PW06_ copertina_R_OK C August 20-28,2004 Florence -Italy

Field Trip Guide Book - PW06 Post-Congress I. Bruchev, G.Frangov, N.Dobrev, A.Lakov Conveners: MONUMENTS AND ARCHAEOLOGICAL OF MAJORNATURAL GEOTECHNICAL HAZARDS GEOLOGICAL AND 32 Volume n°6-fromP55toPW06 GEOLOGICAL CONGRESS nd INTERNATIONAL PW06 21-06-2004, 11:15:54 The scientific content of this guide is under the total responsibility of the Authors

Published by: APAT – Italian Agency for the Environmental Protection and Technical Services - Via Vitaliano Brancati, 48 - 00144 Roma - Italy

Series Editors: Luca Guerrieri, Irene Rischia and Leonello Serva (APAT, Roma)

English Desk-copy Editors: Paul Mazza (Università di Firenze), Jessica Ann Thonn (Università di Firenze), Nathalie Marléne Adams (Università di Firenze), Miriam Friedman (Università di Firenze), Kate Eadie (Freelance indipendent professional)

Field Trip Committee: Leonello Serva (APAT, Roma), Alessandro Michetti (Università dell’Insubria, Como), Giulio Pavia (Università di Torino), Raffaele Pignone (Servizio Geologico Regione Emilia-Romagna, Bologna) and Riccardo Polino (CNR, Torino)

Acknowledgments: The 32nd IGC Organizing Committee is grateful to Roberto Pompili and Elisa Brustia (APAT, Roma) for their collaboration in editing.

Graphic project: Full snc - Firenze

Layout and press: Lito Terrazzi srl - Firenze

PW06_ copertina_R_OK D 3-06-2004, 10:24:30 Volume n° 6 - from P55 to PW06

32nd INTERNATIONAL GEOLOGICAL CONGRESS

GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS

AUTHORS: I. Bruchev, G. Frangov, N. Dobrev, A. Lakov (Geological Institute, Bulgarian Academy of Sciences, Sofi a - )

Florence - Italy August 20-28, 2004

Post-Congress PW06

PW06_R_OK A 3-06-2004, 10:27:44 Front Cover: Rock relief of the Horseman

PW06_R_OK B 3-06-2004, 10:27:46 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

Conveners: I. Bruchev, G. Frangov, N. Dobrev, A. Lakov

This field workshop will start at the biggest city in oldest gold treasure (~4000 years B.C.) was found in NE Bulgaria – Varna (Figure 1). The total field trip the city of Varna. distance is estimated at about 800 km. Roads are in good condition. The program will take place over 3 The main goal of the field trip is to present some days. Attention will be paid to the natural (seismicity, selected monuments of culture from different erosion, landslides, and rockfalls) and human- historical periods; the geological conditions in which induced hazards endangering important natural and they are located; the consequences caused on them by archeological monuments. damaging geological processes (landslides, rockfalls, earthquakes, weathering), and to look at the measures taken to prevent such damage. Program Arrival day, 29.08.2004: Arrival of participants The motives for choosing the suggested route are: (max 30 persons) at the airport of Varna and accommodation in the town of Varna, Bulgaria. • In the northeastern part of Bulgaria there are situated historical, cultural, and natural First day, 30.08.2004: Trip by bus between Varna and monuments included in the World Heritage List . The following sites will be visited: of UNESCO - the Madara horseman, the Ivanovo the archeological remains of the fi rst old Bulgarian rock-hewn churches, the Sveshtari Thracian capital , and the Madara Horseman rock relief tumuli, and the natural reserve - Srebarna Lake. monument, which has been affected by earthquakes, • There are many unique geological and historical weathering, and slope processes. Accommo dation in places of interest such as: Pobitite kamani (the Veliko Tarnovo. Upright stones) near Varna, the rock scarps in the Madara and Shoumen plateaus, and Second day, 31.08.2004: Trip by bus between Veliko Veliko Tarnovo and its beautiful landscapes; Tarnovo and Rousse. In the morning the participants there are also mediaeval monuments, such as will see the sights of the mediaeval capital, Veliko the Transfiguration Monastery in the valley of Turnovo, and the nearby Transfi guration Monastery, Yantra River and the city of Rousse; and the affected by earthquakes and slope processes. In problems with loess collapsibility, different the afternoon, Ivanovo rock-hewn churches near types of lay shapes, river valleys, and geological the mediaeval town of Cherven, along the river profiles. Rousenski Lom, which are threatened by natural • Most of the monuments are placed in complex hazards, will be observed. Accommodation in geological conditions. They have suffered from Rousse. collapses and deformations at different levels through geological hazardous processes. Some Third day, 01.09.2004: Trip by bus between Rousse of them are in critical condition. For example, and Varna. The fi rst stop during the trip is the Thracian Tomb at Sveshtari. The next observation locality is the Aladja Rock Monastery, near the city of Varna. The last stop is Chirakman Cape, affected by strong earthquakes in the 3rd Century BC. Accommodation in Varna.

Departure day, 02.09.2004: Departure from Varna Airport. P55 to PW06 n° 6 - from Volume

Introduction Covering a central position in the Balkan Peninsula, and being a crossroad between three continents, the territory of Bulgaria is marked by vestiges and monuments from ancient times till nowadays. The Figure 1 - Location map

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov limestones, K1;6-marlsandsandstones,K1 1 -claysandsands,Qh;2loess,Qp;3limestonewithN1s;4clays,sandssandstones,N1;5 Figure 2-GeologicalMapofNEBulgaria North BulgarianSwellinginthewesternpartand two biggerstructuresoftheMoesianplatformare structures nearthe Veliko Turnovo area. At thispart, platform andpartiallythroughtheFore-Balkan folded The field itinerarypassesthroughtheMoesiantectonic Regional geologicsettings Bulgariawas establishedinthisregion morethan • Someprecautionshave beenapplied,aftermuch • natural andman-madehazardriskonhist During thefi conservation andstabilizationof theaffec ted sites. experience, andideasonthepossibilitiesfor aim ofthediscussionwillbetoshareinformation, and culturalheritagesiteswilltake place. The main and rockfalls duringthe20 destroyed fourtimesbyearthquakes, landslides the Transfiguration Monastery hasbeen sacred places,castles,etc. situated there. There arealsomany monasteries, (Pliska, Preslav, and Veliko Tarnovo), are 1300 yearsago,andthreeoffive ofitscapitals most valuable. discussion, toreducethegeologicalrisksfor eldtrip,discussiononthemitigationof th centuryalone. o rical area around Veliko Turnovo. The scarpsarestrongly Dobroudja, Provadia, andShoumenplateaus,the between 0and500m.Karstedlimestonesbuild the alluvial terraces. The altitudesoftheregion vary plateaus withsteepscarps,andriver valleys with structure, arehillyintheinterfluvialareas,with The reliefforms,whicharetypicaloftheplatform the BlackSea. muds intheplungedterracesofriver thatrunsinto terraces, andmixed alluvial-marinesands,clays,and colluvium ontheslopes,alluviumalongriver deposits cover thehigherpartsof relief,with part ofthe Varna depression. The Quaternaryloess marls, aragonitites,clays,sands)fill theeastern Tertiary andQuaternarysediments(sandstones, alluvial depositsintheriver terraces(Figure2). are covered byloessattheinterfluvial massifs,andby limestones, marls,andsandstonesarerevealed. They western sectionofthearea,mainlyLower Creta by faults, withdepthsofmorethan3km.Inthe the active tectonics,they aredivided intoblocks build thesestructurestodeeplevels. As aresultof the Varna Depressiontotheeast.Sedimentstrata 3-06-2004, 10:28:05 ceous GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

