateror floodwater, and 2) air-dry sand. In addition, a small amount of snow may fall into the fractures, sublimation ice crystals may accumulate, and thelower ends ofthe fractures may fill up as the result of the enclosing ground crumbling down fromthe walls.
Infilling of thefractures with water, which becomes veins cf congelationice upon freezing,occurs only in the spring, when thereis - 301 - significantflooding of thesurface. Wedge ice forms inpermafrost when this process is repeated many times.In STL and SFL in summer theseveins melt and theresulting cavities are partially or completely filled with mud or fa1 1 ingpieces of the enclosing ground. In weakenedzones inthe area of congelationice veins there occur inwash oforganic matter, weathering, underminingor infill ing, etc. The repeatedoccurrence of theseprocesses resultsin the formationof soil veinsin the STL and SFL and, in cases when thefractures penetrate into the permafrost, in the formation of an upper layer of soil above the ice veins.In this way, when congelationice forms in frostfractures, a temperatureseries of polygonal-vein structures is created.Under conditions of relatively high tmeanof therocks in the STL and SF1 (when thefractures do notextend beyond the confines of thelayer) initial-soilveins form, and when the tmeanare 1ow wedge ice forms. As indicated above, thelatter are two-level structures, and as thetemperature of therocks drops (other conditions remaining equal) the vertical extent of theice veins increases, while that of the soil portion within the STL decreases.
Within the range of groundtemperatures at whichfrost fractures penetratefromthe STL intopermafrost there develop transitional polygonal-veinsystems in which wedge iceforms inlow-order generation fractures and initial-soilveins form inhigh-order generation fractures (Romanovski i, Boyarski i, 1966; Romanovski i, 1973). Transitional forms of veinstructures develop under such conditions. During the coldest stages of theperiod of formation of thesetransitional structures they develop as thin wedge ice,extending vertically for up toseveral tens of centimeters. Duringthese stages the thickness of the STL andthe tnleanof therocks exhibitthe lowest values of theformation period. We notethat the vertical dimensions of such iceveins are comparable to the thickness of the "transitionallayer", although they usually slightly exceed it. According to V.K. Yanovskii(1933) and Yu,L. Shur (1975), thetransitional layer is a layer of permafrostbetween the layer of depositswhich thaw annually and the layerwhich is continuouslyfrozen over a specificperiod (in this case, duringthe period of formationofthe PVS). Theupper surface ofthe transitionallayer Att coincideswith the minimum, whilethe lower surface coincideswith the maximum depth of thaw duringthis period. - 302 -
During warmer or more continentalstages, when thethickness of the STL increases,the rocks of thetransitional layer thawand the thin ice veinsmelt. Smallpseudomorphs fornl in theirplace. Continuing frost fracturing and seasonal infilling of the fractures with congelationice causes further vein structures in the STL to develop asinitial-soil veins. They remain narrow in their lower portion but their width usuallyincreases in their upper portion. A drop in the ground temperature and a decrease in thethickness of the STL can again result in theformation of small iceveins in thepermafrost. As aresult, such structures have a transitionalnature notonly between initial-soilveins andwedge ice, but also between pseudomorphs after them, i .e. , between primary and secondary structures.
Infilling of fractures with air-dry sand occurs in regions where surfacemoisture is extremely lowand in thepresence of intenseeolian processes. Under theseconditions dry eo1 ian sand and gravel fall into the frostfractures in winter.Eolian material either gets into the fractures directly,as though intotraps, as it is carriedover the surface by the wind, or it first accumulates in polygonal depressions and then penetrates into thefractures as they form. In the latter case sand-wedges form. These havebeen studied mainly in theAntarctic by the American researchers T. Pewe (1959) and T. Berg and R. Black (1966). Such veins develop under extremely severeclimatic and geocryologicalconditions, forming a paragenetic permafrost-faciesseries with ice and sand-iceveins (composite wedge). There is no doubt that sand-wedges can also form under less severe geocryologicalcircumstances, but theclimate must be very dry, there must be littlesurface moisture, and there must be activeeolian processes. Relicts of sand-wedges are widely found in theperiglacial zone of the last glaciation in Europeand North America.
Under conditions when the infilling of frostfractures with sand alternates in time with infilling by congelationice, transitional varieties form between sand-wedges on the one handand initial-soil veins and wedge-ice on theother. Under thesecircumstances, when the tmeanof the rocks is low, sand-iceveins form. As mentioned above, these have been studied in the Antarctic. The ratio of sand to ice in these composite wedges fluctuates within a very largerange, forming a practicallycontinuous series from - 303 -
whollyice to wholly sand veins. As examples of high-temperaturevarieties of veinsin the form of primary sand-ice veins, we examined theso-called "deflectionveins" described inCentral Yakutiya (Katasonova, 1972). They are associatedwith STL of low-moisturesandy eolian and alluvialdeposits withtemperatures near O°C. Fossilveins of thistype, sometimes having a sand-icecomposite end section(transitional varieties from high-temperature tolow-temperature) , havebeen studiedby N.S. Danilova (1 963) inthe alluvialdeposits of high terraces along the Bilyuya River. Under present conditionsneither veins filled with initial sand norwith initial sand-ice form a singlecontinuous zonal permafrost series. Because ofthis many of theirvarieties havereceived very inadequate study, and certain others we aredistinguishing on a trialbasis. Surveys and additionalresearch are requ ired
Inthe opinion of many authors,infilling of frostfractures with sublimationice may be significant. Sometimes it may evenbe thedeciding factorin the formation of wedge ice,which can be quitethick. These ideas are based on indirectdata on thechemical composition and physical properties of this type of ice, and also on directobservation of crystals of sublimationice in open cracks in winter and in incompletelyclosed fragments offractures in ice vein bodies. We shallskip the indirect data andanalyze the thermodynamic conditions of formation of sublimationice in frost fractures.
V.N. Zaitsev'sstudies of the wedge iceof seacost lowlands in Yakutiya have shown thatin winter, and during much ofthe spring, the conditionsfor the formation of sublimation ice in fracturesby means of the inflow of watervapor from the outside are nonexistent. During these periods thetemperature of the walls of the cracks is higherthan that of theoutside air, and thevapor pressure of the latteris insignificant. As theair seeps intothe cracks the ice sublimates and therock walls dry out. This has been confirmed by the directobservations of Sh.Sh. Gasanov, who establishedthat on cold days steam formsover the cracks. In the spring, as the snow melts, thecracks become filledwith congelation ice, and rarecracks which are not filledclose up as theresult of theexpansion of therocks as their temperature in the massifrises. The accumulation of sublimationice in - 304 -
frostfractures as theresult of the exchange of airwith the atmosphere is possibleonly during a brieftime period, in the spring, before the snow startsto melt. But even duringthis period the conditions for the active formation of sublimationice are not very favorable inasmuch as theexternal air has a highertemperature and a lowerdensity than the air in the cracks. As a resultof this there is no densityconvection of the air. Thus, there is an annualdecrease inthe amount of ice onthe walls of the frost fracturesrather than a buildupof it. Alongwalls composed of permanently frozenrocks a dessicationlayer forms, in whichthe rock has a lower strengththan inthe massif. Crystals of sublimation ice which are present *inthe cracks form as theresult of the exchange ofair within the cracks, when theice in a "wanner"area evaporates and accumulates in another llcol der" area.
Inregions with a highlycontinental climate, a severe deficitof moisture in winter, and thin snow cover,most of whichevaporates by spring, uniquepolygonal-vein structures may form about frost fractures, out of which texturizingice is sublimated in winter, and araundwhich the ground is drained. The formation of such PVS may be accompanied by theaccumulation of sublimationice in the cracks in the spring, and the infilling of their lower portionswith pieces of dessicatedrocks which fall fromthe walls. In some yearsmelt water flows into the cracks in the spring and veins of congelation ice form. Inthe latter case, the formation of frostfractures in the followingyear should occur below the STL alongthe dried rock, which has low tensilestrength, and notalong the ice vein. Undersuch circumstances certaintypes of ice-soilveins develop inthe permafrost,
Generally, the infilling of the frost fractures as describedabove may be provisionally called congelatianal-sublimational, keeping in mind that collapseofthe dessicated rock from thewalls of thecracks plays an importantrole. The temperatureseries established by us for this type of infillingis tentative. No specialstudy was carriedout of thestructures themselves and they do not have individual names. They will probablyinclude many polygonal-veinforms which form under the conditions of thehigh continental and verydryclimate of EasternSiberia. High-temperature varieties of such PVS are to be expected, in SouthernTransbaikalia in parti cul ar . - 305 -
i - 306 -
Based on themain initial positions examinedabove, we have compiled a basic scheme theofinterrelationships of polygonal-vein structures (see figure), the left side of which shows theprimary structures. The horizontal rows of thesestructures show thefeatures which change in them withincreasing severity (from left to right) of the temperature regime ofthe rocks (temperature control).
The vertical rows show the categoriesof PVS as thenature of infilling of thefrost fractures changes. As indicated above, theinfilling ofsuch cracks dependson the moistureat the ground surface andon the presence of eoliantransport of sandy material.There isalso a casual relationship between thesurface moisture and themoisture content of the rocks in the STL (SFL). Thus, when congelationice forms in the cracks, seasonalthawing and seasonal freezing of therocks is classified bymoisture content,in accordance with V.A. Kudryavtsev'sclassification (Dostovalov, Kudryavtsev, 1967) , as belonging to the shallow [wnat > Wuf + 2/3 (wh - Wuf) 1 and average [Wuf + 1/3 (Wh - Wuf) < Wnat < Wuf + 2/3 (Wh - Wuf)] typeswhere Wnat - isthe natural moisture content of therocks, being the average for the STL (SFL), wh - is a rockmoisture content of loo%, and Wuf - isthe quantity of unfrozen moisture.
Inthe case of primary sand infilling,the seasonalthawing (freezing)is ofthe deep type [wUf wnat c wUf + 1/3 (wh - wuf)1. In the case of transitorytypes of frostfracture infilling, when thesurface moisture content of the rocks changes from year to year, the moisture content of the rocks inthe STL (SFL) alsoevidently changes.There cannot be completesynchronicity betweenchanges inthe nature of infillingof the cracks and the moisture content of the rocks because the former is determined by thesurface moisture conditions in the winter and springwhile the latter depends on thepre-winter conditions, the composition of thedeposits, the degree to whichthe area is drained, etc. The limits of changes inthe moisturecontent of the rocks are also not clear. As a firstapproximation on the basis of fragmentarydata it may be supposed thatthe depths of the STL (SFL) withrespect to moisturecontent vary from the shallow to the averagetypes. Thus, thevertical axis in the proposed scheme ofprimary structuresreflects moisture content control over the infilling of frost fractures and thedepths of seasonal thawing (freezing) of the rocks. - 307 -
At present,classification of PVS intoepigenetic and syngenetic formations isgenerally known. Epigenetic PVS arethose which have formed in rockswhich have completed theirprocess of accumulationprior to the start of development of thestructures. Syngenetic PVS formsimultaneously with accumulation ofthe deposits. In theproposed classification scheme forthe interrelationships of PVS such a subdivisionis not graphically represented, but it should be keptin mind that all types and varietiesof the structures whichhave been distinguished canbe eitherepigenetic or syngenetic.
Secondarypolyqonal-vein structures, which are shown on the 1 eft side in theFigure, are forms which appear when theice contained in primary polygonal-veinstructures melts. Thus, theycan form from only certain types of PVS; firstly thoseclassified as low-temperatureformations, and secondly oneswhich have, as an integralpart of thevein structure, inclusions of ice in a volumeexceeding the Wh of therocks which make upthe vein in its thawed state. For this reason,the leftside of thefigure shows relicts of wedge ice (pseudomorphs after wedge structuresice), with congelation-sublimationinfilling, andsand-ice veins. The conditions of formation of pseudomorphs after ice veins,are described quite completely in the literaturethe (Kaplina, Romanovskii,1973).1972, Relicts of low-temperature PVS with congelation-sublimation infilling of thecracks have notreceived any attention so far. It is likelythat they will have characteristicssimilar to those of pseudomorphs aftersmall ice veins, and perhaps will notdiffer morphologically from them. Relicts of sand-iceveins have characteristicswhich are similar to pseudomorphs afterice veins, with inclusion of eolian sand in the structures as an additionalcharacteristic.
The icecontent of low-temperature sand-ice veins does not exceed a 100% moisturecontent for the unfrozensoil. Because of this,the structuresthemselves do not losetheir primary morphological characteristics as theythaw. Moreover, the structural peculiarities of the sandand gravel which make up theveins are preserved in the fossil state.
It should be particularly emphasized thatall types of PVS which form in thepresence of a permafrostsubstrate, i.e., in STL andpermafrost or in STL alone,including ones which do not containground ice, can undergo - 308 - certain changes when theirgrowth ceasesand thepermafrost thaws. These changes will be more pronounced withincreasing icecontent theof permafrost. The effectsof the ice content of the enclosing groundon the PVS relictsare dealt with thein literature mostextensively for pseudomorphs afterice veins. Such studiesare lacking or are of a very restrictednature for other types of veinstructures. Probably the most completedescription of the transformation of sand-iceveins andsand wedges in the process ofthe degradation of permafrost is found in the works of R. Black (1965) and I.Ya.Gozdzik (1973). The importance ofthis question is indisputablesince, in particular, low-temperature fossil varieties of sand wedges may differ fromhigh-temperature onesby thenature of their deformations,which developed as thedepth ofthe seasonal thawing and degradations of ice-bearingpermafrost increased. This is a subject for specialreserach and is notdealt with in this paper. In distinguishing and classifying secondarystructures we did nottake into account deformations associatedwith the thawing of enclosing or underlyingpermafrost. For this reason sand-wedge relicts have not been speciallydistinguished either. Furtherresearch inthis direction andimprovement ofthe PVS "basic classification scheme" will make it possible to distinguishlow-temperature sand-wedge relicts, and possiblyalso sand-ice veins, in accordance withthe a bove princi ple.
It must be notedthat developing polygonal -vein structures and ones which have stoppeddeveloping, i.e.* inthe conservation or burial stages,are not differentiatedin the proposed "scheme". Such subdivision for eachtype of structureis possible, expedient, and is carriedout in specialgeocryological research. Its introduction into the "basic scheme", however, wouldonly complicate it without adding anything significant.
The proposedapproach to theclassification of PVS also does not takeinto account structures associated with llsorted" and "unsorted1'polygons (Washburn, 1965). Inour view,heaving and sorting of therocky material are secondary phenomena inrelation to frost fracturing and thedevelopment of veinstructures.
The aboveapproach to theclassification of polygonal-vein structures,which takes into account"temperature control" over the position - 309 -
of frostfractures and structuresin the STL-permafrost system and I'moisture
1 eve1 control 'I over infill ing of thecracks makes it necessary to take a new approach tothe taxonomy of thesestructures. Thus, "soil"("earth") veins whichthe majority of researchersdifferentiate as a singlebasic type of PVS, aresubdivided into completely different types of veinswhich form under differentpermafrost-temperature and climaticconditions, which are sometimes diametricallyopposite (for example, initial-soil veins and "low-temperature" sand-wedges). Finally, we propose that"primary" and"secondary" PVS be distinguished as basicgroups, that within the group of primary PVS, types be distinguishedby the nature of infilling of the frost fractures (types of infill ing - congelationice, congelation-sublimation ice, sand-ice composite, sand) , and thatstructural types be distinguished(high-temperature, transitional,low-temperature) by the position of thefrost fractures (and structures)in the STL (SFL) - permafrostsystem. Varieties of PVS can be distinguishedwithin the types by thelevel of development,the morphology, and otherfeatures. It is expedienttodivide all structures into two classes, dependingon theirrelation to theenclosing ground, namely: epi- and synsenetic PVS. The taxonomy of a group of secondarystructures subdivided inthis manner is determined by the taxonomy of therespective categories of primary structures.
Inconclusion, it should be mentioned thatthe proposed PVS classification scheme will permit researchersto devote their efforts to the searchforsuppositional structures, to establishingthe distinguishing characteristics of structuresbelonging to differentcategories, and to the detaileddelineation of the complex of conditions(including permafrost faciesconditions) under which they can develop. A more detailedsubdivision of veinstructures will require new special methods of research(geothermal geochemical,lithological, etc.), which is a task forthe imnediate future.
REFERENCES
1. DANILOVA N.S. Primary-earthveins inthe Quaternary deposits of the Vilyuisk Region, Inthe book: Conditions and featuresof development of permafrost in Siberia and the Northeast. Moscow, Pub. ofthe AN U.S.S.R., pp. 25-40, 1963. - 310 -
I-2. KAPLINA T.N. and ROMANOVSKII N.N. Pseudomorphs afterpolygonal -vein ice. In the book: Periglacial phenomena in the territory of the U.S.S.R. Pub. of Moscow StateUniversity, pp.101-129, 1960.
3. KATASONOVA E.G. Cryogenicfornations in seasonallythawing eo1 iandeposits of CentralYakutia. Inthe book: Geocryological and hydrogeological research in Siberia.Yakutsk, pp.80-89, 1972. 4. ROMANOVSKII N.N. The effect of theground temperature regime on frost fracturing and thedevelopment of polygonal-veinforms. Inthe book: Permafrostresearch. No. 10. Pub. of Moscow StateUniversity, pp.164-1929 1970. 5. ROMANOVSKII N.N. Maintypes of polygonal-veinformations, their charac- teristicfeatures and conditionsof development. Moscow University Bulletin, GeologySeriesI No. 6, pp. 44-57,1972. 6. ROMANOVSKII N.N. and BOYARSKII 0.G. Polygonalveins and earthveins in the northeasternpart of theVitim-Patom Plateau. Inthe book: Permafrost research. No. 6, Pub. of Moscow StateUniversity, pp. 124-143,1966. 7. SHUR Yu.L. The transitionalla er. In the book:Methods of geocryological research (Trudy of the A1 T -Union Scientific Research Institute of Hydrogeologyand Engineering Geology), pp. 82-85, 1975.
8. YANOVSKII V.K. Expedition to the Pechora River to establishthe southern permafrostboundary. Inthe book: Trudy of theconrnision forthe study of permafrost.Vol. 11, Moscow-Leningrad, Pub. of the AN USSR, pp.66-149, 1933. 9. BERG T.E. and BLACK R.F. Preliminary measurements of growth of non-sorted polygons.Victoria Land, Antarctica,Antarctic Scil-forming processes. - "her. Geoph. Uni . on Antarctic Research, Nat. Acad. Sci . - NationalResearch Council", Ser. 8, Pub. 1418,pp. 61-108, 1966.
10. BLACK R.F. Ice-wedgecasts of Wisconsin."Wisconsin Acad. of Scie.,Arts andLetters'l, Vol . 54, pp.187-220, 1965. 11 COZDZIK J. Genera i poricyastratygrafictna structyr peryglacjalnych w SzrodkovejPolsce. - "ActaGeographica Ledziensia", N 31 , Lodz, pp. 117,1973.
12. PE/WE/ T.L. Sand-wedge polygons(Tesselation) inthe McMurdo Sound Region. Antarctica - "A progressreport Amer. Journ.Sci .'I, Vol 257, pp . 545- 552. 13. ROMANOVSKJ N.N. Regularitiesin formation of frost-fissures anddevelop- mentof frost-fissures poligons. - "Buln.Perigl ,'I, N 23 Lodt, pp. 237-277, 1973.
~ 14. WASHBURN A.L. Classification of patternground and reviewof suggested origins. - "Geol , Soc, Amer ,'I, July, Vol 67, pp, 823-866, 1956. - 311 -
OFFSHORE PERMAFROST IN THE ASIATICARCTIC
F.E. Are Permafrost Institute, Yakutsk, U.S.S.R.
It is now certain that permafrost is widelydeveloped beneath the Arctic Oceanand its surroundingseas. However, geocryologicalstudy of the sea floorstillis in thevery early stages. The great practical significance and the very inaccessibility of the offshorepermafrost zone make it one of the most interesting and topical problems in present-day permafrostresearch.
One of the first communications concerning the presence of permafrost on the floor of the arctic seas was that of A.E. Nordenshel'd (1880), who observed that the sandy floor of one ofthe bays on the eastern coast of the Chukchi Sea was cemented by ice.
In a monograph by V. Yu. Vize and co-authors (1 946) it was stated that on thefloor in the Laptev Straits,ice had been foundwhich did not thaw, due to thesubfreezing temperatures of the water. There are no further elaborations.
On the whole, factual data on permafrost beneath thefloor of the arcticseas have been, untilrecently, almost exclusively for coastal shallows, They havebeen collected mainly atthe Institute of Permafrost Studies of the Siberia Branch of the Academy of Sciences of the U.S.S.R. by N.F. Grigor'ev (1966). Beginning in 1953, under hisdirection, a great number of borings were madewhich encounteredperennially frozen or chilled earthmaterials near the receding coastlines of the open sea and in shallow gulfs, at adistance of several hundred metres from the shore; they were also
Proceedings Third International Conference on Permafrost, Vol. 1, pp. 336 - 340, 1978. - 312 - encountered on theshores of theestuaries of therivers Yana and Indigirka, at a distance of 25 km fromthe outer limit ofthe delta. In all cases the depth of the water was lessthan 2 m.
Duringthe period 1962-1972, underanalogous conditions, E.N. Molochushkinstudied the perennially frozen and chilledmaterials of the recedingshorelines of Mostakh Islandin Buor-Khara Bay, of Vankina Bay in theLaptev Sea (1973), and thechannels on the shores of the Lena estuary in the region of Olenekskaya.
The first information on thepresence of an offshorepermafrost zonebeyond the 1 imi ts of the 2 m isobath came from V .M. Ponomarev (1960, 1961 ) for Kozhevnikov in Khatanga Bay, where many boreholesrevealed perenniallyfrozen and chilledearth materials. In one of theboreholes, at 3 km fromthe shore and at a depth of 3 m, thepermafrost proved to be 66 m thick.
