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P22 copertina_R_OK C August 20-28,2004 Florence -Italy Field Trip Guide Book - P22 GEOLOGICAL APPLICATIONS EVIDENCE ANDENGINEERING GEOMORPHOLOGICAL TO RECENT ITALY): FROMLATEGLACIAL DOLOMITES (NORTHERN SLOPE INSTABILITY INTHE GEOMORPHOLOGY AND 32 Volume n°4-fromP14toP36 GEOLOGICAL CONGRESS Associate Leader:A.Pasuto Leader: M.Soldati Post-Congress nd INTERNATIONAL P22 21-06-2004, 9:12:56 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)

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

P22 copertina_R_OK D 25-05-2004, 15:28:31 Volume n° 4 - from P14 to P36

32nd INTERNATIONAL GEOLOGICAL CONGRESS

GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE AND ENGINEERING GEOLOGICAL APPLICATIONS

LEADER: M. Soldati1 ASSOCIATE LEADER: A. Pasuto4 EDITED BY: L. Borgatti1, M. Soldati1 CONTRIBUTIONS BY: A. Corsini1, A. Galuppo2, A. Ghinoi1, M. Marchetti1, E. Oddone3, M. Panizza1, A. Pasuto4, G.B. Pellegrini5, E. Schiavon2, C. Siorpaes6, M. Soldati1, N. Surian5, F. Tagliavini4 1 Dipartimento di Scienze della Terra, Università di Modena e Reggio Emilia - Italy 2 Direzione Geologia e Ciclo dell’Acqua, Regione del Veneto - Italy 3 Consultant Geologist, Santa Giustina, Belluno - Italy 4 Consiglio Nazionale delle Ricerche, Padova - Italy 5 Dipartimento di Geologia, Paleontologia e Geoﬁ sica, Università di Padova - Italy 6 Consultant Geologist, Cortina d’Ampezzo, Belluno - Italy

Florence - Italy August 20-28, 2004

Post-Congress P22

P22_R_OK A 25-05-2004, 15:36:55 Front Cover: Vajont landslide (photo A. Pasuto)

P22_R_OK B 25-05-2004, 15:36:58 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

AND ENGINEERING GEOLOGICAL APPLICATIONS P22

Leader: M. Soldati Associate Leader: A. Pasuto

Introduction phological contexts different from the dolomitic ones, Lisa Borgatti and Mauro Soldati will also be shown. The superb landscape of the Dolomites is the result of The main aim is to show significant cases of mass their geology, which is different from the rest of the movements of various types, sizes and ages which Alps and most of the mountains in the world. Here, pale dolomitic cliffs stand above gentle slopes often made up of dark volcanoclastic rock types. The name “dolomite”, which applies to the mineral and to the rock, derives from Deodat de Dolomieu, the French chemist who formerly discovered it. The Italian Dolomites are located in the south-eastern sector of the Alpine chain (Figures 1, 2). They are bounded to the north by the River Rienza, on the east by the River Piave, on the south by the River Brenta and the terminal section of the Torrent Fersina and on the west, for a limited extension, by the River Isarco (between Bressanone and Bolzano) and then by the River Adige. These boundaries correspond to the Pusteria Valley, Piave Valley, Val Sugana and Adige Figure 1 - Sectors of the Eastern Alpine system (after Valley, respectively. The main mountain groups are: Bertoglio and De Simoni, 1979; modiﬁ ed). Croda Rossa Group (3139 m a.s.l.), Dolomiti di Sesto (3152 m), Odle Group (3025 m), Tofàne Group (3243 m), Cristallo Group (3216 m), Antelào-Sorapìs Group (3263-3205 m), Catinaccio Group (3004 m), Sassolungo Group (3181 m), Sella Group (3151 m), Marmolada Group (3342 m), Dolomiti di Zoldo (Mt. Pelmo, 3168 m and Mt. Civetta, 3218 m) and Pale di San Martino Group (3193 m). From the climatic standpoint the Dolomites are quite varied owing to their wide altitude range (1200–3200 m). The area has an Alpine climate, characterised by cold winters and mild summers. Precipitation patterns are typical of the Alpine climate, too: late springtime and summer are the most rainy periods, with a peak in July. Precipitation is intense and concentrated and occurs mostly during violent rainstorms. A secondary precipitation maximum occurs in November, following the prolonged autumn rains. Permanent snowfall Figure 2 - The mountain groups of the Alpine Dolomites in the valley bottom normally begins in December (after Bertoglio and De Simoni, 1979; modiﬁ ed). and lasts until April. On the highest peaks this period have affected the dolomitic valleys since the retreat

usually lasts a couple of months longer. The average P14 to P36 n° 4 - from Volume snow thickness is 50 to 100 cm. of the Last Glacial Maximum (LGM) glaciers, includ- The annual average temperature is around 6°C. In ing the recent catastrophic Vajont landslide which summer, temperature ranges from more than 25°C occurred in 1963. Mass movements often interfere during the day to 7°C during the night. with transport infrastructures and developed areas The field-trip is focused on geomorphology and where a large number of tourists are present dur- engineering geology applied to slope instability in ing both winter and summer. In these conditions of the Dolomites. Along the route to the Dolomites, vast high vulnerability, even mass movements of modest landslide bodies occurring in geological and geomor- magnitude, like debris flows, could have severe and sometimes unacceptable consequences.

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati vided duringtheexcursion. Furthermore,depending layout, sincemoredetailedinformationwillbepro- Authors have preferredtogive thetext amoregeneral of participantswas notyetknown. Therefore, the specific stopsas, at thetimeofprinting,number This guidehasnotbeenarrangedintosingleand esses. ogy, withparticularinterestinslopeinstabilityproc- projects dealingwithbasicorappliedgeomorphol- experience inco-ordinatingnationalandinternational The teamleadingthefield triphashadconsiderable climatic changesonslopeinstabilityprocesses. the otherhand,toshow theinfluenceofHolocene logical structuresandlandscapeevolution and,on hand, tohighlighttherelationshipsbetweengeo- The secondaryaimsofthefield tripare,ontheone paragneisses); 8)maintectoniclineaments;9)secondarylineaments (afterCartonandSoldati,1993). Permian (rhyolites,rhyodacitesanddacites);7)Crystallinebasement,Carboniferous (phyllites,micaschists and 5) clasticrocks, Permian-Lower Anisian (Arenariedi Val Gardena,BellerophonFm., Wengen Fm.);6)volcanic rocks, 4) dolomitic,clasticandvolcanic rocks, Ladinian(SciliarDolomite,LivinallongoFm.,volcano-clastic deposits); 3) dolomiticandclasticrocks, Carnian(DolomiaCassiana,S.CassianoFm.,DürrensteinDolomite,RaiblFm.); carbonatic rocks, Norian-Cretaceous (DolomiaPricipale,Dachstein Limestone,CalcariGrigi, Ammonitico Rosso); Figure 3-Geologicalschematic mapoftheDolomites.Legend:1)Plio-Quaternarydeposits;2)dolomiticand of Italyatthe1:50,000scale.Sheet63“Belluno”. Servizio Geologicod’Italia(1996).Geologicalmap Geological maps Cortina d’Ampezzo,028LaMarmolada. 1:50,000 scale:063Belluno,046Longarone,039 Istituto Geografico Militare Italiano,Sheetsatthe Topographic maps Field references fessional field-geological outfit. proof footwearcouldbenecessary, aswellapro- an umbrella,weather-resistant clothes andmountain- weather conditionsinthe Alps maychangerapidly, rough orwetmountainterrain.Consideringalsothat used, someoftheexcursion routesmaytake across on thenumberofparticipantsandmeanstransport 25-05-2004, 15:37:40 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Figure 4 - Stratigraphic sequence outcropping in the Dolomites (after Soldati et al., 2004, modiﬁ ed).

Servizio Geologico d’Italia (1970). Sheet 11 “M. General references Marmolada”. Geological map of Italy at a 1:100,000 Bosellini, A. (1996). Geologia delle Dolomiti. scale, 2nd edition. Athesia, Bolzano. P14 to P36 n° 4 - from Volume Servizio Geologico d’Italia (1977). Sheet 028 “La Castellarin, A. and Vai, G.B. (Eds.) (1982). Guida Marmolada”. Geological map of Italy at a 1:50,000 alla Geologia del Sudalpino centroorientale, Vol. 2, scale. Società Geologica Italiana. Servizio Geologico d’Italia (2000). Geomorphological Goldsmith, J. and Goldsmith, A. (1989). The Map of Italy at a 1:100,000 scale. Sheet 063 Dolomites of Italy. A & C Black, London; Hunter Belluno. Publ. Inc., Edison (NJ). Panizza, M. (Ed.) (1991). Guide naturalistiche delle Dolomiti venete.

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati the Pre-Alpstosouth. Dolomites fromthe Alps s.s.tothenorthandfrom of view thesestructuralelementsseparatedthe and Pieve diCadore Thrust: fromageologicalpoint to thesouthandsouth-eastby Valsugana (Giudicarie LineandPusteriaLine,respectively) and bounded bytheNeogenePeriadriaticLineament (Figure 4). To thewestandtonorththey are ably overlies theHercynian metamorphicbasement an ancientwarm tropicalseaandwhichunconform- Mesozoic sedimentarycover whichwas depositedin The stratigraphicsequenceconsistsofaPermo- west andtotheeastof Trento plateau(Figure3). during the Tertiary. Two thrustbeltsareevident tothe an earlyEuropeanvergence andan African vergence Late CretaceoustotheQuaternary. Deformationshad continental margin whichwas deformedfromthe belong totheSouthern Alps, asegment ofthe African From ageologicalpointofview, theDolomites Chiara Siorpaes Geological features oftheDolomites Dolomites, sedimentationrecordedshallow marine widespread region insouth-centralEuropeand,the Triassic, amarinetransgressionwestwards occupieda to lagoonandshallow marineconditions. Duringthe an evolution fromalluvialplaintosabkha,andthen bituminous limestones(BellerophonFm.)indicated Gardena Sandstones)andthegypsumblack Bellerophon Formation. The redsandstones(Val are recordedbythe Val GardenaSandstonesandthe graphic settingchangedandsedimentationprocesses At theendofPermianeruptions,paleogeo- dark grey schists,phillitesandparagneisses. metamorphic basement,whichconsistsofgrey and out discontinuouslyasdoestheunderlyingHercynian top ofthePonteGardenaConglomeratewhichcrops actually cropout. The PiattaformaPorfirica lieson only locallyhave thesevolcanic rockseruptedand Atesina” or“Porfidi Quarziferi”);intheeasternpart, consists ofrhyoliticlavas (“PiattaformaPorfirica was affected byvolcanism andthereforeitmostly In theEarlyPermianwesternpartofDolomites lion years. rock falls, slides,andmasswasting inthelastmil- weathering anderosion,glaciation,runningwater, and lastly, themodellingofpresent landscapeby chain building insidethe Alps duringthe Tertiary Triassic, JurassicandCretaceous,laterthemountain sediments intoatropicalseeduringthePermo- into threeperiods:first, thedepositionofdifferent The geologicalhistoryoftheareamaybesubdivided dolomites andlimestonescovering theentireregion. al. ously exiled by Middle-Triassic tectonics”(Pisa domain bytheGermanfacies whichhadbeenprevi- Carnian) “mayrepresentthereconquestof Alpine During theUpperCarnian,RaiblFm.(Upper surrounding theplatforms. deposited inthegraduallyshallowing upward basins nal siliciclasticandresedimentedcalcarenites)was whereas theS.CassianoFm.(marls,clay, extrabasi- up byalgae,coralsandothermarineinvertebrates carbonate platformsof“CassianDolomite”werebuilt evolution isagainrepresentedbyareef-basinmodel: basins (Viel, 1979;Pisa pelagic limestoneswhichprogressively filled the clastic, volcanic andsubordinatemarlyrocks the Wengen Groupincludesvolcanoclastic, silici- recognised (DeZanche,1990).Intheeasternpart, such asgranites,monzonitesandsyenites,canbe Dolomites, basalteruptionsandcomagmaticbodies a strongmagmaticphase.Inthewesternpartof In theUpperLadinianwholeregion underwent present. and rhyodaciticincomposition(Viel, 1979),arealso with ashtuffs andtuffites (“pietraverde”) rhyolitic p.p. Siliciclasticandvolcanoclastic rockstogether the BuchensteinGroupandto Wengen Group were filled bypelagiccarbonateunitsbelongingto Maldives orBahamas,whilethesurroundingbasins up carbonatereefs,quitesimilartothepresent-day Marmolada, andthelower partoftheSella,built Odle (Geisler),Putia(Peitler),Pale diSanMartino, Latemar, Sciliar(Schlern),Sassolungo(Langkofel), Dolomite andCassianDolomite,suchasCatinaccio, during theLadinianandCarnian.Massive Sciliar nous-carbonate sedimentsandcarbonateshelves even tinental environments. The unitsconsistofterrige- by unitsdepositedinbasin,lagoon,peritidalandcon- rise tocomplex paleogeographywhichisdocumented 1990). Tectonics andrelative sealevel changesgave corresponding totheeasternDolomites(DeZanche, ing tothewesternDolomites,andCadoreBasin, identified: theBadioto-Gardenese High,correspond- tectonics. Two zoneswithdifferent subsidencecanbe The Anisian sedimentationwas mainlycontrolledby stratigraphically overlie the Werfen Fm. light grey peritidaldolomite(Lower SerlaDolomite) mites belongingtothe Werfen Fm.(Scitian). White to oolitic limestones,redsandstonesanddolo- of limestones,marlydolomites,gypsum, carbonate andterrigenousdepositsmainlyconsisting , 1980).Itincludespolychromeshales,aphanitic et al. , 1980).Post-volcanic 25-05-2004, 15:37:48 et GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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The deposition of this unit prepared the morpho- the same units on the platform and the basin confirms logical conditions suitable for the formation of the this hypothesis (Bosellini and Doglioni, 1986). As peritidal dolomites belonging to the Dolomia described before, this complex Triassic paleogeo- Principale (Norian-Rhaetian?; De Zanche, 1990). The graphy was partly controlled by extensional tectonics. latter consists of white and light grey cyclic dolomites Triassic compressive features are also documented containing stromatolithic lithozones and fossils such in many parts of the Dolomites (Castellarin, 1982; as Megalodon sp. The famous mountains surrounding Doglioni, 1985, 1987; Picotti and Prosser, 1987; Cortina d’Ampezzo (Tofàne, Cristallo, Pomagagnon, Doglioni and Neri, 1988). The compressive struc- Cinque Torri, Croda da Lago, Averau), the Tre Cime tures have been interpreted as the results of a sinistral di Lavaredo (Drei Zinnen) in Sesto (Sexten), and the transpression, N70 trending (Doglioni, 1984). lower part of Pelmo and Civetta near Alleghe are During the Upper Triassic and Jurassic the Southern made up of Dolomia Principale. Alps became part of a southern passive continental The Uppermost Triassic is represented by the margin when the Ligurian Ocean opened to the Dachstein Limestone. It includes shallow water lime- West. As a consequence, the thickness of the Jurassic stone containing large bivalves such as Megalodon sequence varies considerably from the western to the sp., Dicerocardium sp. and corals. eastern Dolomites. In fact, in the Sella Massif the The Jurassic formations are composed of shallow- thickness of the Dolomia Principale is 300 metres water well-bedded limestones (micritic, bioclastic and the Ammonitico Rosso unconformably overlies a and oolitic limestones) belonging to the Calcari Dachstein Limestone tilted block. On the other side, Grigi (Lias) and by nodular red pelagic ammonite- in the Altipiani Ampezzani area and in the Eastern rich limestones belonging to the Ammonitico Rosso Dolomites, the Dolomia Principale reaches 1000 (Dogger-Malm). metres and the Dachstein Limestone together with The Lower Cretaceous rocks are present only in the the Calcari Grigi is 600 metres thick. These remarks Altipiani Ampezzani area, Piz Boè and Gardenaccia indicate the existence of a buried NNW-SSE striking mountain groups and they are made up of pelagic growth fault which is probably located along the grey-blue marls, marly limestones and reddish to Badia Valley (Doglioni, 1987). greyish silty limestones belonging to the Marne del During the Tertiary (60 to 5 million years ago), the Puez; the Ra Stua Flysch and the Antruilles Fm. collision of the African and European continents dis- (Upper Cretaceous) crop out only in the Altipiani placed, crumpled and uplifted the marine sediments, Ampezzani area and they record turbiditic fine- thus giving rise to the Alpine chain. The Dolomites grained sandstones, turbiditic bio-calcarenites and were deformed by two major compressional tectonic red marly limestones of deep-sea conditions. phases: the W-WSW-verging phase and the S-ESE- In the Dolomites the Upper Oligocene - Lower verging Neogene phase. In fact, the Upper Oligocene- Miocene Monte Parei Conglomerate is the only Lower Miocene Monte Parei Conglomerate sutures Tertiary unit. It crops out near the summit of the Col the W-verging structures and is, in turn, deformed by Bechei relief, between 2550 and 2580 m. The unit the S-verging one. includes polygenic conglomerates and sandstones During the W and WSW verging tectonics only the which unconformably overlie Jurassic limestones. sedimentary cover of the Dolomites was involved They were probably deposited in shallow marine and the main décollement zone is located within waters along an irregular coastline. the gypsum facies of the Permian Bellerophon Fm. The Dolomites are located in the eastern Southern Moreover, important flats are also located at the top Alps and their tectonic history recorded not only of the Dolomia Principale and within the Cretaceous the deformations related to Alpine compressional marls. During this tectonic phase Upper Triassic to phases, but also shows many synsedimentary events Cretaceous rocks were folded and thrust and some of P14 to P36 n° 4 - from Volume occurring after the post-Variscan rift (Winterer and the overthrusts are known as Gipfelfaltungen AUCTT. Bosellini, 1981). (summit overthrusts). The most characteristic struc- During the Permian and Triassic the whole region tures are the Tofana III klippe, the Remeda Rossa- underwent a rifting phase which is documented by Piccola Croda Rossa klippe, the Col Bechei W-verg- paleogeographic and paleostructural elements such ing recumbent fold in the hanging-wall of a low angle as the Atesina Platform and the Carnico-Bellunese thrust, the Sella Overthrusts (Doglioni, 1990). Basin (Bosellini, 1965). The different thickness of The later Valsugana Neogene phase took place in S-

