Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174

The changing nature of periglacial La nature mouvante de la géomorphologie périglaciaire

Hugh French* and Colin E. Thorn**

Abstract Periglacial geomorphology faces the prospect of being consumed or by-passed by the growth of geocryology, the changing nature of geomorphology, and the sophistication of studies. Identification of typical ‘periglacial’ landscapes is tenuous. The core of periglacial geomorphology concerns the study of freezing processes, associated ground ice, and related landforms. Such an approach places in a central, but not defining position, within periglacial geomorphology. Likewise, cold-region geo- morphology, an areal or regional concept, embraces a mix of glacial, periglacial, and azonal processes that assume distinct characteristics in the cold non-glacial regions of the world. Because the ultimate aim of periglacial geomorphology is to create mod- els of cold- landscape evolution, continued growth of the discipline depends upon it maintaining a bridging position between geomorphology, geocryology, and Quaternary science. Periglacial geomorphology must always change in response to the larger sci- entific context of which it is part. Key words: periglacial geomorphology, geocryology, Quaternary science, cryospheric sciences, geomorphology.

Résumé La géomorphologie périglaciaire doit faire face à la perspective prochaine d’être incorporée ou supplantée par la géocryologie qui connaît un retour en grâce depuis quelques décennies, par l’évolution même de la géomorphologie ou par la sophistication des études sur le Quaternaire. L’identification d’un paysage « périglaciaire » typique est délicate. Le noyau de la géomorphologie périglaciaire se concentre sur l’étude des processus liés au gel, sur la glace du sol et les modelés associés. Une telle approche place le pergélisol en position centrale, mais non définie, au sein de la géomorphologie périglaciaire. Au contraire, la géomorphologie des régions froides, concept spatial, englobe à la fois les processus glaciaires, périglaciaires et azonaux qui produisent des modelés caractéristiques dans les régions froides non englacées de la planète. Puisque la finalité de la géomorphologie périglaciaire est de créer des modèles d’évo- lution des reliefs des zones froides, la croissance continue de la discipline est inféodée au maintien d’un pont entre la géomorphologie, la géocryologie et les sciences du Quaternaire. La géomorphologie périglaciaire doit constamment évoluer en réponse à l’élargisse- ment permanent du champ scientifique dont elle fait partie. Mots clés : géomorphologie périglaciaire, géocryologie, sciences du Quaternaire, cryosciences, géomorphologie.

Version française abrégée évolution historique différente, la confusion s’est installée La géomorphologie périglaciaire est une sous-discipline entre la géocryologie et la géomorphologie périglaciaire à de la géomorphologie qui s’intéresse aux modelés et aux cause de relations académiques complexes entre les Acadé- processus des régions froides non englacées de la Terre mies des Sciences et les départements universitaires en (French, 1996). Aujourd’hui, deux questions primordiales Russie et en Chine, et entre les départements de géographie, émergent au sein de cette sous-discipline : premièrement, il géologie, sciences de la Terre, géophysique et ingénierie existe un conflit d’intérêt vis-à-vis du développement rapide dans de nombreux pays du monde. La confusion a atteint de la géocryologie ; deuxièmement se pose le problème de son comble en Russie où les activités de recherche se che- la définition exacte des régions périglaciaires et de l’évolu- vauchent dans des départements entièrement consacrés aux tion de leur nature avec le temps. Cet article s’intéresse à études cryologiques. Il apparaît que la géomorphologie ces deux questions. périglaciaire (et peut-être la géomorphologie en général) se La géocryologie existe depuis au moins 1924 en Russie, sépare à présent de la géographie. Une partie de ce divorce mais apparaît plus tardivement (aux environs de 1940) en repose sur la révélation que de nombreuses notions Amérique du Nord et encore plus tard en Chine. Outre cette anciennes de la géomorphologie périglaciaire n’étaient pas