In 1970, when E.N. Molochushkin(1973) took samples offloor deposits in Ebelyakhskaya Bay and in the LaptevStra,its, permafrost was found inthe lower part of the core sample in severallocations, at a distanceof 30 km from theshore.
According to a report by L.A. Zhigarev and 1.R. Plakht(1974), thereare perennially frozen unconsolidated materials with high ice content in an underwaterbar in Vankina Bay on theLaptev Sea, 10 km f ronl shoreand at a depth of 86 m above the sea floor. The depth of thewater is not indicated.
The discovery of oil in Prudhoe Bay, Alaska, in 1968 was a strong impetusfor research and development in the arctic regions of the U.S.A. and Canada. In 1969 there was a report of thepresence of permafrostbeneath Deception Bay in Northern Quebec, Canada(Samson, Tordon),According to B.P . Pelletier(oral comnunication, 1970), freshwaterIce was extractedfrom the sea floorin the northwest part of the Canadian Arcticarchipelago between PrincePatrick Island and Borden Island, at a depthof 10 m (Mackay, 1972). - 313 -
In thespring of 1970, nearthe Canadian coast in thesouthern part of theBeaufort Sea, between HerschelIsland and Liverpool Bay, cores of ice and frozenunconsolidated deposits were extracted from four we1 1s when drilling on the sea floor foroil; these were studiedin detail by J.R. Mackay (Mackay, 1972). The boreholes were locatedfrom 3 to 25 km fromthe shore, at points where thedepth of water was from 8 to 17 m.
Inthe summer of 1970, a frozen corewith freshwater ice lenses was obtainedfrom the floor of the Beaufort Sea, 30 km north of Bathurst Inlet and at a depth of 37 m, by theGeological Survey of Canada (Yorath et a1 . , 1971 ; Reimnitz et a1 , 1972).
Inthis way, it was empiricallyproven that permafrost is found beneaththe arctic seas several tens of kilometresfrom shore, at a depthof severaltens of metres.
On thebasis of generalconsiderations and very 1imited factual information,I.Ya. Baranov(1958) dividedthe permafrost into two offshore zones. The first extendsover the whole of theAsian arctic shelf to the 100 m isobath;the second, overthe coastal regions of the Kara, theLaptev and theEast-Siberian seas tothe 20 m isobath.This permafrost formed in thePleistocene, and partiallyin the Holocene, when the shelf was dry. The first zone became submerged as a resultof marine transgression; the second as a resultof abrasion at "normal1' sea level In Baranov'sopinion, the permafrost is in a stageof degradation at the present time.
The possibility and theinevitability of theperennial existence ofoffshore permafrost isconditioned by constant subzero temperatures of the layers of sea waterover most of thearctic seasand theArctic Ocean. The thermalconditions of arctic waters havebeen studiedin considerable detail. Therefore, it is now fully possible to compose a map of thedistribution of offshorepermafrost as was done by A.L. Chekhovskii (1972) for theshelf of the Kara Sea. But it is much more difficult to determinethe thickness of materialswith subzero temperatures, andeven more so toexplain the morphology of thepermafrost. In orderto solve this problem, there must be a rationalcombination of geophysical research methods supported by borings. Rough forecastscould be obtained by calculatlon. - 314 -
The followingshould be listed among the most important factors influencingthe formation of the permafrost zone: relativelevels of the sea and dry land,the climate and temperature of the sea floor;the Earth's internalheatflow; mineralization of thelayers of sea waterdirectly above the sea floor and of the watersimmediately below the sea floor; the propertiesof the minerals forming the sea floor;the processes of abrasion and accumulationof sea floor deposits.
Each ofthe above factors will beexamined in greater detail.
Relative changes inthe levels of the sea and the dry land cause transgressions and regressions of the sea and consequentlythe submerging and dryingout of the Earth's surface; this radically changes thetemperature regimeof the earth materials and thehydrogeological conditions of their development. A great amount ofscientific research, the results of whichare in many instancescontradictory, is devoted to explaining either directly or indirectlythe history of marine transgressions in the Earth's geological past
At thepresent time, it isgenerally recognized that shoreline displacement is theresult of the complex interaction of bothtectonic and glacio-isostatic movements of lithospherethe and glacio-eustatic fluctuationsin the ocean level. The processhaving the longest duration, h processthat formed a backgroundagainst which all otherprocesses developed, is the inidirectional tectonic uplifting of theland and theformation of the ocean troughsduring the Quaternary. During the 1ast mi11 ionyears, according to P .A. Kapl in (1973),the ocean 1 eve1 has been lowered in this way by100 m inrelation to the dry land. It was againstthis background that the quickerglacio-eustatic fluctuation in the ocean leveltook place, the limit of which was approximately 120 m in the Quaternary.
Withregard to the intensity and amplitude of the glacio-isostatic movements, theopinions of thevarious researchers are widely divergent. In a number of publicationswhich haveappeared in thelast fewyears, it has been proventhat the most recentvertical movement, at least in some coastal regions of theSoviet Arctic, were essentiallyconditioned, notby - 315 - glacio-isostatic,but by tectoniccauses. Most researchers agree that resultantvertical movements ofthe lithosphere in thecoastal zone of the arctic seas for thePleistocene and the Holocene was, on a regionallevel very uneven, attainingseveral tens of metres inindividual structures.
Withthe advent of theradiocarbon dating method for establishing theabsolute date of earthmaterials, it was possibleto make a qualitative study of the rate of changes in the ocean level during the last 30 years.
H. Godwin, R. Fairbridge and a number of otherresearchers have shown thatin the period between 17,000 and 6,000 years ago there was a eustaticrise of 100 m inthe ocean level;this developed at a relatively evenpace, with anaverage speed of approximately 9 m per 1,000 years. Duringthe past 6,000 yearsthe ocean level has experiencedeustatic fluctuationswithin the limit of nomore that 10 m. Therewere also alternatingfluctuations of the ocean levelduring the period of intensive transgression,but for thepresent, no reliableexplanation of their chronology or amplitude is possible.
Rough estimates and simulation on a hydro-integrator show that, for a quantitativeestimate of thepossible present day permafrost zone beneaththe arctic seas, the dynamics of shorelinedisplacement must be explained in time andspace for thepast 20,000 30,000 years.
It is obviousthat the one-directional regression of the ocean in thePleistocene can be disregarded,since for theperiod of timeunder study, it comprised atthe most 2 - 3 m. As far as theglacio,eustatic fluctuations in the ocean levelare concerned, they have been wellstudied; the main problem is an explanation of theglacio-eustatic and neotectonicchanges.
Analysis of resultsto date shows that on thearctic coastline of the U.S.S.R. it was theuplifting of theland which predominated inthe UpperPleistocene and theHolocene; its magni tudedecreases in aneasterly direction fromthe Kola Peninsula and Franz Josef Land to theshores of the Laptev Sea and theEast Siberian Sea. Beyond thispoint it increases slightly towardsthe Chukchi Peninsula (Kaplin, 1973). - 316 -
The contributionsof G.I. Lazukov(Markov, Lazukov, Nikolaev, 1965)are devoted to thehistory of thedevelopment of thecoastline of the Kara Sea. According to hi5 scheme, transgression was takingplace all the time,beginning with the Middle Pleistocene, inthe northwest part of the West Siberian Lowland. At thebeginning of the Holocene, a shelfexisted in the Kara Sea as far as the 15 - 20 isobath. The present-dayshoreline was formed in theMiddle Holocene and has remainedunchanged ever since. There was no transgression on theWest-Siberian Lowland inthe Pleistocene.
The most detailed scheme of development forthe shelf in the Laptev Seawas drawnup by S.A. Atrelkov(1965). In his opinion, at the time of theZyrian* glaciation the wholeshelf became dryland. Transgression tookplace in theKarginian* period as a result of whichthe shoreline on the Taimyr became almost coincident with the present day line; from the Anabar to the Lena it stretched 50 - 100 rn furtherout to sea; further to theeast, it rantowards the northern extremity of the New SiberianIslands. At the beginning of theSartanian* period it fell byapproximately 50 m, and at the end of theperiod, it rosefor a shortwhile to 15 - 20 m above thepresent level. The proposed risein sea levelis improbable. A considerablepart of the shoreline of the Laptev Sea wasmade up of unconsolidateddeposits with a highice content which were formed no laterthan the middle of the Upper P1 eistocene. They areonly slightly eroded by the sea andtherefore ought to have retainedtraces of theshoreline which had formed when the sea level rose inthe Sartanian period. However, there are no suchtraces.
Towards thebeginning of the Holocene, the sea levelagain fell to 20 m belowthe present day level. The general consensus is that a transgressiondeveloped during the first half of the Holocene and finished 5,000 years ago atthe present day level. This date is supportedby several zoological, and more particularly,archaeological data in the work of V.D. Dibner and K.N. Nesis (Govorukha, 1968).
In theliterature, the history of the development of the shelf in the East Siberian Sea istreated in less detail than is the shelf in the
* The Russianterm for therespective glaciations are: Zyryanka,Sartanka. The third termcould not be found (Trans1 .). - 317 -
Laptev Sea. Accordingto S .A. Strel kov, duringthe Zyrian period the sea level was 40 - 50 m lowerthan the present level ; inthe Kargian period it fell byapproximately 15 m; and in theSartanian time it fell 50 m. Other eventsunfolded in the sameway as those in the Laptev Sea.
To a depth of some 100 m theshelf in the Chukchii Seabecame dry landin the Zyrian period, according to D,M. Hopkins(Hopkins, 1959). The BeringStrait did not exist.In the Karginian period the sea levelrose to the 40 m isobath, and at thebeginning of theSartanian period it fellagain by 10 - 30 m. Alaska'spresent level became establishedabout 5,000 years ago.
Analysis of data on the relative levels of the arctic seas of Asia shows that,at present, large errors of thousands of yearsand hundreds of kilonetres are possible when drawing up a scheme of shoreline dislocation for any part of the she1 f, even for the Holocene.
It isthe climate, and above all, its thermalcharacteristics and its changes in time,which determine the development of a permafrostzone. It is well known thatthe climate changedmore thanonce inthe Quarternary, andvery significantly.
The maintrend inthe Pleistocene was a generalcooling of the climate.Against this background, lesser fluctuations developed. It is generallyaccepted that during the warming period the climate was similar to the presentclimate, or sonlewhat milder, and thatduring the cooling period, it was considerably more severe. G.I. Lazukov(1961) and D. Clark(1974) maintain that the arctic climate in the Pleistocene was never warmer thanthe presentday climate. There are grounds for proposing that throughout the PI eistocene and the Holocenethe cl imaticconditions assured the uninterruptedexistence of thepermafrost zone. It ispossible that during the Holocene climatic maximum there was partial degradation of thepermafrost zone, butthat it wrought no radical changes in thefrozen landscapes of the arctic coast1 ine.
Present-dayknowledge isnot sufficient tofurnish conclusive evidence of the quantitativecharacteristics of thePaleoclimate of the - 318 -
Quaternary.Therefore, th'e majority of researchersrestrict themselves to carefulapproximate comparisons of pastclimates with the climate of today.
One of the most detailedqualitative schemes of changes in mean annual air temperature during thepast 75,000 years was drawnup by €.I. Ravskii (1969) for thesouthern half of East Siberia. This scheme corresponds tothe data of R. Bowen (1969)on changes of climatein the middl e 1ati tudes of the northern hemi sphere in the Upper P1 eistocene and the Holocene. However, theauthor himself points out how little is known onthe subject. An analogous scheme forCentral Yakutia, basedon thestudy of a crosssection of Mt. Mamontovo was drawn up by K.K. Markovand A.A. Vel ichko (1967). It differssubstantially from that of E.I. Ravskii.
Climaticconditions along the arctic coast in the Sartanian period were, withoutdoubt, more severe thantoday, mainly because, with a sea level of 100 - 140 rn lowerthan the' presentlevel, access by the warm Atlantic waters to theArctic Basin was considerablycurtailed (Belov, Lapina, 1961; Govorukha,1968). The cl irnaticconditions musthave been closeto those of present day Antarctica. At present , the mean annual air temperature at the SouthPole is -48.5OC; atthe pole of inaccessibility it is -56OC. The mean annualtemperatures attributed to the sea level, based on a world-wide mean verticalgradient of 0.5°C/100 m will be -34.5'C for the SouthPole and -37.4OC forthe pole of inaccessibility. Themean annual air temperature at theNorth Pole during the marine regression was probably no higherthan the givenvalues, i.e. 15 to 18OC belowthe present temperature of -19OC.On thebasis of thelatitudinal temperature gradient, it can be assumed that the mean annual air temperature on the arctic coast of Asia at thattime was no higherthan -25OC.
The temperature of thebottom water of theAsiatic seas having a continentalshelf havebeen wellstudied. As a rule, it is belowzero, whateverthe season. An exception isthe zone of warming effect of the rivers, and theeastern part of theChukchii Sea (Sovetskaya Arti ka, 1970). Duringthe period of regression, it was probablycloser to thefreezing point,owing to the more severetemperature climate of thebottom water. - 319 -
The opinionprevails that theair temperature during the Holocene climatic maximum rose by 2OC withrespect to the present temperature (Bowen, 1969;Ravskii,' 1969, and others).Taking into consideration the great thermalinertia of thewater masses, it shouldbe considered that the water temperaturerose considerably less.
The continentalslope, the channel bottoms and the deeper parts of thearctic seas are washed byAtlantic waters at a depth of from 200 to 900 m; the sea waters have above-freezingtemperatures of from 0.2 to 1.5OC.
In the depths,situated between the Lomnosov Ridge and the Bering-Karashelf, the deep watertemperature is -0.7 "1 .O°C. Duringthe regression, the temperature of the bottom water within the whole Arctic Basin was apparently close to freezing, i.e., -1.8OC.
The Earth'sinternal heat Slowhas an influence on thepermafrost zone. A largepart of theasian arctic coastline is Characterizedby a flow of 0.04 to 0.06 kcal/m2per hour.
Researchon heat flowoutward through the ocean floors was begun in 1952. A series of tests wasmade inthe Arctic Ocean. The submerged mountainridges of theSoviet sector of theArctic proved to be a regionof heightenedthermal activity. For example, withinthe Lomonosov Ridgethere was a variationin heat flow of from 0.05 to 0.10 kcal/mper 2 hour, and in the MakarovaTrough of from 0.05 to 0.07 kcal/m2per hour (Lyubimova et a1 ., 1973).Taking into account that, according to thepresent view, the arctic shelf is a naturalcontinuation of the continent, it can be assumed thatthe heat flow isclose to that of thecoastline, that is, approximately 0.05 2 kcal/mper hour with possible deviations in theorder of 115%.
Mineralization of sea waterand bottom water has a great influence onthe phase composition of the materialsforming the sea floor on the continentalshelf. Highly mineralized waters facilitate the freezing of the mixingmaterials and form supra-,intra-, and subpermafrost water-bearing zones. Theirdistribution on theshelf is not known; thepatterns of their formation and theirinteraction with the permafrost have received little attention. - 320 -
Upon contactofthe mineralized water-bearing zone withthe permafrost at a sub-zerotemperature higher than the freezing point of the porewater solution, the freshwater ice melts, filling the pores with frozen earthmaterials. An increase inthe mineralization ofthe pore water solutionnear the boundary of thepermafrost (essential for theformation of freshwater ice) takesplace by way of migrationof ions, induced by the concentrationgradient, which decreases as theprocess develops. Thus in the absence of a pressure filtration process, it slows down automatically.
In the opinion of V.M. Ponomarev (1961), themelting of ground ice when exposed to sea watercan only extend to a depthof a fewmetres. This is indirectlysupported by laboratorytests conducted inthe Institute of PermafrostStudies, Siberian Branch, Academy of Sciences ofthe U.S.S.R. by L.V. Chistotinov and L.G. Rogovskaya, who showed thatthe thawing of ice saturated fine-grainedmaterials contiguous with the mineralized water at a temperaturebelow freezing decreases with an increase inthe depth of thaw and thefineness of the materials, and also with a decrease in mineralization of the water.
Withthehelp of a samplingtube E.I. Molochushkin(1973) discoveredboth desalinized thawedand frozenfloor deposits in the Laptev Straits andEbelyakhskaya Bay on theLaptev Sea, at a distanceof 25 km from theshore, where offshore conditions had prevailed for thousands of years.
The length of thecores extracted from the floor invarious samplings ofthe arctic shelf does not exceed 6 m, and forthe most part comprisestenths of a metre. Inthe Laptev Straits and in Ebelyakhskaya Bay thesampling tube didnot penetrate the floor for more that 3.5 m (Molochushkin,1973). Apparently, in many instances,the depth to whichthe tubecould penetrate was restricted by thedepth of the permafrost. Thus, because ofthe melting of theground ice resultingfrom the action of the saline sea water, it isunlikely that a sufficientlythick layer of frozen depositscould form.
In the tone of present-dayaccumulation in the Laptev Sea, frozen floordeposits cementedby ice and at a temperature down to -6OC - 321 -
(Molochushkin,Gavril 'ev, 1970) were discovered and studied. An interesting featureof these deposits is the factthat the mineralization of the pore so'lution is considerablyhigher than that of the sea water. The causehas not been explained. The presenceonthe floor of thearctic shelf of depositsnot cemented by ice gave some researchersreason to question the possibility of theexistence of frozenmaterials at considerabledistances fromthe shore (Govorukha, 1968; Semenov, 1973). However, thefactual data presentedat the beginning of this paper,refutes this opinion. The frozen stateof the deposits on thearctic shelf is evidencethat these are present-daymarine sediments.
The characteristics of the earth materials which form the floor of theArctic Ocean, andwhich must be considered inthe thermophysical calculations of theparameters of thepermafrost, have hardly been studied. Theircharacterizing values can onlybe assigned on thebasis of the general concepts of geologicalstructure of the sea bottomand ontentative assumptions. The results of this can be seenfrom the example of the coefficient of thermalconductivity. According to the researchbythe GeothermalLaboratories, Permafrost Institute,Siberian Branch, Academy of Sciences of the U.S.S.R., the coefficient of thermalconductivity of themost widelydistributed earth materials in Yakutiavaries from 1.5 to 4.5 kcal/m perhour OC, thatis, it can differ by a factor of three. The stable thickness of thepermafrost zone is directly proportional to the value of the coefficient.Consequently, depending on the choice ofthe value for the coefficient of thermalconductivity, thecalculated thickness of the permafrost zonecan differ by a factor of three.
The processes oferosion and accumulation in the coastal zone, withoutdoubt, had, and still have, considerableinfluence on thedevelopment of thepermafrost tone on theshelf. Within the limits of themaritime lowlands of Siberiathe present-day sea level was apparentlyestablished in themiddle of the Holocene, thatis, 5,000 yearsago. During this time, thermalabrasion has developedintensely. On thebasis of present-day observations, it can be assumed that, when exposed to thermalabrasion, shore1ine regression proceeds at a speed of from 2 to 6 m per annum, and in placesup to 10 ITI per annum. Thisindicates that, in the second halfof the - 322 -
Holocene, in many places where there was no change in the sea level , the shore1 inereceded onan averageby 10 - 30 km, and by a maximum of 50 km.
As a result of thermalabrasion, very thick continental permafrost wasnow situated beneath the sea. Its fate depended to a greatextent on the distribution of the warming and distillinginfluences of therivers. These distributionareas have been studied indetail with respect to largerivers. It isalso known thatriver waters on theshelf do not descend lowerthan 20 rn (Sovetskaya Artika, 1970) When exposed to riverwaters with temperatures above freezing,there was degradation of thecontinental , submerged permafrost. Rough calculations by E.N. Nolachushkin (1970) show that, in these regions, dependingon thedistance from the shore and the rate of regression, to date, permafrostcould either me1 t completelyor remain at some depthbelow the sea.
Outsidethe zone affected by therivers, the below freezing temperatureprevailing on the sea floor was considerablyhigher than the temperature on theland. In this case, there was partialdegradation of the permafrost frombelow, and a risein its temperature to an equilibrium corresponding to thetemperature of the bottom water.
New permafrostcan form in the zone of accumulation of present-day floordeposits. Their formation is strongly dependenton themineralization of the sea water. On estuaryshorelines where thereis both fresh and slightly saline water, perennial freezing of the floor starts when there is a reduction in the depth of thewater to about 1.5 m (Grigor'ev, 1966).
Outsidethe zone affected by therivers, perennial freezing of the floorrequires that the water be shallower,depending on the salinity of the sea water and thefloor deposits. It should be emphasized that a reduction in thedepth of thewater when there is any kind of natural mineralization of the sea water and porewater inthe floor depositsleads to perennial freezing of the sea floor, so when shallows are exposed at sea 1eve1 , the mean annualtemperature of theirsurface falls to -10 + -12OC.
The permafrost zone ofthe Arctic Basin. The deep part of the ArcticBasin can be dividedinto two parts: the deep, where the water is - 323 -
belowfreezing (sovetskaya Arktika, 1970), and a zonewhere thewater is from 200 to 900 rn. The latter,is washed by Atlantic waters withtemperatures above f reezi ng .
Apparently,there is a stablepermafrost zone below the floor of the deep. On the sea floorare unconsolidated marine depositions several hundredmetres thick. The coefficientofthermal conductivity of such depositsis approximately 1 .5 kcal /m perhour 0C. The Earth'sinternal heat flow is from 0.05 to 0.07 kcal/mper hour. 2 The datagiven is for a permafrost zone of 15 - 30 rn inthe Flansen Basinand of about 10 m in the BeaufortBasin. The floordeposits within the permafrost zone arefrozen.
In theregion of theunderwater ridges there may be anabsence of sedimentcover in places. The coefficientof thermal conductivity and the abyssalheat-flow must be relatively high here. Under such conditions,the thickness of thepermafrost is in the order of 25 m. It canreach a maximum of 70 m.
Inthe Atlantic water tone, the temperatures are above freezing. Simplecalculations show that there is no permafrostzone here.