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati di CadoreLine(Gianolla along asinistraltranspressionalzoneintothePieve of theDolomites Valsugana Linewas transferred basement withpop-upgeometry. Intheeasternpart verging thrustsandfoldsinvolving themetamorphic Another typicalexample isgiven bythe“cengia”of by volcanic dykes (LatemarandCostabellaGroup). where Ladiniancarbonateformationsarecutthrough tion phenomena,whichcanbeobserved intheareas of theDolomitelandscapeisgiven bymorphoselec- for theevolution ofthelandscape. A particularfeature mechanical behaviour, whichhasbeensosignificant cal andlateralcontactbetweenrockshaving different recurrent magmaticactivity, ledtothepresentverti- different sedimentationenvironments togetherwith Furthermore, thealternationinspaceandtimeof Valparola Pass andFalzarego Pass. determined theformationofsaddles,like thoseofthe Valley. Inaddition,thepresenceofoverthrusts has Tires Valley, upperCismon Valley andS. Vigilio leys andriver cuts,asinthecaseofFunès Valley, have inseveral casesdeterminedthedirectionofval- clearly legible inthelandscape. As forfaults, they overthrusting ofthickpiles sediments, arestill the region sincetheCretaceousfolding,faulting and structures. The tectonicevents whichhave affected are inmostcasescloselyconnectedwithgeological The geomorphologicalfeaturesoftheDolomites Structural landforms which aredescribedbelow (seeFigure5). and surficial deposits(CartonandSoldati,1993), region determinedasignificant variety oflandforms as wellthecomplex Quaternaryevolution ofthe formations (Figures3,4),theintensetectonisation The spatialdistribution ofvery different geological Mauro Soldatiand Alberto Carton Dolomites Geomorphological features ofthe tion oftheDolomiticregion. important featurescontrollingtheQuaternaryevolu- complicated polyphasestructureswhicharethemost stratigraphic andtectonicdiscontinuities,resultingin of eachstructuralphaseiscontrolledbyinherited ing themountain-building process. The geometry Not alltheDolomitesreactedinsameway dur- Marmarole Synclines). ing synclines(Gardenaccia,Sella,PelmoandSorapìs- Line andasetofwidegentleENE-WSWtrend- and the Valparola Lines, the Antelào-Selva diCadore Neogene structuralfeaturesarethePasso Falzarego et al. , 1988). The major during thegeneralmeltingoficecanbeattributed areas, onlylodgementtillandscatteredmaterialleft contained withinthealimentationarea.Inthesesame the permanentsnow-line andthereforecompletely leys. Inthelatter areas,theglacialsurface was above the Dolomitesandnotincentralornorthernval- Maximum, arefoundonlyinthesouthernsectorsof Glacial deposits,ascribabletotheLast 1500 mincertainperiods. ness oftheiceinDolomiteregion reachedover (1745 m)andS.Pellegrino Pass (1918 m). The thick- such asCampolongoPass (1875m),CostalungaPass Falzarego Pass (2105m)andotherminorpasses m), PordoiPass (2239m),GardenaPass (2121 m), as transfluentsaddlesatthetime:SellaPass (2244 over thepresentdolomiticpasses, whichfunctioned network ofintersectingglacialtongues.Someflowed large Dolomite groupsjoinedtogetherandmadeupa remaining uncovered. The glacierscomingfromthe valleys withonlythehighestpeaksandplateaus masses reachedrelevant heightsinalltheDolomite to the Würm glacialperiod.Duringthisperiod,ice These aretheformsthatprevious Authors attributed attributable totheLastGlacialMaximum(LGM). oldest observable landformsarealmostexclusively Ponte nelle Alpi (PenckandBrückner, 1909). The and perhapsalongtheRiver Piave inthevicinityof located intheareaofBrunico(Klebesberg, 1956) and datablewithcertainty. Onlylimitedoutcrops are or erosionallandformsolderthanthelastglaciation present thereisnoclearevidence ofglacialdeposits very evident tracesoftheirpresence.However, at four times)occupiedtheDolomitevalleys andleft During theQuaternary, glaciersrepeatedly(atleast Glacial landforms ing dolomites. are shapedonclasticrocksweaker thanthesurround- Sella Pass, PordoiPass andCampolongoPass, which this is,forexample, thecaseofGardenaPass, linked tothepresenceofmoreeasilyerodiblerocks; The locationofsomepassestheDolomitesisalso of theS.CassianoFm. Antelào lieover thehighlyerodiblemarlsandclays like Tofàne, Cristallo,Pomagagnon,Sorapìsand Cortina d’Ampezzo,wherevery steep-sidedgroups rocks overlie clasticformations,like intheareaof contrasts canbeobserved onslopeswheredolomitic all over thewesternDolomitesstrongmorphological bottom andDolomiaPrincipaleatthetop.However, Fm. areinterposedbetweenDolomiaCassianaatthe the SellaGroup,wherepeliticrocksofRaibl 25-05-2004, 15:37:51 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Figure 5 - Geomorphological schematic map of the Dolomites. Legend: 1) orography; 2) glaciers; 3) main glacial deposits; 4) movement direction of the Pleistocene glaciers; 5) rock glaciers; 6) ice- and snow-related phenomena; 7) main landslides; 8) areas intensely affected by karst phenomena; 9) troughs; 10) deeply eroded ﬂ uvial valleys; 11) talus cones and alluvial fans (after Carton and Soldati, 1993; modiﬁ ed).

to the peak of maximum advancement. shaped valleys, the most frequent are: steps, hanging

The most evident traces linked to glacial morphogen- valleys, sharp rocky crests and cirques. The freshness P14 to P36 n° 4 - from Volume esis observable today, can be attributed to the subse- and permanence of some of these landforms is related quent melting phases, which took place intermittently to the type of bedrock. For this reason, their presence and in a discontinuous manner, as defined in the clas- in the Dolomite area is not homogeneous, but fol- sic model introduced by Penck and Brückner (1909) lows the distribution of the Ladinian carbonate rocks. for the Alpine region, that is Lateglacial stadial phas- Traces of glacial erosion are better preserved in the es. The reduction, followed by the complete disap- latter, compared with volcanic rocks. Hanging valleys pearance of glacial masses, exposed various erosion are particularly evident at the junction of small val- landforms, among which, besides the well known U- leys with a main valley: the junction occurs through a