* Departments of and Earth Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada. E-mail: [email protected] ** Department of Geography, University of Illinois, Urbana, Illinois 61801, USA. E-mail: [email protected] Hugh French and Colin E. Thorn

très argumentées et que plusieurs processus azonaux crédibilité de la géomorphologie périglaciaire. Une telle devaient être inclus dans l’examen des régions traditionnel- perspective fait du pergélisol un élément central, mais non lement définies comme périglaciaires. limitant, de la géomorphologie périglaciaire. De même, de La géomorphologie périglaciaire s’est rapidement déve- nombreux éléments d’étude qui constituent la géomorpholo- loppée après la Seconde Guerre mondiale, mais elle a gie périglaciaire contemporaine doivent également être véhiculé deux pièges importants. Le premier est la suresti- considérés comme une composante de la géocryologie. mation de la météorisation liée au gel/dégel et de son Néanmoins, d’autres composantes de la géomorphologie occurrence, ce qui sera débattu dès les années 1970. périglaciaire englobent l’impact du gel saisonnier ou le rôle Aujourd’hui, on sait que la météorisation en régions froides du manteau neigeux et des couvertures de glaces marine, est complexe, car elle englobe également des mécanismes fluviale et lacustre (Thorn, 1978). En outre, la géomorpho- biologiques et chimiques. Le second piège réside dans le logie des régions froides non englacées doit prendre en fait que cette sous-discipline a insuffisamment pris en considération l’étude, non seulement de la géocryologie et considération, non seulement la lithologie, mais aussi la de la géomorphologie périglaciaire comme définies ici, durée et l’efficacité des conditions climatiques froides. mais également les processus azonaux qui montrent des Nous pensons que la géomorphologie périglaciaire contem- fonctionnements et/ou une fréquence ou une magnitude dif- poraine devrait être perçue comme une sous-discipline férents dans les régions froides. Au cours de notre époque consacrée aux processus géomorphologiques, sur le modè- caractérisée par des changements scientifiques rapides, la le de la géomorphologie fluviale ou éolienne, par exemple. géomorphologie périglaciaire, comme toute autre science, Ainsi définie, une géomorphologie périglaciaire s’attachant doit s’adapter à de nouvelles attentes plus rigoureuses, afin principalement aux modelés ne manquera pas de chevau- d’éviter le risque de flétrir puis de disparaître. cher considérablement la géocryologie dont le champ d’étude est consacré aux conditions thermiques dans le sol Introduction et à la glace du sol. Cependant, de tels chevauchements thé- matiques sont fréquents dans le monde scientifique et des Periglacial geomorphology is the sub-discipline of geo- disciplines connexes s’appuient clairement sur leurs exper- morphology concerned with the landforms and processes of tises respectives pour permettre, grâce à cette fertilisation the cold non-glacial regions of the world (French, 1996). croisée, de renforcer le progrès scientifique. However, while this definition captures the traditional Nous pensons que la géomorphologie périglaciaire doit essence of the sub-discipline, it does not reflect, nor address, désormais se concentrer sur : 1) la nature des processus liés two important emergent issues within periglacial geomor- au pergélisol, à la glace du sol et aux modelés associés ; 2) phology. The more fundamental is the relationship between les processus azonaux qui opèrent dans les environnements the older sub-discipline of periglacial geomorphology with froids mais non englacés ; 3) les espaces à la périphérie des its roots in climatic geomorphology, and more broadly geog- glaciers (zone proglaciaire) et les transitions paraglaciaires raphy; and the younger, presently more vigorous discipline qui leurs sont associées ; 4) les environnements alpins of geocryology, here defined simply as permafrost science. (montagnards) ; 5) les reconstructions paléoenvironnemen- The latter discipline is one of the cryospheric sciences and tales des climats froids pléistocènes, et enfin ; 6) les études has a sharply different disciplinary heritage to that of géotechniques et environnementales associées au sols gelés, periglacial geomorphology. These overlapping, even con- au gel du sol et au changement climatique global. flicting, interests can be viewed as an illustration of Le but fondamental de la géomorphologie est l’élabora- M. Church’s (2005) recent observation of the drift of geo- tion de modèles d’évolution des paysages. Cependant, la morphology away from geography. Probably, the situation nature de l’évolution des paysages sous conditions froides et also reflects the normal ecological development of any sci- non englacées reste largement négligée en réalité. Une telle entific discipline that sees it invading new territory tâche est certainement ambitieuse. Pourtant, elle doit être opportunistically, dying back when the prevailing paradigm entreprise car actuellement les progrès les plus substantiels appears stale, and dying out when it has been exhausted. At nous viennent de la géocryologie et des sciences du Quater- the disciplinary scale these steps seem traumatic, but for sci- naire plutôt que de la géomorphologie périglaciaire. Aussi ence overall they invariably represent healthy growth. suggérons-nous que la géomorphologie périglaciaire doive The second issue is the origin and development of se libérer de ses fondements morphoclimatiques et devienne periglacial landscapes as traditionally defined. Here, the une discipline fondée sur l’étude des processus. Ainsi, en tant debate is not among disciplines, but rather reflects matura- que sous-discipline dédiée à l’étude de processus, la géo- tion within periglacial geomorphology itself. It is seen in morphologie périglaciaire serait plus rigoureusement définie H.M. French’s (2000) discussion of the nature and variety of et contribuerait à la connaissance des régions froides. contemporary periglacial environments and M-F. André’s En conclusion, nous pensons que le noyau de la géomor- (2003) scrutiny of the possible temporal development within phologie périglaciaire contemporaine devrait comprendre periglacial regimes. These concerns are ultimately interwo- l’étude de la glace du sol, à la fois pérenne et saisonnière, ven with the first issue because, whether the matter is ainsi que le développement des modelés qui en résultent. considered in its spatial and/or temporal form, evaluation Ces questions sont au cœur de la sous-discipline et doivent must embrace a functional definition of what is, and what is fournir une base scientifique solide sur laquelle ancrer la not, periglacial geomorphology.