Conclusion.Analysis ofthe given data shows thatthe offshore permafrost zone occupies a largepart of theAsian arctic shelf and the ArcticBasin. It is absent from theupper part of the continental slope and from thedeepest parts of thearctic seas (depth 200 - 900 m), and possibly fromthe areas with the warming effect of large riverss when there is a depth of no lessthan 20 rn.
Relic permafrostoccurs in the coastalstrip of theshelf 10 - 30 K wide,providing it became submerged as a result of thermal abrasion. It can onlyexist in that part of theshelf which became dryland inthe recent geologic past. Outside these areas, the earth materials of the offshorepermafrost zone exist in a chilled state.
The thicknessof the permafrost zone in the deep part of the ArcticBasin between theBarents-Kara shelf and the Lomonosov Ridge is in the orderof 15 - 30 n-1; beyond the ridge it is in theorder of 10 m. - 324 -
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VIZE, V.Yu. et al. SovetskayaArktika. Morya i ostrova.Fitiko-geograficheskaya kharakteristika.(Soviet Arctic. Seas and Islands.Physical Geography). M-L., Izd-voGlavsevmorputi, p. 150, 1946.
GOVORUKHA, L.S.Ya.Ya. Gakkel' ob Arktike. (Ya.Ya. Gakkel' : The Arctic) -V kn.:Problemy polyarnoi geografii. (Problems ofPolar Geography). L., Gfdromoteoizdat,Trudy AANII, t. 284, pp. 31-51 , 1968,
GRIGOR'EV, N.F. Mnogoletnemerzlyeporody primoskoi zony Yakutii.(Permafrost of theCoastal Region of Yakutia). M., "Nauka", p. 180, 1966. ZHIGAREV, L.A. and PLAKHT, I.R. Osobennostistroeniya, rasprostraneniya i formirovaniyasubakval 'noi kriogennoi tolshchi. (Features of structure, distribution and formation of offshorepermafrost). -V kn.: Problemy kriologii (Problems ofCryolithology). vyp. lU, IZd-vO MGU, pp. 115-124, 1974.
KAPLIN, P.A. Noveishaya istoriyapoberethii mirovogo okeana.(Recent history of the Ocean Coastline).Izd. MGU, p. 265, 1973.
CLARK, D. Paleoekologiya i osadkonakoplenie v nekotorykhchastyakh Arkticheskogo basseina.(Palaeoecology and sedimentation in parts of theArctic Basin). -V kn.: Chetvertichnoeoledenenie Zemli. (Quaternary Glaciation of theEarth). M., "Mirl', pp. 227-241 1974. LAZUKOV, G. I. 0 sinkhronnosti i metakhronnostichetvertichnykh oledenenii i transgressii.(Synchronism and Metachronism of QuaternaryGlaciations and Transgressions). -V kh .: Paleografiyachetvertichnogo perioda SSSR. (Paleography of theQuaternary Period inthe U.S.S.R.). Izd-vo MGU, pp. 139-150, 1961.
LYUBIMOVA, E.A. et al. Obzordannykh PO teplovym potokam v SSSR. (Heatflow data forthe U.S.S.P..). -V kn.: 'Teplovyepotoki iz kory i verkhnei mantii Zeml i Verkhnyaya Mantiya. Resul I tatyissledovanii PO mezh- dunar.geofizicheskim proektam No. 12.(Heat flow from the Earth's Coreand Upper Mantle. Upper Mantle, Results of the International GeophysicalProject No. 12). M., "Nauka'l, pp. 154-195, 1973. - 325 -
MARKOV, K.K., LAZUKOV, G.I. and NIKOLAEV, V.A. Chetvertichniiperiod. (QuaternaryPeriod). T. 1, Izd-vo MGU, p. 371 1965. MARKOV, K.K. and VELICHKO, A.A. Chetvertichniiperiod T. 111. Materiki i okeany.(Quaternary Period v. 111. Continents and Oceans). bl. "Nedra",p. 440, 1976.
MOLOCHUSHKIN, E.N. Teplovoirerhim gornykh porod v yugo-vostochnoichasti morya Laptevykh. (Thermal Regime of EarthMaterials in the South- East ofthe Laptev Sea). (Avtoref. kand. diss.). M.,, p. 20, 1970.
MOLOCHUSHKIN I E .N. Vl iyanie termoabrazi i na temperaturu mnogoletnemerzlykh porod v pribrezhnoi zonemorya Laptevykh,(Influence of thermal abrasion on permafrost of thecoastal region of the Laptev Sea). -P Mezhdunar. konf. PO merzlotovedeniyu.Dokl. soobshch.vyp. 2. Yakutsk, pp. 52-58, 1973.
MOLOCHUSHKIN, E. N. and GAVRIL'EV, R.I. Stroenie,fazovyi sostav i termicheskii rezhimgornykh porod, slagayushchi kh dno pribrezhnoi zony morya Laptevykh.(Structure, phase composition and thermalregion of earth materials comprising the floor of the coastal region of the Laptev Sea). -V kn : SevernyiLedovi tyi okean i ego poberezh'e v kainozoe. (The Arctic Ocean and itscoastline in the Cenozoic). L. Gidrometeoizdat, pp. 503-508, 1970. NEIZVESTNOV, Ya.V. and SEMENOV, Yu.P. Podzemnye kriopegishel'fa i ostrovov SovetskoiArktiki. (Subsurface Cryopegs of theshelf and islands ofthe Soviet Arctic). -P Mezhdunar. konf. PO merzlotovedeniyu. Dokl. i soobshch.vyp. 5, Yakutsk, pp. 103-106,1973.
NORDSHEL'D, A.E. Shvedskaya polyarnayaekspeditsiya 1878-1879 gg. Otkrytie severo-vostochnogoprokhoda, (Swedish Polar Expedition 1978-1979. Discovery of the NortheastPassage). S.-Peterbur, p. 207, 1880.
PONOMAREV, V.M. Podzemnye vody territorii s moshchnoi tolshcheimnogoletnenerzlykh gornykhporod. (Subsurface waters of regionswith thick permafrost). 81.9 Izd-vo AN SSSR, p. 200, 1960. PONOMAREV, V .M. Formirovanie mnogol etnemerzlykhgornykh porod i podzemnykh vod na me1 I komor'esevernykh morei . -V kn.: Fiziko-khimicheskieprotsessy v promerzayushchikh i merrlykhgornykh porodakh. (Formation of permafrost and subsurfacewaters in theshallows of theNorthern Seas). -V kn.:Fiziko-khimicheskie protsessy v promerzayushchikh i merzlykh gornykhporodakh. (Physico-chemical processes infreezing andfrozen earthmaterials). M., Izd-vo AN SSSR, pp. 95-101, 1961. RAVSKII , E. I. Csnovnye cherty kl imatov Sibiri v antopogeneEvrazii . (Basic features of the climates of Siberia in the Quaternary of Eurasia). Ma, "Nauka", pp. 111-120,1969. SOVETSKAYA ARKTIKA (Morya i ostrova Severnogo Ledovitogookeana). (Seas and Islands of theArctic Ocean), M., "Nauka", p. 526, 1970. - 326 -
STRELKOV, S.A. Istoriyaratvitiya rel'efa Sibiri 5 Dal 'nego Vostoka. Sever Sibiri. (Historical development of the landscape of Siberia and the Far Eastern Regions). M. , "Nauka", p. 336, 1965. CHEKHOVSKII, A.L. 0 rasprostranenii mnogoletnemerzlykh porod pod she1 'fom Karskogo morya. (Permafrost distribution beneath the shelf of the Kara Sea). -V kn.: Eeokriologicheskie issledovaniya pri inzhenernykh izyskaniyakh.(Geocryological research during technicalexplorations). M., Trudy PNIIIS, t. XVIII, pp. 100-111, 1972. HOPKINS, D.M. Cenozoic history of the Bering Land Bridge. Science, vol . 123, N 3362, pp. 1519-1528, 1959.
PACKAY, J.R. @ffshorepermafrost and ground ice, southern Beaufort Sea. Canada, Canadian Journal of Earth Sciences, vol . 9, n 11, pp, 1550-1 561 , 1972. REIMNITZ, E. , WOLF, S.C. and RODEICK, C.A. Preliminary interpretation of Seismic profiles in the Prudhoe Bay area, Beaufort,Sea, Alaska. Open-file report. U.S. Dept. Inter. , Geol . Survey, p. 11 1972. SAMSON, L. and TORDON, F. Experience with engineering site investigations in Northern Quebec and Northern Gaffin Island. Proc. 3rd Canadian Conference on Permafrost. NRCC, Tech. Mem. 96, pp. 21-38, 1969. YORATH, C.J., SHEARER, J. and HAVARD, C.J. Seismic and sediment studies in the Beaufort Sea, Geol. Surv. Can. Pap. 71-1A, pp. 242-244, 1971. - 327 -
STRUCTURE OF THE NORTHERN CIRCUMPOLARPERMAFROST REGION
I.Ya. Baranov Industrial and Residential Institute of Engineering Surveys in Construction Moscow, U.S.S.R.
I I secondThe criterion ofEarth's the cryogenic process, apart from the lowering of the temperature of matter in the geosphere to below O°C, is the crystallization of water; this occurs unevenlydepending on its phasal states, and degree of freedom;which are due to the enclosing matter, mineral ization , etc
On thisbasis, the following conceptual categorizations can be made: freezing - associated with the crystallization of water; cooling - associated with the lowering of the temperature of matter to below the natural low point of crystallization of mineralized water (brine); super-cooling of water below O°C (vapour; water which issufficiently liquid to form drops; and mineralized liquid) in a stable or unstable state, by the inherentconditions for cooling and bonding with matter. As a result,the Earth's cryosphere is a region of frozen ground features, of cooling and super-cooling;there is interpenetration, with each form serving as either a continuation of, or interfering with, the other.
The differences between the cryogenic process* and the processes of cooling and supercooling lies in the fact that, in the former, there is phase transition from water to ice with therelease of latentheat; in cooling, eitherlatent heat is not released or it is only released momentarily during transition This unconditionally plays an important role in the formation of seasonally and perenniallyfrozen earth materials and
* Cryogenic processes: physico-chemical processes resulting fromenergy and massexchange in freezing, frozen and thawing earthmaterials.
ProceedingsThird International Conference on Permafrost, VOI . 1 9 pp. 342 - 347, 1978. - 328 -
cooled materials; in thedifferences of their thermal inertia; their dynamics when exposed to uniform sources of heat; and in changes in theirproperties during freezing and warming, etc.
During cryogenic processes,the diapazone of energy- and heat-emission due to the phase transition of water into ice and ice into vapour-ice (whichby-pass the liquid phase) , depends on the degree of freedom of thewater, itsrelationship with theenclosing matter and the forms of theserelationships, and on mineralization.Therefore, crystallization takes place in a wide temperaturediapazone; therelationship between thewater, theenclosing matter, and the state of the latter, and themineralization of the water substantially reduce the point of Crystallization.
According to texture,the cryosphere isreally nonuniform and complex; it is characterized by a combination of processes of crystallization, cooling, and supercooling of water, of the matter enveloping it (atmosphere, 1 i thosphere) or shaping it (hydrosphere). Hence, the elements of the cryosphere are:the atmocryosphere, the 1 ithocryosphere and the hydrocryosphere, each of whichhas its individualmaterial characteristicsrelated to the energy- and nlass-exchange. All of the above are connected by the unity of theirinternal thermodynamic systems. Therefore, changes in oneelement inevitablyleads to a change in theother elements.
Within the atmosphere (troposphere), at various temperatures and humidities,the basic frozen ground featuresare formed - snowand hail, developing from water vapour and drop1 ets of water, When the temperature is lowand thereis low absolute humidity, supercooling of themoisture takes place. In a severeclimate, there is crystallization of supercooled vapour and of vapour whichhas been sublimated from thefrozen ground (snow) during sharp drops in temperature, and in still air, it forms a very fineice spray (a suspension) of acicularcrystals. Similar formations arealso characteristic of the stratosphere,
The atmocryosphere enclosing the stratosphere, the mesosphere, and part of thetroposphere have the form of an envelopingsphere which "leans"
1 - 329 -
On thecircumpolar region and is bounded fromabove by thethermosphere (at a height of 120 km) The lowertroposphere is verydynamic having a seasonally variabletemperatures ranging from subzero to above zero values.
Forthe troposphere, perennial (even togeologically lengthy) pulsationsare characteristic. These aremanifest ascontractions and expansions of thepart with constant above-zero temperatures and form a "ring"thatextends to theequatorial-tropical zone affecting(not systatically)the subtropic regions that are influenced by the warm seas and oceans; its a1 titude is notrestricted. Above the equator, at an altitude of 5 - 6 km, theexistence of snow and firn, ice andseasonally and perenially frozen ground is assured.
It is known that seasonal changes in the temperature of the troposphereare due to the movement of the Earth in orbit and to the angle of inclination of its axis. A change in the incidenceand speed of theEarth's rotation causes a change in the climate of theplanet, and of the quantitative and qualitativecharacteristics of theelements of the cryosphere.
The internal boundary of theatmocryosphere is formed by the mobile isothermic surface with a temperature of O°C,
In precedinggeological epochs,and thein Cenozoic, the atmocryosphere,particularly in the Quarternary,experienced substantial expansionsduring the epoch of fa1 ling temperatures, and contractions in the warmingepochs.
Inthe lower troposphere (mainly to an altitude of 3.0 - 3.5 km), is concentratedthe prevailing moisture, inits various phases. The upper surface of thesphere of greathumidity is dynamicand is dependentupon changes in thetemperature of the air and of thedaytime surface temperature.
The temperature field of the atmosphere, as is well-known, is formed as a result of internal heat sources, mainlyabsorption of ultraviolet rayswith a wave length of 2000 < X < 3000 1 (mesosphereand stratosphere), - 330 - and of apparent and infraredradiation with a wavelength X < 3000 (Earth's surface,troposphere). Above the atmocryosphere (inthe thermosphere) the thermalstate is formedunder exposure to shortwave radiationwith a wave 1 ength of h < 1000 8.
The remainingradiant energy of the second diapamone of the wavelengths is convertedinto heat energywhich takes part in theinternal thermalregime of the troposphere in its heat- and mass-exchange interactions with land and the oceans, their water and ice surfaces, and becomes subjected to thespecial features of theplanet. Periods of cooling and warming and the dynamics of the atmocryosphere reflect shifts and changes in theEarth's internal thermodynamic system.
As is we1 1- known , a consequent lowering of energy-exchange with increasingaltitude is characteristicof the troposphere and its temperature field. This determines the a1 ti tudinal zonal elements of the 1i thocryosphere and thepossibility of accumulativefrozen ground features (ice covers), which change thelandscape of the surface in circumpolarregions. A sequentiallowering of energy-exchange away fromthe equator to the poles determinesthe 1ati tudi nal tonal elements of thecryosphere of the dry land and the oceans.Comparison of two spatialtypes of heat-exchange ( planar and altitudinal) creates a true schema for texture of theEarth's cryosphere, of theinteraction of theenveloping elements on the basis of their differences in heatenergy.
The stratosphere and the mesosphere, and the sphere of constant coolingplay a decisiverole in the thermal regime of theEarth, and inthe Earth's development. They form the second step of theEarth's "cryogenic screen";the troposphere, changed withtime, isthe first step. The Earth's ''cryogenicscreen" impedes the"escaping" of watervapours and their dissipationinto the ionosphere; it substantiallyrestricts this process. It is thisvery "cryogenic screen" that creates thestability of the hydrosphere, and thepresent day energy levelat the Earth's surface, and establishesthe possibility and thetype of development of thematerials in the 1 ithosphere, and the development of the biosphere. The occurrence of the "cryogenicscreen'' atthe boundary of transitionfrom planetary development - 331 - togeological development has played,and continues toplay, a specialrole; thisrole differs from those acting as similarItscreenst' on otherplanets in the solar system, forthey haveformed duringdifferent, less critical conditions and other combinations of determining factors and conditions.
Phase transitions of water,against a background of seasonal changes in the 1eve1 of energyexchange between the 1and and oceans and the atmosphere, aremanifest as theessentials of mass exchange inthe troposphere, and exert andinfluence on the approach of radiant energy, influencingits absorption and radiation and its heatloss in various zones of theEarth. Ice covers, together with snow coversexert an influence on the cold and warm seasons of the year,limiting heat penetration through albedo, and increasingheat-losses in thawing; thislowers the general energy potential at theEarth's surface. Their influence in a periodof cooling playsthe most substantial (global) role in the heat- and the mass-exchange of theEarth's enveloping elements, inthe development ofthe cryogenic processes in the cryosphere.
Warming epochshave a substantial influence on thedevelopment and distribution of circumpolarregions, on altitudinal zones of frozenground featuresand onthe contraction of thecryosphere due tothe Earth's ervelopi ng elements,
Cooling epochs activatethe development of frozenground features and widen their spheres of distribution,In both cases, a change in the (changes in distribution) does not change its texture; this reflects unity in thecryosphere. The enveloping air plays a large role in this.
Forthe atmosphere, short-period(non-seasonal ) and seasonal frozenground features are characteristics; inthe stratosphere, it isice suspension (a non-seasonalfeature), and when there is cyclonicturbulence, it is snow; inthe troposphere, it is snow, sleet,hail ice suspension and supercooledvapour; forthe Earth's surface and objects, it is hoarfrost, glazedfrost, etc. They developeither bysupercooling (vapour, water droplets),or by thepresence of primarycentres ofcrystal1 ization (snow, hail).Their development is completed when they fall to thesurface of the - 332 -
land or oceans due to gravitational attraction, where they thaw, transforming into seasonal orperennial accumulative covers, or evaporate, or convertto drop1 ets of water, without reaching the Earth's surface.
Latitudinal zonal changes inthe energy levelof exchange within the atmosphere is manifest in the formation of theEarth's therKodynaKic belts.
The hydrocryosphere is characterized by its complex structure and boundaries. It comprises oceans and seas, and, inthe case of dryland, lakes,rivers, etc.
The hydrocryosphere is polar and isdivided into two circumpolar regionswith distinguishing features. These regionsare divided into subregions: ice covers, and thechilled waters of seas and oceans. The ice covers within the boundaries of seas and oceans are formed by a change in the physico-chemicalcomposition of thewater, andby distillationduring Crystallization. As Is well-known, layers of waterchilled below O°C form in areaswith seasonal ice-formation and regions of perennialmarine ice; these aretens andhundreds of metresthick, and up to several(1 - 3) kilometres inpolar regions. Regions withchilling of ocean waters lie withinthe boundaries of the permafrost regions of the continents (northern hemisphere), or withinthe region ofpotential development of permafrost(southern hemisphere). The nearborder zone is characterized by deep bedding of lenses of chilledwater which outline regions where theirdistribution is uninterrupted (Okhotsk and Beringseas) The chilledwater has a temperature of about-1.8 tc -1.goC, even in the warm season, corresponding tothe mear, annualtemperature for thisdepth of water. In the cold season, thewater belowthe ice has a lowertemperature, and thisallows the crystallization process totake place. The icecover starts to form with the supercooling of the water and the formation of fraril ice.
The temperature field of the oceans and seas in circumpolar regions is characterized by a continentaltype of temperaturedistribution. Dependingon the depth,the main body of water(shelf seas inthe central part of the shelf, outside the direct influence of the warm marinecurrents; - 333 -
polar ocean deeps) is at subzerotemperatures in places, changing to above zero temperatures in extrenle regions. For the extreme tones, a flow of chilled water is characteristic in near bottom areas of the ocean deep. Two chil led layersare observed within them: a surface layer and a near bottom layer. The boundary between thechil 7 ed water and the above zerowater is determined by the thermodynamic equilibrium of the aqueousenvironment. In the zone with two layeredchilling of water,the temperature curve changes, forming two bends into the region of above zerotemperatures (the surface 1ayer, even in a mass delimiting upper and lower 1ayers) , This situation is alsocharacteristic where there is submergence of warm water(Gulfstream, etc . ) into a cold mass of water.
For oceans outsidethe circumpolar limits, the characteristic distribution of watertemperature by depth, is thereverse of continental distribution,i.e., basically it decreases with depth. Only in a few places, usually in areas of tectonicfaults and fractures, and subaqueous volcanoes, is there an observablerise in thewater temperature; this is associated with theconsiderable, deep, warm currents.
From geophysicaldata obtained during thelast twenty years, it follows that the thickness of the Earth'scrust beneath the ocean bottom varies within the limits of 5 - 10 km; whilebeneath the continents it is from 35 to 45 km, and in places, in mountain regions to 70 or even to 120 km. The greatthicknesses of theEarth's crust restrict the magnitude of the internalheatflow. The presence of coldwater in the near-bottom regionsof theoceans, when there is 1 imitedthickness of the 1 ithosphere, seems paradoxical .
The bottom of oceandeeps is composed of basalt, which is characterized by its high thermal conductivity; in thelithosphere and on its surface,there can nobe mass- or heat-exchange typical of continental regions,only that which is capable of causing chilling resulting from direct heat exchange with the ocean waters. In such circumstances,considerable warming Of the near bottom water might be expected, resulting from probable annualtemperature gradients in thelithosphere below the ocean bottom of 10 - 2o0/l 00 m. However , there i s no observable warming of water,except in - 334 - rift zones. The heat flowthrough the ocean bottoms does notdiffer from that calculated for theancient platform. This paradox cannot be explained by the chilling of the bottom of the deep, since movement of thenear bottom layerof water is not great enough to counteractthe influence of the deep heatflow corresponding to the temperature gradient, without leaving a trace inits temperaturefield. An increasedheat emission through the ocean bottommust be manifest in a restrainton the chilling of thewater, in particular, in thecase of the Arctic Ocean, which is one of themain sources of chilling of water masses from contiguous areas of the oceans.