Figure 3 - Structure of the geological hazards in NE Bulgaria vertical, and usually reach 100 meters high. They limestones. Along the peripheral parts of the positive form canyon-like valleys that are characteristic for relief’s units, many steep gullies have developed on Dobroudja’s landscape. River and the Black the slopes. At the Varna depression, the geomechanical Sea are important hydrographical units, which border models are more complicated, due to the formation the area in the northern and eastern parts. Few lakes of alternations between hard (limestones, sandstones) have formed. The most important of them is Srebarna and plastic (marls) rocks. They build a complex Lake, which is a biological reserve. Varna Lake system of rocks with contrasting physical-mechanical is a very large seaside lake, and it is also used for properties. commercial purposes. The landslide pond Tuzlata (eastwards from ) is used for rehabilitation Geological hazardous processes in NE Bulgaria therapy due to the healing properties of its mud. complicate the sustainable development of this territory. They endanger and affect urban and rural The Engineering Geological conditions are areas, seaside resorts, economic activities, etc. They predetermined by the distribution of sedimentary affect the cultural and historical monuments of P55 to PW06 n° 6 - from Volume rocks on the surface. The sedimentary rocks are very various ages. variable in composition and physical-mechanical properties (Kamenov et al., 1963). Horizontal layers, The structure of the geological hazards involves with a slight inclination to the east, determine the many and variable destructive geological processes geomechanical model of this area. For the interfluvial (Figure 3). Seismic intensities of the region are massifs and the plateaus, there is the characteristic from 7 to 9 degrees MSK-64. The most important availability of loess lying over marls and karsted earthquake sources are located in the areas of Shabla-

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov ed., 1994). recent infrastructure,andtheenvironment (Broutchev, consequences onthenaturalandhistoricalheritage, human processeshave hadextensive detrimental water saturationandloading. A large number of on theplateausandterracesarecollapsibleunder Transfiguration Monastery, etc).Eolicloessdeposits Aladja Monastery, Ivanovo rock-hewn churches, arrange thesacredplaces(nearMadaraHorseman, and therockscarps.Suchkarstformswereusedto riverbank. The karstiswidespreadontheplateaus well astheunilateralerosiondestroys therightDanube changed theBlackSeashorelinetowestdirection,as the Yantra River, KamchiaRiver etc.Sea erosionhas shoreline, Danuberiverbank, andthevalley banksof and rockfalls have greatlyaffected theBlackSea , Veliko Turnovo, andDoulovo. Landslides remains ofthefirst oldBulgariancapitalPlis follow ing siteswillbevisited:thearcheo Trip bybus between Varna and Veliko Tar no vo. The DAY 1 DAY 1 Figure 4- View oftheUprightstones ka, and logi cal slope pro has beenaffec ted byearth quakes, weatheringand the MadaraHorse part ofthe Varna columnsisonthesiteof“Pobitite described intheliterature(Figure5). The famous phenomenon, anddon’t have acompleteanalogue The stonesarearemarkablenaturalandgeological geological sectionhasathicknessof40-45m. by shallow-marine limestonelayers. The whole there are5levels ofcolumns,whichareseparated host rocksareloosesandsandsilts.Insomeplaces, groups, whichareexposed over anareaof70km Varna columns. The columnscanbedivided into5 The “Pobititekamuni”siteisapartfromtheso-called Bulgarian, thenamemeans“Uprightstones”. of nationalandinternationaltourism.(Figure4)In West of Varna City, anditisavery interestingobject The “Pobititekamani”siteislocatedabout20km Pobitite Kamani cesses. Accommo man rockreliefmonument,which

dation in Veliko Tarnovo. 3-06-2004, 10:28:09 2 . The GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

(Figure 6). The city comprised of an inner and an outer part, and the area was about 23 km2. A defense embankment surrounded the city. It was 21 km long, with a fortress wall 2.9 km long and 8-10 m high. Inside the city, a great number of houses, stone palaces, and churches were built. The Big Basilica was one of the most impressive religious structures built on the Balkan Peninsula at that time (Figure 7).

The inner town had an area of 0.5 km2, and was rectangular in shape, and had about 12 m high fortress walls. In the inner town, there was situated the Big Palace (or ’s palace), which had its own defensive walls and towers.

In 811, the town was reduced to ashes by the Byzantine army of the emperor Nicephorus I. After that, Preslav was declared capital of Bulgaria (893), and Pliska fell into decay.

The terrain where Pliska was built is rather dry, and has the relief of loess plain. The relief is flat, with a slight inclination to the south. The geology is represented by a topsoil layer (1 m thick); a carbonate Figure 5 - Geological profile at the Upright Stones soil layer (0.5 m thick), and loess (thick between 2 (after Nacev & Nacev, 2001). and 9 m) (Evstatiev et al. 1983). kamani”. It is included in the UNESCO program for the preservation and protection of scientific According to the older descriptions, a part of the geological heritage. ancient capital of Pliska was founded on marshland area. The main hazards are the high seismicity (8th The “Pobitite kamani” (the Varna columns) have degree MSK) and loess collapsibility (Figure 8). been studied for a period of 170 years. There are Various approaches to strengthen the soil were many hypotheses on their origin, and more than 60 applied during the construction of the city. The publications. Some of these hypotheses are very builders were aware that they had to cope with old and are not supported by facts. They have only weak soil, and therefore they took measures to historical significance. At present, it is generally prepare it in advance before starting to build the accepted that there is no viable hypothesis or foundations. They applied the following methods for explanation. that purpose: Some of the most interesting theories about the origin of the columns are as follows: (1) remains of castles 1. The building of a cushion of compacted soil 0.2- or temples; (2) weathered sandstone remains; (3) 0.4 m deep, on top of which a layer of mortar concretions; (4) infiltration stalactites; (5) coral reefs; was poured; (6) stone forest or trees; (7) stone cavities of trees; (8) 2. The building of a substrate that consisted of a wooden raft with mortar poured on top of it; algal build-ups; (9) algal annelida bioherms etc.