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati main Dolomitepasses. of thistypearefoundbelow, inthevicinityof becoming partofthemoraines.Significant examples rock falls thatoccurredontheancientglaciersthus areas, shouldalsobementioned. They resultfrom similar tolandslidedeposits,but distributed over vast Other accumulationshaving anoverall appearance Lagorai Group)(Figure5). Valparola (Tofàne Group),Calaita(Cimad’Asta- Group), d’Ayal inthevicinityofCortinad’Ampezzo, Group), S.Pellegrino andLagusel(Marmolada lakes Misurina(CristalloGroup),Carezza(Latemar during theLittleIce Age. Stadialmorainesenclose especially incomparisonwiththemorainesdeposited rounded andnotvery prominenttopographicprofile, sequences offrontalridges. They normallypresenta They canbefoundwithinmany valleys, mainlyin quite frequentintheDolomites(Castiglioni,1964). retreat phasesoftheLGM(Lateglacial A as afew examples. Glacialdepositsascribabletothe Pale diS.MartinoGroup,arementionedhereonly is deeplycarved inthenorth-westernflankof Croda Rossacirqueandthe Travignolo cirque,which the MarmaroleGroup,isolatedandwellformed the entireyear. The flanked glacier cirquespresentin of snow patchesuntillatesummeroreven throughout matic conditionsforthepreservation andpermanence often show very steepridgesandoffer suitablecli- arranged ingroupsorastep-like morphology. They semi-circular toelongatedshapesandareisolatedor cially nearthevalley heads. The cirquesvary from Glacial cirquesarescatteredalmosteverywhere, espe- Contrin Valley, Ciampac Valley andDuron Valley. slopes oftheFassa Valley attheconfluenceswith were formedbyminortongues,arepresentalongthe valleys, hangingabove aprincipalvalley sincethey step (outletstep).Significant examples ofsecondary walls greatlyreducestheslopesurface arealying vourable elementforglaciation:thesteepnessof rising toabove 3000m,highreliefenergy isanunfa- although therearenumerouspeaksintheDolomites relatively low meanaltitudeforglaciation.Moreover, and maintenanceofglaciers. The Dolomiteshave a with favourable climaticconditionsfortheformation tion ofsurfaces lyingwithinthealtimetricintervals altitude fromwesttoeast,withtheresultingreduc- opment ismainlyduetothe Alps’ decreaseinmean the Dolomitesaresmallinsize. Their limiteddevel- activity arenotlacking,even iftheexisting glaciersin Landforms relatedtorecentorpresent-dayglacier UCTT .) are In theDolomitesalsorockglaciersarefound, geomorphological risk. lages, woods andcrops,thuscreatingconditionsof Avalanches insome casesmaythreatenroads,vil- have given risetomorphologicaldiscontinuities. by densejointingorvolcanic intrusionswhich the slopes;thisiscaseofslopescharacterised especially wherestructuraldiscontinuitiesaffect Avalanche conesaretypicaloftheDolomites, Pordoi Pass (Meneghel andCarton,2002). in thehighCordevole Valley between Arabba and and clayey formations.Several casesareobservable etc.) especiallyonslopesconsistingofvolcanoclastic dent morphologicalfeatures(scars,lobes,smallflows groups. Gelifluctionprocessesalsogive risetoevi- on plateauareas,like ontheSellaandCatinaccio and/or tosnow arelocallyobservable athighaltitudes Patterned groundsduetodiscontinuousfrostaction walls andslidingonsnow patches. to theslopesandarefedbydebrisfalling fromrock ramparts, whichmake upelongatedridgesparallel Other widespreadperiglaciallandformsareprotalus tectonic jointingoftheslopeitself(Soldati,1989). of thesourceareasandoncharacteristics the lithology(i.e.physicalandmechanicalproperties) and particle-sizedistribution dependsvery muchon retreat fromthevalleys. The extension, inclination which have taken placesincetheLGMglaciers’ groups. These areduetofrostshatteringprocesses of theregion, linkingattheirbasemany mountain a very commonandsometimesspectacularfeature (frost-thaw cycles). Talus conesandscreeslopesare its variability withpassagesabove andbelow zero (with frozengroundforpartoftheyear)and an importantrôle,bothforitsstabilityminus0°C Dolomites. At thesealtitudestemperatureplays Periglacial landformsarealsovery typicalofthe Periglacial landforms at alltoday. Rossa, SassolungoandSellagroupshave noglaciers present atthebeginning ofthecentury, theCroda Pale diS.Martino. Although therewereglacierets Marmarole, Antelào, Marmolada,Pelmo,Civetta and from westtoeast:Popera,Cristallo, Tofàne, Sorapìs, small icemassestodayarelistedinthefollowing, The mountaingroupswhichstillhave extremely over anentireslope. surfaces suitableforreceiving glaciersthatextend few glaciersarelocatedonrelatively upward-sloping within altimetricintervals ofaccumulation.Onlya 25-05-2004, 15:37:56 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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although they are not a typical landform of this occurred during the Sub-boreal (about 5800 to 2000 mountain environment. They have the traditional cal BP), when slope processes mainly ascribable to shape of flows elevated over the surrounding terrain; rotational slides and/or flows took place in both the the forms held to be active terminate at the front in study areas. In the light of collected data, the events a high, steep slope. They have an important rôle in dated may be considered reactivations of older events climatic and paleoclimatic reconstructions, since they linked to the phase of precipitation increase which mark the lower limit of the discontinuous mountain has been documented in several European regions permafrost. A comparison with other sectors of the during this mid-Holocene period. Alpine chain reveals an almost complete absence of The recurrence in time of this landslide activity was active and inactive forms; nearly all of them can, in certainly influenced also by other non-climatic fac- fact, be considered relict forms. The altitudes of the tors, in particular geological-structural ones. First of frontal margins of the active rock glaciers decrease to all the spatial distribution of geological formations 2225 m, whereas the inactive ones reach 1750 m. On (Figure 3) with different mechanical characteristics the other hand, volcanic rocks (porphyries) appear to must be taken into account. In particular, the occur- be quite suited for the formation of rock glaciers, as rence of landslides is high where rigid and resistant observable in the Lagorai Group (see Figure 5). The rocks (dolomites, limestones etc.) showing brittle most spectacular form is found at S. Pellegrino Pass: behaviour, overlie weaker rocks characterised by it consists of a tongue with convoluted troughs which ductile behaviour (marls, clays etc.). This is typical attains a length of some 1200 m. of the area of Cortina d’Ampezzo and of the valleys around the Sella Group (Figure 5). Furthermore, also Gravity-induced landforms where the effects of tectonics were most intense, Gravity-induced landforms are widespread in the in correspondence with faults or overthrusts, mass Dolomites and mainly consist of mass movements movements have been favoured. occurring from the Lateglacial to date (Soldati et al., Gravitational landforms are also connected with the 2004). The frequency and magnitude of gravitational existence of deep-seated gravitational slope deforma- phenomena is proved to be very high in the last Post- tions, recently recognised in the Dolomites and par- glacial period when slopes no longer sustained by ice ticularly in the area of Cortina d’Ampezzo (Pasuto et masses, were affected by many large scale landslides. al., 1994; 1997). With respect to morphological evi- Panizza (1973) showed how these landslides seem dence, they are generally characterised by the pres- to be concentrated downstream of the confluence of ence of trenches, gulls and uphill-facing scarps in the glaciated valleys where “glaciopressure” might have upper parts of the slopes and bulges in the lower parts been more intense, like downstream of the conflu- (e.g. Tofàne, Lastoni di Formin and Faloria groups). ence of the T. Costeana and T. Boite valleys (south It must be emphasised that deep-seated deformations of Cortina d’Ampezzo), where large landslide accu- may be the initial stage of large-scale mass move- mulations are still visible today. Several mass movements whenever the deformation belt develops into a ments have been recently dated in the area of Cortina sliding plane. However it has been observed that the d’Ampezzo and in the Upper Badia Valley (Alta Val presence of these processes favours or induces “col- Badia), where surficial deposits mostly consist of lateral movements” (rock falls, slides and flows) in landslides. The analysis of the dated landslides has the surrounding areas. allowed correlations to be outlined between increases in landslide activity and climatic changes in the study Karst landforms areas. The first phase of marked slope instability is Karst phenomena in the Dolomites are strictly related observed in the Preboreal and Boreal (about 11,500 to structural and morphological conditions (Mietto to 8500 cal BP) and includes both large translational and Sauro, 1989). Karst phenomena basically take P14 to P36 n° 4 - from Volume rock slides, which affected the dolomite slopes fol- place in the higher parts of the valleys and are mainly lowing the withdrawal of the LGM glaciers, and located in the high carbonate massifs (1200 to 3000 complex movements (rotational slides and flows) m), which rest on formations with little or no ten- which affected the underlying pelitic formations dency at all to undergo karst processes. Among the probably favoured by high groundwater levels due numerous carbonate formations of the Dolomites, to an increase of precipitation and/or permafrost only the Marmolada Limestone, Sciliar Dolomite, melting. A second concentration of landslide events Dolomia Principale and Calcari Grigi are particularly

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati the Flandriantransgression–whichcausedaretreat undergone arathercomplex evolution, startingfrom the Holoceneareanearesttocoastlinehas deposits aremadeupofsilty-clayey sediments.In also bygroundwater. At thesurface thesealluvial inclined slope,runthroughbynumerousstreamsfed the Venetian watercourses. We crossamildly SE A27 motorway, acrossthealluvialdepositsof teristic lagoon,weproceedtothenorthalong After leaving thecityof Venice anditscharac- Mauro Marchetti From Venice toFadalto Field itinerary erosion andalsobykarstmorphogenesis. tures oftherocksinvolved, themodalitiesofglacial often complex formsaffected bythestructuralfea- floors oftheglacio-karsticdepressions. They are slightly inclinedslopes,inhighlandplainsandthe frequent. They occupy wideextensions, mainlyon in theseenvironments. The karrenarealsovery peri-glacial processesthatareparticularlyeffective the margins oftheseforms have beenmodified by diameters rangefrom50to150m. Very often, Dolines arenumerous:inthe Alpe diFosses their inside thedepressions. Dolomites. Perennialortemporarylakes oftenexist and nearPianiEterni,inthe Vette andtheFeltrine Alte, Sponde Alte, BusediColl’Alto,Riviera Manna the Pale diSanMartinonearForck diSopra,Buse Popera, at Alpe deiPiani,northofMontePaterno, in di Fosses, Tondi diSorapìs,LagoNeroonMonte at theLagoGrandediFùsses,RemedaRossa cal examples ofglaciokarsticdepressionsarefound 500 to1500m;depth:2060m). The mosttypi- are thelargest andmostcharacteristicforms(length: slope karren.Undoubtedly, glacio-karsticdepressions karstic karren,landslidescreeheapswithkarrenand valleys, fluvio-karsticdryvalleys, dolines,glacio- Dolomites arelarge glacio-karsticdepressions,blind and ridges. The mosttypicalkarstlandformsinthe hanging valley floors,onlevel summitareas,scarps are prevalent onplateaus,incirquefloorsorglacial From amorphologicalstandpoint,karstphenomena ley floorshasalsoundergone karstprocesses. Fm.), outcroppingonseveral slopesandinsomeval- gypsum ofPermianand Triassic age(Bellerophon suited forkarstprocesses. The formationcontaining DAY 1 modelling isstillobservable. Croce Valley, whereevidence ofglacialandfluvial narrows. Onceacrossthisanticline,wereachtheS. tongue intotheplainthrough Vittorio Veneto amphitheatre bearswitnesstotheoutletofaglacial as suchbyPenckandBrückner(1909). This moraine moraine hillsof Vittorio Veneto, alreadyrecognised towards theCansiglioreliefs,travelling acrossthe After leaving Conegliano tothewest,weproceed Cordevole, isstillactive. was occupiedwith continuitybyitstributary River direction, acrosstheQueronarrows, whichinthepast sion) hasnow beenabandoned,whereasthewestward Lapisina Valley (whichwewillvisitduringourexcur- the eastward direction acrosstheS.Croce Valley and of theriver’s downflow, forcingitintwo directions: the Pre-Alpinechaincreatedanobstacleinpath was changeable duringtheQuaternary. The upliftof position. Therefore, thecourse oftheRiver Piave underwent adiversion totheeast,upitspresent and archedonthewestside,whereasRiver Piave characterised byfluvialterraceswhichwereuplifted chain’s uplift. The living Montelloanticlineis,infact, and Montebelluna,witharateequaltothethatof through theMontelloreliefs,betweenConegliano of overimposed hydrography, sinceitcutitscourse boundary. The River Piave isasignificant example tually emerges downstream, beyond thefan’s lower lation throughthesedeposits. This groundwater even- proximal portion,impliesconsiderablewater perco- mainly gravelly grainsizedistribution inthefan’s apex locatedattheriver’s outletintotheplain. The features arelarge fan-shaped fluvialridges, withthe of present-dayRiver Piave. The mainmorphological make upthesurface portionof thelarge alluvialfan bution rangingfromsandtogravel. These deposits the sedimentsgrow coarser, withparticlesizedistri- of thewater table).Eastward of thecity Treviso, reclamation activities andconsiderabledrawdown sediment compaction)andartificial (following land trend was partlycounterbalancedbynatural(dueto slow progradationuptothepresentsituation. This of several kilometresofthecoastline–followed by the BellunoPre-AlpsfromCansiglioPlateau the Lapisina Valley, atransverse valley separating The Fadalto landslideis locatedintheupperpartof Introduction Giovanni BattistaPellegrini andNicolaSurian Fadalto Landslide Stop 1.1: 21-06-2004, 9:17:17 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Figure 6 - Geological section across the Lapisina Valley (after Pellegrini and Surian, 1996).

(Venetian Pre-Alps). Since the retreat of the Würmian Geological setting glaciers, 14,000-13,500 years BP in the nearby The tectonic structures had a main role in the Vallone Bellunese (Surian and Pellegrini, 2000), Neogenic deformation of this sector of the Venetian the River Piave has flowed only through the Vallone Pre-Alps. The layout of the Lapisina Valley has in Bellunese, abandoning its course through the S. Croce fact been conditioned by the presence of a structural – Lapisina Valley. Even if glacial over-deepening depression existing between the “ramp anticline” of could have taken place, the data available on bedrock Col Visentin, which borders the Belluno Prealps to morphology suggest that the Fadalto landslide could the east, and the Cansiglio massif. The complex syn- be the main cause of valley damming, the formation cline of the valley bottom, dislocated by a system of of the Santa Croce Lake and the subsequent change in inverse and transcurrent faults connected with the line the course of the River Piave. Nowadays, the Lapisina “Longhere-Fadalto-Cadola” (Figure 6), has meant valley-bottom is filled with debris from several large that the Lapisina Valley has developed as a transverse landslides and the Fadalto Col is a wind gap. Along valley in the Pre-Alpine chain. the valley there are three lakes, following the axis of The eastern slope of the Lapisina Valley is mostly the valley: Lake Morto at 274 m, Lake Restello at 177 made up of Fadalto Limestone (bioclastic calcarenite m and Lake Negrisiola at 160 m. These natural lakes and calcirudite stratified in beds). The strata, with an have been transformed into hydroelectric basins. average N 300° direction, dip towards the valley bot- The Fadalto landslide is a complex process involving tom with average inclinations of around 25°, while several types of movement (rock slide, debris slide the boundary with the underlying Soccher Limestone etc.) which has been reactivated on several occasions (finely stratified micritic limestone, with thin argilla- since the Late Glacial (Pellegrini and Surian, 1996; ceous interstrata in the upper part) is located at about Pellegrini et al., 2004). The landslide affects the 1000 m (Figure 6). No faults were found in this slope

eastern slope of the Lapisina Valley, which is mostly of the valley. However, here a series of joint planes is P14 to P36 n° 4 - from Volume built up of Fadalto Limestone, a bioclastic calcarenite visible at a mesostructural scale in the lower part of and calcirudite with strata dipping towards the val- the slope, while at a larger scale they look like deep, ley bottom. The main scarp is about 7 km long with vertical, N-S oriented cracks which isolate portions vertical walls reaching a height of 400 m, whereas of the wall occasionally subject to collapse. The joint the accumulation zone is about 1.6 km2. The highest planes are all approximately perpendicular to those point of the scarp is at 1400 m in altitude whilst the of the bedding. The most frequent ones show a N lowest point of the accumulation is at 305 m. 120° direction; also those around N 160° and N 270° are statistically significant, while there is a smaller