Thisvery unusual temperature field in the hydrosphereoccurs as a resultof the arrival of heat from an externalheat source, and by way of heat exchange with the air masses above the seas,oceans and continents,and alsoon account of theinflow of deep seatedheat as a consequence of the thermalconductivity of thebottom rock and the subaqueous extrusionof magma,
It iswell known thatthe redistribution of heat inthe oceans takesplace by means of wave motion, warm and coldcurrents, and convection which,together, play an important role in the formation of the climate above themand overthe continents. A highdegree of mixing of water in the oceans is restricted to theupper layer, which is up to 200 rn thick.Global convectionof water masses affectinggreat depths, and indirectly, even the nearbottom layers of water,gives rise to cold currents. The temperature field of the oceans reflectsthe thermal state of the water, which depends not onlyon external sources of heatbut also on thechilling inherited from cold epochs. It didnot materialize inline with the thermodynamic conditions at the surface.
The transfer of moistureby oceanic air masses determinesthe formation of accumulativefrozen ground features on land.
As forthe temperature fields of thelakes and rivers,they exhibiteither similar (lakes) or different (rivers) characteristics. For deep lakes,an oceanic type of distribution is usual. Wave dislocation and a normaltemperature distribution to depths equal to the zone ofdislocation - 335 -
aretypical (to 20 rn or more). The formation of theice cover is associated with a certainiriitial supercooling of thewater and with subsequent crystallization of the intermediate volumes of water.
The formationofice covers on rivers takes place with the participation of frazilice, which assists in theacceleration ofthe formation of the ice cover and its growthfrom below.
Forthe hydrosphere, the following are characteristic: fratil ice, andseasonal and perennial icecovers. Lenses of chilledwater and seasonal icecovers both correspond tothe boundaries offrozen ground features on thecontinents and in the oceans; the perennial ice in the oceans occupiesthe most extreme circumpolar position, i.e., far fromthe permafrost boundaries.This is connectedwith the qualitative difference between the water mass and the earth materials.
Anotherfrozen ground feature inthe hydrosphere isice cf continentalorigin (icebergs), which is most widelydistributed inthe SouthernHemisphere withits vast continent. In the Northern Hemisphere the main sources of such ice are the eastand southwest coasts of Greenland.
The lithocryosphereis characterized by thegreat conlplexi ty of the phenomenon of cryogenicprocesses. On landsurfaces, non-accumulative andaccumulative features develop. Non-accumulative features are divided intocondensation-Crystallization and migration-crystallizationfeatures. The formerare associated with the near-surface layer of the air; the latter withheat exchange throughthe ground surface. lo thefirst groupbelong: hoarfrost, glazed frost,etc., to the second belong: "ice-stems" - "ice grass" ar;d therelated "ice drusesI1, and "iceflowers", "ice tetragons", etc. Theirformation takes place selectively on various surfaces (denuded ground, soils, snow, ice,vegetation, etc.) undervarious types of external conditions ar,d development mechanisms. Theirrole is lircited.
Accumulative features are widelydistributed circumpolarin regions, and alsoin the south, incountries with high mountains. It is well-knownthat their basic form is snow cover. Under certainconditions, it - 336 -
is transformed into firn, both as an independent feature (in flakes) and as an intermediatefreature which transforms into the ice of glaciers and ice covers.
Snow cover influencesthe rate of freezing of earthmaterials and the temperature field of the underlying rocks is formedunder its influence throughout the winter and into the beginning of the following warm season.
Perennial ice covers on land exert a considerableinfluence on the perennialfreezing of their underlying materials. In this case, a single temperature field is formed for theice cover and the permafrost layers. The ice cover removes the surface conditions which influence their dynamics.
To local formations belong seasonal and perennial icings of groundwater and surface water courses.
Within the li thocryosphere, the basic featuresare: frozen, chilled-frozen,chilled features and theirchilled counterparts in earth materials. They are divided intoshort-period, seasonal and perennial. In distribution, they areeither isolated or occupy the same regions of development, i.e., they areeither connected or not connected with the transitions from oneform to another.
Frozen and chi1 1ed-frozen materialsare common types of frozen ground features in the lithosphere; they are formed by the crystallization of saturant groundwater which is either fresh water or water that is undergoing distillation (during crystallization). The difference betweenthem depends on the composition and characteristics of theearth materials (granular, cohesive, fissured), and the degree of water saturation. In granular and cohesive (clayey)materials, crystallization of water takes place during freezingsubject to its bonding with the particles of theearth materials as a function of the temperature spectrum with formation of various cryogenic structures. In fissuredmaterials, the water crystallizes at a relatively uniform temperature. The distribution of ice depends on the degree of water penetration and on the types of fissuring, and their distribution in the rock mass. - 337 -
Chilled ground results from the cooling of the materials (fissured or monolithic) to below O°C, in the absence of visiblewater. Freezing is replaced by cooling. The propertiestheofmaterials do not change (monolithicnature, fissured state, porosity).
There is a basically different typeof earth material known as cooledmaterial (below OOC), which fallsinto a separatecategory. It is saturated with mineralized(saline) water and is very corrmon in Eurasia, and less common in South America, and within the confinesof the shelf. We drew attentionto this in 1956. Cooled materialsreplace frozen, chilled-frozen, and chilledmaterials. In thelayer of seasonalfreezing and in the upper part of the permafrost,there are many accompanying (short-period,seasonal and perennial ) frozen ground features : polygonal -fissured heave , textural , etc.Their classification was given in 1962-1965.
The complexity of theEarth's cryosphere can be seen from the above; thediversity ofthe elements of the geosphere of which it is comprised, and of the classes, types and species and variety of featuresthey contain .
The substantialdifferences between frozen ground featuresof the northern and southerncircumpolar regions result from the non-uniform nature of energy at the Earth's surface, the geographicaldislocation of continents, theirareas, the dislocation of oceans,differences in types of matter forming the geosphere and theirproperties. This determinesthe polar and internal non-uniform structure of the cryosphere.
The Earth'scryosphere is characterized by its complex conjugate temperaturefield which reflects the non-uniform nature of energy and matter of the envelopingelements, of its surface, and of thematter-energy interaction
In the vertical section, thecryosphere is dividedinto two subdivision,the boundary of which is the matter-thermodynamic interface. The lower subdivision is formed by the 1 itho- and hydrocryospheres;the upper subdivision - by the atmosphere. Each of theseelements of thecryosphere is - 338 - characterized by theinherent characteristics of thematter of which it is composed, by the method of formation, and by thedifferences in the dynamics of theirtemperature fields compliancein with planetary and cosmic conditions
The temperature field of the 1 ithosphere is formed under the influence of itsinternal heat source, which is of a complex nature (gravitational compression, radioactive decay, etc .) heatemission from the uppermantle - the astenosphere. The deep seatedheatflow (excluding local inclusions of magma), has anuneven influence, depending on thethickness of thelithosphere, its dynamics and properties(composition of therock, tectonic activity, and directivity of movements in the Earth's crust, and its geological-tectonicstructure), Judging by its influence on the 1 ithosphere and itsrelationship with it, it would seem to be external ; thereare processes in the 1 ithospherewhich require great expenditure of heat (thennometamorphism of earthKaterials). The remainingheat generates a heatflowwhich foms theEarth's external exothermal zone. Its temperature field is formed withthe participation of its own heat sources (radioactive decay,and geochemical reactionswhich havetwo thermaleffects, etc.) . They participatein the internal heat exchange. Itsresulting heatflow, within geologically long periodof time, is dynamic and depends on external thermodynamic causes and conditions. The externalconditions exert an influenceagainst a background ofcryogenic processes(subsidence and uplifting of theEarth's crust). Their total influenceis manifest in the range of depths (measured in kilometres)i.e. by thethickness of the 1 ithosphere.
The magnitude of the resultant deep seatedheatflow within the 1 imits of the dry land and the ocean bottom is known to be several gram calories cm 2 per annum; thisis commensurate withthe magnitude of heatflow beinggenerated by theexternal heat source - the Sun. It is exactly this thatcreates the fundamental conditionfor the creation of thelitho- and hydro-sphericelements of the Earth's cryosphere.
The levelof thermodynamic equilibrium at theEarth's surface (mean perennialtemperature) varies within the ranges of +25 to +3Ooc in the - 339 -
NorthernHemisphere (Greenland),and to-600~ in theSouthern Hemisphere (Antartica).Glac iers,ice covers, and vastcooling regions lower the temperature of the remainingsurface. Outside the regions ofglaciation, thereis a temperaturevariation of 40 to 50'; within them, it increases to 55 to 90'. Duringthe Cenozoic, the level of thermodynamic interaction betweenland, oceans and theexternal environment varied considerably: in the case of their uplifting, it was theTertiary; and for subsidence, it was theQuarternary. In the Quarternary, there was anincrease in heat emission inthe external environment (this is the distinguishing characteristic of the period),especially inindividual stages. Apparently it isthe increased area of the continents in the polar regions of the hemisphere, resulting from severaluplifts of the continental shelf, that is the cause of thecooling epoch. The orogenicprocesses of Southern Asia andEurope, South and North America,which didnot lead to a globalcooling of the elementsenveloping theEarth, played a definite role inthe fcrmation of the general background preceding it. The role of themountain systenls ismanifest inits restriction of penetration by air masses onto the continents.
The lowering of thelevel of thermodynamic interaction of the Earth envelopingelements during the cooling epoch was accompaniedby the development of thickice covers on theoceans, deep cooling of the ocean waters, glaciation of vast land surfaces, formation of regionsof deep-seated cooling of earth materials over great areas, the strengthening of the role of cold marine currents,etc. Ice coversand glacial covers, by their expansion bothareally and latitudinally,directly and indirectlyreduce the general energylevel of theEarth's surface. Glaciationof the land led to the differentiation of its surface regions; these were characterized by different conditionsof cooling of the earthmaterials The presentday temperature fields of the oceansand continentsare forming in accordance with the externalthermodynamic conditions thatarebecoming established. The numerous noncomformitieswith present day conditions are evidence of intense cooling in the past, in some places,the no toodistant past.
The structure of theEarth's cryosphere reflects the thermodynamic conditionsthat formed and exist in geologically long periods of timein the nearsurface zones of the envelopingelements incontact with it. It is dependent upon: - 340 -
a)the spherical shape of theEarth, the position of its axis, its distancefrom the Sun (solarconstant);
b)the presence of envelopingelements: enveloping (atmosphere) , the element forming it (1i thosphere) the superimposed(hydrosphere) , and their spatial distribution;
c) composition and propertiesof the matterforming the elements, their matter-energy interaction, the autonomous mobility or immobility of the constituent matter;
d)the presence of water as the matter formingthe elements, and as matter distributed within other environments, and as matter constituting the basis for development of thecryogenic processes and frozen ground features, by its properties , mineral- ization , etc "
Mobility and freedom of water have a special role in the heat- and mass-exchange (in the atmosphere, the lithosphere and thehydrosphere), which affectsthe development of thecryogenic processes, theirintensity, and the spatial distribution and differences in their development in time.
Inthe formation of the Earth's cryosphere and its structure, all of the above factors and conditions which are found in specific relationships and interactionsplay a decisive role. Thus, thespherical shape ofthe Earth and thematerial differences of its envelopingelements play a decisive role in the nonuniformeffect of its externalheat source (solarradiation), which is differentin each elementcomprising the inherent structure of the Earth'scryosphere. If, for example, thebasic thermodynamic characteristic of Mars were transferredto Earth (reducing the flow of solar energy by 1.4 to 0.6 x 10 erg/cm 2 s) then, in time, this would leadto freezing of the oceans, probably to a considerabledepth, and to the establishing of a severe climateover the whole planet.Patterns of change in magnitude of solar - 341 -
radiationfrom the equator to the poles forms a basisfor the division of thermodynamic belts and regions,within the confinesof which,conditions. of development of the cryogenicprocesses are various.
Forthe equatorial -tropical zone, seasonaland perennial processes whichonly develop at altitudes greater than 5 - 6 km, are characteristic.
Fortemperature (transitional) zones, lower 1evels of energyare characteristic.Therefore, within its boundaries, the processes develop in regionswhere there is a lengthylowering of air temperaturesbelow O°C. Perennialfrozen ground features outside the permafrostregion develop in mountainouscountries, the absolute altitude of which exceeds 2000 m in the north and 3000 m in the south. Within the confines of plainsthey develop in regionswhere there is a systematictransition from seasonal to perennial freezing. For thesubarctic and arcticregions permafrost and cooling of Earthmaterials is characteristic.
As iswell known, theboundaries of the thermodynamic beltson landare latitudinally non-uniform, they are non-linear. and discontinuous; thisis connectedwith the influence of cold and warm marinecurrents, varying expansesand contours of the continents,and by thepresence of mountainsystems strengthening the continental nature and limitingthe influence of the oceanic air masses.
Forthe Northern circumpolar region, the following dependence is characteristic: where warm oceanic air masses influencethe continents, the southernboundary mingles with the subarctic and arctic environmental zones; where the continent is the source of climate formation,the southern boundary mingles, to thesouth, into the limits of thetemperate zone. Minglingis mostpronounced in mountainousregions within the continents.
The prevailinginfluence of thesevere climate inthe Arctic is manifest in themingling of the southernboundary intothe limits of the Atlantic and Pacific oceans, inthe western part, i.e., in the Northern Hemisphere. Inthe SouthernHemisphere the influence of Antarcticaleads to a displacenient of thenorthern boundary over the Pacific, the Indian and the Atlantic oceans, far beyond its limits. - 342 -
The surfacesof ocean waters are also warmed non-uniformly ; a directional change inthe level of energy exchange canbe traced from the equator tothe poles. Its schema of change is complicated byocean currents: warm currentsin the temperate belts and arcticregions, and cold in the equatorial-tropical zoneand thetemperature zones, mainly inthe Northern Hemi sphere
The cooling of earth materials saturated with mineralized (saline) water,and the cooling of seas andoceans to below O°C occupies a special placeinthe lithosphere andhydrosphere elements theofcryosphere. Seasonalspheres of cooling which form without phase transition of water into ice, orresulting from it, are: inthe lithosphere - unconsolidateddeposits (beaches , spits, bars, etc.)and fissured rocks; in the hydrosphere - bodies of waterunder ice covers in saline lakes, seas andoceans orover areas not covered with ice when there is wave movement and cold currents.
The perennialelements of thecooling part of the hydrosphere are restrictedto the polar seas andoceans, where thethickness of the body of cooled waterreaches several kilometres; it issimilarly restricted to the seas of the arctic shelf.
Cooling of theoceanic bodies of water is connected with geologicallylong periods of coolingvia the surface in conditions of low levels of energy exchangeand convective submergence of cold volumes of water when there is nearbottom outflow into the intermediate parts of the oceans (SouthernHemisphere) or into neighbouring oceans.
In continentalconditions, the occurrence of cooledmaterials is connectedwith the conditions of thesubaerial formation of lowtemperature permafrost, thecontinuation or replacement of whichare the horizons of perenniallycooled ground. The cooledearth materials have the same temperature field as that of the frozen ground.
In the northern regions of Siberia and Canada, within the confines of theancient platforms and several troughs and Quarternary subsidences which wereaccompanied by transgressions,the cooled materials have a depth of severalhundred metres, and in places, of more than a kilometre. - 343 -
Withinthe limits of theshelf, in places below the bottom of the polar oceans where thewhole body of water has a constantsubzero temperature,the presence of shallow,cooled materials is to beexpected (trough,deepwater part ofthe shelf). In thepredominant parts of theshelf whichhave been periodicallyuplifted above sea level and loweredbelow seas level(eustatic movement of theEarth's crust, raising of thelevel of the world'soceans?), the interaction of permafrost and cooled materialsis complex.Frozen and cooledmaterials exist in severe climatic conditions. Depending on theperiod of cooling,the thickness of the zone of cooling is considerable; the thickness of permafrostcorresponds to thethickness of the zone of distillation and isrestricted by the depth of bedding of saline waterand brines.
In theshelfIn region, as a result of marineabrasion (characteristic of disintegratingmarine shores of continents and islands) thecontinental cooling zoneundergoes changes in the structureofthe heat-exchange(subaerial-subaqueous) atthe surface; this leads to sharp increases in temperature at the surfacewith a mean annualtemperature of -15, -2OoC, to -1.8, -1.9OC, and higher and to a decrease in amplitude to zero. On this basis, when there is a small thermal inertia (absence of ice), a reductionin the thickness of the zone of deep seatedcooling takes place f rorn below and there is a warmingand thawing of theupper 1eve1 s of the permafrost to a depthcorresponding tothe new thermodynamic conditions ar;d theisolated thermal resistivity of thepermafrost. Parallel to thethawing ofporous and fissuredicy materials, there is a diffusedislocation of marinethaw water.
Withintheconfines of theshelf, onthebasis the of paleogeographicaland geocryological phenomena, thereare assumed to be complexcombinations of present dayand relicpermafrost with horizons (1ayers) of earthmaterials exhibiting primary andsecondary cooling(in regions of recenterosion, this is thick low temperaturepermafrost similar tothat of theadjoining areas of thecontinent (islands); permafrost which has horizons of relic, cooled materials at the base; permafrostwhich ha5 not undergonethawing from above with the accompanying substitution of cooled water; layer of cooledmaterials formed as a resultof cooling bymarine waters,etc. - 344 -
The southernpolar region of frozen ground features is analogous with the northernregion. The differenceslie in a number of causes and conditions .
The southernregion is characterized by thepolar location of a continent covered with a thickice cover, which hasan absolutealtitude of up to 4000 m. In the northernregion the polar location is occupied by an ocean containingperennial ice; the islands and theirarchipelagos have small icecaps; Greenland possesses the largest ice sheet.
The southernregion comprises parts of three oceans within the 1 imits of which are found all the zonal boundaries of frozen ground features; it characterizedis by its greatoceanity. The northernregion is predominantlyland; this constitutes a second importantdifference with regard to the northernregion.
The southerncircumpolar region has the followingboundaries: within the oceans - the boundary of seasonalcooling of thetroposphere and the surface 1ayer of water, and of calving of icebergs (to 56 - 42'5) ; seasonalice formation and perennial deep cooling outlining the continent; on landoutside the Antarctic continent, - boundaries of seasonalfreezing of earthmaterials and cooling of thetroposphere, which in principle,coincide with the boundary of perennialcooling of ocean waters.Tierra del Fuego, the FalklandIslands and Kerguelen andHeard Islands in the Indian Ocean, etc., lie within thepermafrost region.
Outside the limits of thesouthern region, seasonal freezing of earthmaterials takes place in southern South America, in Australia, in southernAfrica (in the Drakensberg);there is perennialfreezing in the Cordilleras and in the mountains of New Zealand.
In thesouthern region, the main part of thepermafrost area coincides with the boundaries of the icecover, and is dependent on the latter(its thickness, temperature in the base). In the extreme zone of the ice cover of the arcticcontinent, and probablybeneath thecentral area, consideringthat the mean annual temperature of the icesurface is (about - 345 -
-5goC), the permafrost is a continuation of theice cover. The development of thesefrozen ground featuresoccurred under variable thermodynamic conditians. The development of theice cover caused the upward displacement of the zone of annualtemperature fluctuation, which could have restricted theperennial freezing of earthmaterials, atthe same time, it was responsible for a lowering of the mean annual temperature of the ice.
From the above, it follows that the southern circumpolar region of frozenground features, despite the presence of a unity of structure, differs substantially from that of thenorthern region by distribution of its frozen groundfeatures. Many of those whichare typical of thenorthern region have no placein the southern region; others are restricted, and a third group prevails in accordance withthe environmental features of theregion.
REFERENCES
BARANOV, I .Ya. Vechnayamerzlota" , ee vozniknovenie v khode evolyutsii Zemli kak planety.("Permafrost", its occurrenceduring the evolution of the planet, Earth). - Astronomicheskiizhurnal , VOI.4, NO. 4, pp. 846-853, 1966. BARAMOV, I.Ya.Voprosy kriologii. (Problems of cryology). - 11. Mezhdunar. konf. po merzlotovedeniyu Dokl . i soobshch. vyp. 1 . (Proc. of theInternational Permafrost Conference Papersand Communications. No. 1)Yakutsk, pp. 3-11, 1973. VERNADSKII, V. I. Ob ablastyakhokhlazhdeniya zemnoi kory. (Regions of coolingin the Earth's cruts). Izbrannye trudy. (Selected Works), Vol. 4, Bk. 2. M., Itd-vo AN SSSR, pp. 637-649, 1960. DOBROVOL'SKII, A. Istoriyaprirodngo 1 Ida.(History of EnvironmentalIce). Varshava, p. 191, 1923.
- 347 -
MORE PRECISE POSITION OF THE SOUTHERN PERMAFROST BOUNDARY BETWEEN THE URALS AND THE OB RIVER
G.I. Dubikov Industrial and Research Institute of EngineeringSurveys inConstruction, MOSCOW, U.S.S.R.
Massivepermafrost was encountered150 - 200 km south ofthe generally acknowledgedpermafrost boundary forthe first time, when service routes werebeing selected on thevast terrain between theUrals and the Ob. As a result,special research hasbeen undertakenwhich has allowedus to modifyexisting views on the southern permafrost boundary, and also to reveal the patterns in its formation, distribution and structure.
The map (Figure 1) shows theevolution of views and propositions concerningthe position of thesouthern permafrost boundary inthis terrain duringthe last 20 years. A.I. Popov (1953) was the first to assign separate southernboundaries formineral andorganic (peat) permafrost.