166 Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174 The changing nature of periglacial geomorphology

In an attempt to address these problems, our paper identi- studies and geocryology are usually undertaken within fies current trends in periglacial geomorphology and dis- engineering and science contexts. cusses the disciplinary considerations that are involved. We focus upon the fact that (i) geocryology is now a recognized The changing nature of geomorphology member of the cold-climate earth-science disciplines, (ii) and Quaternary science the nature of geomorphology and Quaternary science is changing, and (iii) traditional periglacial studies As M. Church (2005) laments, geographical geomorpho- are in decline. logists are slowly losing their discipline to geophysicists and to programs located in refocused Earth sciences depart- Disciplinary considerations ments. This trend, ongoing since the 1960s, came first as the result of quantification, then of increasingly rigorous pro- The growth of geocryology cess studies founded on Newtonian principles, and finally, as the inevitable product of the all-embracing theory of plate The early development of geocryology occurred in Rus- tectonics which ultimately led geophysicists to be interested sia where, as early as 1924, an Institute of Permafrost was in topics previously held to be largely geomorphological. established at Yakutsk, central Siberia, by the Soviet Aca- M. Church (2005) goes even further to suggest that the demy of Sciences. By 1940, the first edition of what was to Newtonian approach of geographic geomorphologists is become a standard text in the Soviet Union, Obshcheye actually a shriven one in comparison to that undertaken by Merzlotovedeniya (General Permafrostology) was publi- those entering geomorphology from other disciplines. shed (Sumgin et al., 1940) and by the mid 1960s the first of Within periglacial geomorphology this approach produced a many undergraduate textbooks had emerged. By compari- sub-discipline focused largely upon quantitative process stu- son, North American geocryology is of relatively recent dies. By the early 1990s process measurement had clearly origin with interest in permafrost only becoming important demonstrated not only the serious shortcomings inherent to during and immediately after the Second World War (Mul- traditional versions of periglacial processes (and especially ler, 1943) and geocryology emerging initially from within of processes) but also that the azonal processes (Lachenbruch, 1957). In , geocryology operating in cold environments, such as running water, developed even more recently than North America but in a wind, waves, and gravity-controlled mass movements, dif- Soviet-style context (Academia Sinica, 1975). Expansion of fer little, if at all, from similar processes in other climatic permafrost studies into alpine regions is also relatively new environments. As such, the study of these processes rightly and has centred largely upon rock glaciers and the creep and constitutes a sub-set of mainstream process geomorphology stability of frozen rock masses, especially in Europe (Hae- because they vary only in their magnitude and frequency berli, 1985). rather than in any so-called ‘unique’ manner. For several reasons, the relations between geocryology Thus, it might appear that a distinct sub-branch of geo- and geomorphology are complex. First, for many years, morphology devoted specifically to the operation of permafrost studies were conducted in North America and ‘mainstream’ processes in cold is now unnecessary. the Soviet Union not only in relative isolation to each For example, in the introduction to a volume of collected other, but also in isolation from mainstream (geographical) papers recently published, H.M. French (2004) has explicit- geomorphology. Second, both Russian and Chinese ly characterized modern periglacial geomorphology as a geocryology adopt a holistic, all-encompassing approach branch of geocryology, leaving the common azonal pro- whereas North American permafrost studies are usually cesses associated with running water and wind action to characterized as being either ‘science’ or ‘engineering’. companion volumes in the series. However, this operational Thus, there is no North American text that equals the definition is not without criticism because it neglects the breadth and depth presented by the most recent Russian important and unusual role played by snow in controlling and Chinese texts, General Geocryology (Yershov, 1990) ground temperatures and in influencing soil moisture condi- and Geocryology in China (Zhou Youwu et al., 2000). tions and slope runoff regimes. It also fails to consider the Third, permafrost studies sit awkwardly between the disci- enhanced action of wind in high latitudes (Seppälä, 2004) plines of and geography. For example, in North and the role of sea ice in Arctic and Antarctic coastal pro- America, periglacial geomorphology is taught usually in cesses. Furthermore, it is telling indeed that no papers geography departments while permafrost is within geology, dealing with the operation of these azonal processes in cold geophysics or Earth sciences departments. In Europe, climates were included in the paper selections made by the many geography departments exist in Faculties of Science, editors of the other volumes. An earlier concern with such others in Faculties of Arts. Fractionation also occurs in issues led C.E. Thorn (1978) to emphasize the role of snow Russia, where, at Moscow State University, a Department as a unifying concept within periglacial geomorphology and of Cryolithology exists within the Faculty of Geography subsequently (Thorn, 1992) to attempt a definition of per- while a Department of Geocryology exists within the Fac- iglacial geomorphology in purely process terms. Finally, the ulty of Geology. Finally, Chinese universities exhibit recent trend that recognizes the importance of ‘non-perigla- comparable divisions with periglacial geomorphology cial’ contributions to cold region landscape development found within departments of geography while permafrost (André, 1999) serves both to further undermine traditional

Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174 167 Hugh French and Colin E. Thorn

climatic geomorphology precepts while simultaneously not only frost action but also other mechanisms such as ther- sharpening the question ‘what precisely is periglacial geo- mal stress and hydration shattering. These processes were morphology?’ D. Barsch (1993) took C.E. Thorn to task for not unknown and are not unique to periglacial environ- producing an overly narrow definition of periglacial geo- ments. In recent years, K. Hall (1997) has taken the lead in morphology that would create a sub-discipline akin to promoting the role of thermal stress as a mechanism of rock glacial, eolian, or fluvial geomorphology. The counter to disintegration in cold climates. Today, it is increasingly D. Barsch’s perspective is clear. If contemporary resear- understood that a variety of chemical, biochemical, physical chers in cold regions find many important contributing and mechanical processes operate, and often interact, in cold factors to be ‘non-periglacial’ in the traditional sense, then it regions (Pope et al., 1995; Dixon et al., 2002; Hall et al., makes infinite sense to identify a suite of periglacial pro- 2002; Etienne, 2002). cesses, but to refrain from calling cold regions ‘periglacial’ The second weakness was that insufficient consideration out of recognition of their hybrid genesis. was given to, first, the influence of lithology upon so-called The nature of Quaternary science in the last 50 years has ‘periglacial’ landscapes and, second, the variability, duration also changed due largely to the expansion and proliferation and efficacy of cold-climate conditions. This second weak- of sophisticated dating techniques. Today, studies involving ness is still largely neglected in most regional periglacial paleo-environmental and paleo-geographical reconstruction studies and in standard periglacial texts (Washburn, 1980; no longer rely solely upon descriptions of the morphologi- French 1996). The possible exception is the Antarctic cal and stratigraphic evidence of cold-climate conditions periglacial literature which, by necessity, focuses upon the that was typical in traditional Pleistocene periglacial studies. bedrock terrain exposed in the relatively small areas that are Instead, a broader range of features and organisms is now ice and vegetation-free. In hindsight, it can be seen that the utilized. For example, the study of ground ice, in the form process assumptions underpinning traditional Pleistocene of thaw unconformities, truncated ice bodies, and cryo- periglacial geomorphology were erroneous. Not only were structures can now be used to infer previous freezing and the necessary observational data lacking but also the con- thawing events, and permafrost history (Burn, 1997; Mur- ceptual or theoretical framework was flawed. While such ton and French, 1994; Melnikov and Spesitvsev, 2000; judgement may seem harsh, virtually all science ultimately Murton et al., 2004; 2005). Thus, traditional Pleistocene falls victim to such an evaluation. periglacial geomorphology has been largely replaced by the appropriate application of Quaternary science and cryostra- Interactions and overlap tigraphic studies. We believe that modern periglacial geomorphology should The weakness of traditional periglacial be viewed as a process sub-discipline of geomorphology that geomorphology is distinct from both geocryology and Quaternary science. It should be similar to the better known process sub-disciplines The growth of periglacial geomorphology occurred main- of, for example, fluvial, hillslope, eolian, glacial, coastal and ly in Europe in the two decades following 1945 (French, karst geomorphology. For example, in the case of karst geo- 2003). Most dominant were Pleistocene studies dealing with morphology, the central process is that of solution, in the paleo-geographic reconstruction in the mid-latitudes. The case of hillslopes it is gravity. In the case of periglacial geo- ‘periglacial fever’ of the time (André, 2003) fostered a morphology, the key processes are those associated with sea- trendy sub-discipline of climatic geomorphology, but one sonal and perennial frost. So, while geocryologists prefer to whose underlying tenets were dubious. Two widely-held focus upon the thermal implications of the terrain and the assumptions or interpretations fuelled this intense disci- presence of ice within the ground, periglacial geomorpholo- plinary growth. First was the uncritical acceptance of the gists prefer to emphasize the associated landforms and their importance of mechanical (frost) weathering in cold regions growth and modification through time. Obviously, there is and of rapid cold-climate landscape modification. In considerable overlap between the two. For example, the re- Europe, a sequence of widely-regarded texts by J. Tricart cognition of anti-syngenetic wedges on hillslopes (Mackay, and A. Cailleux (1967) and J.Tricart (1970) promoted these 1990, 1995) is a classic illustration of the overlap between ideas. At the same time, an IGU Periglacial Commission landscape evolution (i.e. geomorphology) and permafrost- under the leadership of J. Dylik was especially active related processes (i.e. geocryology). Likewise, there is an between 1952 and 1972 and an international journal, Biule- even more complex overlap between periglacial geomor- tyn Peryglacjalny, was started in Lódz, Poland. phology and Quaternary science because this occurs via geo- As early as the mid 1970s, this first assumption was being cryology. This is best illustrated by the geocryological sub- seriously challenged. Initially, air climates were shown to be discipline of cryostratigraphy, where ice and sand wedges, poor indicators of the relevant ground climates. Ground truncated ice bodies, thaw unconformities and the nature of observations in both high latitudes and at high elevation cryostructures and cryotextures allow one to infer past per- (Thorn and Hall, 1980) failed to record the numerous freeze- mafrost history. It is now common to see cryostratigraphy thaw cycles that were thought responsible, a shortcoming applied to problems within the more traditional fields of both also compounded by a lack of moisture in many situations. geomorphology and Quaternary science (Burn, 1997; Shur It was quickly realized that mechanical weathering involved and Jorgenson, 1998; Murton et al., 2005).

168 Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174 The changing nature of periglacial geomorphology