3. The compaction of the bottom of a ditch made P55 to PW06 n° 6 - from Volume for the foundation of wooden piles, stuck in the Stop 1.1: soil: 0.6-0.8 m long, with a diameter of 0.08-0.10 Pliska m; The ruins of the ancient city of Pliska are situated 3 4. The construction of a substrate, consisting of a km northward from today’s Pliska village. wooden raft on piles, with mortar poured onto Pliska was the first capital (from 681 till 893) of the them. first Bulgarian Kingdom, founded by Khan Asparuh Consequently, all methods of foundation work on

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov g/cm too. The deformationsreach0.15-0.20m. under thefoundationhasbecomecompactedto has cracked. As a resultofthesettlement,loess of theuppermostrow ofthewall ofthefoundation bending accompanying thesettlements,masonry overloaded pilastersofthecentral nave. Duetothe and subsidences,reachingto0.3mbelow the weight ofthestructure,thereoccurredsettlements 0.3 mthick,andpiles,was used.Duetothegreat was beingprepared,asubstrateofcompactedsoil loess, 2-3mthick(Figure9). When the soilbase The large Basilica was alsofoundedincollapsible foundations arestillnotbyfar completelysafe. weak soilsknown atthattimewereused.andyetthe eastern peripheryofthevillageMadara,andis17km The historicalcomplex Madaraissituatedinthe Madara Horseman Stop 1.2: 1.65 g/cm 3 . Irregular subsidence ofthewall canbeseen, 3 , whereasoutsidethefoundation Figure 6-TheruinsofPliska ρ d = 1.35 ρ d = The relictsofalarge Romanvilla(2 to bere discovered atthetopofMadaraPlateauarestill studied atthefootofPlateau. The Thracian hills peoples. Sometracesofa Thracian settlementwere inhabited by Thra cian, Roman,Slav, andBulgarian In different periodsoftime,theLittleCave was Nymphs, theNymphsofnatu m highentrance.Itwas alsoknown astheCave of mainly forspiritualrituals. The BigCave hada70 time. The Big Cave was consideredsacredandused of MadarawereinhabitedstartingfromtheNeolithic The Madaraareahasavery longhistory. The Caves archeological andhistoricalreserve (Figure10). historical monumentsthatareinvolved intheMadara bas-relief issituatedinaplacewithmany other Bulgarian capital-thetown ofPliska. The historical of thetown of Varna and10kmtotheSSWoffirst to theeastoftown ofShoumen,70kmtothewest an areaof5,000sq.m,areplacedontheterritory 4 th century A.D.), including45roomsandcovering sear ched. re, water, andtheforest. nd Century A.D.- 3-06-2004, 10:28:14 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

565), up to the Bulgarian Middle Age (1386). The relicts of the Proto- Bulgarian Pagan sanctuary (9th century A.D.) and of the Orthodox monastery (9th century A.D.- 10th century A.D.), were situated at the foot of the Plateau. Another rock monastery (12th century A.D.- 14th century A.D.), was placed on the western Madara Plateau slope. Certain small karst niches, fractures, and man-made constructions had permitted the creation of the rock monasteries. The monastery relicts now are marked now by the holes in the high part of the western slope of the Madara Plateau. The historical relicts supply very useful information for state development during the First (9th century A.D.- 11th century A.D.) and the Second (12th century A.D.- 14th century A.D.) Bulgarian States.

The Madara Horseman is a magnificent bas-relief cut into a vertical rock surface at a height of 23 m. The bas-relief represents a scene of a horseman, who is said to be Khan Tervel, piercing a lion with a spear and followed by a dog, all to life size. The details speak in favor of the Figure 7 - The ruins of the Big Basilica Bulgarian origin of the bas-relief. between the village of Madara, and the slope of the Madara Plateau. The villa testifies to the good economic development of the locality at the beginning of the first millennium. The Madara castle (6th Century A.D.- P55 to PW06 n° 6 - from Volume 14th Century A.D.) ,indicates the important strategic position of the Madara Plateau, from the Roman period of Justinianus I (527- Figure 8 - Loess subsidence affected the Pliska walls

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov century A.D.- 9th century A.D.). 9th century A.D.- ’s reignandthatofKhanOmurtag(8th of successfulStatedevelopment duringKhan Emperor JustinianusIIin705,thefollowing periods and hissignificant militaryhelptotheByzantine They arethefollowing: theperiodofKhan Tervel, interpreted asbeingrelatedtothreehistoricalperiods. Bulgarian state. The text isonlypartiallysaved. Itis chronology forthecreationanddevelopment ofthe sides ofthebas-relief. They representthefirst short tions areplacedontheleft,right,andbottom depicts Khan Tervel asawinner. The Greekinscrip- There isanassumptionthattherelief 7-sand; 8-weathered marl;9-marl 4-palaeosoil; 5-sandy-siltyclay;6-sandy-gravelly clay; 1983): 1-topsoil;2-calcareouslayer;3-loess; Figure 9-GeologicalprofileofPliska(Evstatievetal., importance fortheregion andforthestate.Now the first halfofthe20thcentury. Hiswork was ofgreat Madara Museumandthereserve areainthe Popov was theinitiator fortheestablishmentof The BulgariangeologistandarchaeologistRaphail in 1979. of the World CulturalHeritageSitesofUNESCO Europe. ItisamongthesitesincludedinList The rockmonumentistheonlyoneofitskindin the BulgarianKingdombyByzantineEmperor. monument testifies tothetriumphantrecognitionof events withBulgarianparticipationarenoted. The Bulgarian isused,andwheresignificant historical of Madaraisthefirst documentwherethename for Bulgariancultureandhistory. The Horseman The bas-reliefandthetext areofgreatimportance 3-06-2004, 10:28:20 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

national archaeological and historical Madara reserve characteristic of a plateau and its surface is about 400 area, with the famous The Horseman of Madara, is m a.s.l.. Madara Plateau is in the range of the northern among the major tourist attractions in Bulgaria. flank of the Provadia Syncline, with layers inclined by 5 to 7 to SE (Figure 11). The rock massif consists of 10 a two complexes (Figure 12): the upper one comprises limy-sandy sedi ments of Upper Cretaceous - Cenomanian age; the low er one is mar ly of the Lower Creta ceous - Haute ri vi an age (Tzankov, 1943). The A borehole carried out in the year relief 1990, and located in the bas-relief of the profile in the pla teau, found 137.50 m of the Ceno man ian rock complex, showing several lithologic grades. Originally, it had been desc rib ed as chara c ter istic of the lower one - conglomeratic, and the upper one - fine-grained, which is ge ne r al ly in accordance with the drilling investigations (Frangov et al. 1992). The bas-relief was carved out of yel low ish

10 b

Madara area is Volume n° 6 - from P55 to PW06 n° 6 - from Volume

Figure 10 - a) General view of the Madara Plateau periphery; b) rock relief of the Madara Horseman on it.