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati is distributed, some1.6km Costa andtheareawherelandslideaccumulation The Fadalto landslideincludesthelarge scarpofMt. Zambrano, 1979). to glacialand/orlandslidedeposits(Pellegrini and of anobstructionintheupperpartvalley, due Lapisina Valley, therefore confirming thepresence glacier astreamcouldnothave flowed towards the deposits meansthataftertheretreatof Würmian presence oflacustrinedepositsontoptheglacial – have provided theonlyreliableinformation. The that boundsthenorthernshoreofLake SantaCroce and carriedoutatLaSecca,alongtheearthdam Some boreholes–extending asfar asthebedrock rocks ofthe Alpago syncline. intense glacialover-excavation affecting the Tertiary of thelake, andwhichhadbeenformerlycreatedby on topofarocky thresholdformingthesouthernbank maintains thatthelandslidedebrisbodyaccumulated of Lake SantaCroce.For instance,Brückner(1909) relationship betweenthelandslideandformation Various hypotheseshave beenformulatedastothe gravitational process. tried toinvestigate thespecific causesofthiscomplex and, bydatingseveral massmovements, have also These Authors have mappedthelandslideindetail and Surian(1996)Pellegrini More recently, thelandslidewas studied byPellegrini 1909; Panizza, 1973;EisbacherandClague,1984). mulation astheresultofalandslide(e.g.,Brückner, Venzo, 1939),whereasothersconsideredtheaccu- glacial originforthesedeposits(e.g.,DalPiaz,1912; the formationofLake SantaCroce.Somesuggesteda Lapisina Valley andontheroleoflandslidein of thedepositsthatshutoff theupperpartof In thepastmany Authors argued aboutthenature of theFadalto landslide Geomorphological analysis to new failures. joints intersectingthelayers,thusexposing theslope bottom andparalleltothebeddingopenswide component ofextension orientedtowards thevalley cm the rockintoblocksranginginvolume fromafew systems intersectthebeddingplanes,subdividing number ofplaneswithN200°direction. These joint and 537matColBrustolade,inthecentralpartof mulation attainsaheightof587matColdeiMasarei, the Fadalto valley fromLake SantaCroce. The accu- a seriesofhillswhichseparatethenorthernpart 3 tohundredsofm 3 . Gravity actstogether witha 3 . This areaismadeupof et al . (inpress). between climaticperiodswithdifferent characteristics 4900 yearsBPand AD 1300-1450)oratatransition spells ofacolderandmoredisturbedclimate(5350- movements intheFadalto landslidetookplaceduring results donotruleoutthepossibilitythatsomemass dating bymeansofdendrochronologyanalyses. The reason anattemptwas madetoimprove radiocarbon especially whendealingwithhistoricaltimes.For this mainly duetotheinaccuracy ofradiocarbondating quakes) hasturnedouttobeadifficult task. This was relationship betweenlandslidesandclimate(orearth- landslides tobeinvestigated; althoughestablishinga chronology hasallowed thespecific causesofthese in historicaltimes(withinthelast14centuries). This tional slideonColdeiMasareisub-unit)tookplace on ColBrustolade–delle Vi sub-unitandarota- ± 95yearsBP),whiletheothers(arockavalanche at Coldelle Vi) datesbacktothelate Atlantic (5375 small rotationalslidewithintheaccumulationzone Glacial (Pellegrini event thatdammedtheLapisinavalley intheLate during theHoloceneandaftermainrockslide tion anddatingofseveral massmovements occurring slide improved significantly thankstotheidentifica- Our knowledge ofthechronologyFadalto land- logical dating. samples suitableforradiocarbonanddendrochrono- sections withinthelandslidedepositsandtocollect has provided uswiththeopportunitytoobserve new Brustolade –Coldelle Vi landslidesub-unit,andthis ity isparticularlyintenseontheeasternsideofCol the Fadalto landslide. At presentquarryingactiv- have beenexcavated intheaccumulationzoneof Over several years,large volumes ofsediments Masarei andSassoi(Figure7). sub-units: ColBrustolade–delle Vi, Coldei These landslidesmaybegroupedintothreelandslide bodies wereidentified in theaccumulationzone. geomorphological investigations, various landslide concerning thelandslideaccumulation.Bymeansof tors correspondingtodifferent evolutive processes reveals thepresenceofdistinctmorphologicalsec- of hillsanddepressions,but anattentive analysis At first sightthere seemstobearandomdistribution of about280m. tion, thelandslidedebrisoccupiesanaltimetricbelt the highestandlowest altitudesoftheaccumula- lowest elevation ofthedebrisis305m. Considering level is380m.Downstream, next toLake Morto,the southern banksofLake SantaCroce,whoseaverage the Fadalto Col(475m). The debrisconstitutesthe et al ., 2004).Onelandslide(a 25-05-2004, 15:38:05 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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(such as Atlantic and Sub-boreal). On the other hand, according to dendrochronological analysis, no relationship between the historical rock avalanche and climate (or earthquakes) can be inferred. Therefore, this rock avalanche is likely to have been triggered by a single meteorological event during a warm climatic spell rather than during a particular climatic phase.

Hazard implications As for landslide hazard, it must be stressed that during the Holocene this landslide underwent several reactivations, which involved both the main scarp on the eastern slope of the valley and the accumulation zone. Besides, it was recognised that the landslide can be reactivated not only through rock slide, rotational slide and debris flow, but also through rock avalanche, a complex landslide not uncommon in the southern Alps. Since the geometry of the main scarp has not significantly changed through time, it can be argued that movements such as rock avalanche and rock fall might still take place in the future. On the other hand in the accumulation zone, rotational slides are more likely to happen. Figure 7 - Geomorphological sketch map of the Fadalto From Fadalto to Longarone landslide. Legend: 1) slope debris; 2) earth ﬂ ow; 3) Alessandro Pasuto rotational slide; 4) rock avalanche; 5) rock slide; 6) After leaving the Fadalto saddle (488 m) which glacial deposit; 7) bedrock; 8) landslide scarp; 9) debris divides the Livenza basin from the Piave basin, we ﬂ ow; 10) location of the exposures; 11) area where rock go down as far as the shores of Lake Santa Croce, avalanche deposits were exposed; 12) motorway (after whose reservoir collects most of the water from the Pellegrini et al., 2004). Alpago valley and is exploited for generating hydro- secondary watercourse originates on the slopes of electric power. Mts. Pelmo and Civetta. On the opposite slope we Subsequently, we go along the relict Piave Valley and, can observe the deep gorge of the Torrent Vajont. after La Secca, forms ascribable to slope movements affecting these ridges in the very early Post-glacial DAY 2 can be observed. From Longarone to the Tessina landslide After going through the village of Ponte nelle Alpi, Alessandro Pasuto we eventually reach a bridge over a deep, narrow gorge cut by the River Piave when it was diverted by Proceeding southwards on a recently built stretch of the damming of the Lapisina valley. Following the motorway along the Piave Valley, one reaches the river’s right bank, we go upstream along the no. 51 Tessina landslide. At La Secca the road turns to the state road to the north. Here the course of the River left along the earth dam along the northern boundary Piave is anastomosing, although its riverbed has nar-

of Lake Santa Croce, and eventually arrives in the vil- P14 to P36 n° 4 - from Volume rowed considerably owing to the presence of infra- lage of Puos d’Alpago. structures. Due to morphological conditions, there The Alpago area is an asymmetrical brachysyncline are almost no human settlements on the opposite with a curved axis turning from a SW-NE to an E-W slope. Small streams running through deep valleys direction. Stratification is markedly inclined towards can here be seen, some of which have been exploited N and NE (60-70°), whilst it decreases considerably for hydroelectric purposes. Just before arriving in to the east and south (10-20°). The outcropping rocks Longarone, the confluence of the Torrent Maè with belong to the Jurassic, Cretaceous and Tertiary for- the River Piave can be observed. The basin of this mations, whereas the Quaternary deposits are mainly

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati which hadnever causedparticularrisksituationsfor its movement bymeansofprogressive displacements Until 1991the Tessina landslidehadalways resumed stopped aftertendays. gered inthelower accumulation area;thisepisode maintained itsmotionforanother200m,was trig- occurred. Following thisevent, an earthflow which ing theupperpartoflandslide’s easternsector In August 1990animportantreactivation involv- its activity was extremely reduced. not recordconsiderablereactivations andupto1987 by oneofthemostdisastrousfloods,landslidedid In 1966,althoughalltheBellunoterritorywas struck Lamosano. ally cametoastandstill600mfromthevillageof led totheformationofanearthflow whicheventu- place, affecting thesameamountofmaterial. They considerable precipitation,threereactivations took of October).Inthefollowing fouryears,always after lowing intenserainfall (398.7mmjustinthemonth landslide describedatthenext stop. which occupiesthe Tessina valley whichispartofthe it isalsopossibletoobserve thefootofearthflow In correspondencewiththevillageofChiesd’Alpago up to30-35mthick. a slow rotational-translationalslideaffecting material many buildings. This slopemovement isascribedto are witnessedbyseveral cracksvisibleinthewalls of the village. The displacementscausedbythelandslide the first important caseofalandslideaffecting partof Once inthecentreofChies,itispossibletoobserve covers. filled riverbeds owing tothepresenceoflarge debris bodies withsteepslopesandwatercourses withover- d’Alpago itispossibletoobserve numerouslandslide Indeed, alongtheroadleadingfromPuostoChies a considerablepropensiontodisarrayprocesses. rock types,the Alpago basinischaracterisedby Owing totheextensive presenceof Tertiary flysch made upofglacialandgravitational sediments. It was triggeredon30 ley intheProvince ofBelluno(north-eastern Italy). Mt. Teverone, intheeasternpart ofthe Alpago val- The Tessina landslideislocatedonthesouthslopeof Introduction Alessandro Pasuto andFabrizio Tagliavini The Tessinalandslide Stop 2.1: slide involving some1,000,000m th October1960byarotational 3 ofmaterialfol- the following April a40,000m in theeasternsectorofsourcearea,whereas light seismicshock,significant movements occurred In December1991,perhapsinconcomitancewitha the villagesofFunesandLamosano. which mobilisedsome20,000m In Julyand August 1993new reactivations tookplace, to theFlyschdell’Alpago(Lower Eocene).It ismade The materialinvolved intheslopemovement belongs thickness andarepermeableduetofissuring. Paleocene), aremainlyorganised inlayers ofvariable and cherty-calcareousformations(UpperCretaceous- lowermost portion. The calcareous,marly-calcareous Miocene) areonlymarginally affected bytheflow’s the subsequentones(i.e.,fromOligoceneand as far as the Tessina landslideisconcerned,whereas and pre-OligoceneCainozoicformationsareimportant the Quaternarycropout(Figure8).OnlyMesozoic tratigraphic sequencespanningfromtheJurassicto Alpago valley, formationsascribabletoachronos- tant NNW-SSE arrangedtectonic alignments. Inthe part, thissynclineisalsoaffected bysomeimpor- its axis(Mantovani Tertiary formations,shows aslightlycurved trendof catchment basin;thisstructure,whichdeveloped in of theasymmetricalbrachy-syncline ofthe Alpago affected bythelandslidebelongstonorthernflank From thegeologicalstandpoint,slopeportion Geological settingandmorphological evolution went asfar asthevillageofFunes. scarp andgiving risetoaflow whichinafew days resumed itsmovement, thusdisplacing allthemain triggering cause,thewholeupperaccumulation Finally, inSeptember1998, without any apparent ment affected theeasternsectorofsourcearea. moved 300mdownstream. Onceagain, thedetach- the onsetofaflow whichinthefollowing tendays the movement, was recordedon15 advancement, whichwas followed byadecreaseof the hamletof Tarcogna. The maximumlandslide the flow wentasfar astheembankmentbuilt near May anew reactivation affected thesamesectorand the monthwentover theFunes-SanMartinoroad.In collapsed, giving risetoaflow whichattheendof situation. This reactivation startedon21 Lamosano forthefirst time,causingaseriousrisk In 1995thedisplacedmaterialreachedvillageof mum widthofabout500m. longitudinal extension exceeding 2.5kmandamaxi- After theseevents, thelandslideshowed anoverall et al. , 1976).Initsnorthernmost 2 3 wideareasuddenly ofmaterial. th June1992. st Maywith 25-05-2004, 15:38:11