We also believe that permafrost, being a purely thermal to understanding permafrost history, to the interpretation of concept, cannot be the only diagnostic criterion for permafrost-related landforms, to describing periglacial sedi- periglacial geomorphology. This is because geomorphology ments, and when one undertakes inferences as to past is concerned primarily with landforms and periglacial land- climates or Pleistocene paleo-geographic reconstruction. forms that are not primarily controlled by ground A number of frost action processes operate in the near- temperature alone. Instead, the broad features of cold-cli- surface layer subject to seasonal thaw (the active layer), the mate terrain are largely influenced by lithological near-surface permafrost located above the depth of zero variability, the nature and distribution of any ice contained annual amplitude, and the zone of seasonal freezing and within the bedrock or surficial materials, and the action of thawing in non-permafrost regions. These processes include azonal processes. A classic example is provided by the struc- moisture migration within frozen ground and numerous turally-controlled landscape of Ellef Ringnes Island in the processes associated with repeated freezing and thawing Canadian High Arctic that is currently being fashioned by (e.g. soil churning or cryoturbation, frost creep, solifluction running water, wind and frost (St-Onge, 1965). On the other and gelifluction, the upfreezing of stones and particle-size hand, permafrost, ground ice, and the thawing and refreez- sorting). Many of these processes give rise to distinct small- ing of permafrost, must be central concepts in periglacial scale forms of patterned ground that complement the geomorphology in the same way that hillslopes and running large-scale polygons that result from thermal-contraction water are central components to geomorphology at large. It cracking. follows therefore, that there is some overlap between Slopes that are frozen, or are thawing, experience rela- periglacial geomorphology and geocryology. tively unusual conditions associated with pore-water expul- Periglacial geomorphology must also be viewed as one of sion and thaw consolidation. These can promote rapid mass the group of sciences that concern the cryosphere. The latter failures that are relatively distinct from other failures that is defined as that part of the Earth’s crust, hydrosphere and might occur on slopes that evolve under non-frozen condi- atmosphere subject to temperatures below 0 ºC for at least tions in either temperate or warm climates. It is in the study part of the year. Obviously, the cryolithosphere (i.e. peren- of all these processes, either in the field, the laboratory, or nially and seasonally cryotic ground) is central, and the by modeling and simulation, that periglacial geomorpholo- cryohydrosphere (i.e. snow cover, glaciers, and river, lake gy has become a sub-branch of the broader discipline of and sea ice) slightly less central, to periglacial geomorphol- geocryology. An understanding of all these processes con- ogy. Periglacial geomorphology has a special interest in the stitutes the essential underpinning to modern periglacial ge- thawing and freezing of ground. A schematic summary of omorphology. the interactions between geomorphology, periglacial geo- Some processes, not necessarily restricted to environ- morphology, geocryology and the cryospheric sciences ments traditionally labelled periglacial, are important in cold appears in Figure 1. non-glacial regions on account of either their high magni- tude or frequency, or their widespread occurrence. These The scope of periglacial often centre upon the seasonal freezing of soil and bedrock, geomorphology including the disintegration of exposed rock by either mechanical (frost) wedging or the poorly understood com- Here, we outline what we perceive to be the salient com- plex of physical, biochemical or physico-chemical processes ponents of modern periglacial geomorphology. We do so in that are sometimes referred to as ‘cryotic’. Slightly better the following sequence: i) the nature of permafrost-related understood are the azonal processes associated with running processes, ground ice, and associated landforms; ii) the water, wind, snow, and waves. These may assume distinctive azonal processes that operate in cold non-glacial environ- characteristics under traditionally-defined periglacial condi- ments; iii) the ice-marginal (proglacial) environment and tions but do not require either an excessively cold climate or associated paraglacial transitions; iv) the alpine (montane) a peripheral ice-marginal location for their effective opera- environment; v) Pleistocene cold-climate paleo-environ- tion. Nevertheless, their study complements many other mental reconstructions; vi) environmental and geotechnical aspects of geomorphology, permits comparison and, as a studies associated with frozen ground, ground freezing and result, better comprehension of the process involved. global . Some azonal processes are of special interest to Processes that are clearly unique to periglacial environ- periglacial geomorphologists. For example, the role of snow ments relate to ground freezing. These include the growth of as an important source of moisture must be highlighted segregated ice and associated frost heaving, the formation of because, by definition, most cold non-glacial regions are permafrost, the development of cryostructures and cryotex- also arid. Snow is also important as an abrasive agent at low tures in perennially-frozen soil and/or rock, the occurrence temperatures and acts as a local source of soil moisture and of thermal-contraction cracking, and the growth of frost hence ground heaving and frost action. However, the normal mounds of various sorts. The stratigraphic study of frozen effects of aridity in cold environments are lessened by low earth material, especially the amount, distribution, and ori- evaporation and/or evapotranspiration rates. For example, gin of the ice that is contained within it, constitutes the the boreal forest is not usually regarded as typically geocryological sub-discipline of cryolithology. Although not ‘periglacial’ in nature, yet it experiences cold-climate condi- strictly geomorphological in nature, cryolithology is relevant tions and is commonly underlain by permafrost. Wind

Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174 169 Hugh French and Colin E. Thorn

AB Periglacial Geomorphology

Engineering

Human Physical Geo- Geography Geography morphology Geocryology

Quaternary Geology- C Science Geophysics

Periglacial Geomorphology

Snow

Seasonal Sea Frost Azonal Cold Region Ice Geomorphology Perennial Processes Frost