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov rybus ly d altns creep marlstones, laye red grey-bluish se cond low limy sand er complex ismar stones foundbetween17and100 ly, andconsistsof m. A 7 MadaraHorsemanlocality and slidingcolluvialdeposits;5fault;6plateauscarp; terrace deposits;2gully;3alluvialfan;4creeping of theMadaraPlateau(after Angelova 1995):1alluvial Figure 11-Geomorphologicalmapofthewestern part ode. e we the Between load ed. limonite flakes. TheThick limonite carbonate con have beendis covered. Itcon com plexes, alay tent -upto7.5%,grainsofquartzand er ofyellow plasticsil ty clay

Hauterivian andCeno ness ofthispar ticular layer an montmorillonite, tains ing ifheavily manian as X1andX2,separateSlices56inthe and mostextended fissures atpresent,are des Kossev 1974; Frangov etal.1992). Two upper most given sign“X”bydif ferent investigators (Venkov & ex tens ion inthisslopeandthesplittingofit,were Fissures thatdevelop duringthegravitational plateau bytra can bede Formation oftwo orthreenew slicesabout3 m wide fourth rockslice,whichisfollowed byotherones. their to wer ing heads. The bas-reliefiscar tec ted be hind thefurthermostedgeof ces ofcracks. blocks whichdi wall andarerelicsofoldfrontal steps inthelow est sectionofthe can befoundnow asve ry low pla teau. The first threeofthem like that,separatedfromthe cross sectiondeveloped sixslices ave rage. The MadaraHorse a thicknessoffrom1to3 m on 13). The slicesorblocksshow a released fromtheedge(Figure de vel oped specific structureofrockslices Plateau Madara The peripheralzoneofthe 10 to20. colluvial deposits,slop ing from slope, marlstonesarecovered by limy-sandy complex. Down the wall isal by atwo-layer mo Madara Plateauisdetermined in theNWperipheryof The morphologyoftheslope Plateau. the westernslopeofMadara The Caves layinthebasementof corrections inthenaturalforms. later was manifestedincertain and ofhumanactivity. The earthquakes, gravity phenomena), - partiallymoderateandstrong natural phenomena(karst,tectonic under acomplex influenceofthe The Caves ofMadarawereformed of 110mfromthepla under ground wa The ter tablewas foundinthedepth nominally. m va m, about1.5 ries from0.4to6.5 most ver ti cal, built ofa tgae in s integrated del. The rock del. The teau surface. ried bythe 3-06-2004, 10:28:28 cribed man GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

6 m lower, the exten sion reads 3 m. It has been in spec ted to the depth of 12 m, then filled up with broken ma te r ial. The fissure X1 is extended to 1 m, and expected to reach a depth of 6 m.

Slice 4 carries the Madara Horseman. It is cut by three basic cracks which threaten the com pac t ness of the bas-relief, and these are numbered as No. 1, No. 2, and No. 3 (Ven kov & Kossev 1974). Crack No. 1 forms the northern boundary of Slice 4. It is almost all its length vertical from the top down to the level of the bas-relief where it turns into an “S”, and disap pears behind the tail of the dog. An erosional fur row identifies with most of the length of Crack No.1, and traces the wall to the bottom.

Crack No.2 cuts the horse into two parts, and reach es the depth of the fifth slice from the surface. Four to five other different cracks are detected between Slice 3 and the base of the massif. The cracks join together to form a single one near the head of Slice 3, and they are opened 20-30 mm under the bas-relief.

Crack No.3 is the most dangerous one for the monu ment. Extending to 20 mm out of the rock wall, near the bas-relief and above, it becomes wavy, and about 6 to 7 m above the monument, it Figure 12 - Engineering-geological profile of the Madara disappears. Thus, the crack is most likely going to rock wall (after Fran gov et al. 1992): 1 - colluvial slope separate a prismatic piece of rock between No.3 and mate rials; 2 - whitish sandy lime stone; 3 - yellow ish No.2 cracks. It is described as a “rock flake”, and P55 to PW06 n° 6 - from Volume cal ca re o us sandstone; 4 - con glo meratic limestone; threa tens the frontal part of the monument. 5 - yel low clay; 6 - grey marl; 7 - ground water table; 8 - gauge TM-71. The stability of the rock mass is a function of rock plateau, respec tively. Fissure X2 is oriented 150 to properties and jointing, and is also affected by seismic 170° (SSE), dipping 80° to W from horizontal. It is events, erosional processes, climatic conditions, and extended by 1.2 m in its uppermost part, and 5 to human activities.

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov moni toring) areeasilyaccessible fromthesur It isevident thatthemonitored cracks(selectedfor down neartherockbas-relief. 2003, whenalarge blockofafew cubicmetersfell The lastrockfall happenedinthemiddleofMay established bythehighprecisemonitoringsystem. large dis place the strong Turkishments betweenrocklamellaewere earthquake on17July1999, hu man lives atthefootofplateau.During stone blocksfelldown fromthescarp,endangering the Vrancea earthquake on30May1990,when The mostsignificant influenceswerenoticedduring more than5couldbegenerated. seismicity, wherebyearth qua and itswiderregion ischaracteristicofhighpotential kes withmagnitudes prognosti cation ofNEBulgaria,theMadaraPlateau in 1990(Figure14). According totheseismotectonic rock stab i li ty pro jects, weresuccessfullyinstalledhere Crack gaugesofthetype TM-71, asappliedtomany Figure 13-Rock slicesdividedfromtheplateau face, famous foritsfrescoes,“TheCircleofLife”,and national heritagemonument,“The Assu” Church, Actually theMonasterycomplex includesthe painted the Transfiguration Church. Bulgarian architect,Kolyu Ficheto.ZacharyZograph The constructionwork was leadbythefamous residential wings(1849-1851),andtheguesthouse. 1825. Initwerebuilt thesecondchurch(1832), the ground. The rebuilding ofthemonastery startedin the SecondBulgarianStatein1393;itwas burned to Alexander (1331-1371). The Turks tookthecapitalof The monasterydatesbacktothereignof Tsar Ivan second BulgarianState(1189-1393). 7 kmNfrom Veliko Turnovo –the capitalcityofthe The Transfiguration Monastery (Figure15),islocated Trans fi Stop 2.1: guration Monastery am plitude, asseenatM8andM9. mm seasonal recorded, resultinginupto1.6 in aspanof45°C,from-7°Cto+38°C,as Temperature varia tions intherockappear X, sometimesproducedin Y orZ,also. cracks, resultinginaseasonalcharacter reflect summer opening,andwin They temperatures. volumetric changesintherock,mainly seasonal to one canseeatfirst certaindelayedresponses To characterizethedisplacementdiagrams, An turns roundaxes Y andZ,respectively. cracks. in ves tigaed deviations indexed XZandXYrepresent three the of represents theopeningorclosinginall mostly represents horizontal shear, whereascom Y component The crack. most ly ashearchar seen inconnectionwithsub the powerful gra vi tational for ces, Zistobe Y arehorizontal,andZ-vertical. Regarding three com ponents X, Y, andZ,whereX The dataaboutdis pla ce men ts aregiven in instability. its in cluding some deeperprocessesinthemas discontinuities whichgive aninsightinto and, atthesametime,representdeep DAY 2 ac ter intheres sidence, having ter clo ponent X n, of s ing, 3-06-2004, 10:28:38 pec ti ve gu lar sif, GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