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati riverbed where,owing toitscontinuousremoulding tured anddismembered,was channelisedalongthe The materialfromthisarea,whichisintenselyfrac- material. June, causingthemobilisationofanother30,000m sity ofaboutseveral tensofcentimetresperday, upto The movement inthisareacontinued,withaninten- years earlier. and destructionofthedrainagesystemssetupsome consequent disarrangementofalltheunstablemass scarp anda100mdisplacementdownstream, with rock. Initiallyitcausedtheformationofa15mhigh deep failure surface, affecting alsotheflyschbed- corresponds toarotationalslidewith2030m approximate volume of1millionm on thelefthand-sideof Tessina stream,withan the April 1992event occupiesa40,000m same level asthemudflow. The collapsedsectorof quite highabove theriverbed, but now nearlyatthe of Funes,whichissituatedonasteepridgeoriginally These movements seriouslyendangered thevillage valley withdisplacedmaterial30to50mthick. material, occurred,causingthefilling ofthe Tessina several reactivations, involving about5millionm sion andflanked bysteepslopes.Duringthe1960s Before 1960the Tessina valley was deeplycutbyero- its mid-lower part. and translationalslideinitsupperpartaflow in sified ascomplex movement includingarotational stretches from1200mto640m. The landslideisclas- From atopographicviewpoint, the Tessina landslide are arrangedonbothsidesofthevalley. glaciers arefound. The latter, intheformofglacis, moraine depositsfromthePiave glacierandlocal vast detriticcovers foundatthefootofMt. Teverone, ing formationswithvariable thicknesses. Apart from foot oftheMt. Teverone slopes,covering theunderly- Holocene inageandcropoutwithcontinuityfromthe The QuaternarydepositsarePleistoceneand downstream withlow angle. More downhill theattitudeissouth-dipping,dip- with themainscarpandupperlandslideportion. upstream, withoverturned strataincorrespondence from tectonicstresses.Itsattitudeisgenerallydip- to thehighdegree offissures mainlyresulting area. This formationisparticularlypermeableowing m; itmakes upthesubstratumofwholelandslide The overall thicknessoftheformationis1000to1200 and calcarenitelayersupto1mthick. up ofarhythmicalternancemarlstones,clayshales with atotalvolume ofabout2millionm 3 . The movement. The 3 ofdisplaced 2 widearea, 3 of 2 , from theoriginal300,000m led toaconstantwideningofthesourcearea,which The landslide’s evolution isstillinprogressandhas evacuated. events theinhabitantsofFunesandLamosanowere converging intothemainflow body. After these more fluidified, thus giving risetosmallearthflows and increaseofwater content,itbecamemoreand data arethenrecordedonacomputerandsenttothe placements withrespecttoprevious readings. The of morethan30benchmarks,assessingtheirdis- also installed.Every 6 hoursitmonitorsanetwork mark detectorformeasuringsurface movements was measurement system(EDM)withanautomaticland- On theupperlandslidesectionanelectronicdistance detecting movements assmallonemillimetre. of 12measuringpurpose-built apparatuses,capableof with anappropriatescalersystem,consistofaseries on themovement atthesurface. These units,fitted tion ofthelandslideinordertokeep aconstantcheck ing 280mand390m,wereinstalledintheuppersec- Two multiple-basewireextensometer units,measur- of dangeroccur. signal tosuitablylocatedstationsshouldasituation at theBellunoFireStationandsendingoutanalarm situation onanappropriateperipheralunitinstalled It processesthedata,thusgiving avisuallayoutofthe of themudflow andoftheuppersectionslide. receives informationaboutchangesandmovements The stationisinstalledinabuilding inLamosanoand a centralstationbymeansofperipheralreceiver units. measuring instrumentswhichtransmittheirsignalsto The systemconsistsofanarrangementsensorsand antee asufficient level ofsafetyforthe population. matic alertandmonitoringsystemthatcouldguar- of innovative solutionsfortheinstallationofanauto- location oftheslidemadeitnecessarytoplanaseries extent ofthemudflow movement andtheintensedis- of theslide,extension oftheareainvolved, the The particularevolution andtypologicalfeatures Instrumentation to 30m/daywererecorded. period, inproximityofFunes,velocities ofabout25 of 70to100m/dayalongthemainflow. Inthesame uphill ofLamosanoinMay1992,withdisplacements ered. The maximumvelocities attainedwererecorded erably accordingtotheepisodesandsectionsconsid- The velocity ofthemovement seemstovary consid- as about7millionm m 2 . The totaldisplaceablevolume hasbeenassessed 3 . 2 isnow about500,000 25-05-2004, 15:38:31 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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control centre, situated inside the Town Hall of Chies Through the continuous monitoring of slope move- d’Alpago in Lamosano. ments, the proposed technique has allowed the imple- On the body of the mud flow two alarm units, one mentation of real-time maps showing the deforma- comprising three directional bars and an ultrasonic tion field of those landslide sectors characterised by echometer, the other with two directional bars and an a good radar reflectivity and coherence (i.e. scarcely echometer were installed upstream of the villages of vegetated areas). These deformation maps are a tool Funes and Lamosano. for the interpretation of landslide kinematics and Three videocameras were also installed for the pur- short term-evolution, providing, at the same time, pose of recording and monitoring the slide movement data for an accurate analysis of temporal and spatial in the areas considered as the most critical, that is, the displacement fields. upper accumulation zone and the two areas uphill of Funes and Lamosano. From the Tessina landslide to Vajont The control centre receives data from the peripheral Alessandro Pasuto stations to which the sensors are connected. It also The route towards the Vajont landslide is the same as defines possible situations of danger and sends data the one followed during the transfer trip in the oppo- and signals via modem to an alarm station located at site direction. Having arrived in Longarone, we turn the Belluno Fire Station. to the right across the River Piave going up the left- In order to follow the developments of this process hand side of the valley. In correspondence with the the station is integrated with an image acquisition and first tunnel, we follow the valley of the Torrent Vajont recording system which allows direct visual observa- going towards the administrative border between the tion of the upper landslide section. regions of Veneto and Friuli-Venezia Giulia. This road The peripheral units receive and perform preliminary was purposely built for the construction of the dam. processing of the data from the instruments (i.e. Before the 1950s there was only the steep and narrow echometer, directional bars, extensometer) and verify road going up the Vajont valley on the opposite slope. their effectiveness. After passing some narrow tunnels dug directly into In the event of a critical development of the situ- the rock, we arrive in proximity of the dam whose ation, various alert levels can be determined (i.e. reservoir caused the terrible disaster of 1963. pre-alarm, normal alarm, serious alarm), with an indication of the peripheral units and sensors directly Stop 2.2: involved. It is also possible to have access to the data The Vajont landslide in real time mode, by connecting up each peripheral Emiliano Oddone, Alessandro Pasuto and device and checking the instrumentation, as well as Fabrizio Tagliavini providing access to data concerning daily, weekly or monthly trends of each sensor by means of special Introduction programmes. The Vajont reservoir in Italy’s eastern Alps is located In recent years an innovative technique, based on along the lower reaches of the River Vajont, close radar interferometry and implemented using ground- to its confluence with the R. Piave. Some 100 km based instrumentation, has been applied for monitor- NNW of Venice, the reservoir was created artificially ing the Tessina landslide. This technique has allowed in 1960 after the T. Vajont was dammed as part of multi-temporal surface deformation maps of the entire regional expansion in hydroelectric-power genera- depletion zone of the landslide to be derived with a tion. The dam is 261.60 m high and 190 m across the high resolution and accuracy. The application of the top, and at the time of construction was the highest ground-based SAR interferometry to the Tessina and one of the most advanced double-arched dams landslide has been implemented by using portable in the world. After the reservoir level had been raised P14 to P36 n° 4 - from Volume field instrumentation that can be installed in a very and lowered several times, the southern margin of Mt. short time (few hours). Derived data have shown Toc became eventually destabilised and, after nearly the evolution of ground movements over almost the three years of intermittent creeping, it catastrophi- entire depletion zone of the landslide. Displacement cally collapsed at 22:39 hours on 9th October 1963 rates up to about 1 m/day have been assessed with (see cover photo). Within 30-40 seconds, some 270 a millimetric accuracy and a pixel resolution of million m3 of rock crashed into the reservoir, expel- approximately 2x2 m. ling a wave of water about 100-150 m high over the

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati 270 millionm for 300to400mhorizontallyinvolving avolume of This slidedisplaceda250-300mthickmassofrock the Fonzaso Fm.(seebelow). ing thesameangleasslope,whichcharacterise to oneormoredip-downstream clayey interbedshav- slide, startedtomove alongasurface corresponding dam. The vast slopemovement, ascribabletoarock the valley follows thatofitspre-glacialpredecessor, a widthof150mto20m. The currentE-Wtrendof has decreasedtoavertical dropof240mandfrom ducing thedeepandnarrow Vajont gorge thattoday ily erodablematerialsofthelandslidedeposit,pro- river subsequentlycutanew coursethroughtheeas- truncated byanorth-east-directedlandslide. The the lower reachesofthe T. Vajont werecompletely Authors suggestedthatduringthelastdeglaciation morphological assessmentofthe Vajont area. These be consideredasthestartingreferenceforgeo- The reportbyCarloniandMazzanti Geological andgeomorphological setting Vajont withtheformationofanimpoundment. the Vajont slide,whichhadpreviously dammedthe T. ancient landslide,LaPinedaupstreamof by the T. Vajont. They alsoidentified anothermassive northern sideofthevalley, isolatedbythegorge cut a slidewithanabnormalattitudeontheopposite deposit, citingamyloniticbeltandtheremainsof that Mt. Toc was covered byanancientlandslide inferred. GiudiciandSemenza(1960)first realised landslide depositandnotofbedrock,asinitially the mountain’s outerflanksconsistedofanancient were morepronetoinstabilitythanexpected, since Mt. Toc andthesouthernslopeof Vajont valley of thereservoir reached168millionm was eventually completedin1959. The water volume of thedam,whichattainedheight261.60m, War II,theprojectwas modified andtheconstruction high damhadstartedinthelate1920s. After World Geological studiesfortheconstructionofa200m villages, claiming1909lives. destroyed thetown ofLongaroneandneighbouring eventually fellontothePiave valley floor, whereit It sweptacrossthedamand Vajont gorge and elevation of935m(235above thereservoir level). and downstream. This wave reachedamaximum causing awave ofwater propagatingbothupstream the valley andthereservoir inafew tensofseconds opposite slopeofthe Vajont valley. The slidefilled 30 m/sbeforerunningupandstoppingagainstthe 3 . Itreachedavelocity ofabout20to

3 (1964) should . breccias andconglomeratesarecharacterisedbygreat associated withstratigraphicunconformities. The and conglomerates-and-brecciasthataresometimes can befurthersubdivided intobioclastic calcarenites scars. The coarsercomponentsoftheslumpmaterial intraformational discordancesinterpretedasslump with nodulesandbedsofchert. There arenumerous micrites andmarls,thatcanbegrey, redorgreenish is madeupofdecimetriclayersmicrites,marly coming fromtheFriulishelf. The fine component calcarenites andbioclastic-intraclasticcalcirudites thick). An alternationofmicrocrystallinelimestones, Soccher Limestone whole area. pre-existing topographybecauseitcovers evenly the typical facies ofScaglia. This formationlevelled the stones, completelylackinggravity resedimentsisthe monotonous successionofmarlsandredmarlylime- Scaglia Rossa litharenites. bated, containingrarethinlayersofcalcarenitesand subordinate grey marlylimestones,intenselybiotur- Rossa andtheFlyschisformedbymarls mal unitrepresentsthetransitionbetweenScaglia Erto Marls by marlsandgrey marlyclays. grey oryellow litharenites;themudstonesareformed arenitic fractionismadeupofcalcarenitespassingto turbiditic arenitesintercalatedwithmudstones. The Flysch Bedrock from marineshelves. formations reflectvariations inthematerialcoming Indeed, mostofthecharacteristicdifferences between from marineshelves aroundthebasinmargins. they weredriven intothebasinbygravity currents and ooliticorbioclasticcalciruditesareoftenfound; pelagic fauna accumulated.Interbedsofcalcarenites was partofabasininwhichchertymicriteswith (Flysch) (Figure9).DuringtheLower Liasthearea Triassic (DolomiaPrincipale)totheMiddleEocene geological formations,rangeinagefromtheUpper In the Vajont valley andadjacentmountaingroup debris, allQuaternaryinage. vial andtorrential),sometimescemented,slope of morainedeposits,ancientalluvialdeposits(flu- of thegorge withlooselandslidematerialconsisting following the1963slide,especiallywithinfilling topographic featuresoftheareachangedenormously determined inturnbyaregional tectonictrend. The (Eocene;>200mthick). A successionof (Paleocene; 100-150mthick). This infor- (UpperCretaceous;~300mthick). A (Lower-Upper Cretaceous;150m 25-05-2004, 15:38:36 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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lateral continuity and are visible in the mass which trunks. There is no evidence of significant interaction slid from Mt. Toc. between this unit and waves produced by the collapse Ammonitico Rosso (Kimmeridgian Titonian; 5-15 and this is consistent with a second-stage collapse, m thick). Nodular reddish and grey micrites with shortly after the displacement of subunit A. ammonites, occurring as massive units or as layers of Subunit C is the portion of the landslide deposit more than 1 m thick that differ only in colour from the directly against the dam, south of state road no. classic facies outcropping in the Veneto area. 251 (Val Cellina-Val di Zoldo) and north of subunit Fonzaso Fm. (Oxfordian; 10-40 m thick) The A. The surface is lower than that of subunit A and complex succession of levels between the Vajont consists mainly of sand and gravel. The loose surface Limestone and the Scaglia Rossa have been attri- material completely covers the originally displaced buted to the Soccher Limestone. The Fonzaso Fm. is slope (which underneath may be continuous with the formed by finely graded biocalcarenites and chert- adjacent subunit A) and appears to have been derived rich, brown micritic limestone in 5-20 cm thick beds from fragments washed back onto the landslide by the with parallel and oblique laminae. Interbedded layers return wave immediately after collapse. of green claystone (5-10 cm thick) are of particular interest because of their role in the movement of the Future perspectives Vajont landslide. At present the areas affected by the 1963 slide are Vajont Limestone (Dogger; 450 m thick). Hazelnut subject to numerous environmental and town plan- oolitic calcarenites, massive or layered in thick beds, ning restraints. Recently, in-depth investigations intercalated with decimetric layers of brown basinal have been carried out in order to define the residual micrites and intraformational breccias (clasts formed geological risk and facilitate the upgrading of the ter- from the erosion of the micrites). The latter are more ritory. These investigations, though, have identified a frequent in the upper part of the formation. Nodules rather serious risk situation for the hamlet of Casso, and beds of brown chert can be locally present. owing to a rock fall accumulation located upstream Sedimentary structures are represented by graded of some houses in the upper part of the village. As beds with parallel or oblique laminae. for the slide deposit of 1963, no particular stability problems have been identified, whereas the surfaces Landslide morphological features of rupture are still affected by circumscribed debris The Vajont landslide deposits can be divided into slides which, nevertheless do not cause risk situations three kinematic subunits, following the order of considering the inaccessibility of these areas. events occurring during the 1963 collapse (Figure 9). Numerous initiatives have been enterprised in order Subunit A describes the northernmost part of the land- to assess this territory and contribute to keeping the slide which, now infilling the valley, was originally memory of the catastrophic disaster alive. Among at the toe of the unstable slope and represents the these, are the creation of a permanent laboratory for material that displaced the water of the Vajont res- the study of hydrogeological hazard and the spreading ervoir. It consists of a single mass of layers strongly of information concerning the increased perception of deformed during collapse. All prefailure vegetation these kinds of risk. This laboratory is jointly run by an Italian-Japanese team promoted by the Italian Foreign was removed. However, it has been possible to map Ministry within the framework of the 7th Executive the principal surface fractures and prefailure surface Programme for Scientific and Technological Co- material which survived the return water wave after operation between Italy and Japan. collapse (ancient collapse and glacial deposits). At present, other initiatives concern the creation of These features are interspersed with zones of frag- the so-called “multi-centre museum”, consisting of ment accumulation – the fragments being poorly- historical-naturalistic paths, permanent exhibitions, sorted mixtures ranging in size from gravel to blocks video-cassettes and other educational and/or popular P14 to P36 n° 4 - from Volume – produced during deposition by the return wave. multimedia material about the sites where the cata- Depressions are also visible along its western margin, strophe occurred, in order to keep alive the historical above the dam. memory of what happened – especially among youn- ger generations – and increase awareness of natural Subunit B is an intermediate unit between the present risks. failure scarp (at a higher elevation) and subunit A below. Prefailure vegetation is visible, trees showing classic landslide deformation marks along their