Glaciers

Geocryology

Fig. 1 – Schematic diagram illustrating the disciplinary interactions and overlap of periglacial geomorphology. A: relations between , geomorphology and periglacial geomorphology. B: relations between periglacial geomorphology and geocryology and their interactions with Quaternary science and other natural sciences. C: periglacial geomorphology and its overlap with certain cryospheric sciences. Note: All disciplinary boundaries are porous and those marked by dashed lines are particularly so. For example, in C, the broken line between perennial and seasonal frost indicates that periglacial geomorphology extends into geocryology and that geocryology extends, but to a more limited extent, onto periglacial geomorphology. Similarly, the two unbroken lines between seasonal frost and snow, and bet- ween perennial frost and glaciers, must also be regarded as porous boundaries. Fig. 1 – Diagramme illustrant les interactions disciplinaires et les chevauchements au sein de la géomorphologie périglaciaire. A: la relation entre géographie physique, géomorphologie et géomorphologie périglaciaire. B : la relation entre la géomorphologie périglaciaire et la géocryologie et leurs interactions avec les sciences du Quaternaire et d’autres sciences naturelles. C : la géomorphologie périglaciai- re et ses chevauchements avec certaines sciences de la cryosphère. Remarques : toutes les frontières disciplinaires sont poreuses, en particulier celles soulignées par un trait en pointillés. Par exemple, en C, la ligne brisée entre le gel saisonnier et le gel permanent indique que la géomorphologie périglaciaire s’étend dans le domaine de la géocryologie et que cette dernière s’étend également, mais à un moindre degré, dans la géomorphologie périglaciaire. Pareillement, les deux lignes continues entre la neige et le gel saisonnier et entre le gel per- manent et les glaciers doivent être considérées comme des frontières poreuses.

action is also of interest to periglacial geomorphology The study of all these processes constitute a part of geo- because the limited vegetation north of the tree line in high- morphology, irrespective of the direction in which er latitudes, and above the timberline in montane geomorphology is currently moving. Yet an understanding environments, allows wind to have important erosional and of such processes is also essential to an understanding of transportational effects (Seppälä, 2004). Finally, sea ice and cold region landscapes. river ice (‘ice-infested waters’), by restricting the time dura- While the majority of periglacial environments do not tion of wave action and/or open channel flow, and through demand an ice-marginal location for their cold-climate cha- ice-pushing, ice-jams and other impacts, can produce rela- racteristics, those areas that are immediately adjacent to tively distinct coastal, river channel and lake conditions. major ice sheets and/or glaciers experience cold-climate