Figure 14 - Measured displacements along crack no.2 Volume n° 6 - from P55 to PW06 n° 6 - from Volume

Figure 15 - View of the Monastery after the rock-fall

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov registered onthe cliff. The siteislocatedinahighly Three majorfaults andfourjointssystemswere (Figure 17). deposits ofrockblockswithsandyandclayey filling age. The bottomoftheslopeiscovered bycolluvium depth, they areunder beddedbymarlsofthesame limestones (Baremian- Aptian age). At about10m colored todark-grey coloredlower Cretaceousflint The cliff is42-45mhigh,andcomposedofcream- processed limestoneplateau(Figure16). formed byriver sideerosionofthetectonically- cliff ofthe Yantra River canyon. The rockslopeis level, atthetoeofapicturesque120mhighlimestone The monasterycomplex islocatedonacolluvialplane Kolyu Ficheto. its bell-tower, built by thefamous Bulgarianarchitect, movement, which damagedtheMonastery, 6-well. deposits, 3-rocky crown, 4-rockfall, 5-landslide 1- Lower Cretaceouslimestones,2-Quaternary colluvial Transfiguration monastery(afterIlievetal.1993). Figure 16-Geologicalandreliefmapofthe buildings. the mostdangerousblocksabove the Monastery An alertsystemhasbeendesignedandinstalledon destruction processesalongthejoints. by creepprocesses,andtheweathering the weathereduppersectionofmarlsaffected the unequalsupportofhardlimestonesfrom massif, theinverse strengthstructureofthecliff, as majorfactors forthe“development” oftherock The studiesoftherockpropertieshave revealed by atreeandranoneithersideofit. preserved whentherockflow was divided intotwo casualties occurredandbychance,theChurchwas the westernwingsofMonastery. Luckily, no extended cliff sectionandcompletelydestroyed rainfalls, a300m ties andadrainagegallery. In1991,afterintensive consequence, thelandslidewas reinforcedbyback complex, anddirectlyendangeringtheChurch. As a slope, completelydestroying theeasternwingof In 1974,alandslidedeveloped onthecolluvial rock blocksduringtheGornaOryahovitza earthquake. Monastery was partiallydestroyed afterthefalling of seismic zoneof VIII degree MSK.In1913,the Greece), hehewed acellandsmallchurch inthe from Athon Monastery(now inChalkidikiPeninsula, Pat riarch JoachimIin13thCentury. After hisreturn Cherven. The first informationaboutthissiteisfrom religious complex inthe areaoftheancienttown of existed herefrom 12th-14thcenturyasapartofbig Historic sourcesrefertoamonasterycomplex that corridors. At someplaces,2or3fl the river canyon. Someofthecellsareconnectedby above theriver, anddeveloped inthekarstformsof composed ofgroupscells,hewn atdifferent levels scarps, 50mabove theground. The churchcomplex is issichasts (monks),canbeseenonthevertical river inhabited inearliertimesbymedieval hermitsand Some openingsofpictur m. The altitude ofthesiteisabout120ma.s.l.. are almostvertical, andtheirheightoftenreaches100 a bigmeanderwithwidevalley. The highrockscarps Reservation (Figure18).Inthisplace,theriver forms picturesque canyon oftheRoussenskiLomRiver Ivanovo Village, 25kmsouthofRousseCity, inthe The Ivanovo rockchurchesarelocated5kmoutside Ivanovo Rock-hewnChurches Stop 2.2: 3 rock-fall occurredfromthe esque caves thatwere oors arepresent. 3-06-2004, 10:28:47 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

river scarp with the assistance of three disciples. Later on, Joachim became patriarch of the Bulgarian Church (1235) when he created a big rock monastery complex near his first church. A great number of cells and churches were hewn in karstic voids and sites and were additionally enlarged by the monks. The patron of the rock monastery was St. Archangel Michael. Monks inhabited the Figure 17 - Geological cross section of the slope (after monastery until the Iliev et al. 1993)., 1 - Colluvial slope deposits; 2 - Lower 17th century. Cretaceous marls, sandy, calcareous, fractured; 3 - Lower Cretaceous limestones, karsted; Most of the monks were grammarians and manuscript 4 - Lower Cretaceous marls illustrators. They used the walls to make mural paintings, Volume n° 6 - from P55 to PW06 n° 6 - from Volume

Figure 18 - The side of the canyon of the Rusenski Lom River

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov murals thathave survived over thecenturies,those of medieval paintinginEasternEurope.Ofallthe which rangeamongthemostessentialmonuments Figure 20-Geologicalprofile Figure 19-Frescoes fromthechurch ofthe Holy Virgin life ofJesus. The illustrationsoftheanonymous the New Testament, showing thelastdaysof The imagesinthemrepresentpopularscenesfrom frames ontheceilingoutline25quadranglefields. images onthewalls arequiteindistinct.Decoration the frescoesonceilinghave endured,while the Of thewholewealthofmuralsinChurch,only levels. an altarspaceandtwo otherpremisessituatedon2 is shapedina55mhighrockcliff, andconsistsof preserved one,withoriginalconserved frescoes. It are irreversible. The church“OurLady”isthemost the walls. Inmostofthechurches,theseprocesses Over time,blockshave fallen fromtheceilingsand boring bishopric,administrative andmilitarycenter. the SecondBulgarianStateandCherven -theneigh- the Monastery, Veliko Tarnovo -thecapitalcityof illustration ofthecloselinksbetweenmonksin The presenceoftheirimagesinthechurchisan - arepaintedonthenorthwestwall (Figure19). Ivan Alexander (1331-1370)and Theodora Full-length por traits ofthechurchdonors- Tsar in theHoly Virgin Churcharethe bestpreserved. 3-06-2004, 10:28:55 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

The main geological hazards which are dangerous for the church’s constructions and mural paintings are as following: cracking, karst, seismicity, weathering, and ground water impact. The slope and a part of the churches are partially affected by local demolition and the influence of superficial water.