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati Figure 9-Geomorphologicalsketch mapofthe Vajont landslidearea 21-06-2004, 15:26:19 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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From the Vajont landslide to Cortina stones and dolostones with subhorizontal bedding d’Ampezzo characterise the valley’s left flank, whereas at the Anna Galuppo, Alessandro Pasuto foot of the slopes thick talus fan covers are found. and Enrico Schiavon On the contrary, on the right flank the strata bedding Starting from the Vajont dam, we go down the same is dip-downstream and the big step-like features are road that leads to Longarone, then follow the state due to tectonics. road to the north running parallel to the R. Piave. Owing to this geological setting, the left slope, which Upstream of the village of Castellavazzo, the valley is more densely inhabited, is subject to several debris becomes rather narrow, with steep rocky slopes rising flows which seriously threaten some villages such as above a flat and overfilled valley floor. A new diver- Cancia and Acquabona. sion of state road no. 251, which has been recently constructed, further reduces the already narrow river- Debris flows at Cancia bed, thus increasing a serious hydraulic risk situation. Debris flows have repeatedly struck the village of The valley of the R. Piave becomes wider at its Cancia, affecting the western slope of Mt. Antelào confluence with the right-hand side tributary Torrent and mobilising vast volumes of material. The dolom- Boite. This portion of the Dolomites where the villa- itic rocks cropping out along the slope are intensely ge of Perarolo di Cadore is situated, shows a rather jointed and partially covered by a thick debris complex situation from both the structural and hydro- deposit. These processes have been described in geological disarray point of view. This area is, in fact, chronicles since the 14th century. In 1868, during the subject to numerous disarrangement processes, some most destructive event ever recorded, a debris flow of of which directly affect inhabited areas, inducing high over 100,000 m3 buried the centre of Cancia claim- risk situations for the population. ing 11 lives. Starting from the 1950s, all the area has undergone intense development. In particular, a tour- S. Andrea landslide, Perarolo di Cadore ist village and a new area of Cancia have been built, The bedrock corresponds to the most recent terms whereas the manifold canal was artificially prolonged of the Triassic sequence (Dolomia Principale, Raibl downstream. and Dürrenstein formations). The large S. Andrea On 7th August 1996, following very intense, con- landslide, just upstream of Perarolo, affects both state centrated, though not exceptional, precipitation, a road no. 51 and the railway. The active portion of debris flow was triggered which struck Cancia after the landslides has an approximate volume of some travelling about 2800 m (Panizza et al., 1998). The 4-500,000 m3 and is constantly monitored by the area affected by the latest flows is some 70,000 m2, Veneto Region. Observations from aerial photographs whereas the area which has been involved in more and field surveys have allowed a vast relict landslide ancient slope movements may be estimated as about involving gypsum and dolomite formations to be 200,000 m2. identified. Uphill of the accumulation of the active This process tends to reoccur with time, often creat- landslide a dormant earth flow affecting the red clays ing high risk situations for the inhabitants of the area. of the Raibl Fm. is found. Its accumulation material, In addition, it can be assumed that interventions made which is substantially impervious, conveys surface in the territory have probably had a negative influ- water towards the active landslide. ence on the transport and accumulation patterns of the landslide material. In particular, the construction Having arrived at the village of Tai di Cadore we of check dams and bank reinforcements have con- turn left, going up the valley of the Torrent Boite. strained the debris flow into a narrower channel, thus After a few kilometres, we reach the village of Valle increasing its velocity and energy. Since it is practi- Volume n° 4 - from P14 to P36 n° 4 - from Volume di Cadore, which has been subject to instability cally impossible to stop possible new flows along processes since the disastrous flood of November the defile, remedial measures have been directed to 1966. After this village, the valley becomes gradu- mitigate the consequences in terms of risk. For this ally wider, assuming on its left flank the typical “U” purpose, a flow control and containment weir has profile resulting from the intense glaciation of the been constructed at the confluence of the two defiles LGM. This valley is characterised by the presence at an altitude of 1300 m circa. of a W-verging overthrust front, which conditions its marked asymmetry. Vertical rock faces of lime-

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati Berti Mass wasting processesoccuringat Acquabona (see Acquabona debrisflow larly pronetodisarrayprocesses,withthepresence the area.Indeed,valley aroundCortinaisparticu- these rocksaffects alsothestabilityconditions ofall dable Triassic rocktypes.Naturally, thepresenceof even widerowing tothepresenceofparticularlyero- we arrive inCortinad’Ampezzo,wherethevalley is After leaving the Acquabona area, systems. deep pressuretransducersandvideo eters, raingauges,superficial and utilised aregeophones,anemom- rate. The measuring instruments performs datatransmissionatfaster value isexceeded, the“event” mode “pre-event” mode. When athreshold sion timeinterval isfive minutesin to Padova University. The transmis- master station,andthenviamodem radio. Dataaretransmittedtothe small dataloggerandatwo-way on-site stationisprovided witha 1.3 kmfrom Acquabona creek.Each site mastercollectionstationlocated site monitoringstationsandanoff- University. Itconsistsofthreeon- installed at Acquabona byPadova trolled monitoringsystemhasbeen A fullyautomaticandremote-con- viduated atthenaturalrocky dam. where anotherpossibleinitiationareaistobeindi- ty andlightlycementedmaterialsinthechannelbed, in whicharapidinflow ofwater mobiliseslow densi- flows arelikely tobestartedbythe“fire hoseeffect”, upper channel,between1550mand1650m.Debris The initiationareaofdebrisflow islocatedinthe built forroadsafety purposes. The terminaldepositsareconfined byadebrisbasin dam whichmaycauseavulsion oftheflowing mass. decreases, thechannelispartiallycloggedbyadebris tion area(about1200m),wheretheslopelocally the slope. Approximately 500muphillthedeposi- lobes) arevisibleonthemiddle-lower portionof vegetated debrisflow deposits(laterallevees and do notconstituteaneffective boulderdam.Partly present justatthebottomofrockcliffs, but they scree andancientdebrisflow deposits.Bouldersare The debrisflow channelisdeeplycutmostlyintothe flows intheDolomites. et al ., 1999)aretypicalexamples ofdebris Figure 10-PhysiographicsettingoftheCortina d’Ampezzoarea. forecast futuremovements systems onthemostlandslide-proneslopessoasto slide hazardandthereforeplaninstallmonitoring evolution inthestudyarea,but alsotoassessland- a generalpictureoflandslidecauses,occurrenceand This hasenabledtheresearchersnotonlytodefine geology, geomorphologyandengineeringgeology. research projects,involving primarilyexperts in the beginning ofthe1990smainlywithinEuropean been carriedoutonamulti-disciplinarybasissince d’Ampezzo (Province ofBelluno)(Figure10)have Landslide investigations intheareaofCortina Introduction Mauro Soldati Landslides intheCortinad’Ampezzoarea dimensions. of numerouslandslideshighlydiverse typesand In fact, duringthelast Alpine glaciationthestudy Holocene, inparticulartothepost-Würmian period. deposits, areascribabletotheUpperPleistoceneand of superficial deposits,mainlymadeupoflandslide The geomorphologicalevolution andemplacement Landslide causes Stop 3.1: DAY 3 25-05-2004, 15:39:04 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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area, apart from the highest peaks, was covered by a As regards earthquake-induced slope instability, the considerable ice thickness up to 1000 m. Of the vast only confirmed case of correlation is the Cinque glacial deposits which occupied the study area after Torri earth flow which occurred nearby in concomi- the glaciers’ withdrawal, only a few remnants were tance with the quake which took place on the 15th of found, probably ascribable to Lateglacial stadial phas- September 1976 in the Friuli-Venezia Giulia Region es, which have been preserved thanks to the presence (Zardini, 1979). In general, no relationship was found, of rocky rises which hindered their erosion. On the mainly because the time scale of landslide occurrence contrary, no trace of deposits from the LGM phase has and of the seismic series recorded are not comparable, ever been found. This is mainly due to the numerous, since the latter refer only to historical time. vast mass movements occurring during the withdrawal of glacial masses. During this period the area was Description of the main landslides affected by several slope movements which in most Over thirty landslides of different type, size and age, cases involved dolomite rock types; their accumula- some of which still active, have been identified in tions could have been reworked afterwards by slide the whole area (Panizza, 1990; Panizza et al., 1996; and flow processes affecting the S. Cassiano Fm. Pasuto et al., 1997; Soldati, 1999; Soldati et al., 2004) At present, the climate of the area can be defined as and many of these were dated by means of radiomet- Alpine type, from cold to temperate, with variably ric methods (for landslide location and dating infor- cold winters and mild summers. The pluviometric mation see Figure 11 and Table 1). The landslide characteristics of the area were deduced from data characteristics are generally linked to both lithologi- recorded at two meteorological stations: Cortina cal and structural conditions; rock falls occurred in d’Ampezzo (1275 m) and the Codivilla-Putti Institute the higher parts of the slopes, where the dolomitic (1350 m). The data cover a time span from 1920 to rocks outcrop, whereas slides and flows took place 1990 with a yearly average of about 1108 mm. Late in the medium and lower sectors of the slopes, where springtime and summer are the most rainy periods, marly and clayey formations are present. Extensive with a peak in July. In this case, precipitation occurs movements affecting the slopes from the top to the mostly during violent rainstorms, with intense, con- bottom have been ascribed to those of the complex centrated events. type. The types of slope instability also seem to have The area of Cortina d’Ampezzo appears to have changed through time. From the data gathered so far always been prone to slope instability processes for through 14C dating, it seems clear that the Lateglacial various reasons. First of all, the structural conditions and early Post-glacial period witnessed the majority of the valley should be taken into account. The strati- of the largest mass movements in the area of Cortina graphic succession, in fact, features an alternation of d’Ampezzo (Soldati et al., 2004). Huge rotational dolomite rocks showing brittle mechanical behaviour block slides occurred, involving both clayey and and rocks with ductile mechanical behaviour. This dolomite materials; their occurrence is still clearly situation has favoured the development of mass witnessed by geomorphological evidence. Actually, movements and deep-seated gravitational slope the slope evolution of the area has always been deformations; the latter, which have been widely rec- characterised by the presence of recurrent landslides, ognised in the area, may have favoured or induced the mainly flows and slides involving the S. Cassiano occurrence of several landslides (Soldati and Pasuto, Fm., generally of minor dimensions and higher fre- 1991). Furthermore, the incidence of tectonics is also quency than those mentioned above, which have had significant. In fact, the dolomites were affected by a shorter persistence in time. For this reason only the intense jointing in correspondence with the princi- most recent ones, as well as those still active today, pal faults, thus creating discontinuities that became are recognisable. Reactivations of older landslide potential sliding surfaces and preferential seepage deposits, which generally involved relatively small P14 to P36 n° 4 - from Volume zones where the water could reach and moisten the thicknesses (up to 15-20 m circa) of material in earth underlying marly and clayey formations. flows, may also be ascribed to this group. Particularly rainy periods occurred during the years The main landslides in the area of Cortina d’Ampezzo 1965 and 1966, when many Italian regions suffered are described below (Figure 11 and Table 1) (see disastrous floods. On that occasion the Cortina Pasuto et al., 1997). d’Ampezzo area was affected by numerous mass movements which mostly consisted of reactivations Col Drusciè landslide of older landslides. This is a complex landslide whose body corresponds