170 Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174 The changing nature of periglacial geomorphology conditions that fluctuate in time and space. In the early (ACD) initiative of the International Arctic Science Com- beginnings of periglacial geomorphology, the ice-marginal mittee (IASC). We can think of many other examples environments of and were regarded as where periglacial geomorphology should play a useful so- the typical high-latitude analogs for the periglacial condi- cietal role. tions that probably existed in the mid-latitudes of Europe during the cold periods of the Pleistocene. While this is The ultimate goal of periglacial clearly not the case, and Lozinzki’s so-called ‘periglacial geomorphology realm’ finds no modern counterpart, ice-marginal environ- ments, by virtue of their proximity to glaciers and the A major aim of geomorphology is to create models of cold-climate conditions that they experience, provide an ins- landscape evolution. Such models embody assumptions as tructive example of specific and specialized periglacial to the processes involved, their speed of operation and their terrain undergoing paraglacial transition. associated rates of , transport and deposition, and the Like the proglacial environment, the alpine environments manner in which surface morphology changes through time. that occur above timberline were initially regarded as typi- While various cyclic and non-cyclic (equilibrium) models cal ‘periglacial’ environments. However, they also represent characterize the history of geomorphology, only the des- site-specific and specialized terrains in which steep slopes criptive and non-quantitative cyclic models of Boch and and gravity-controlled processes play a critical role together Krashnov (1943), Hopkins (1949), and Peltier (1950) expli- with cold-climate processes aided by wind and snow. As citly apply to cold-climate terrain. The reality is that the na- such, they are also instructive for periglacial geomorpholo- ture of landscape evolution under cold non-glacial condi- gy. Many recent studies focus upon the occurrence of tions remains largely neglected in cold region geomorpho- mountain permafrost, the controls over its distribution, the logy. The task is daunting but notable exceptions already creep of ice-rich debris (rock glaciers), and the instability of exist such as the application of thaw-consolidation theory to frozen rock masses as bedrock temperatures warm. These creep and deformation of permafrost (McRoberts and Mor- examples of alpine geomorphology are equally an integral genstern, 1974; Morgenstern, 1985), the evolution and sta- component of geocryology. bility of thawing slopes (Harris and Lewkowicz, 2000; Da- The growth of cryostratigraphy, together with the increa- vies et al., 2001), and recent laboratory attempts that simu- sing sophistication of Quaternary science, means that late solifluction (Harris et al., 2001). traditional Pleistocene periglacial paleo-geographic studies One must reluctantly conclude that much geographically- have become obsolete. Morphological and stratigraphic evi- based periglacial geomorphology lacks a rigorous theoreti- dence must now be interpreted within the context of a more cal base. It remains characterized by flawed thinking that realistic appreciation of permafrost and the climatic and reflects its qualitative and climatic heritage. Unless a re- other controls over related cold-climate processes, augmen- search agenda that rectifies this weakness is put in place, ted by isotopic and other dating techniques. In other words, so-called ‘periglacial geomorphology’, as presently confi- advances in cryostratigraphy and Quaternary science have gured, runs the risk of falling by the