Popov pointedout the island character of permafrostnear the southernboundary and the coincidence of itsdistribution with that of peat frost mounds; he notedthat the permafrost was shallow,with negative temperaturesnear O°C, and a1 so thatthere wereindisputable signs of permafrostdegradation. Moreover, Popov acknowledged thatthere may be individualpermafrost islands south of theboundary he haddrawn. On the basis of new data, a1 1 of thefollowing: Baranov, 1955; Kunitsyn, 1958; Lur'e, Polyakov, 1966; Baulin et al., 1967;Shpolyanskaya, 1971; Belopukhova, 1972 correctedthe position of thesouthern boundary on this terrain, and in a1 1 cases a more southerlyposition was attributed to thepermafrost peatlands. Ourproposed variantis similarly basedon new factualmaterial
ProceedingsThird International Conference on Permafrost, Vol 1, pp. 355 - 358, 1978. - 348 -
Figure 1
Map of the position of southernmineral (1) and organic (2) permafrost boundaries between theUrals and the Ob: 1 according to L.F. Kunitsyn I1 - according to E.B. Belopukhova; I11 - accordingto A.I. Popov and N.A. Shpolyanskaya; IV IV - boundaryproposed by theauthor. andon directobservations made duringthe large scale permafrost research conducted between theUrals and the Ob. As thesouthern boundary is both a physical and a geographicalboundary, it reflects thedistribution of large permafrostislands and massifs, which formed in theLate Holocene. The position of the boundary on the map has changed significantly: it has moved latitudinally 1 & - 2' farthersouth than was everproposed earlier. From the settlement of Polunochnoe, thesouthern boundary crosses the upper reaches of the Pelym River,the source of the Konda and Malaya Sos'va rivers, and veers towardsthe Ob just to thenorth of thesettlement of Oktyabr'skoe. During thelast few years,there have also been discoveries of large permafrost massifs and islands on the West Siberian Lowland,considerably farther south thantheir generally accepted boundary. When theSamotlor deposit was developed, theirexistence in thenorthwest limb Gf thestructure between LakeSamotlor and theVatinskii-Ergan River was established. Members of the - 349 "
Second Hydrogeological Directorate'sexpedition mapped the permafrost of the 1 atitudinal segment of the Ob which lies in the basin of the Bo1 Yugan River;the permafrost is severalmetres thick.
The pinpointing of such a preciseposition for the southern boundary is in itself of greatimportance from both a pragmatic and a scientificpoint of view: for the planning and thetechnical andeconomic jusEification of construction sites; in the selection of rational methodsand technicalresources exploration;for constructionfor methodsand environmental protection measures.
A clearlydefined regularity in permafrostformation has been establishedfor the region between the Urals and the Ob. It is encountered exclusively in forested,drained areas surrounded by swamps and lakes, mainly in river valleys on high flood plains and the terraces above theseplains. Moreover, permafrost is confined to individual groups of frost mounds or to hillockyterrain and is concentrated in dense,dark coniferous cedar, and fir-cedar or mixed forests with suglinok* or peaty soils. In poorlydrained and swampy forest stands permafrost degradation can be observed. Its protectivecovering is found to a depth of 3 - 5 m from thesurface. After they havebeen studied in place,permafrost areas can easily be interpreted on large scale aerial photographs because of theirdarker background (densest forest) and hillockyterrain,
Permafrost sonletimes occupies such a considerablearea in these lati tudesthat it cannot be ignored when developing a region, i .e. when routingutility corridors. For example, where pipelinesintersect the high floodplains of the blalaya Sos'va andKoly-Khulyum riverspermafrost occupies 30 - 35% of the route;for the floodplains of the Pelym River it is approximately 10 - 15%, and for the first terrace above theflood plain of the Pungi River it is about 25 - 35% (Figure 2). The depth of permafrcrst varies from a few metresto 20 metres,increasing proportionately to the size of thefrozen massif. Themean annual temperature of pemafrostvaries fron,
* Sugl inok - clayey silt with some sand,clayey silty loam (Trans1 .). - 350 -
0' to -0.5OC; the lowest temperaturesare observed in peat frost mounds covered by trees where the surface is subjected tothe greatest amount of shadeand has a thick groundcover of moss.
Figure 2
i/r2 'C : 9 Y
67 65 M
Permafrost-li thological sections and diagrams of distribution of total moisture and temperature of permafrost: A- on the high floodplain of theKoly-Khulyum and Malaya Sos'va rivers (at theirconfluence); B- of the first terrace above the floodplain of the Punga River (near the settlement of Svetlyi) ; c- of the high floodplain of the Pel8m River (near the settlement of Pelym, 61 N) ; 1- peat; 2 - clay; 3 - suglinok; 4 - sand; 5- intercalation of sand andsuglinok; 6 - ice; 7- permafrostboundary; 8 - borehole. - 351 -
The causeof permafrost formation in these latitudes lies in the peculiarcombination of many generaland local conditions, of which we list the mostimportant: 1) negative mean annual air temperatureover a period of years in thefollowing settlements: -2.6' in Igrim; -3.2' in Oktyabr'skoe; -2.7' in Sartyn'ya; -2.4' in Khongokurt;and -1.8' in Shukhturkurt. 2) soils,clayey and peat composition, and highmoisture content inthe upper horizonlowering the temperature of theearth materials owing to differences in their thermophysicalproperties in the frozen andthawed states; 3) dense, dark,coniferous forests and brush,shading the ground surface and lowering the surface temperature to that of the layer of air directly above theground (approximatelyby 2.0' - 3.0'); 4) moss-lichenground-cover up to 30 cm thick,cooling the ground by 2' in dark,coniferous forests (Chernyad'ev, 1970). The retardation of snow meltin dense forestsafter positive air tmperatures have returnedis of indisputableimportance. As therough calculations of S. Yu. Parmuzin indicate, the delay of about 13 months in the meltingof snow lowersthe mean annualtemperature- of theground surface by 0.5' - l.O°C.
The above listedfactors which, in most instancesdetermine the conditions for summer thawing of theground surface, neutralize the warming influenceof the snow cover on theearth materials (up to 3' - 4'). The depth of the snow coverduring the two-year period of steadyobservation was from 30 - 40 cm. These factorsneutralize the warming influence of snow to a significantlyhigher degree in drained areas consisting of clayeymaterials or peat, where heatcirculation is considerably less than in swampy areas. Moreover,the presence of moss groundcover isnot alwaysessential for the existence of permafrost in clayeysoils near its southern boundary. Thus, alongthe streams and smallvalleys on the gentle terrace slopes in the dense (crowns 0.7 - 0.8) fir and fir-birchforests without moss groundcover or shrub in their interior, permafrost is at a depth of 1.0 - 1.5 m.
Permafrostdeveloped inthe region under observation lies in the Upper Pleistoceneand Holocene alluvial and organicdeposits; among these, peat,suglinok and claysare widely distributed, occasionally underlain with sands.This isillustrated in the permafrost-lithological section of the floodplain of theMal, Sos'va, Koly-Khylyum and Pelym rivers and of the - 352 - firstterrace of the flood plain of the Punga River(Figure 2). Peat is foundvirtually everywhere on theflood plains: it reaches a thickness of 5 - 6 m. Peat is heavilyice saturated; the total amount of moisture in frozenpeat varies with the area, within the range of 550 - 1000%. On the terraceswithin the permafrost area, peat is much less abundant; its thickness is only 1.5 - 2.0 m and theice content is considerably less; peat frost mounds are the exception.
Clays and suglinoks are highly ice saturated. At times, ice inclusionsof various dimensions form complex combinations inthe cryogenic structure of thesection. Stratified and stratified-reticulatestructures withoutdistinct ice lens boundaries are characteristic: in the upper part of thesection of suglinok, dense, finelenses predominate; inthe middle, thicklenses predominate and inthe bottom part there are a few finelenses andporphyraceous structures, although, even inthis instance, the earth materials have a highmoisture content. However, such a distribution of structurefrozenin suglinok and clay does not alwayshold true. Occasionallylenses of largecrystal ice 1 - 2 m thickare found in sections of clayeydeposits.
Wide distribution of permafrost with a high ice (moisture) content is determined bychanges in the properties of theearth materials, their epigeneticfreezing and moisturemigration. This ensues from theanalysis of frozenclayey sections of floodplain facies in which the anisotropy is establishedfor the distribution of total mGisture along the strike and throughoutthe depth of the wholefrozen massif (Table). A uniformvariation in the spatial distribution of totalmoisture in permafrost is noted for the upper (to a depth of 3.0 m) and for thelower (interval of depth 8.0 - 10.5 m) horizons:the variation coefficient is up to 30%. Inother words, thecryogenic texture and thedistribution of moisture inthe upper andlower parts of thefrozen massif are characterized by their uniformity. The maximum quantityof ice is concentrated in the middle of thepermafrost horizon(interval of depth 3.0 - 8.0 m); thearithmetical mean ofmoisture varieswithin the range of 70 - 100%. Inthis case, thevariability in the spatialdistribution of totalrmisture in this horizon is non-uniform:the coefficientof variation is more than 30% (up to 50 - 60%). The highice - 353 -
TABLE
The distribution of total moisture in the permafrost of clayey materials in thefloodplains of the MalayaSos'va and Pelym rivers and of the first andsecond terraces of the Punga River(based on 43 boreholes).
Depth, m I Arithmetical I Number of mean individual tests ical mean arithmetical the
1 .o 39.1 9 12 30 1.5 36.2 12 9 25 2 .o 51.6 21 15 29 2.5 62.7 14 16 25 3 .O 69 .O 23 26 38 3.5 75.1 20 27 36 4 .O 81.9 30 54 66 4.5 101.4 22 60 58 5.0 80.3 24 42 52 5.5 80.5 20 34 42 6.0 79.9 24 35 44 6.5 80.9 16 37 46 7.0 70.9 23 38 54 7.5 80.6 13 39 49 8.0 77.7 14 32 41 8.5 72 ,a ,8 22 30 9.0 69.7 9 20 29 9.5 87.6 6 27 30 10.0 58 .O 7 17 28 10.5 53 .O 5 11 20
content of clayeyalluvial deposits of thefloodplain facies canbe traced throughthe sections from all boreholes throughout the depth of the frozen massif(independent of itsthickness) and along thestrike. For example, on thefirst terrace of the Punga River,the arithmetical mean fortotal moisture of frozen clayeymaterials for the 10 m layerover a distance of 20 km, variesfrom place to placewithin the rangeof 40 - 80%. Moreover , the repetition of themoisture value 50 - 70% is ascertained in approximately GO% of all calculations (Figure 3).
In the 1 iterature on thetransformation of sedimentaryrocks, evidence is given of watersaturation in clayey materials in the vertical section. According to theresearch of B. Fillinius present-day, plastic - 354 -
Figure 3
wt, % roo- 80 -
20 - ~3~~~~].4_1~f~fO~91r5~1I~~8IB14J12~ff11916jfC[f6~- " - Number of individual tests Spatial change of the arithmetical mean of total moisture for the 10 m layer of frozen suglinok on the first terrace of the Punga River (distance covered - 20 km) . marineclays with a highwater saturation havebeen found inItlaidas"* in Sweden: inthe upper 20 m layer,the clays are in a fluidstate and their moisturecontent varies within the range of 80 - 100%; inthe 20 - 30 m intervalsthe moisture content decreases to 60 - 70%; andlower, at a depth of 30 - 40 m, it increases to 35 - 50%. According tothe data of I.V. Save1 levpresented inthe paper by L.B. Ruchin (1969) thethickness of the saturatedlayer of viscous silts and claysalong the coastline of theBlack Sea is about 6 - 7 m. Therethe moisture content of the sediments decreases with depth from 170 to 75% and consistently remains within their flow limits. Thisinformation canhelp inclarifying the reasons for the formation of ice-saturatedhorizons in clayey materials during freezing, In our case, the highice saturation of clayeymaterials of theflood-plain facies could be due to the fact thatthey were particularlywater-saturated to a greatdepth when they became perenniallyfrozen, as a result of thegeneral swampiness and the peatcontent of the surrounding terrain.
The above analysis of geological andgeographical factors determiningthe thermal conditions of thepermafrost is convincingevidence that a change in any of theseprocesses of natural or contriveddevelopment wouldlead to disturbance of thepermafrost conditions, that is,thawing of permafrost or permafrostformation. Owing to thehigh temperature of permafrost,disturbance of the ground cover on thisterrain serves as an impetusfor permafrost thawing and thermokarst formation. The calculations of V.P. Chernyad'ev(1970) show that underthe conditions of natural snowfall,removal of the moss coverbrings about the thawing of permafrost to
*l'laida" - lowlying coastal areas bordering the northern seas; usually swampy with hummocky relief, permafrost often close to the surface;flooded during high tides. - 355 - a depth of 4.8-m in 8 years; when thearea has been completelyfree of snow for 20 years,permafrost forms to a depth of 7 - 8 m. Fieldresearch supportsthese calculations. Innatural circumstances, the processes of permafrostformation and thawingwould then be repeated as a result of the dynamics of vegetativecover, of the change inthe moisture content of the materials and of shortterm fluctuations climate.in The established features of permafrostformation allow forecasting of their changes inthe courseof normal and contrived change in the natural factors.
When landis developed, it isthe vegetative cover (felling of trees andclearance of shrub), the snow cover and the moisture content of the earthmaterials which are first affected. These disturbances change the existingconditions of heat exchangebetween theground and the atmosphere and create a new thermalregime. This isfirst reflected in the dynamics of thelayer of seasonalthawing and freezing.For example, during the period 1964 - 1972where, on theterraces above the Punga River,the trees had been felledin the dark coniferous forest and themoss-lichen ground cover had either been interrupted or totally destroyed,the amount of solarradiation penetratingthe ground increased, perennial thawing began, and theprotective coveringover the permafrost settled 2.5 - 4.2 m in suglinoksand 2.0 - 2.6 m in peats(without the formation of thermokarstlakes). During this period, the combined influence of thedisturbance of the surface condition and the presenceofthe gas pipeline caused permafrostthawing to a depth of 5.0 - 6.5 m. Sincepermafrost which starts at a depth of 2 - 3 m is characterized by a highice content, thawing is usually accompanied by surfacesubsidence, and, when the watercannot drain away, by theformation of thermokarstlakes.
Conclusion
1. A new variant has been establishedfor the southernpermafrost boundary:between theUrals and the Ob it is moved latitudinally 14 - 2' farthersouth than previous variants.
2. Permafrostformation in theselatitudes is determinedby a combination of many conditions, of which, the main factor is - 356 -
insufficient summer warming of the earth materials in shady forests.
3. Observed regularities a1 low the creation of a special zone of massive and islandpermafrost in clayey and organicmaterials, which are restricted exclusively to denseconiferous forests.
4. The permafrost of thistone is characterized byanextremely unstablethermal regime and high ice content. On thebasis of ice content$ it is comparable withsyngenetic frozen deposits.
REFERENCES
BARANOV, I. Ya. 1955. Yuzhnaya granitsaoblasti rasprostraneniya mnogoletnemerzlykh pored.-V kn.: Materialy k osnovam ucheniya o merzlykhzonakh zemnoi kory, Moscow, Izd-vo AN SSSR, NO. 2, pp. 38-44. BAULIN, V.V., DUBIKOV, G.I., BELOPUKHOVA, E.B., SHMELEV,L.M. 1967. Geokriologicheskieusloviya Zapadno-Sibirskoi nizmennosti. Moscow, "Naukal' p. 212. BELOPUKHOVA, E .B. 1972. Osobennostirasprostraneniya mnogoletnemertlykh porod v Zapadnoi Sibiri. - Trudy PNIIIS, t. 18, Moscow, pp. 94-99. KUNITSYN, L.F. 1958. Mnogoletnyayamerzlota .i svyazannye s nei formy re1 I efa na severo-tapade Zapadno-Si birs koi nizmennosti. - "Voprosyfizicheskoi geografii". MOSCOW, pp. 312-337. LUR'E, I.V.,POLYAKOV, S.S. 1966. K voprosu o yuzhnoigranitse rasprostraneniya mnogol etnemerzlykh porod v zapadnoi Sibiri. - "Mertlotnyeissledovaniyall, No. 6, Izd-vo MGU, pp.155-159. POPOV, A.I. 1953. Vechnaya merzlotaZapadnoi Sibiri. MOSCOW, Izd-vo AN SSSR, p. 230. RUKHIN, L.B. 1969. Osnovy Litologii. M., "Nedra",p. 704. CHERNYAD'EV, V.P. 1970. Issledovaniyadinamiki sezonnogo i mnogoletnego promerzaniya-protaivaniya v usloviyakh Zapadnoi Sibiri . - Trudy PNIIIS, t . P, Moscow, pp. 6-91 . SHPOLYANSKAYA, N .A. 1971. Osnovnye zakonomernostirasprostraneniya vechnoimerzloty i etapy ee ratvitiya - V kn.: Prirodnye usloviya Zapadnoi Sibiri, No. 1, Izd-vo MGU, pp.102-123. - 357 -
PERMAFROST IN THE MOUNTAINS OF CENTRAL ASIA
A.P. Gorbunov PermafrostInstitute, Yakutsk, U.S.S.R.
Permafrost in themountains of CentralAsia covers approximately 1 mil lion km 2 . The mainpermafrost bodies are widespread inTibet, Kunlun, Tien-Shan , Pamir-Alai , Hindu Kush, Karakorum,Nien-Shan, in theHimalayas and theSino-Tibetan mountains. In thefar north of the region, in the northern ranges of Tien-Shan, at approximately 43'N, thealtitudinal boundary of permafrostislands coincides with the 2700 m contour; tothe far south, in theHimalayas and inthe Everest region, at approximately 28'N, this boundary extends upwards tothe 4900 - 5000 m level(Fujii, Higuchi, 1976).
In Tien-Shan and Pamir-Alai(within theboundaries theof u.s .S.R.) permafrost occurs over an area of approximately 110,000 km 2 .
Presentknowledge concerning the permafrost of Tien-Shanand Pam ir-Alai allows us to establish the a1 titudinalboundaries of thesporadic, island,discontinuous and continuoustypes of permafrostdistribution. The followingcriteria are proposed forestablishing the above categories. The lowerboundary of sporadic distribution of frozenground is determinedby the presence of permafrostbodies in coarse,granular tal us and scree. The lower boundary of islandpermafrost isdetermined by theoccurrence of frozen groundon steep northern slopes of more than 30'. The lowerboundary of discontinuouspermafrost is determinedby the presence of permafrost on all slopesexcept those with a southernaspect. Within the zone of discontinuouspermafrost, open taliksare widely developed in detrital fans alongthe beds and floodchannels of mountainrivers. The lowerboundary of continuouspermafrost, including south facing slopes, reflectsthe general
ProceedingsThird International Conference on Permafrost Vol. 1, pp. 373 - 377, 1978. - 358 -
L lL E aJ .. Q i + t 0 ln QJ R % I-
0 E
W Q rc 0 - 359 -
developnlent of thefrozen ground. Within this zone, open taliks may exist along water penetratedtectonic faults, under deep lakes and largevalley glaciers.
The altitudinalboundaries of thepermafrost types found in Tien-Shanand Pamir-Alaiare set outin Table I and theirdistribution is shown on the map (see Figure).
TABLE I
Distribution of permafrost with a1 ti tude
Type of permafrostAbsolute a1 titude of Percentage of total distributionlowerboundaries of permafrost , X distribution types , m Northern South-West. Tien-S han Pami r Sporadic 2200 3200 Less than 5 Island 2700 3700 5 - 30 Discontinuous 3200 41 00 30 - 70 Continuous 3500 4400 More than 70
The specialcircumstances of seasonaland perennial freezing can be observed inthe coarsegranular talus and screes.Talus containing no filler silt issubject to very deep seasonalfreezing when thereis a thin, unstable snow cover.For example, in northernTien-Shan, even at an altitude of 1600 m above sea level , where the mean annual air temperature is 5 - 6OC, seasonalfreezing of talus rarely reaches 3 m, whereas insuglinok-detrital* soils on the same slopes,seasonal freezing never exceeds a few tens of centimetres.This isrelated to the fact that in winter, in the mountains in thelatitudes underobservation, there is a highdegree of insolation. Therefore,the snow on east and westfacing talus is unstable, Waterfrom me1 ting snow infiltratestalus and freezes, fillingthe voids with ice between fragments.the This turn,in sharply increases thethermal conductivity of the medium, so thatllairll talus becomes transformedinto
* Suglinok - clayey silt with some sand, clayey silty loam(Transl.). - 360 -
''ice"talus. The former, on account of its thermophysicalproperties is closerto air, thelatter to ice.Moreover, the more voidsthat become filled with ice the truer is the comparison.
The icecontent of talusis determined by a number of factors, the mostimportant of which is the snow regimecovering the talus. Frequent lightsnowfalls alternate with groundthaw. The thawingleads topartial or completedisappearance of snow fromthe talus. The snowfallsgreatly favour thesaturation of talus by ice formedby seepage. This sharply increases the thermalconductivity of thetalus, so that it inturn predeterminesthe possibility of yet deeper freezing.Inspring and sumner theopposite situation canbe observed: surface thaw of talus and thedisappearance of ice from thevoids, form ba surfacelayer with anextremely low thermal conductivitywhich protects the underlyingice horizon from seasonalthawing. Moreover,colder but consequently denser air remains inthe voids in the summer, impedingthe thawing of thetalus. Therefore, permafrost frequently forms inthis type of talus above certainabsolute a1 titudes (i.e., above 2200 m in Tien-Shan). It has been establishedthat it can form and exist for severalyears, when the mean annual air temperature is 3 - 4OC and the mean monthly air index is 6OoC or less.
Incontrast, the formation of a thick,stable snow coverhelps to protecttalus from deep seasonalfreezing, even at considerable a1 titudes where the mean annual air temperature is -3OC orcolder. Such a situation for example,can be observed inthe Gissar Range (Mai khur Val 1ey and the Varzob Basin) where at an a1 ti tude of 3600 m the coarse granular talus on the northernslope freezes to no more than 2 - 3 m.
Recently,data on thicknessand temperature of permafrost at variouspoints in the region began to appear.This has made it possible to estimate changes in the valueswith altitude (Table 11).
It should be mentioned at this point that, within the distribution limits of unconsolidatedgranular materials, the thickness of thepermafrost layer does not exceed 200 m in Tien-Shan and 150 m inthe Pamir, and the temperature of frozenground at a depth of zeroamplitude does not exceed - 361 -
TABLE I1
Estimate of temperature (I) and thickness(11) of permafrost in Tien-Shanand Pamir-Alai
Absol Ute I NorthernTien-Shan 1 South-EasternPamir altitude, m I, OC 11, m I, OC 11, m
.