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati is therelictremnantofalarge complex landslide S. CassianoFm.Itmaybeinferredthatthisdeposit matrix resultingfromtheweatheredrocktypesof and DolomiaPrincipalemixed withaclayey-silty some tensofcubicmetreslarge, ofDolomiaCassiana The landslidebodyismadeupofboulders,to Pierosà landslide manner, mixed withpolygenicdetritus. boulders ofDolomiaPrincipalearrangedinachaotic et al. produced aminimalageof9000±150years(Zardini allowed radiometricdatingtobecarriedout,which finding ofatreefragmentatdepth ofabout15mhas to theoldestsectorofawideraccumulation. The Table 1(afterSoldati etal.,2004). 2) landslide;3)screeslope;4)debris ﬂ Figure 11-Geomorphologicalsketch oftheCortinad’Ampezzoarea(heightsaregiven inmetres).Legend:1)bedrock; , 1984). The landslidebodyismadeupofhuge ow and/oralluvialfan;5)lacustrinedeposit;6)landslidenumberingaccordingto Colle diS.Roccoasfar asthepresentareaofPezziè. on theslopeofFaloria massif,stretchingfromthe movement thatwas triggeredintheearlyPost-glacial The Zuellandslidebodyispartofavast complex Zuel landslide 0.5 cm/year. moving tothesouthatadisplacementrateofsome in thepastyearshasshown thatthePierosàridgeis BP. Precisiontopographicmeasurementcarriedout has allowed thisevent tobedated10850±80years trunk atadepthofabout4-5minGrava diSotto, mobilised byflow processes. The finding ofatree Part ofthisaccumulationmaterialwas subsequently that detachedfromthecrestofMt.Pomagagnon. 21-06-2004, 9:18:15 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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The landslide crown is quite visible, and consists of frequent fragments of organic material. These depos- a regression of the rock walls between 2055 m and its are now stabilised and correspond only partially 2115 m. To the south a portion of slope, which is still to the “Begontina landslide” as mapped by Panizza in precarious equilibrium conditions, is confined by and Zardini (1986). The most ancient landslide event the scarp. Displacements, which have prevalently so far detected, corresponding to an age of 8710±70 affected the Dolomia Principale Fm., have been years BP, has been identified by means of a peat favoured by the structural conditions of the slope, sample found at a depth of 23 m in a borehole near which is characterised by a dense discontinuity net- the centre of Staulin. A later reactivation was dated at work. 4350±60 years BP thanks to a wood specimen found The dating of two tree fragments found in a trench south of Verocai (Cianderies). Further displacements near the fork between state road no. 51 and the go back to 3315±140, 2560±80 and 2465±125 years local Pezziè road has produced a conventional age BP, as witnessed by the dating given by organic mate- of 9440±105 and 9215±105 years BP, respectively. rial recovered at various depths from boreholes near These finds were also reworked by the subsequent Staulin. Another radiometric dating carried out on a Pezziè landslide. On the basis of geomorphological tree trunk found at a depth of 7 m in the centre of observations, it is assumed that the two dates refer to Cortina has allowed an event from 1460±30 years BP the same event. to be dated. At present, two portions of the Cortina d’Ampezzo Cortina d’Ampezzo landslide landslide are active in correspondence with the This slide has involved the eastern sector of the Staulin and Alverà hamlets (Figure 12). They are Pierosà body in slow flows which have given rise to made up of two earth flows stretching from 1700 and a fan-shaped deposit on which the town of Cortina 1500 m as far down as 1300 m, respectively, affecting d’Ampezzo is situated. Associated lacustrine depos- surfaces of some 40 and 10 hectares, respectively. In its resulting from the damming of the Torrent Boite 1935, both villages were listed among the settlements have been found in the Ice Palace area and palustrine to be transferred. deposits in correspondence with the Post Office Subsurface investigations have allowed two failure square. surfaces to be identified at depths of about 25 m and The materials making up the landslide body are 8 m in the Staulin landslide, and 23 m and 5 m in the prevalently composed of grey clays and silty clays Alverà landslide (Angeli et al., 1996; Gasparetto et incorporating large blocks of Dolomia Principale and al., 1996). Volume n° 4 - from P14 to P36 n° 4 - from Volume

Table 1 - Radiocarbon dating in the area of Cortina d’Ampezzo; data calibrated with Radiocarbon Calib. Program 4.1 by Stuiver and Reimer (1993), data set by Stuiver et al. (1998) (after Soldati et al., 2004, modiﬁ ed).

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati There arethreemainactive landslidesthe Alverà, Active landslides ing animpoundment,thatstillexists. houses, barredthecourseof Torrent Boiteform- state roadno.51“Alemagna” and,aftersparing some Pomagagnon nearthehamletofFiames,blocked flow, whichaffected thetalusfans atthe footofMt. a roadbridgeandkilledpoliceofficer. A second had seriousconsequences.Onedebrisflow destroyed was affected byaseriesofdebrisflows, two ofwhich northern sectorofthevalley ofCortinad’Ampezzo September 4 have severe consequences. As amatteroffact, on even massmovements ofmodestmagnitudecould of tourists.Intheseconditionshighvulnerability, all theDolomiteregion isvisitedbyalarge number areas andtake placeespeciallyduringsummerwhen interfere withtransportinfrastructuresanddeveloped large amounts of detritus. These debrisflows often arranged ontectonicstructureswhichcanconvey to silt.Nearlyallofthemcomefromnarrow defiles with particlesizedistribution rangingfromblocks al. and Acquabona (Pasuto andSoldati,2004;Berti originated bythistypeofprocesssouthFiames alluvial fans canbenoticed. They weremostly material. IntheCortinad’Ampezzoarea,large rainstorms canmobiliseconsiderableamountsof The debrisflows occurringduringheavy summer Debris flows atFiamesand Acquabona age ofabout9270±105yearsBP. recovered fromadepthofabout22mhave given an and buildings. Dating carriedoutontreefindings causing seriousdamagetotransportinfrastructures ments have attainedvelocities ofabout2mperyear, below thegroundsurface. Inthepastyears,displace- at adepthofsome10mandsecondarysurface 6m Boreholes have identified amainsurface ofrupture the fan-shaped accumulationzone. ment assumeshighervelocity incorrespondencewith is clearlyactive (RioRoncattolandslide). The move- marginally. Along theRoncattotorrentmovement state roadno.48andsomehouses,thelatteronly of sandstonesandcalcareniteswhichhave affected made upofsiltyclaysincorporatingbroken fragments fan-shaped accumulationzones. The materialsare which have contributed tothefeedingoftwo large bodies characterisedbytwo separatesourceareas This ismadeupofthedepositssomeearthflow Lacedel landslide , 1999). These materialsareofdolomiticorigin th 1997,following aheavy rainstorm,the et sliding surface hasbeenrecognisedatadepthof10.5 Concerning theRioRoncattolandslideaprincipal recorded is182.5mm/year. about 5mand23(Figure13). The movement rate ments revealed two slidingsurfaces atadepthof As forthe Alverà landslide,inclinometric measure- The movement raterecordedisof15.6mm/year. ing surface was foundat19.5mdepth(Figure13). As regards theStaulinlandslide,awelldefined slid- data transmission. been connectedwithamodemwhichallows real-time located inCortinad’Ampezzo. The systemhasalso using instructionssentviaradiofromthecentralunit linked tofourperipheralunitswhichacquiredataby connected totherecordingsystem. The sensorsare gauge (giving thesnow cover depth),hasalsobeen gauge, anairthermometerandultrasonicsnow climatic station,consistingofatippingbucket rain Casagrande piezometersandwireextensometers. A holes have beenequippedwithinclinometrictubes, et al. by meansofautomaticsystemssince1989(Angeli ties, theseslopemovements have beenmonitored Because oftheirpotentialriskforhumanactivi- landslide effects onconstructions. slides inthelastfew yearswiththeaimofmitigating remodelling, have beencarriedoutontheseland- of superficial drainage,retainingwalls andsoilmass on theroadswerefound.Remedialworks, consisting a few recordsregarding periodicmaintenanceworks which consistsalmostentirelyoffarming land,only expense oftheItalianGovernment. As forLacedel, included inthelistoftowns toberelocatedatthe 1942 and1951;in1935,boththeselocalitieswere events occurredin1879,1882,1924,1927,1935, have affected thevillagesof Alverà andStaulin:major Historical recordsreferabove alltolandslideswhich dormant atpresent,ofafew centimetresperyear. 20 cm/yearandtheStaulinlandslide,whichisalmost the vicinityofLacedel; Alverà landslideofalmost landslide shows displacementsofabout2m/yearin evolve withsimilarmechanisms. The RioRoncatto show different ratesofdisplacement,althoughthey the Lacedellandslide(Figure12). These phenomena the RioRoncattolandslideisapartialreactivation of d’Ampezzo landslide,asmentionedabove, while considered aspartialremobilisationsoftheCortina Fm. The movements at Alverà andStaulinshouldbe rial derived fromtheweatheringofS.Cassiano according toBritishusage)whichaffect clayey mate- Staulin andRioRoncattoearthflows (mudslides , 1996;Gasparetto et al. , 1996). A few bore- 25-05-2004, 15:39:13 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Figure 12 - Location of the active mass movements: 1) Alverà, 2) Staulin and 3) Lacedel (after Soldati, 1999).

m (Figure 13). The average rate of movement record- confirmed by repeated topographic surveys (Angeli ed is 2.55 m per year for the recorded period. Another et al., 1996). sliding surface has been found at a depth of 7.5 m. A good correlation between groundwater levels and The life of the inclinometric tubes has been quite displacements has been obtained, especially for the short due to significant displacement. Nevertheless, Alverà landslide to which a visco-plastic rheological the data subsequently obtained from the wire exten- model, capable of simulating the movement rate on someter has shown continuous deformation without the basis of recorded groundwater levels, has been a significant variation in velocity. This has been applied. The model has been appropriately calibrated Volume n° 4 - from P14 to P36 n° 4 - from Volume

Figure 13 - Inclinometric curves of the Staulin, Alverà and Rio Roncatto landslides (after Soldati, 1999).

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati groundwater levels. the basisofafouryearrecorddisplacementsand ments. The validity ofthemodelhasbeenverified on groundwater level andtherateoflandslidemove- fore gives anexplanation oftherelationshipbetween using thelarge amountofdatacollected,anditthere- wall. Halfway upthewall, itispossibletonoticea active scree-slopedepositsandavertical dolomitic the topofMt.Lagazuoi,wecrossamoraineridge, (2105 m)toward the LagazuoiRefuge(2752m)at As wegoupbycablecarfromtheFalzarego Pass Alessandro Ghinoi The LagazuoiRefuge Stop 3.2: by theFriuli Venezia Giuliaearthquake of15 side oftheroad,landslidethatwas triggered Falzarego Pass. After about3km,ontheleft-hand- From Pocolwemove westwards towards the features inthevalley. observation oflandslidesandothergeomorphological d’Ampezzo area;sothisisanideallocationforthe we canhave analmostcompleteview oftheCortina Having reachedthe Belvedere ofPocol(1539m), Pocol relief(DolomiaCassiana). witnessing rockfalls fromtheoverlying dolomitic tinues acrossawood whichcontainshugeboulders mark thisroute. After some500mtheexcursion con- on theroadinvicinityofhamletLacedel Lacedel landslide.Evidentdisplacementsandsteps slope ofthevalley andcrossthetrackzoneof lowing stateroadno.48,wegoalongthewestern After leaving the centre ofCortinad’Ampezzo,fol- Mauro Soldati to theFalzarego Pass From Cortinad’Ampezzo rock cliffs ofCinque Torri. Averau (2647m)andNuvolau (2574m)aswellthe hand sidethereisagoodview ofthedolomiticpeaks avalanche conesanddebrisflows, whileontheright- observed. After awhile,they areinterruptedby mountain groupsurroundedbyscreeslopescanbe the Falzarego Pass, theimposingcliffs ofthe Tofàne On theright-hand-sideofroad,goinguptowards crown area(Zardini,1979). the RaiblFm.,thatareclearlyvisibleinlandslide movement affected thereddishclaysandmarlsof ular dolomiticreliefofCinque Torri (2361m). The earth flow affecting theslopeunderlyingspectac- September 1976canbeclearlyobserved. This isan th