wayside. Currently, now encroached upon, and largely superseded, the traditio- more progress is being made in geocryology, Quaternary nal Pleistocene and climatically-based ‘periglacial’ studies. science, and geomorphology, even as the latter is losing its All disciplines thrive best when they have societal rele- geographical base to ‘reductionist’ science, than in perigla- vance, and periglacial geomorphology is no exception. cial geomorphology because these disciplines are seen to be Here, the opportunities are many and potential growth is more ‘scientific’ and to have more pragmatic and pressing large. For example, the development and utilization of the research agendas. natural resources of the northern regions of North America We argue, therefore, that a strong periglacial geomorpho- and Eurasia will require sound engineering and infrastruc- logy must be firmly process-based. It must clearly reject its ture design. Man-induced thermokarst and other distur- climatic geomorphology underpinnings. For example, so- bances need to be minimized through management and reg- called ‘periglacial regions’ exist only as cold-climate zones ulatory practice. The fact that global climate change may in which seasonal and perennial frost, snow and azonal pro- first become apparent at high latitudes, and that permafrost cesses operate. There is no ‘core’, or typical, or definitive can be regarded as a temperature archive, both in terms of periglacial region, and Lozinski’s ‘periglacial realm’ is a lar- past and future temperatures, has promoted recent monitor- gely academic concept that does not exist today. Instead, it ing studies such as Circumpolar Active Layer Monitoring is more realistic to think in terms of areas of the world that (CALM) and Permafrost and Climate in Europe (PACE). In are of interest to geomorphologists wishing to understand alpine regions, the increased utilization of upper slopes for cold-climate, but not glacial, landscapes. While most of recreation activities, and the potential for slope instability these areas contain permafrost as a central element, there are consequent upon permafrost thaw, has promoted the study no clear-cut boundaries. In short, periglacial geomorpholo- of mountain permafrost. Likewise, the thinning of sea ice gy needs to sharpen its scientific rigor before it is either and the potential expansion of arctic shipping lanes has consumed or by-passed, as the case may be, by either geo- prompted international attention towards cold-climate cryology, Quaternary science or the other sub-disciplines of coasts, as illustrated by the Arctic Coastal Dynamics geomorphology.

Géomorphologie : relief, processus, environnement, 2006, n° 3, p. 165-174 171 Hugh French and Colin E. Thorn

Conclusion lation 242, Division of Building Research, National Research Council of Canada, Canada Institute for Scientific and Technical We conclude that the core of modern periglacial geomor- Information, 146 p.) phology should concern the study of both perennial and André M-F. (1999) – La livrée périglaciaire des paysages polaires: seasonal ground ice and related landscape development. l’arbre qui cache la forêt ? The periglacial scenery of polar areas: These subjects lie at the heart of the discipline and must sup- a smoke-screen? Géomorphologie : relief, processus, environ- ply the solid scientific base upon which periglacial nement, 3, 231-252. geomorphology relies for its credibility. Such a perspective André M-F. (2003) – Do periglacial landscapes evolve under makes permafrost a central, but not defining, element of periglacial conditions? Geomorphology, 52, 149-164. periglacial geomorphology. Therefore, much that constitutes Barsch D. 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