3000 0 - -1 0 - 50 I I 4000 -5 200 0 - -1 0 - 50 5000 -1 1 400 -7 300 6000 - * -13 800 7 000 " - more -19 than 800
-5OC inthe former and -3OC inthe latter region. High values for the thicknessand temperature of permafrostare characteristic of solidrocks only.
Permafrost in unconsolidatedgranular materials developedis mainlyat the watersheds of InnerTien-Shan and on the plateaus of Eastern Pamir where theyvary more in mechanicalproperties and in origin.
The Paleogene and Neogene - Lower Quaternaryformations froze epigenetically.In the initial stages of freezing,they werecompressed due todiagenesis and, in a number of cases, became sufficientlymonolithic and for the most partdehydrated rock types such as conglomerates,limestones, mudstones,sandstones, etc. Dehydration was furtheredby their being drawn intoorogenic movements. Thereforethese formations have a lowice content. The ice they contain is dispersed inthe form of veryfine crystals. The mostcompressed rocks contain virtually no ice.
MiddlePleistocene strata are found mainly influvioglacial and morainedeposits and arerare within the permafrost zone.There are no data concerningtheir cryogenic texture and therefore it is not possible to assess the type of permafrost.
The freezing of themoraine layers of the Upper Pleistoceneand Holocene epochs took placeunder very specific conditions, which is still the - 362 -
case today. These conditions are mainly determined by an increased water content of the ground; this is associated with meltwaterseepage into unconsolidated talus and with its subsequent freezing. The degree of moistening of earthmaterials is significantly dependent on the character of the relief. The freezing of moraines is mainly syngenetic.
The frozen lakedeposits wereformed inthe Upper Pleistocene and Holocene epochs. These frozen depositsare usuallycharacterized by a striated cryogenic structure, which usually follows primary stratification of the deposits. Together with the lenses of segregated ice, thethickness of which for the most part does not exceed 15 - 20 cm, lake strata contain lenses, stocks and veins of Injected ice. The largestice lenses havebeen found on the banks of the Karakul (Eastern Pamir) where theyreach a thickness of more than 5 m and extend from 10 to 14 m.
The perennial freezing of lake sediments under the aridconditions of Inner Tien-Shan and Eastern Pamir occurred and is still occurring in a subaqueousenvironment on littoral shoals at a depth of up to 1 - 1.5 m. This gives rise to the veryhigh ice content in lake deposits. Only in rare instances, when there is a rapiddischarge from thelake basin, does permafrost form epigenetically in subaerialconditions. When this occursI icelenses form only in the upper 1 - 2 m of the permafrost. Below this, the structure of the sediment is massive with little ice content.
Owing to their considerable water content, lake sediments and the underlying depositsare susceptible to severe permafrost conditions. This is reflectedin the processes of active frost heave. It is in these very deposits that perennial hydrolaccol iths and other humocky formations occur.
On theslopes, the coarse granular talus has the highest ice content. This talusfreezes both syngenetically and epigenetically. Its ice content depends on the size of the fragments, the type of filler silt, the type of seasonal thawing and freezing, and the water content. The highest ice content is found in talus with large fragments without filler "suglinok".
Porous, and lessfrequently, basal-massivepermafrost structure is characteristic of syngeneticallyfreezing talus deposits. An important
i I - 363 -
featureof their structure is the ice layers, which are relatively recurrent formationsalong the strike (to depth of 3 - 5 m andapparently still deeper).Their thickness if from 10 - 20 cm, and thedistance between the layersvaries within wide limits, usually from 20 - 30 cm to 1 m. The ice in the 1ayers has no inclusionsof large fragments. The presence of layersis animportant indicator of thesyngenetic freezing of talus.
Perennial and seasonalfreezing of a1 pine peat bogs and swamp meadows leads to theformation ofsegregated and injectedice, and of hummocky compl exes.
In the mountains of CentralAsia, frozen bedrock occupies at least 75 - 80% theofpermafrost area. Inregions where thevertical and horizontalseparations are particularly great (Western Pamir, theGissar and Zavershanranges) frozen unconsolidated materials are virtually non-existent.
Frozenbedrock must be dividedinto two categories:frozen and chilled. The former contain ice, thelatter do not,despite the negative temperatures of therocks themselves. This isrelated to the fact that some rocks , either owing to theirmonolithic nature, or for some otherreasons contained no water at the moment of freezing.
Frozenand chilledrocks can alternate even within a petrographically homogeneous massif. Therefore, atthe present time, it is impossibleto estimate even approximatelythe correlation between the volume of frozen and chi 1led bedrock.
In bedrock, iceis usually concentrated along fissures which are of diversebut mainly tectonic origin. Usually, the thickness of fissure ice variesfrom a few nlillimetresto 20 - 30 cm. The layeringof ice veins,the absence of strong parallelism in the layers, compression of air cavities, are all evidence of repeatedice flowage and of thefreezing of water in closed systems.Apparently, it continuedwith the shift of solid blocks along tectonic faults.
The depth of seasonalthawing decreases steadily with altitude. Thus in NorthernTien-Shan, inthe altitude range of 3100 m 4100 m, the - 364 - thickness of the seasonally thawed (active) layer decreases to approximately 2C cni for everyrise cf 100 m. But frequently, a change in the strlrcture of the earth materials and exposure of the slopes has appreciably more influence on the thickness of the seasonallythawed layer, than does a rise of several hmdredsletres. @wing to the fact that earth r(lateria7s fr! the snow belt are very homogeneous, the thickness of theseasonal layer is characterized in thisregion by its stabilitywith identical exposure and a1 ti tude.Within the alpine zane, where thetexture of earth naterials variesgreatly, the depth of seasonal thawcan change sharply over a smalldistance.
f?inimur;l depthof the seasonallayer (30 - 40 cm) is observed in peatlands and lake silts, whichare both enriched by organicmaterials. The niaxirnurrl thickness is in gravelsand detrital deposits (450 - 5GO cm)
The wedging out of the seasonally thawd layer above 450C - 5500 m is a feature of the region'shigh mountains, where earthmaterials thaw to a depth of a few centimetresduring the day and freeze completely at night. At a1 titudes of more than 6600 - 6500 rn on steep northern slopes~there is, as a rule, RO daytimethawing of solid or talus surfaces
Steadythawing of seasonally thawed layersbesins in May and reaches its peak in September. In Tien-Shanfreezing of a 1 m thick layer at an altitude of more thari 3600 I(! is canlpleted in the firstten days of October;for a layer 2.5 - 3 m inthickness at an altitude of approxitxately 3200 m it begins in December and laststhraugh the beginning of January. Seasonalthawing proceeds 2 - 4 times more slowly than freezing.
Formation of diverse forms of permafrcst terrain in alpine region: is associatedwith perennial and seasonalfreezicg. Maxirnuni concentration cf permafrostterrain forms is observed withinthe alpine zone. Thisis brought about by permafrost, deep seasonal freezing,frequent transitions of surface tcrcperaturesthrough O°C and relativelywide distribution of fine-grained earth rilaterials which must become sufficientlymoist. Above and below the alpine zone, the number and variety of permafrostterrain fcrms diminishes.
Most types of cryogenicterrain ibcluding solifluction features, patternedground and icings are not a reliableindication of permafrost. - 365 -
Thermokarst subsidence in lakedeposits, hydrolaccoliths and rock glaciers aregenetically related to permafrost.
Permafrost processes play an important role in theevolution of glacial moraines, alpine rock glaciers and mudflows,
In present day moraines, formation of large masses of secondary iceis taking place. This is connected with thefreezing of melt water in permafrost. Theme1 ting of primary and secondary ice and its forward movementdue to ice flowage leads to moraine deformation (cave-ins, fissuring, etc,).
Rock glaciersare permafrost-glacial forms; their genesis and development is possible within a permafrost zone. Injectedice plays the dominant role in their formation, for it fills the large voids between rock fragments. Plastic deformation of the ice is responsiblefor the movement of rock glaciers. Rock glaciers,despite their external similarities with moraines, differ from the latter in theirinternal structure and their surfacemicrorelief. Two generations of rock glaciers havebeen discovered in Tien-Shan: ancient(inactive) and present-day (active)types.
The foci of glacial mudflows originate in thetalik zonesand lakes of present day moraines, Taliks and rapid lakedischarges result from the upward migration of glacier water into frozen moraine deposits. The possible volume of a mudflow isrestricted by the volume of the unfrozen ground and the capacity of the themokarst and other moraine lakes.
Formation of permafrost in Tien-Shan and Pnmir-Alai is inextricablyassociated with thetectonic development of mountain regions, with a generalcooling, with increasing aridity and with a strengthening of thecontinental climate in the Neogene-Quaternary period. Analysis of data on the development of theancient glaciation in the mountains of Central Asia, of the occurrence of relic permafrost, on cryoturbations andremnant permafrost structures, allows us to form a general picture of the evolution of permafrost in Tien-Shan and Pamir-Alai. The first permafrost masses could have appeared in thePleistocene Epoch in the upper altitudes of Central - 366 -
Tien-Shan and Pamir. Sincethe climate inthe Pleistocene and the Lower Pleistocene was less continental and there was essentially less precipitation than at present,permafrost formed at thesnowline, is., exclusivelywithin thesnowbelt. Therefore, massive freezing took place insolid rock. In the MiddlePleistocene, in connectionwith the evolution of thecontinental climate, it became possiblefor terrain lyir,g belowthe snowline to freeze. This gave rise to the first expanses of frozen unconsolidatedgranular material.According to preliminaryestimates, the lowering of the permafrost boundary inthe Middle andUpper Pleistocene, when compared withthe present-dayposition, was no lessthan 1000 m.
Permafrostconditions inthe mountains of CentralAsia vary considerably from placetoplace. Differences inthe morphology of the permafrost, its temperatureconditions and itsmaterial composition, give grounds for dividingthe mountains of Central Asia into 7 permafrost (geocryological)provinces: 1) Morthern Tien-Shan, 2) WesternTien-Shan, 3) Inner Tien-Shan, 4) Alai, 5) Gissaro-Turkestan, 6) WesternPamir, 7) Eastern Pami r
The NorthernTien-Shan province incl udes Zailiiski i andKungei Alatai , Ketmen, most of the northernslopes of theKirgiz Range and the northernslope of Eastern Terskii Alatai. The province'ssnowline lies at 400 - 1000 m above thepermafrost boundary. The areaof glaciation is approximately 1600 km2; thepermafrost area is 9000 km2, This is 30.2% of theglaciated area and15.7% of thepermafrost area of the whole of Tien-Shan. As forthe Quarternary formations of unconsolidateddeposits in valleys anddepressions, they occupy no lessthan 20% ofthe area of the permafrost zone. In thisregion, continuous permafrost prevails. The depth of thepermafrost is from 0 to 400 m, its temperature is from 0' to -1OOC.
WesternTien-Shan province comprises Western Tien-Shan. The snowlinecoincides with or ishigher than the permafrost boundary by no more than 400 m. The glaciatedarea is approximately I600 km 2 , thatof the permafrost is 3450 km 2 . Accordingly, this is 9.4% of the glaciated and 6.1% cf thepermafrost area of Tien-Shan.Metamorphic aRd carbonate formations are themost comon. FrozenQuaternary deposits arenot represented. - 367 -
Present day terminalmoraines are mainly unfrozen. In this province, island anddiscontinuous permafrost aredominant. Permafrost is fron.1 0 to 250 - 300 m thick,the temperature from 0' to -7OC.
InnerTien-Shan province consists basically of Tien-Shan. The Snowline at 700 - 18CO m ishigher than the boundary of thepermafrost zone. The area of present day glaciation is approxinlately 3200 km', and thearea of Permafrost is 44,900 hi2. Thisaccordingly comprises 60.4% ofthe glaciated and 78.2% ofthe permafrost area of Tien-Shan.Magmatic, metamorphic and carbonateformations have roughlythe same distribution.Quaternary formation of frozenunconsolidated earth materials in the valleysand depressionsoccupies at least 35% of thepermafrost province. In this area continuouspermafrost prevails. The thickness of thepermafrost zone is froK: 0 to 800 m or more, its temperature is 0' to -20' - 25OC.
AlaiProvince covers the Alai Range fromthe upper reaches of the TarRiver to the upperreaches of the Soch River. On the average, the snowline in the area is at 1000 rn above theperrrrafrost boundary. The area of 2 glaciationis about 700 km 2 that of thepermafrost 7000 km Thisis 6.5% of the glaciated and 11.45; cf the permafrost area of Pamir-Alai.Quaternary depositsare relatively widely distributed in this area and are represented mainly in present dayand Upper Pleistocenemoraines and rockglaciers. Discontinuouspermafrost is predominant The depth of permafrost within the boundaries of thisprovince reaches 300 - 350 m; its temperatureranges from -7O to -9OC.
Gissaro-Turkestanprovince i ncl udes the Turkestan,Zavershan, Gissar andKarategin ranges. Here the snow1 ine coincides with cr is higher thanthepermafrost boundary. The area of present day glaciation is 1147 krr;2 , thepermafrost area is 5400 km2. Thiscorrespondingly ccrnprises 10.5% cf theglaciated area and 8.3% of theperniafrost area of Pamir-Alai. Thereare no Quaternarydeposits in this area; islandpermafrost predorrinates.Permafrost inthe high altitudes reaches a thickness of 350 - 40@ m and its temperature goes down to -1OOC.
WesternPani r provinceincludes the fol lowing main ranges : Petr PervYi9 Darvaz, Vanch, Yazgulern, Ryshan, Shugnan, Shachdar,Akademii Nauk, - 368 -
Tanyrnasand Beleuli . The snowlinecoincides with or is nomore than 400 rr~ above the permafrost boundary. The area of present day glaciation is approximately 7300 km 2 , that of thepermafrost 19,700 km2. This is 66.6% of theglaciated area and 29.55 of thepermafrost area of Pamir-Alai. As a rule,there are no frozenQuaternary formations, a1 though there may be some small stretches in the extreme east of the province.Present dayand ancient moraines are unfrozen. Continuous and islandpermafrost is predominant. The maximum thickness of thepermafrost exceeds 800 m and its minimum temperature reaches -2OOC.
Eastern Pamir provinceincludes the Zaalai Range as far as the upper reaches of the AltyndaryRiver in the west, Sarykol , blutkol* Zulymort, North-Alichur,South-Alichur, and the Vakhan ranges. The snowline lies on average at 1500 m above the permafrost boundary in theregion. The area of present day glaciation is approximately 1800 krn 2 , thepermafrost area is 2 33,800 km . This is 15.4% of the glaciatedarea and 50.8% of the permafrost area of Pamir-Alai. A wide distribution of Paleogenic, Neogenic and Quaternaryfrozen, unconsolidated n;aterials particularlylacustrine and morainicdeposits, is characteristic of this province. All types of permafrostare represented to approximately the same degree. The maximum thicknessof frozen, unconsolidated deposits is 150 nl, thetenlperature goes down to -3OC. Themaximum thickness of permafrost in the bedrock is 800 IL or more, it has minimum temperatureof -2OOC.
Permafrost and the permafrostprocesses influence many conponents of a1 pinelandscapes (subsurface and surfacewater, vegetation, soils, terrain, ground animals). The action of permafrost on thelandscape has bath negative and positiveeffects, The former are we1 1 known, the latterare exhibited mainly in the increasedmoisture content of the ground, and in the improved conditionsfor vegetation in thtl interior dry regions of Tien-Shan and Panli r .
The development of the alpire regions of Cwtral Asia (construction, recovery of minerals, highways, power 1 itxs, commur!ication lines and the study of rudflows) all call for further permafrostresearch and both mall- and large-scalerapping. E - 369 -
REFERENCE
FUJI1 Y and HIGUCHI K. 1976. Ground temperature and its relation to permafrost accurrences in the Khumbu Region and Hidden Valley. Journal of Japanese Society of Snow and Ice, vol 38, pp. 125-128.
- 371 -
ZONAL AND REGIOKAL PATTERPlS CF FORMATION OF THE PERMAFROST REGION IN THE ti.S.S.R.
V.A. Kudryavtsev, K.A. Kondrat'eva and N.N. Romanovskii Moscow StateUniversi'ty, U.S.S.R.
A permafrostregion is defined as a regionin which the temperatureof the earth materials remains at or below O°C for no less than three years. In order to studythe main features of the permafrostregion and to comprehend its fundamental patterns of forniation and distribution withlk the U.S.S.R. geocryologicalregionalization is essential. This involves dividing the earth'scrust into areas which reflect the conditionsof fornlation,distribution and structure ofthe permafrost region. In each area, the qualitative and quantitativecharacteristics selected as criteria for regionalizationfor have their own particularsignificance. These characteristics must be typicalfor the designated area, i .e., they must be predominant throughout permafrostformation and evolution.Geocryological regionaliration is complex, since it must take into consideration the dependence of the criteria on geological geomorphological climatic, palaeographic,thermcphysical and other environmental conditions. The regionaliration of the permafrost zone reflectsthe viek prevaler,t in permafroststudies for theperiod in which thegeneral map of the permafrost regi on was compi 1 ed,
At this point, two fundamentally different approaches to rcgi ona.lization should be pointed out.
In the first method, the dercarcation of zones takes place direc%ly cn the survey maps (scale 1 : 10,000,000 or smaller)during cornpilatien. This is done by making generalizations and by analyzingexistins factual informationinterpreted from the standpoint adopted in local permafrost: studies .
ProceedingsThird International Conference on Perrmfu'ost, VO~. 1 I pp. 420 - 426, 1978. - 372 -
The second method involves the demarkation of zcnes or! geocryological maps of a largerscale, with a view to generalizing factual material for a specific purpose, and to revealingregional, zonal patterr?: of fcrmation in the permafrost region.
The main task of geocryologicalregionalization is to show the heat exchangebetween latitudinal and high altitude zones and the geological and geographicalconditions of the region;because this furnishes a possible explanationfor patterns of formation and evolution of the permafrGst reyior;. Therefore, the principles of regionalization must take into account regic~txl and zonal patterns of formation of geocryologicalconditions, This can be accomplished by factor analysis. Environmentalconditions influencing the evolution of the permafrost region and its present day condition are: the present day climate and the changes it underwent in theCenozoic; formation of re1 ief, and sedimentation in recent times;landscape conditions and chapges during this period; thetransformation of earth materials and groundwater;change in the level of heat exchange at the ground surface; relatedmodifications and periodicchanges in climate, etc, In connection wi th this, yeocryological regional ization must be supported by geological , geomorphological,neotectonic, geobotanical and climaticregionalization. Such a correlation would be possible if a common zonal and regional classification system for geological and geocryologicalconditions in the permafrostregion were established. However, to date, no fullclassificatior, system has been devised,although there are detailed and generalizedsystems for individualaspects of the occurrenceof geocryological conditions, The explanations in the legend of the geocryological map of the U.S.S.R. on the scale 1 : 2,500,000 can be considered as just such an all-regional classification system. For the very first time, this mapmade it possible to show patterns of formation of geocryologicalconditions for the whole U.S.S.R., with a view to compiling an aggregate ofthe basicgsncryological features and environmentalfactors
Regionalization maps of the permafrostregion of the U.S.S.R., conpiled in the first instance by the methods indicatedabove, were the first geocryological maps toappear in theearly days of permafrost studies. ?he first regionalization maps, compiled by M.I. Sumgin (1927,1937), S.G. - 373 -
Parkhomenko (1937) and V.F. Tumel I (1946), were mainly permafrost distribution maps.However, as there was a verylimited arriount of data, these maps were actually a. reflection of thelatitudinal zonal ity of permafrostdistribution.
Subsequentaccumulation of factualmaterial on thefrozen region of thelithosphere, connectedwith the development of Siberia,the Far Easternregions and future development of regionalpermafrost studies demanded the compilationof new, improved maps. Therefore,geocryological regionalization maps began to be compiled on a systematic,integrated, environmental basis,reflecting permafrostfornlation as the result of heat. exchange in specific geographical and geologicalconditions.
These conditions were met by permafrost-temperaturethe regionalization map of V.A. Kudryavtsev (1954), compiled on thebasis of: a) considerationofthe close dependence of geocryologicalconditions and geological and geographicalconditions, b) both qualitative and quantitative evaluation of theseinterdependencies, c) clarification of the influence of eachenvironmental factor on theformation of the mean annual temperature of theearth materials, which links the thermophysical aspects of the cryogenic processes* with thegeological and geographicalaspect. This approach made it possible to distinguish between environmental and permafrosttemperature zones belonging to specific geological-geomorphologicalprovinces and climatic-geobotanicalzones, but different in distribution, mean annual temperatures and thickness of permafrost, Thus, this schematic mqp reflected theregional classification of permafrost and patterns of formation of geocryologicalconditions which later made geocryologicalforecasting possible. In the Department ofPermafrost Studies at Moscow University, further work concerningthe geocryological stirvey and mapping continuedin thisdirection.
In subsequent years, a number of reyionalization maps were conjpiled on which various combinedand individualgeocryological features were depicted. It should be noted that, since the permafrostregion is a
* cryogenicprocesses - physico-geologicalprocesses resulting from energy and Rass exchangesir! freezing,frozen and thawing earth materials (Trans1 .). - 374 - complex, natural system of matter, formed eithersyngenetically or epigeneticallyinspecific earth materials under specificclimtic and 1 andscapc conditions and developed in the Pleistocene and Holocene, each aspect of interdependence cif the permafrostregion and the environment demands special study and is itself both thesubject of regionalization and an identifyingfeature. In this case, whatever aspect of interdependence is exhibited or whatever characteristics are revealed, the orientation of classification and regionalitation cf thepermafrost region are genetic.