Totally four sets of joints, and about 20 individual fractures, were established for the site and the church. Some joint groups are parallel to the bedding planes (Figs. 21, 22). Probably they were initially Figure 21 - Internal view of the Church, with the fractures and blocks outcrop. formed with the rock lithification. Other joint groups are younger and with tectonic origin. medieval icon painter are colorful and realistic; the The relationship between joint systems and the local scenes are close to reality and to ordinary people, and tectonic lineaments and positive structures is not that makes the frescoes different from the asceticism clear. and austerity that predominat ed in the paintings of that period of the Middle Ages. The nude human Within the Church, the joints systems are presented bodies and the architectural details are clear signs of by individual fractures that occur on the floor, the the revival of the Hellenic tradition, hence the murals walls and the sealing surfaces, and create more than in The Church are considered a supreme achievement 10 separate blocks. of medieval Bulgarian art. The church complex was included in the UNESCO’s List of World Cultural and Wildlife Heritage in 1979. Stop 3.1: The Thracian Tombs at Sveshtari The rock massif is built by organogenic reef- Some joints from the church rooms have apertures limestones of a Lower Cretaceous age. The from 3-4 to 10-15 cm, with a rapid convergence of churches are created in the karst forms of the Lower their walls up towards the cliff top. Only a frontal Cretaceous (Hauterive-Barremian age) porous and blocks system, engaging the outer part of the Church P55 to PW06 n° 6 - from Volume water permeable limestone. Three levels have been premises, outcrops today’s surface and was estimated defined – an upper level with a more micritic texture, to be free to fall (slide) at the front (northern) wall of a middle detrital level, and a lower level with larger the cliff. It is the only one with a visible displacement fragments from shells and corals (Figure20). of a gypsum mark by 1-2 cm up until 1983. All other blocks occurring inside the church seem to be interlocked and not vulnerable to falling. A similar pattern of destruction of the cliff is observed along

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov fractures. Figure 22-InternalviewoftheChurch withthe Figure 23-ThraciantumulusatSveshtari area layer system,withlarge differences inmechanical From ageomechanicalpointofview, thereisatwo- Formation, covered byQuaternaryloessdeposits. Cretaceous limestonesfromtheRousse geologi cal profile consistsintheLower Necropolis, theuppermostpartof in layering.IntheareaofSveshtari sedimentary complexes, almosthor izontal The region of Sveshtari iscon The tumuliaresituatedonaflatarea. religious processionfollowing her. garland fromthehandsofagoddesswith depicts ahorsemanwhotakes agolden decorated asthefacade ofatemple,which central chamberhasmany ornaments.Itwas different sizesandspecifications. The Necropolis consistsofmany tumuliwith BC, fromtheearlyHellenisticera. The 25). They aredatedaroundthe3rdcentury were discovered in1982(Figure23,24, The Thracian tombsnearSveshtari village the destructionofmassifinarea. past isestimatedtobethetriggerfactor for degree MSK,andtheseismicimpactin lo cated atahighlyseismiczoneof VIII and noimpactonthechurch. The siteis infiltration torestricted depthsinthecliff, suppose aquickwater draw andinsignificant and thevertical walls oftherockcliff, In general,thesmallwater-collecting areas both sidesofthecanyon inthearea. stituted by 3-06-2004, 10:29:01 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

Figure 24 - Cross-section of a Thracian tumulus (Christoskov et al., 1995)

properties, rigid at the base, and plastic in the layer of Shabla in Bulgaria and in the Vrancea region in where the monument was built. This system is Romania. not favorable to stability because the contrasting On the map of the prognostic seismic zonation of parameters between the limestone and loess layers Bulgaria (for a period of 1000 years) the region under amplify the seismic effect. investiga tion shows the same parameters with an iso- seismic line of intensity VIII passing very close to New experimental data on the physical properties of it. There are data on the most important earthquakes the loess deposits, using seismic prospecting, gave us in the re gion in the last thousand years, but not on

Vp = 330-390 m/s, Vs = 130-180 m/s, and a Poisson’s the previous historical period of the existence of the ratio of 0.36-0.47, with a rigidity modulus of 30-40 monument under study (from 2400 years ago). After kg/m.s and a density - obtained by laboratory tests the discovery of the main tombs, many displacements - of 1,8 g/cm3. were found, whose origin is presumed to be seismic

considering that strong earthquakes happened in the P55 to PW06 n° 6 - from Volume The necropolis of Sveshtari is located in the eastern past (Figure 26). part of the Moesian Platform, in a re gion bordered by a seismogenic area. In accordance with the Stop 3.2: seismological data of the region, over the past 100 Chirakman Cape years the examined area has been affected by several Among the few Thracian centers investigated, special seismic shocks (eight of them were up to VII MSK interest has been aroused by the ancient city of in the tumuli site), with epicenters both in the region Bizone, located on the easternmost part of Chirakman

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov Figure 25-TheentranceoftheThracianTomb Figure 26-Displacementsofbuilding blocks byseismicimpact(Christoskov etal.,1995) in anuncertainage, the sink ing happened by anearth quake; - tosinkingcaused given byPosidonio the writtenindications attri buted -following end ofBizonewas doboni, 1989),the dei Terremoti”(Gui- In the“Catalogo many ancientauthors. has beenmentionedby ction byanearthquake catastrophic destru- City (Figure27).Its northward from Varna coast, about40km Northern BlackSea town onthe present-day harborof Cape, closetothe and thelstcentury earthquake (373B.C.) between theBura 3-06-2004, 10:29:09 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

Figure 27 - Map of the region (Evstatiev & Rizzo, 1984)

B.C. (the time of Demetrio da Callatio who gave clear ly denotes that the end of the city was caused the infor mation of such an event to Strabo). in the by a fall-type landslide, that slid into the sea. On the “Catologo dei Terremoti” the date of the banking has basis of ar chae ological data collected in Bulgaria the been orientatively assigned to the 3rd century B.C.. In aban don ment of the ancient city dates back to the lst the same book the words of Strabo were reported as cen tury B.C. follows: “…there was Bizone that was almost entirely The relief is characterized by a large plateau which swallowed up by earthquakes”. reaches the sea shore and large landslide strips below The actual observation on the morphology of the site the peripheries of the plateau. The Dobroudja Plateau Volume n° 6 - from P55 to PW06 n° 6 - from Volume

Figure 28 - General view of Chirakman Cape (Evstatiev & Rizzo, 1984

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov plateau isnominally20-30mhigh. The dipofslope and 70mfromtheKaliakraCape. The scarpofthe resort of Albena, 140mfromthetown ofKavarna, is elevated about200mabove sealevel atthesea-side 6 -Springattheslipsurface;7 - Sea-level. 5 -Disintegratedmaterialandredepositedaragonitites; patches; 4- Ancient earthflow witharchaeological relics; limestones; 2 - Landslide block; 3 - Oriented limestone micrite limestoneandclayinterlayers,covered byshell Cape (modi fied afterIliev1973).1 - Aragonitites with Figure 29 -Schematic profileoftheChirakman 5 - Aladja Monasterysite;6-resortarea (Frangov &Dobrev2000):1-plateauscarpofcliff; 2 -marshland;3spring;4catchment drainage; Figure 30-SceneofFrangya plateauabove theZlatniPyassatzisea-sideresort build large landslideblocks. in theplateau. The materials ofthe Topola Formation of thisFormation isabout140m,fixed byboreholes sediments areslightlyinclinedtotheNE. The width from Al bena uptothewestofKaliakraCape. The investigated area,the Topola Formation isrevealed the materialsofEuxinogradFormation. Inthe The sedimentsofthe Topola Formation lieover (Kamenov etal.,1972). between 100and110m. The dipofstratais1-3°NE to thevillageof Topola. Their thicknessranges revealing alongtheBlackSeashorefrom Albena The sedimentsoftheEuxinogradFormation are and clayey aleurolites. formation isbuilt up ofgrey, grey-blue, orbuff sandy Euxinograd, Topola, andKarvouna. The Euxinograd layers. Three formationsbuild thearea:namely, It isbuilt entirely ofMiddleSarmatianhorizontal below theplateauscarpis7-15º. 3-06-2004, 10:29:17 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

The Topola Formation is built up mainly of white uncon solidated aragonite sediments (ara gonitites) of Sar ma tian age. The thickness of different strata va r ies from 0.30 up to 1.00 m, nominally. White and light grey micrite limestones alternate with them with the thickness of the different strata being 0.07-0.30 m.

Karsted shell lime- s tones build the Karvouna Formation. The karstic voids are filled by terra rossa. Figure 31 - General view of Aladja Monastery The se limestones build the upper part side denotes an evolution by falls, whose cause is in of the geolo gi cal profile, and their thickness is small. relation to the combined action of seismsc activity They do not take part in landslide processes in the and sea erosion. Previous studies have pointed out the investiga ted area. rule of seismic shock on the landslide mobilisation in this area, where - from a geotechnical point of view Geological and archaeological research has shown - the outcrops are made up of brittle materials. As a that Bizone was located at the end of Chirakman recent example we recall the landslide of Momchil, Cape. The southern part of the cape collapsed, about 15 km south-west from the site), caused by a th together with a part of the city, and tank into the sea, fall following the earthquake at the beginning of 20 where ceramic fragments, remnants of walls, etc. century, that moved down, on a similar slope, about have been found, chaotically mixed with rock massef 20 million cubic meter soft material. below sea level. The result of seismic activity can still be seen in The morphology of Chirakman Cape on the sea front the frontal part of the cape, towards the sea, by the open fissures running parallel to the angle of the front of the cape (Figure 29), where we can observe recurrent slidings below them. The landslide bodies at the base of Chirakman Cape have been destroyed by sea erosion; they have been preserved in P55 to PW06 n° 6 - from Volume the lateral side, where one can observe the rounded relief typical of this material. The landslide that tore off the frontal part of the cape so that it falls in the direction of Figure 32 - Geological profile between Frangya Plateau and the the valley and into the present-day (Avramova-Tacheva et al., 1998) harbor, is of great interest. By sea

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov of thelastcentury, putthebeginning ofsystematic brothers KarelandHermengildŠkorpil attheclose Bulgaria. The first Bulgarianarcheologists-the rock monasteriesfoundintheNortheastpartof (Figure 30,31). This isoneofthemany medieval Frangya Plateau,about14kilometersfrom Varna City limestone rockscarpoftheeasternperiphery The rocky Aladja Monastery iscarved intothe Aladja Monastery Stop 3.3: was probablydamaged. events, thetown ofDionisiopolis (modernBalchik) and the4thcenturyB.C.Duringsameseriesof by strongearthquakes, inaperiodbe direction causedbymassive landslideswas in duced of alarge partofthe capeinasouthernandeastern observation ofthatplacesuggeststhedestruction the fate ofBizoneandcurrentgeomorphological The coincidencebetweenhistoricalevidence on landslide body. with horizontallayersfromthestronglydisturbed surface whichdistinguishestheimmobilemassif blocks, slopinglayers,disturbedzones,asteepsliding to seethetypicallandslideelements,destroyed rock transverse profile ofthelandslideanditispossible erosion alongtheshoreline,seahasexposed the - Sarmatianlimestones (Frangov &Dobrev, 2000):1-fissures;2soilsurface; 3 Figure 33-Cross-sectionatthe Aladja Monasterylocality

tween the1st the dominationof Turks attheendof14th Aladja MonasterydeclinedwhenBulgaria fellunder depicting the Ascension Day. Probably, lifeinthe today. Bestpreserved istheceilingcomposition, some oftheoriginalfrescoeshave survived upuntil like outletinthecliff. Thanks toitsdifficult access, staircase fromthefirst level, fixed inachimney - only accesstothechapelwas byawooden corkscrew recess intherock,withachapelatitseasternend. The The secondlevel ofthemonasteryactuallyisanatural a thronewiththeInfant onherlap. was madeinthe30s.Itdepicts Virgin Marysittingon discernible andthereisacolorcopy preserved, which their destructionpossible.OnlyFragmentsarestill frescoes, but unfortunatelytheeasyaccessmade churches, thisonehasalsobeendecoratedwith to theMinster(church).SimilarotherOrthodox a narrow passageleadingthroughastonestaircase can stillbeseen. Westwards, thecorridorreaches served, ofwhichonlythenorthernandeasternwalls was achapelwheremassforthedeadusedtobe Immediately above theentranceand crypt,there to therefectory, thekitchenandsix monks’ cells. in therockstaircase,leadingtoaninsidecorridorand the crypt(tomb).Leftofentrance,thereisacut behind astonewall, (partofwhichstillexists), was to themonastery. At thefar endoftheentrancehall, the mosteasternsideoffirst level, istheentrance nowadays isonlyapartoftheone-timecloister. At corrosion oftherock,itissupposedthatwhatseen rock almost40metershigh.Duetotheextensive been cutinhighsheerlimestone situated ontwo levels, andhave The premisesofthemonasteryare plateau edge. the secondone-6-8mbelow the 3-5 mabove thefootofscarp; The first floor is situatedabout high about25-30matthisplace. niche andachapel. The rockwall is “crypt”. The secondfloorhasalong “church forrequiescats”andthe cells”, “diningroomandkitchen”, “the monasterychurch”,“monastic rock wall. Inthefirst floor, thereare arranged intwo floorshewn intothe Century. The monasterycomplex is from the4thCenturyuntil18th Hermits inhabitedthemonastery . explorations ofthisoldmonument 3-06-2004, 10:29:26 GEOLOGICAL AND GEOTECHNICAL HAZARDS OF MAJOR NATURAL AND ARCHAEOLOGICAL MONUMENTS PW06