In 1956, P.F. Shvetsov introduced the concept of geocryological formation as the basis of geocryologicalregionalization. Having defined it as permafrost,typical for a given section,area, region of theearth's surface,relatively homogeneous compositicn,in structure, temperature, thickness, depth of occurrence,degree and type distributionalof discontinuity,water bearing capability and ability to permeate the eart,h materials (p. 29), Shvetsov introciuced a regionalization unit whose characteristics on any scale, from survey rr'aps to plans,could only be read from a table and not from the map itself. This approach has not received wide acceptanceas a principle for geocryoiogicalregionalization, for although it depicted a multiplicity of permafrost zone characteristics and patterns of fomation, their connectiorl with environmental change could not be traced. Moreover, such an approach had been employed earlier by all researchers, beginning with M. I. Sumgin, V. F. Tumel' , V. K. Yanovskii , V .A. Kudryavtsev, etc. At thepresent time it is being employed as the basis of 1 andscapenlicroregional ization in geocryologicalsurveying and is supplementary to basicgeocryological regionalitGtion. On the other hand, it isalso used as the basis forgeneralized regionalization. Geocryological conditionsdelineated on thedetailed map aregeneralized into a larger system for specific purposes such as indicating the zonal patternsof fomationin the permafrost region cr the cor,nections between hydrogealogical textures and thepermafrost region, or for geologicalengineering evaluations of geological, structuralsubdivisions in the permafrost zones, etc.
Therefore,regionalization should he based on genetic classification so that, on the one hand, it makes it possible to trace patterns of permafrostformation, and on theother hand forregionalization - 375 - purposes, to recognizegeneral , zonal and regionalpatterns of heat exchange between earthnaterials and the,atmosphere by way of basicgeological parameters.
I.Ya. Baranov,A.I. Popov, P.1,Mel'nikov, A.I. Kalabin and others,continuing in the same direction as V.A. Kudryavtsev, have developed principles for regionalization.
I.Ya. Baranov published the first geocryologicalrap of the U.S.S.F. on the scale 1 : 10,000,000 in 1960, which generalized the factual materialaccumulated atthat time and reflected the current views on the natureof the permafrost zone in the U.S.S.R. The map is compiled on a schematic,geological basis, with generalizations in the form of contour i ines indicating"plakory"* conditions, zonal and (to a lesserdegree) regional traits of distribution, thickness and mean annualtemperature of permafrost,Cryogenic and postcryogenic features are also shown in a generalized form. Moreover, there are six geocryological zones distinguished on the map and described in the text; two of these are oceanic, The features which formed the basis ofthe previous map are developed further on the new geocryological map of the U.S.S.R. compiled by I.Ya. Baranov in 1973 on the scale 1 : 5,000,000.
Having developed a cryolithological approach to regionalization, A. I. Popov compiled a map of permafrost-geologicalareas of the permafrost region cf the U.S,S.R, (1958) and a permafrost map of the U.S.S.R. (1962) on the scale 1 : 20,000,000, which shows the types of ground ice. Popov has also compiled a schematic map of cryogenic earth materials of Western Siberia on the scale 1 : 5,000,000 (1 959) , and a number of other maps.
A considerable number of regionalization maps have been compiled for individualareas of the perrnafrost region of the U.S.S.R. For example, the permafrost-hydrogeological map of the North-East U.S.S.R. on the scale 1 : 10,000,000published by A.I. Kalabin(1960); P.1. Mel'nikov's schematic geocryological map of the Yakutsk A.S.S.R. (1970), first compiled on the
* Plakory - slightlyundulating, well-drained interfluves (Trans1 .).
I
I I :I i - 376 - scale 1 : 5,000,000; a number of schematicgeocryological maps of Mestern Siberia on the scale 1 : 10,000,000 - 1 : 5,000,000 by V.V. Baulin and co-authors (1967, 1972); a geocryologicalregionalization map of the U.S.S.R. on the scale 1 : 20,000,000 by I .A. Nekrasov (1970); a schematic geocryological map of CentralSiberia on thescale 1 : 7,500,000 by S.M. Fotiev and co-authors(1974) ; and many others.
Intensive development of thepermafrost region during the past decade has, on the one hand, led to theaccumulation of diversefactual materialand, on the other hand, to the need forscientific regionalization and the compilation of a more detailed Rap of the permafrostregion to fill the growing reeds of the economy. A whole series of general and thematic maps has been compiled forthe individual regions during the past decade; theirscale is 1 : 2,500,000 - 1 : 5,OCO,OOO.
The new regionalization map of the permafrostregion of the 1I.S.S.R. represented in this paper was compiled on the scale 1 : 25,000,000 from thegeocryological map of the U.S.S.R. on the scale 1 : 2,500,000 and provides a visualrepresentation of the zonal and regionalfeatures of heat exchange within the permaf rast region
The regionalization map illustrates 3 c;f the region's basic traits established during analysis of zonal heat exchange characteristics under local geological and geographicalconditions: 1) distribution of permafrcst according tcj degree of discontinuityover the area and throughout its deptl;; 2) nature of change in level of heat exchange of earth materials,established from thetypical mean annual tenlperatures for a given latitudinal or altitudinal zone; 3) thickness of permafrost. Patterns of formation of these characteristics were establishedduring the mapping of geocryological ccnditions on thescale 1 : 2,500,000, by factoranalysis. Ar! analysis was undertaken when the followingfactors were being taken into account: dependence of the geocryologicalparameters of Seologicalstructure; historical development of the geology,hydrogeological and geothernric cclnditions of Earth'sthe interior; and integratedfactors of 1 andscape-geomorphology and surface cltmate, Mapping proceeded in accordance withthe analysis of thesefactors. - 377 - - 378 -
During compilation of thegeneral map, traits which are similarly conditioned by: the permafrostregion; geological, morphostructural and landscape environments, andwhich comprise theprinciple features of the geacryological map, scale 1 ; 2,500,000, were generalized to a great extent. This made thegeneralized regional-zonal patterns of heat exchange between earthmaterials and the atmcsphere more distinct.Finally, land was subdivided on the general rap in accordance with latitudinal zonality based on: receipt of solarradiant energy; distribution of the land n:asses and oceansdetermining t.he degree of continentality of the heatexchange; and on surfacerelief and Gtlier surfaceconditions determining the level of heat exchange within the 1 arge orographic subdivisions.
A scheme for dividing thepermafrost regior! has beendrawn up on the basis of depth of occurrence with respect to thesurface, where heat exchange between the atmosphere and thesoil takes place; and on the basis of pecularities of individualparts of thecross section, with respect to age and features of the permafrostregion associated with thegeological and palaeographic conai tions of its developnxnt.
Figure 1 shows that the permafrost,regl'on can be divided into threeparts: 1) thepermafrost region developed within thecontinental mass - subaerial; 2) theregion developedbeneath glaciers - subglacial; and 3) the region developed under theseas and oceans - submarine. The subaerialregion is in turn subdivided into Holocene and Holocene-Pleistoceneoccurring below the layer of seasonal thaw; therelic Pleistocene permafrost lying at sotlie depth from the surface of the layer of seasonal thaw. The age of the pernafrostgeneralized ir! the classification system is differentiated on the geocryological map of the U.S.S.R., scale 1 : 2,00@,000. Furthersubdivision of the subaerialregion is in accordance with the presence of ice(permafrcst in earth nlaterials) or chilling below O°C for salt. vjater or brine (kriopegs). Within the submarineregion, a distinction is n!ade between the shelfarea with therelic, Pleistocene permafrost, kriopey-containinglayers chilled below O°C and the deep ocean zone with Pleistocenekricpegs.
A more detailed account of the subaerial zone is included in this paper, This zone has beer; studied for more tknt; 41, ye:srs i - 379 - Figure 1 Holocene (withtransitional and semi- transitionaltype of heat Hol ocene-P1 eistocene 1 (with stable, long-stable, Arctic and polar type of heat exchange 1 P1 eistocene re1i c (permafrost) (continental -submerged permafrost and chilledlayers with kriopegs. r Ocean P1eistocene (chilledlayers with kriopegs). i Subdivisionof permafrost region for the geocryological map, scale 1 : 25,000,000 The subaerialtype of continentalpernlafrost region is the most common, as it isassociated with present day conditionsof heat exchange at theearth's surface and it includedthe northeast part of the European U.S.S.R., West and NorthSiberia, the Northeast and East of the SovietUnion, Prebaikal and Transbaikal, -and thehigh mountain regions of ttte southern U.S .S.R. Owing to thefact that the type of heat exchange at theearth's surface is associatedwith such factors as composition,structure and characteristics of theearth materials, snow and vegetative cover, summer settlement and infiltration, swamp, and runoffconditions, etc,, the subaerial zone is subdividedinto tworegions according tQ type of temperatureregime and its degree of activity. The first region is a - 380 - The most variegated dynamicand regionis the southern geocryologicalregion. This region has 4 zones, delineatedaccording to the prevalentlevel of heat exchangeand typeof permafrost distribution. The distributiontype is determined on thebasis of area, that is, the area occupiedby permafrost and thearea of thewhole zone. Divisionsare made in a south to northdirection, and inthe case of mountainareas, on the basis of a1 titude: 1) zone of severewinter freezing and short-termpermafrost, 2) zone of sporadicfreezing (5 to 30% of the areaoccupied by permafrost) , 3) zone ofisland permafrost (permafrost occupies from 40 to 60% of the tone) and 4) zone ofmassive-island permafrost (permafrost is from 70 to 90%). The sporadicHolocene and present day permafrostdeveloped in this zone is forthe most part, frozen epigenetically and is characterizedby a thermodynamicallyunstable temperature regime The temperatures of the permafrost in this zone aremainly within the interval of 0 to -0.5' and less frequently at -l°C; they arebasically organogenic and organomineral sandy loam and clay loam soils, restricted to swampy depressions at watershedsand in Val 1eys, and also to slopes with a northern exposure. Inthe island permafrost, the prevailing mean annualtemperatures of thepermafrost are from 0 to -loand less frequently -2OC (southCentral Si beria) and areassociated with organogenic and organomineralearth materials(north of the European part and West Siberia) and withmineral sandyfoam - clay loam materialsin valleys and at watersheds. Permafrost formation in this zone is determinedby the present day complex environmental conditions, the combinedinfluence of which,under favourable Conditions of thermalinsulation and infiltration,lead tothe thawing of the earth materials, and, underunfavourable conditions, to freezing. The freezing of uncmsolidateddepositions of thesyngenetic type can be accompanied by swamp - 381 - formation:the epigenetic freezing of bedrock in a fissured zone canlead to frost heave. When permafrost thaws, settlement,thermkarst and other processes occur. Towards theboundary of the zone of massive-island permafrost,the permafrost becomes more continuousand its temperature usuallyfalls to -2OC. In this zonel thawing is associatedwith the presence of a fissuredarea in the bedrock and with sandymassifs which provide favourableconditions for infiltration of summer settlement,both inthe Valleys and at thewatersheds; in theseareas it is also associated with snow cover. The thickness of thepermafrost underlying the layer of seasonal thaw theinsouthern region is found in accordance with existing environmentalconditions and is mainly up to 15-20 m for sporadic permafrost, from 50 to 100 m forisland permafrost, and from 100 to 150 rn for massive-islandpermafrost. Thezones withthe southern type of heat exchange, that is, zones alongsuch major rivers as the Ob, Yeniseiand the Lena, penetrate far into theregion of continuouspermafrost, and are azonal when surroundedby plakoryheat exchange conditions, The development of azonalgeocryological conditions in thesevalleys is conditionsby their historical development in theCenozoic and by present day heatexchange regimes conducive to thawing or tohigh temperature permafrost. The pecularities in theformation of geocryologicalconditions in themountains of Central Asia, Kazakhstanand the Caucasus, alllying within the southern-type heat exchange area, areassociated with altitudinal differentiation of thefactors causing permafrost formation. The phenomenon of massiveand island permafrost inthe mountains isrestricted to coarse granulartalus and stone blocks on steepslopes (greater than 35O) at a1 titudes from 1500 to 3000 rn, with 1i ttle snow andhaving a northern exposure(Gorbunov, 1974). Continuouspermafrost with temperatures below -1 -3O, is,according to A.P. Gorbunov (1974), characteristic of mountainranges with an altitude of from 3000-4500 m and higher,depending on their exposure, steepness of slope,and the general morphostructure of themountain region. - 382 - The northerngeologic province covers the area where, for the most part,continuous permafrost extends right tothe surface. Along its southern periphery,there is a zone within which thereareoccurrences of massive-islandpermafrost; however, the taliks are mainly of theclosed type. Mean annualtemperatures of permafrost in this zone lie mainly within the range -1 to -3OC. Its formation is associated with theinfluence of the continentali ty of theclimate and on thefairly favourable heat exchange conditionsat the surface. Under thelocal conditions, this combined influenceleads to theformation of permafrost which is predominantly from 100 to 300 m thick. In theparts of the fissured area and sandy massifs which intrude into the summer settlement, and also under largerivers and lakes,the continuouspermafrost is interrupted by thawed ground,occupying from 5 to 15%of the zone. The zone of continuouspermafrost with temperaturesranging from -3 to -15OC and below is divided on the map into subzones at intervals of Z0C on thebasis of heat exchange. The principle*of using temperature regime subdivisionsas a means ofestablishing zones (at intervals of 5OC) was formulated earlier by Kudryavtsev (1954). Analysis of existingfactual material undertaken during compilationthe of the geocryological map ofthe U.S.S.R., on ascale of 1 : 2,000,000, made it possibleto differentiate geocryological zones with predominant mean annual temperature of the earth materials of from -3 to -5O, from -5 to -7O, from -7 to -go, from -9 to -1l0, from -11 to -13O, from -13 to -15' and those below -15OC. This method of subdividing adquatelycharacterizes the percularities of the heat exchange regimes (structural-geological , geomorphological and landscape-cl imatic) which exist under specific 1 oca1 conditions. Characteristic of these zones isthick permafrost, whichformed in thePleistocene and is still forming atthe present time, and the presence of tal r'ks, found only under bodies of water,rivers and in places where groundwater is discharged. The lowest mean annual temperatures of from -13 to -15OC and lower are found in theearth materials high in the Byrrangs mountains on the Taimyr; in areas of the Novosibirsk Islandsnot covered by glaciers; and atthe top of high mountain ranges in North Transbaikal, particularly in the Pamirs and Tien Shan. Mean annual temperatures of from -9 to -13OC occur in theearth materials of the Putoranmountains, in the mountains. and interior areas of Taimyr, on the ridges of the Verkhoyanskand - 383 - The thickness and structure of thecontinuous permafrost has no directconnection with thepresent day climaticconditions; it depends upon thetime they were formedand thedegree of changeability of the thermodynamic conditionstheyasdeveloped. All this, in turn, is essentially dependent on thepalaeographic conditions, geological structure, composition and moisturecontent of the earth materials, geomorphological ana hydrogeological factors and theheat flow from theearth's interior: the latter is essentially determined by the age of the geologicaltextures increasing with decrease in age of thepermafrost. Therefore, the tendency of COntinUOUS p@r"nafrOStto be thicker towards thenorth and, in the mountains, with increase in altitude, is complicated by a number of other factors(Presence Of relic permafrost and chilling to below O°C for earth materials containing kryopegs) . The thickness of thepermafrost is dependent on the time of its formation,therefore, within thestretch of Holocene marine terraces,the thickness of thepermafrost does not exceed 100-200 m in the European, Northeast U.S.S.R. or 200-300 m in northernSiberia. Itlies next to the older,Pleistocene, surface permafrost of a differentorigin, where the thickness can be as great as 500-700 m. In mountain regions,the thickness of the permafrost can increase considerably, owing tothe influence of the verticalgeocryological zonality of the temperature of the earthmaterials; the large surface area of the mountain blocks, which is conducive to cooling;the well-drained earth materials and their hlgh thermal conductivity during theperiod of freezing. As a result, the permafrost found at high a1 titudes in the mountain ranges is 200 to 300 m thickerthan that of thegeocryotemperature zone delineated on the map. In the mountains of North Transbaikalthe thickness of the permafrostreaches 1200 to 1300 m, despitethe region's southerly position. The verticalzonali ty of thepermafrost in thesouthern ha1 f of Central Si beria is conditioned by the fact that earthmaterials I chi1 1 ed - 384 - Where the tone of fresh and subsalinewaters extends below the depthof perennial freezing, the layer of perenniallyfrozen earth materials comprisesthe whole cross-section and virtually coincides with the zero geoisothenn as isthe case in the Verkhoyansk-Chukotskaya fold mountain region;in the artesian basins of the larger part of the Western Siberian Basinand part of the YakutskBasin. The permafrostregion in the ancient shields(Anabar, Aldan) has two layers:the upper layer, restricted to the zone of exogenicfissuring andcomprised of permafrost,and a lowerlayer, restrictedto non-fissured, chilled earth materials which are penetrated by wateralong the veins. The permafrost in the Anabar is, on the average,700 to 900 m thick,fluctuating between 600 and 1500 m dependingon relief features,composition of theearth materials and theinterior tectonic zone (Yakov et a1 ., 1976). On thebasis of thetype of freezing,regions with predominantly syngeneticpermafrost extending right to the surface are distinguishedfrom the prevalent epigenetic permafrost. The upperlayer of the permafrcst cross-section is comprised of syngeneticallyfrozen layers with a thickness of from 1-2 to 50-100 nl differing in origin and age.These layersusually contain wedge ice and have evenlydistributed layered . structuresthroughout the section. The ice content of the syngeneticallyfrozen earth materials often reaches 70-95% of thetotal volume.These depositionsare mainly restricted to the low aggradationplains, and, in mountains andon plateaux, to rivervalley and intermontane Meso-Cenozoic depressions. On plains formedfrom syngenetically frozenlayers, the following features are widely developed: thermokarst lakes;thermoabrasion; thermal erosion; frost fracturing; ice wedges, etc. An extensiveshelf formed near theshores of Siberia due to abrasion of these depositionsby the Holocene sea. - 385 - Withinthe plateaux, fold mountain regions anddenuded plains, therearemainly epigenetically frozen and chilledconsolidated and semi-consolidatedmaterials. Inherited cryogenic structures (fissures, fissure-vein,fissure-karst, etc.) and relatively low icecontent decreasing withdepth are characteristic of theserocks. Cryogenic slope processes and frost heave inrock materials are widelydeveloped, and inthe valleys and depressions of thefold mountain region, there are icings. In the West Siberian Lowland, in thenorth of Central Siberia, EasternSiberia and the AnadyrLowland there are widely developed, epigeneticallyfrozen, unconsolidated sandy clay loams lacustrine,of alluvial , glacial,meltwater or seawaterorigin; their structure and ice contentvarying within wide limits. The highestvolumetric ice content (40-60%) is found in thelayers nearest the surface (up toseveral tens of metresthick); youngdeposits have a higherice content than the ancient, cons3lidated and lithifieddeposits; formation of thick,segregated and injectedice (up to 10 m or more) is associatedwith the freezing of the waterbearing layers cf unconsolidated materials. Thermokarst, frost heaving and frost fracturing are also characteristic of this terrain. Re1 ic P1 eistocenelayers of permafrost are developed inthe EuropeanNortheast U.S.S.R. (Oberman, 1974), in Western Siberia(Zemtsov, 1958; Baulin, 1962; and others) and, inthe south of CentralSiberia (Fotiev et a1 ,, 1974) withinthe southern region ofmassive-island, island and sporadicpermafrost. The reliclayer of frozenearth materials up to 200-300 m thicklies at, from 80-100 to 200-250 m from the surface and is characterized by temperatures slightly below O°C. In areaswhere Holocene permafrostextends from the surface, the permafrost isin twolayers. In Western Siberia , thesouthern boundary of re1 ic permafrostextends 2 to 3' further south thanthe present day permafrost, Where thepresent dayand Pleistocene permafrost meet along the boundary of thenorth andsouth geocryologicalregions, the thickness of the permafrost increases sharply (Oberman, 1974; Fotievet a1 ., 1974). Inthe North-East European part of the U.S.S.R. and inCentral Siberia, the present day permafrost boundary 1 ies furthersouth than that of the relic permafrost, and the two layer band of permafrost is not very wide. - 386 - A subslacialpermafrost zonehas developedunder glaciers in the mountains andon theArctic islands of thePolar Basin, the Novaya Zemlya archipelago,Franz Josef Land, Severnaya Zemlya, SchmidtIsland, Ushakov Island andBennet Island. The formation of the subglacialpermafrost zone is associatedwith the thickness of theglaciers, with the type of temperature regime inthe layer of temperaturefluctuations and with heat flow fromthe earth'sinterior towardsthe base of theglaciers; this is related to the type of geologicalstructure and its neotectonic development. The arcticislands were, in a geocryological sense, characterized for the firsttime on thegeocryological map of the U.S.S.R., scale 1 : 2,500,000. Both on this map andon the map presented inthis paper, demarcation of geocryological zones is made on thebasis of thedegree of heat exchangeon theice sheets, from -1 to -3OC onthe ice of Novaya Zemlya, from -3 to -1lOC on the ice caps of Franz Josef Land,and from -5 to -15OC on theice capsof Severnaya Zemlya. Calculations wereperformed forthe above mentionedregime of mean annualtemperatures existing atthe base of the layer of annualtemperature fluctuations of glaciers and ice sheetswith predominantthicknesses of from 200-300 to 500-600 m. Usingtemperature gradientstowards the base of lo/10O m andZo/l0O m, calculations of temperatures at the base of glaciersindicated that beneath them was developedmainly permafrost with temperatures from O°C (Northisland of Novaya Zemlya, Alexandra Landand George