century, but the local people continued to honor it karst – mentioned above. Additionally, subsurface and to come to this place long afterwards – evidence erosional processes in the fine sands of the Frangya of which is an 18th century silver ring-seal, found in Formation create voids in them, which can provoke one of the tombs at the entrance. a cracking in the upper limestones and additional stresses in the last ones. The cracking of the peripheral The Christian name of the monastery is unknown. zone usually precedes the falling and toppling of rock The name Aladja has a Turkish origin, meaning blocks Relics of a toppled rock slice reveal just below “parti-colored”, “patterned”, and perhaps the reason the recent rock scarp Vertical rates of positive tectonic the monastery to be called so were the frescoes in movements between Kaliakra Cape and the town of the Minster (church) and in the Chapel, that were Varna (in the Aladja Monastery locality) are within preserved till the beginning of 20th century. the limits from 2 to 4 mm annually. For the same reason, many large landslides have occurred along No written documents about the Aladja Monastery the shore line north of Varna, and landslides are less and the Catacombs have been found. There are only distributed in the western part of the region. the legends of forest deities and untold riches, maybe According to the seismotectonic prognostication of true, hidden in bottomless underground labyrinths NE Bulgaria, the research region is characterized by connected with the past days of this beautiful and a high potential seismicity, where earthqua kes with mysterious place. magnitudes more than 5 can be generated. Just 50-60 km ENE from Aladja Monastery, the Shabla focal Miocene sediments build the region of Aladja zone is to be found, and many strong and catastrophic Monastery (Figure 32). Three lithological formations earthquakes have happened here. There is an account build the geological profile – from limy clays (in the of a catastrophic earthquake that happened in lower parts), and fine sands and limestone in the upper 1444, when the towns near Varna were completely parts of the plateau. The strata are slightly declined 3- destroyed. The last catastrophic earthquake happened 4° to ENE. The edge of the Frangya plateau is 270 m on March 31, 1901 (M = 7.2). The local earthquakes a.s.l. at the Aladja Monastery site. in the last few years are connected mainly with the Provadia focal zone. At the same time, the region is The slope below the plateau begins with a vertical influenced by seismic events co m ing from outside. rock scarp that is built up of limestone. The dip of This may be exemplified by the Vrancea earthquakes slope is 7-15° nominally. Its relief has a characteristic (Romania), and the North-Anatolian earthquakes landslide geomorphology. The foot of the slope (Turkey). During the last strong events, many cases finishes with the cliff or beach strip. The cultural site of rock fallings and topplings took place in NE of the Aladja Monastery is situated in the northern Bulgaria. part of the Aladja Monastery landslide cirque. This landslide is 1.5 km wide and 2.5 km long. Acknowledgments The weathering of the limestone is the most serious The present guide has been prepared under the problem of the Aladja Monastery. It is not uniform in financial support of the Bulgarian Ministry the variable layers. The rapid weathering of the weak of Environment and Water. The Ministry of (clayey) layers forms niches along the rock scarp. Culture financed the investigations of most The karsting is a process connected partially with the of the monuments mentioned in the guide. weathering and cracking of the limestone. Erosional couloirs and hollows are formed, and the weathered References: materials (“the rock meal”) are transported down Angelova, D. 1995. Neotectonics and geodynamics

slope by the ephemeral streams. of the Madara Plateau. Problems of Geography, Bulg. P55 to PW06 n° 6 - from Volume Acad. Sci., 2, 75-85 (in Bulg.). Cracking and toppling affect the peripheral zone of the Frangya plateau (Figure 33). The cracks are of a Avramova-Tacheva, E., B.Kostak, N.Dobrev. 1998. different origin. Their formation is connected with the Present dynamics of a landslide process in the Black change of the stress-strain state in the peripheral zone Sea coast region north of Varna (Bulgaria). - Acta of the rock massif after the exogenic geodynamic Montana IRSM AS CR, Prague, Series A No.12(107), processes - sea erosion, landslides, weathering, and 5-15.

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Volume n° 6 - from P55 to PW06 PW06 PW06 - Conveners: I.Bruchev, G.Frangov, N.Dobrev, A.Lakov Portugal, 1425-1435. Deterioration andConserv. ofStone, Lisboa, horseman”. In:Proc.ofthe7thInt.Congr. on Stability problemsoftherockmonu ment “Madara Frangov, G.,P.Ivanov, N.Dobrev, I.Iliev. 1992. Proc. of8thInt.IAEGCongress,4007-4010. affected therock Aladja Monastery, NEBulgariaIn: Frangov, G.&N.Dobrev. 2000.Destructive processes Monuments, V. 23,5-6,18-23.(inBulg.). soil baseofthePliska.MuseumsandCultural Evstatiev, D.,Rashev,R, P.Georgiev. 1983. The 907-918. sites inBulgaria. Annali diGeofisica, Vol. 38,5-6, 1995. Traces ofseismiceffects onarchaeological Christoskov, L.,D.Gergova, D.,I.Iliev, V.Rizzo. Troyan, andCGMR,. (inBulg.). Bulgaria. Scale1:500,000andexplanation text. MTS, Broutchev, I,ed.1994.GeologicalHazardMapin monuments inBulgaria,83-97(inBulg.). Vol. Investigation andconservation ofcultural Madara Horsemanareaformonumentconservation. Venkov, V., N.Kossev. 1974.Investigation ofrocksin a eilagl columns. bac terial-algal Nachev, I.,Ch.Nachev. 2001.“Pobititekamani”- Soc. Vol. 54,p.2,3-12(inBulg.) the Preobrajenskimonastery. Rew. ofBulg.Geol. Iliev, I.,D.Evstatiev, V.Rizzo. 1993. The rockfall at 75-85 (inBulg.). Black Seacoast.Rev. Bulg.Geol.Soc., Vol. 24,1: and activation oflandslidesalongtheDob Iliev, I.1973.Effect ofearthquakes ontheappearance sismologia, (ING-SGABologna,768pp. Italia enell'areamediterranea.Storiaarcheologia Guidoboni, E.1989.IterremotiprimadelMillein Artik-2001. 110p. (inBulg.). 3-06-2004, 10:29:30 roudja Back Cover: fi eld trip itinerary

PW06_ copertina_R_OK E 3-06-2004, 10:24:56 FIELD TRIP MAP INTERNATIONAL GEOLOGICAL CONGRESS nd 32

Edited by APAT

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