Land: the Franz Josef Land archipelago) to -ll°C (Gukera Island:Franz Josef Land, etc.). The thickness of theearth materials below the glacial cover, both those which are perenniallyfrozen and thosewhich are chilled below O°C and which containsaline water, depends. on the above listedconditions and is presumablybetween 100 and 400 rn. The submarinepermafrost zow encompassing the bottom of the northern seas, is dividedinto a shelf zoneand a deep oceanzone. The earth rrlaterialsof the shelf zone underwentpermafrost transformation on dryland, mainlywithin the 1 imits of the aggradationplains andwere later submerged as a result of transgression. The upperlayers of thedepositions, which have a highice content, were reworked by the sea; the mean annual terpperature of the sea floordepositions ~OSCto -1.9, -0.7OC; the ice of the 387 - upper layersdissolved and mixed with theseawater. Consequently, a layer of earthmaterials containing saline water formed, below which lies relic permafrost degradingnot only from above, but also below, due to theearth's internalheat. The degree of degradation depends on the time it became submerged. Because of this , thethickness of thepermafrost zone decreases and thediscontinuity increases away from thecoast towards the water. In theshallow ar'ea of theshelf, there is seasonalthawing, and coastal marine syngeneticallyfrozen depositions form. Near theestuaries of major rivers either there is an absence of permafrostor else it is 'island' in character. The deep ocean permafrost zone is made up of seawatersaturated earthmaterials with temperatures to -0.7Oc. Apparently, it occupies a large part of the Polar Basin and is characterized by a thickness of severaltens of metres. b In conclusion, it should be noted that regionalization of the permafrostarea on a general scale allowsthegeneralization of the characteristics of geocryologicalconditions with a view to reflectingthe common zonal and regionalpatterns of their formation. The regionalitation map discussed can be used as a geographicalbasis for comnunicating the construction normsand regulations beingcompiled for development of the permafrost region. REFERENCES BAULIN V.V. Osnovnye etapy istoriirazvitiya mnogoletnemerzlykh porod na territorii Zapadno-Sibirskoinizmennosti. (Basic stages in the history of development of thepermafrost in the West Siberian Lowland). - Trudy In-tamerzlotovedeniya im. V.A. Obrucheva, Vol. 19., Moscow, Izd-vo AN SSSR, pp. 5-18, 1962. BARANOV I.Ya. Geokriologicheskayakarta SSSR. (Geocryological Map of the U.S.S.R.). Scale 1 : 10,000,000. Poyasnitel'naza Zapiska(Explanatory Notes). Moscow, 48 pages, 1960. GORBUNOV A.P. Poyas vechnoi rnerzlotyTyanl-Shanya. (The permafrost zone of Tien Shan').Avtoreferet dokt, diss,(Abstract of Doctoral Diss.) Moscow, 33 pagesz 1974 DQSTOVALOV B.N. and KUDRYAVTSEV V.A. Obshchee merzlotovedenie. (General Permafrost Studies). Izd-vo MGU, pp. 235-278, 1967. - 388 - ZEMTSOV A.A. 0 rasprostraneni i mnogoletnemerzlykhgornykh porod v Zapadnoi Sibiri. (Permafrost distributionin Western Siberia), "Nauch. dokl. Vyssh. shkoly.Geol-geogr. nauki", No. 3, pp. 43-49, 1958 KALABIN A. I. Vechnaya merrlota i gydrogeologiyaSevero-Vostoka SSSR. (Permafrost and hydrogeology of the Northeast U.S.S.R,). TrudyVNII-1 Vol. 18, Magadan, 471 pages, 1960. KUDRYAVTSEV V .A. Temperaturaverkhnykh gorizontov vechnomerzloi tolshchi v predelakh SSSR. (Temperature of theupper permafrost horizons in the U.S.S.R.). Moscow, Izd-vo AN SSSR, 183pagesp 1954. MEL'NIKOV P.I. Skhematicheskayageokriologicheskaya karta Yakutskoi ASSR. Schematicgeocryological map of theYakut ASSR). Scale 1 : 5,000,000 - Inthe book: Gidrogeologiya SSSR. (Hydrogeology of the U. S .S .R. ) . Vol . XX, Yakutskaya ASSR., Moscow, Nedra, 1970. NEIZVESTNOVYa.V., OBIDIN N.1.) TOLSTIKHIN N.I. and TOLSTIKHIN O.N. Gidrogeologicheskoeraionirovanie i gidrogeologicheskieusloviya sovetskogosektora Arktiki . (Hydrogeologicalregional ization and hydrogeologicalconditions inthe Soviet Arctic). In the book: Geol ogiya i poleznye is kopaemye severa Sibi rskoipl atformy. (Geologyand minerals of the north of the Siberian Platform). L., pp. 92-105, 1971. NEKRASOV -I.A. Movye dannyeob osobennostyakh stroeniya i ploshchada razvitiyakriolitozony v predelakh territorii SSSR. (New data on the peculiarities of the structure and area of development of thepermafrost zone inthe U.S.S.R.). "Dokl. AN SSSR", Vol.194, NO. 3, pp.643-646, 1970. OBERMAN N .G. Regional'nye osobennosti merzloi zonyTimano-Ural 'skoi oblasti. (Regional peculiarities of thepermafrost zone of Inlano-Ural'skaya Province) Izv. Vysshykhuchebn. zavedenii.Geologiya i razvedka. NO. 11, pp.98-103, 1974. PARKHOMENKO S.G. Skhematicheskaya kartaraionov merzloty i glubokogopromer- zaniya SSSR. (Schematic map of theregions of permafrost and deep freezingin the U.S.S.R.). TrudyTSNII geodez. aerofotos' emki i kartoyr., No. 16, pp. 18-24, 1937. POPOV A. I, Merzlotno-geologicheskoe raionirovanieoblasti vechnoi merzloty v SSSR. (Permafrost-geologicalregional ization of thepermafrost zone in the U.S.S.R.). Inform.sbornik o rabotakh PO merhdunar. geofiz. godu geogr. f-ta.(Information on projectsundertaken by the Faculty of Geography at Moscow University for International GeophysicalYear). MGU I Moscow, No. 1 pp. 239-264, 1958. POPOV A. I. Chetvertichnyiperiod v Zapadnoi Sibi ri. (The Quaternary period in Western Siberia). In the book: Lednikovyi period na territorii Europeiskoichasti SSSR i Sjbiri. (Ice Age in the European part of the U.S.S.R. and Siberia). Izd-vo MGU, pp. 88-102, 1959. - 389 - POPOV A.1, Vechnaya merzlota.(Permafrost). In the book: AtlasIrkutskoi oblasti. (Atlas of IrkutskProvince). Moskva-Irkutsk, 36 pages, 1962. SUMGIN M.I. Vechnaya merzlota pochv v predelakh SSSR. (Permafrost soils in the U.S.S.R). Vladivostok, 372 pages, 1927. SUMGIN FI.1. Vechnaya merzlota pochv v predelakh SSSR. (PermafrostSoil5 in the U.S.S.R.) MOSCOW, Izd-vo AN SSSR, 380 pages,1937. TUMEL' V.F. Karta rasprostraneniyavechnoi merzloty v SSSR. (Map of permafrost distributionin the U.S.S.R.). Merzlotovedenie,Vol. 1, No. 1, pp. 5-11, 1946. FOTIEV S.M., DANILOVA N.S. and SHEVELEVA N.S. Geokriologicheskieusloviya Srednei Sibiri . (Geocryologicalconditions in Central Siberia), Moscow, Nauka, 147 pages , 1974. SHVETSOV P.F. 0 printsipakhraionirovaniya kriolitotony. (Principle region- alization of thepermafrost zone). In the book: Materialy k osnovarn ucheniya o merzlykh zonakhzemnoi kory.(Basic material for study of thepermafrost zone of the earth's crust). Moscow, Izd-vo AN SSSR, NO. 3, pp. 78-39, 1956. YAKUPOV V.S., ALIEV A.A. and DEMCHENKO O.V. et al.,Moshchnost' merzloi tolshchi na Anabarskom kristallicheskom massive (PO dannym VEZ). (Thickness of permafrost on the Anbar CrystalineMassif (according to vertical electronicsounding data)). In the book: Geofiticheskiemetody issle- dovaniyamerzlykh tolshch. (Geophysical methods in permafrostresearch) Yakutsk, pp. 22-28, 1976. - 391 - CRYOLITHOLOGICAL MAP OF THE U.S.S.R. (PRINCIPLES OF COMPILATION) A.I. Popov, E.E. Rozenbaum and A.V. Vostokova Department of Geography, Moscow State University, U .S .S.R. Inrecent years, lithogenetic research into aspects of thesteady cooling of theEarth has resultedin the developmentof a new branchof science - cryolithology. The objectofresearch thisin science is permafrost:the product of a particulartype of 1 ithogenesis,namely cryolithogenesis,which is inherent to cold regions. Cryolithogenesisresults from specific regional conditions. It is a combination of processesexisting inthe lithosphere, i.e., inthe landscapefeatures of arctic and subarcticregions, the northern part of the humid zone,and high a1 tituderegions; for these allprovide the conditions necessary for permafrost formation Study of thestructural patterns of permafrost, theof distribution of icewithin the permafrost, of the processes connected with theformation and thawing of iceare of greatimportance for thedevelopment and utilization of natural resources in the north and thenortheast U.S.S.R., forthe protection and rational use of theenvironment in theseareas. This has promptedthe compilation of a cryolithological map of the U.S.S.R. Available work thetheoreticalon principles of cryolithology,the formulation of a scientifically based classification systemfor permafrost, andthe accumulation of extensivefactual material concerning the permafrost in theseregions ofthe U.S.S.R. make thistask feasible. However, the scientificdata only allow compilation at a scale of 1 : 4,000,000 andno larger. It should be notedthat this is the very first time that such a map hasbeen produced. ProceedingsThird International Conference on Permafrost, VO~. 1, pp. 435 - 437, 1978. - 392 - An exposition of the principles used in the compilation of a cryolithological map must be prefaced by the presentation of certain basic positions held in the field of cryolithology; for itis these positions which form the basisof the very principles themselves. Cryolithogenesis as a specific processof 1 ithogenesis acts in two capacities: as cryodiagenesis andas cryohypergenesis. Cryodiagenesis is the process of protracted, irreversible formationof ice, and the transformation of the mineral substratum itself (consolidation, dewatering, cementation, etc.), without any significant changes in dispersion either in recently deposited sediments or in materials lithified at an earlier date. In this case, the ice is an authigenous mineral, a stable, long-lasting componentof the permafrost. Cryohypergenesis is the process of frost weathering of various materials as a result of repeated freeze-thaw cycles (mainly seasonal); this process is the reversible, systematic (i.e., sporadic) formation of ice, leading to a significant change in dispersion, to a gradual refinement not only of massivematerials, but also of unconsolidatedmaterials with particles greater than the silt fraction, and to an aggregation of clayey particles. In this case, the ice is a temporary,active, authigenous mineral, often not confining itself to the eluvium which was already formed. In its capacity as a process of cryodiagenesis, cryolithogenesis isactive in theformation of permafrost;and as processa of cryohypergenesis, it extends beyond this sphere, into the realm of seasonal freezing of materials. Two types of cryogenic materials result from cryodiagenesis: kryol ity and kryol itity. Kryol ity are materials containing only pure ice: monomineral materials ; kryol i tity are polymi neral materials, where ice is only one of the mineral components, Cryogenic eluvium whichforms as a result of frost weathering is a product of cryohypergenesis. In winter, when the cryogenic eluvium of the active layer is frozen, it becomes transformed into kryolitity. - 393 - A cryolithological map must show, as fully as possible, the genetic diversity Of permafrost,. the characteristics of its structure, and itsdistribution, However, in thiscase, certain difficulties arise restricting the possibilitiesin this regard. The mapping of this type of permafrost, both within the limitsof perennial freezing and beyond, is complicated by the following factors: a) genetic interpretation of the loess silts which exist in both permafrost and theareas of seasonalfreezing is open to dispute; b) insufficient theoretical work has been done on matters concerned with the processes of cryohypergenesis, leaving the questions of diagnosis and classification of cryogenic eluvium unresolved. Moreover, the mapping of cryogenic eluvium in the layer of seasonal thawing creates additional technical difficulties when depictedon a mapshowing the cryogenic structure of itsunderlying permafrost. At this stage, all these complications can only be overcome by excludingcryogenic eluvium from the map, therefore, the information presented on the map must be limited to depicting two observed genetic types of permafrost - kryolityand kryol itity, which are the products of cryol ithogenesis in only one of its capacities, i .e., of cryodiagenesis. Consequently, only permafrost was depicted on the map. The smal 1 scale of the map does not permit the marking of permafrost islands, nor does it allow the basic distribution patterns to be depicted by a generalization. This makes it particularly difficult in the case of mountainous regions, where the exposure, the density of the broken relief, and other factors of geomorphology, physical geography and geology influence the distribution of permafrost, As a result, the island character of the permafrost near the southern boundary notwas depicted on the map. Owing to the complexity and number of stages in the permafrost structure, mapping had to be restricted to the uppermost horizon 20 m in thickness. The entire permafrost structure for individual regions is shown in the cryol ithological columns. The main principles behind the map's legendare the identification of the genetic types of frozen earth materials and their combinations, - 394 - together with theidentification of the types of cryolithogenesis characteristic of these materials. As was previouslynoted, the map reflects two genetictypes of frozenearth materials: kryolity and kryolitity.It is usual forkryolity to occurnaturally with kryolitity, whichform the acconmodating materials. The onlyexception is surfaceice, such as alpineglaciers, icings, etc. Kryolitityoften form independently and, over a greatdistance, will contain no bodies of ice; that is, no kryolity. On account of this, the"types of frozenmaterials" shown inthe legend aredivided into the following groups: kryolitity;kryolity with accomnmdating kryolitity; and kryolity. To the second ground belong the earthmaterials with icecontent; this includeskryolity manifest as polygonal ice wedges which, in combination with their accomnodating kryolity, can form eitherpatterned ground, or the ice core of a hydrolaccolith. The t hi rd group (kryol i t,y) includessurface ice; alpine glaciers and icings. ,,.I ,:: zy./,9 fi '? Kryol i ty occurnaturally as variousgenetic types of ground ice, which are combined i nto two groups:konthel ity and I' khionol ity. Only the first group appear in the legend sincekhionolity are rare. Kryol ity (konzhel i ty) appear inthe legend as thefoll owing types of ground ice: polygonal wedge ice;sheet ice; or icecores of hydrolaccoliths. Polygonal ice wedges are subdivided into relic and active. Two genetictypes of ice are active in the formation of kryolity: segregated ice and ice cement. Combinations of these two genetictypes are particularly wi despread ; this is ref1 ected in the 1 egend. The variousstructures are determined by thedistribution of ice in thematerial s. A simple classification system is used in thelegend. The followingdivisions are nlade: streakycryostructures formed by segregated ice(layered; reticulate; icelenses), and othermodifications and cryostructures formed by ice cement; massive,basal and crustalstructures in unconsolidatedmaterials, and fissuredstructures in solid and semisolid materials. - 395 - Structuretype, characteristics of distributionthrough the section, and participation of variousgenetic types of ground ice are, to a large degree,determined by ttie type of freezing, i.e., bythe type of cryolithogenesis. The typeofcryolithog’enesis can vary depending on the conditionsunder which it takesplace: the physical geography, temperatures, lithology and facies,etc. A1 1 possible occurrences of cryol ithogenesis canbe reduced to two basictypes - epigenetic and syngenetic.Epigenetic cryolithogenesis takes place inmaterials which haveundergone some degree of lithification. Syngenetic cryol ithogenesis is fundamental to 1i thogenesis that is, freezing is a basic factor in lithification; it accompanies sedimentation. Bothtypes of cryol ithogenesis a each in its own way, exert an influence on theformation of frozenmaterials, on theinternal distribution and amount of icethey contain, and on structuretype. Characteristic of epigeneticpermafrost are: a decrease inice contentthroughout the section, by the replacement (inthe northern regions) of thethin layers and reticulatestructures, by thicker layers and a more distinctly reticulate structure and finally by massivestructure as thedepth increases and thetemperature gradient decreases. Characteristic of syngeneticpermafrost is aneven distribution of icethroughout the section, infrequent occurrence of polygonal wedge ice, a specificcombination of reticulate and distinctlyreticulate structure, ice lenses,and a high ice content. There is a definiteconnection between genesisand age of materials,zonal geographical conditions and thetype of cryolithogenesis. In so far as permafrostformation firststarted at thebeginning of the Pleistocene,all of the more ancientrocks froze epigenetically. During the Holocene maximum, inthe south of thepermafrost zone, thematerials thawed almost completely,with the exception of thelowest relic layer, which had become establishedinthe southern regions. So that,regardless of age, (withthe exception of presentday deposits - i.e. , thoseafter the Holocene - 396 - maximum), genesisor lithology, all present-day permafrost in this zone froze epigenetically.Its loss of water is, to a certaindegree, connected with itsrefreezing, as is its relatively low icesaturation, even in thenear surfacehorizons. Moreover, here,there is a directrelationship between physicalappearance of thestructure and the small temperaturegradients at the timethe structure was formed; these were close to present day temperatures. In this case,distinctly reticulate structures with thick layers; ice lenses; and massive structuresare the most widelydeveloped structures in the thinlydispersed deposits. Here, the great depth of seasonal thaw accounts forthe absence of polygonal wedge ice. In thenorthern part of the permafrost zone, thereis a clear connection between type of cryolithogenesis and facies-genetic affiliation of thedeposits. Frozen marine deposits, marine depositscontaining ice, glacialdeposits, etc., belong tothe epigenetic type of cryolithogenesis: a1 luviallake deposits, etc., to thesyngenetic type. Consequently, epigeneticpermafrost prevails on the vastplains of Western Siberia, where thereare marine depositscontaining ice; and on the Yana-KolymaLowland and on theplains of CentralYakutia, there is syngeneticpermafrost resulting from the wide occurrence of alluviallake deposits, By takinginto account theclose affiliation of type of freezing,structure type and the genesis, age, and lithology of the accommodating materials to ensurecorrect spatial distribution and re1 iabil i ty of boundaries , 1 ithologicalgenetic maps prepared the way for thecompilation of thecryol i thological map.Maps of Quarternarydeposits and geologicalengineering maps were used as the basic sources for the compilation of the 1 ithogical maps, A combination of two types of cryolithogenesis(polygenetic permafrost) is very common in permafrost profiles. This isillustrated by the following examples: thelake and swamp deposits of the alasplains*, a1 1uvial deposits with epigenetically frozen river beds and syngenetically frozenfloodplain a1 1 uvium; and talus-solifluction deposits frozen syngenetically and coveringepigenetically frozen, solid and semi-sol id * Alas - depressionwith gentle slopes and flat bottom, typical of some permafrostregions (Trans1 .) . - 397 - materials,etc. Such combinations figure in the legend. Moreover, in the mountain regions, different typ,es of cryolithogenesisalternate within short distances. The impossibility of reflectingthese alternations to scale led to the necessity of introducingcombinations of the two types of cryolithogenesisinto the legend, to reflecttheir occurrence not only in the profile, but alsospatially. Apart from type of conditions and type of freezing,structure type is directly dependent on lithology and humidity. For example, massive, crustal, and basal structures formed by ice cement aretypical of thickly disperseddeposits (sands and coarsegranular) ; a fissuredstructure, a1 so formed by ice cement, ischaracteristic of solid and semi-solidmaterials. High humidity leads to the formation of thickly dispersed deposits: low humidity to ,theformation of a basal structure. In finelydispersed deposits (clayey and sandy),ice lenses, partiallyreticulate structures and, in thecase of high compaction,nlassive structure occur when there is low humidity and a considerable admixture of sandy orcoarse-grained material. It is the frequency and depth of the ice layers, apart from thelithology and humidity, which determine the rate of the freezing . As a rule,great variations in lithology and humidity throughout theprofiles and over thearea of dispersion,create certain difficulties when thestructures are being mapped. These circumstancesare presented in the legend by combining various structures. The lithologicalvariation throughoutthe profile within the 20 m horizon is shown as a fraction, in which thestructures of the uppermost horizon are given above the line, the structures of the underlyinghorizon - below the line. For example: massive reticulate with thick layers signifies massive structure in the uppermost horizon, formed by ice cement in either sandy and coarsegranular deposits or inpeat, this a1 ternates downwards through the profile with thicklayers distinclty reticulate in structure, which are formed by the segratedice in theunderlying clayey or sandy clayey deposits - 398 - An importantfactor in the compilation of the map is theworking out ofthe principles used in theformulation and selection of methods of depiction;these are always closely related to thecontent and function of the map: as a wall map, orfor demonstration purposes. For the depiction of types of frozen materials and types of cryolithogenesis,the basic method was selected, i.e., a colouredbackground. Thus thedifferent types of cryolithogenesisare clearly distinguished by sharp differences in colour; and kryolitityare distinguished from the kryolity and their accommodating materials(inthe cooler colours) byvarious colour ranges. Kryolity, manifest as sheetice,ice cores of hydrolaccoliths,icingsor are represented on the map bysymbols. The map'sexpressiveness, itsclarity of representation and its readabil ity at a distanceare ensured by using colour tofull advantage. The variationsin structure of thematerials determined bycryogenic structure are reflected by the shade of colourassigned to the givengroups. The 1 ithology of the unconsolidated materials accommodating theice is indicated by differenttypes of colouredhatching. The genesis and age of the materials is shown in the key. The cryolithological columns containinformation on the stratigraphy,genesis and lithologyof the materials, and indicatesthe thicknessofthe individual stratigraphic horizons. The presence of the remains of flora andfauna, concretions, andpseudomorphs in the ice veins is markedby the special, conventional symbols. The columnssupply the detailed characteristicsof the permafrost structure, indicate the thickness, the mean annualtemperature of thematerials (the latter indicates the level of heat exchange),and the distribution of volumetricice content throughout the horizon . These arethe mostimportant principles of compilation and the mainfeatures of thecryolithological map ofthe U.S.S.R. It is the first attempt to depictpermafrost as a singleentity manifest in different forms. Unlikeother permafrost maps, whichusually depict a large number of differentpermafrost features but do not show a clearconnection betweenthem all,this map onlydepicts those characteristics which primarily reflect the casualrelationships between thestructure and lithology,the facies genetic affiliation and the age of the accommodatingrocks. Moreover, the map - 399 - illustrates the spatial distribution of the types of cryolithogenesis and reflects the zonality of processes and the morphological results of cryolithogenesis, which are all largely subordinate to the temperature zonali ty of the permafrost. I