away 10,000tonsofrock(17 creating apronouncedconcave shapeandsweeping destroyed thenaturalprofile ofthemountaincrest, 20,000 deadbytheendofwar). An Italianmine that itwas renamedColdiSangue(BloodyHill;some battles betweentheItaliansand Austrians, sobloody Lana, too,was thesettingofsomebloodiest of frontalmorainesandtill,visibleatitsfoot.Coldi side usedtocontainaglacierwhosedepositsconsist Upper Ladinian)ofLa Valle Fm.ItsNEbowl-shaped sandstones (depositedbyturbiditiccurrentsduringthe m) canbeseen,whichiscomposedofvolcanoclastic To thewestdarkshapeofColdiLanarelief(2464 till deposits. tional activity representedby its topleaving clearsignsofitserosionalanddeposi- toward NNW. Itusedtohostaglacierthatsculpted Lagazuoi itselfisastructuralplateauslightlyinclined showing allthebeautyofDolomitescenery. Mt. Once atthetop,thereisaspectacularpanoramicview mountain boots. visited ifoneisequippedwithhelmets,torchesand an open-airmuseumof World War Ithatcanbe Italian, Austrian andGermansoldiersthey form tunnels werere-openedbyapeacefuljointteamof the closerenemywas. A few yearsago,those could beheardfrombothsides:theloudersound, ing positions.Usuallyatnight,dynamiteexplosions with theaimofgettingclosertoenemyandgain- armies built aseries oftunnelswithinthemountain ernmost partofitwas under Austrian control.Both was conqueredbytheItalian Army whilethewest- armies (von Lichem, 1993). This partofMt.Lagazuoi no significant advances foreitherofthetwo opposing 1918), therewas adisastrousposition-war thatledto Armies iscloseby. For threeyears(from1915until ning betweentheItalianand Austrian-Hungarian for amineattack.Infact, theformerfront-linerun- the Italian Army in World War Iasstrategic location “cengia” (atypicalstep-like morphology)chosenby 1998). During World War Itheglacierhosteda around 2700m,usingthe2:1-isolinemethod(Masini, topographic ELAforthisglacierhasbeencalculated Altitude) isbetween2800mand2900m,whilethe The currentregional climatic ELA(EquilibriumLine Lower Ladiniannamed“Marmolada Limestones”. massive limestones(bothdetritalandorganic) ofthe steep inclination. The mountainisformedbygrey descends, from3343m,facing north,witharather Behind ColdiLana,theglacierofMt.Marmolada 2000). roches moutonnées th April 1916)(Dibona, 25-05-2004, 15:39:20 and GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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network of tunnels and rooms where the Austrian- sive and rapid uplift and emersion of the dolomitic Hungarian Army had one of its most important area. One of the highest peaks of the group is Mt. headquarters at the front. The temperature inside the Sassongher (2665 m) overhanging the village of glacier was much more favourable than the outside Corvara in Badia; a source of rock fall events in one and the snow-avalanche risk was avoided. This the past it is likely to cause others in the future. under-ice protection system was called “the ice town” Significant landslide events have recurred on the east- (Bobbio and Illing, 1997). Nowadays the glacier sur- ern side of the Puez-Gardenaccia Group, sometimes face is used for skiing and for different events: one of creating natural dams which favoured the develop- the most curious being a golf tournament (!) in 1997. ment of lakes (Corsini et al., 2000). If we look towards the west we encounter the Looking north we face the Conturines Group (3077 bowl-shaped morphology of Mt. Settsass (2571 m). This is a thick sequence of Dolomia Principale m). The clino-stratification of the dolomitic rocks cut by a 45° south-verging thrust (Neogene) and mainly composing it (Dolomia Cassiana, Carnian) with a summit of scattered Calcari Grigi di Fanes can be observed, with a dip-direction and inclina- (Lower–Medium Lias). The slightly NE-inclined flat tion N30°. Of interest is also the so-called Piccolo top was covered by an ice cap whose outlet lobes Settsass (Small Settsass), which lies beneath the reached both the Valparola and the Boite Valleys major peak looking south. Its presence seems to be (Sauro and Meneghel, 1995). Still well preserved are ascribable to a sort of aborted coral reef, covered some frontal and lateral moraines of the Lateglacial by deep-sea sediments coeval with the S. Cassiano whose relative dating allowed the reconstruction of Fm. Environmental conditions then became favour- that period’s geomorphological evolution (Masini, able for the development of a wider and thicker reef 1998). In 1987, a man from Val Badia discovered the on top of deep-sea scarp sediments, which form the fossilised remains of a species of bear called Ursus main body of Settsass (Panizza, 1991). On top of Mt. speleus. These remains were found inside a hidden Settsass is a cap of thinly stratified dolomites of the cave called “the hall of skulls”, inside the mountain. Dürrenstein Fm. (Upper Carnian), formed above and This species is thought to have become extinct around within a tidal flat. 25,000 years ago, probably because of unfavourable Behind Mt. Settsass, the Sella Group (3151 m) rises. climatic conditions and to hunting by man (Dibona, Its base is formed by the south-verging progradation 2000). of a Carnian coral reef, with mega-breccia clino- One of the most famous mountain groups is visible if forms shifting upward to massive dolomites. The we look SE: the Cinque Torri (Five Towers, 2361 m). depositional sequence continues with a toplap of These are completely formed by Dolomia Principale, the Dürrenstein Fm., followed by layers of marls, overlying the plastic terrains of the Raibl Fm. Their multi-colour clays, limestones and dolomitic sand- spectacular pillars are a clear example of lateral stones of the Raibl Fm. (Upper Carnian). The top spreading that evolved into block slides, affecting a of the mountain is formed by Dolomia Principale former plateau isolated by erosive processes active (Upper Carnian-Norian), followed by a tiny summit during the last glacial period. The pillars are now of Calcari di Dachstein (Rhaetian) and nodular lime- affected by degradation phenomena (mainly frost- stones of the Ammonitico Rosso Fm. (Malm-Dogger) shattering), giving rise to rock falls and topples. The at Piz Boé (3152 m). The two uppermost formations overload caused by the weight of the pillars causes are separated by a well developed iron-manganese bulges to develop within the plastic material of the crust (Bosellini et al., 1996). Raibl Fm. (Soldati and Pasuto, 1991). The flat top of the Sella Group favoured the develop- Closing the panoramic circle there is, towards the ment of an ice cap that has mainly sculpted the eastern east, a mountain group called Tofàne composed of side of the mountain. A well-developed glacial cirque three peaks: Tofana di Rozes (3225 m), Tofana di P14 to P36 n° 4 - from Volume is visible on that side, with high vertical surrounding Mezzo (3243 m), and Tofana di Dentro (3237 m). All walls and a frontal moraine. three are good examples of the Triassic stratigraphic Looking NW, the Puez-Gardenaccia Group (2918 sequence of the area, with Dolomia Principale as the m) shows a depositional sequence similar to the dominant formation and only a small cap of Jurassic Sella Group’s. More frequent, at the top, are Jurassic Calcari Grigi. As for Mt. Settsass and Mt. Conturines, and Cretaceous formations (Ammonitico Rosso and the dip-direction of the strata is towards N and, as for Marne del Puez, respectively), testifying a progres- Mt. Lagazuoi, the same south-verging thrust system

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati cal behaviour. displaying diverse mechani- the alternationofrocktypes selective erosiondriven by di Rozes,resultingfrom the southernslopeof Tofana characteristic “cengie”on logical pointofview, arethe est, fromthegeomorpho- Tofana diDentro.Ofinter- of the Tofana diMezzoand runs onthewesternsides Tofàne, whileanotherline di Rozesandtheothertwo direction separates Tofana tectonic linewithaSE-NW ern platforms. An important group ontopofthesouth- has partlysuperimposedthe (Bosellini a successionofCarnianbasinalfacies inbetween two distinctCarniancarbonateshelves, squeezing Valparola Line. The thrustcomplex hasoverlapped two parallelthrustplanes:theFalzarego Lineandthe complex, whichis thoughttobecomposedofatleast lel totheFalzarego-Valparola south-verging thrust Martini. The roadrunsparal- especially fromtheCengia of Worldexplosions WarI, bled down afterthefrequent the blocksprobablycrum- of theLateglacial. Part of of thetillleftsinceend which have covered much parts androckfall deposits debris flows, protalusram- deposits, debrisconescutby are formedbyscree-slope Both sidesofthevalley Sass deStria(2477m). Mt. Lagazuoiand flat valley-bottom between road goesthroughalong, for the Valparola Pass the Leaving theFalzarego Pass Alessandro Ghinoi Valparola Stop 3.3: there isaformer Austrian bunker whichhasbeen Before reachingthe Valparola Pass, ontheleftside, et al. , 1982). Figure 14-Physiographicsketch mapof Valparola; bedrock isdepictedingrey discovered, probablydatingbackto10,000-7500 plants. Nearthelake someMesolithicsiteshave been mountain lakes, withhydrophyteand hygrophyte (Figure 14);thelake’s vegetation istypicalofhigh- a shallow lake formedbyglacialerosion isvisible metres beneathit.Rightatthepass,anexample of tongue crossestheroadendingupafew hundred better visiblethroughaerialphotographs,whose museum. Oppositethebunker isafossilrockglacier, recently refurbishedandopenedasa World War I 25-05-2004, 15:41:47 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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years BP (Panizza, 1991). also during the Daun stadial, thanks to their N orien- A set of parallel normal faults (NW-SE direction) tation and to protection against direct solar radiation have led to a complicated relationship between the given by the surrounding vertical walls. formations outcropping NE of the pass, putting After the end of the Lateglacial, on the slopes left together, for instance, the Raibl Fm. (Upper Carnian) free by the glacier bodies, debris cones and scree- and the Dolomia Cassiana (Carnian). These faults are slope deposits began to accumulate, owing to the structures that formed during a Mesozoic extension mechanical action of the frost/thaw cycles affecting phase and were reactivated as strike-slip faults during the tectonically fractured dolomitic walls. During the Alpine phases. this phase some rock fall deposits (some of which of From the pass as far as the northern foot of Mt. gigantic proportions) can also be placed. These rock Settsass (Pre da Ciamena), three small parallel crests falls resulted from a lack of support of the vertical crop out from the red clayey terrains of the Raibl Fm., slopes, previously provided by glacier bodies and to creating an interesting triple step-like morphology. the erosional action that these bodies had carried out, These crests are made of the arenaceous layers of the widening and deepening tectonic discontinuities. uppermost part of the Raibl Fm. and, in this area, they The rock glacier at Valparola Pass may have been show a clear cross-stratification. active during this period: it has been demonstrated, The easternmost part of Mt. Settsass has been round- in fact, how permafrost was active in the Dolomites ed by a glacier whose scouring effects are especially starting from 10,500 years BP. visible on the northern slope. Right underneath the As in adjacent areas (Soldati et al., 2004), with the highest peak (2571 m) facing N, two small glacial onset of the Holocene, a more humid and less severe cirques now host debris cones covered by snow fields climate is likely to have favoured landslide activity which sometimes last for an entire year. within the plastic terrains of the S. Cassiano and La The discovery of till deposits, lateral and frontal Valle formations. Currently we have datings (in this moraines (most of them widely covered by vegeta- valley) for only two landslide events which allow us tion, therefore uneasy to detect) have led to a rela- to place them within the Upper Sub-boreal. tive dating of the Lateglacial dynamic phases of the Currently, debris flows are the most important glacier bodies hosted within the valley. The oldest geomorphological agent of the valley. Generated phase may date back to the Sciliar stadial. Testifying by debris deposits accumulating within the major this phase are seven front moraines near the locality fractures of the dolomitic massifs, they cut deeply L’Armentarola (1615 m) and a lateral moraine, at the through the apexes of the debris cones, leaving their foot of Mt. Les Pizades, whose upper end is at 2025 deposition lobes at their bottom. The most impres- m. At that time, it can be assumed that a consider- sive example lies beneath the Conturines Group, able portion of the Valparola was still covered by at the northern end of the valley. Its deposits have an almost continuous ice body which may have left frequently dammed the Torrent Saré, but nowadays just a few peaks uncovered like, for instance, the Piz they have become a profitable source of income for Ciampai (2295 m), near the pass. a private mining company producing cement for the Getting closer to the Gschnitz stadial, the almost building industry. Active, but smaller debris flows continuous glacier body might have showed exten- descending from Mt. Lagazuoi affected the old path sive fragmentation: the front moraine at Casere of the State Road and are approaching its new path, Eisenofner (1749 m) and another front moraine at lower down the valley. Prei Glira (1996 m) belong to this period. The lat- Even if they are not of great importance among active ter is completely covered by dense forest, its front is geomorphological agents, a few examples of earth very high and steep and formed by huge dolomitic slides-earth flows have to be mentioned, especially blocks. A small slope glacier on the northern side of near springs at the permeability boundary between P14 to P36 n° 4 - from Volume Piz Ciampai belongs to the same period. dolomitic formations and the plastic terrains of the Before the onset of the Daun Stadium, one glacier Raibl and S. Cassiano formations. tongue was hosted by the Vallone Pudres, a narrow Concerning the presence of man in Valparola, during N-S oriented valley at the westernmost part of Mt. the Middle Ages the valley was an extremely impor- Settsass, while at the foot of the highest part of the tant stretch of the so called Strada della Vena (Road mountain (2571 m) two glacierettes were located. The of the Vein) that was used for the transit of iron, cast latter were probably the last glacial bodies to remain iron and steel from the mines of Fursil (Province of

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati the Italianadversary comingfromFalzarego Pass. cial observation pointforanticipatingthemoves of strategic positionofthemountaintopmadeitacru- Mt. Settsasswereperfectnaturaltrenchesandthe for storingammunition. The deepfractureswithin inside themountainasashelterfromavalanches and ern sideofMt.Lagazuoi).Sometunnelsweredug a trenchformedbylateralspread(PlandeLot,west- Their headquarterswereonadebrisdepositthatfilled of themostimpenetrablefrontlines World War I. advantage ofthevalley’s morphologytocreateone The soldiersofthe Austrian-Hungarian Army took was built forsmeltingiron. the sidesofColdaiFurns Torrent, ablast-furnace always beenrichinwater andwood therefore,along Belluno) tothe Tyrolean markets. The valley has rocks cropout. from theoverhanging ColdiLana,wherevolcanic mitic cliffs ofLagazuoi and SassodiStria,not (Figure 15). These blocksclearlycamefromthedolo- top ofonetheseblocksthe Andraz Castleisbuilt torrents. Hugedolomiteblockscanbeobserved; on just aftertheconfluenceofFalzarego and Valparola whose frontalmorainecanbefounddownslope, flat shapeandmakes uptherightlateralmoraine, Falzarego and Valparola passes. This deposithasa the southernslopeofLagazuoi,otherfrom that herewereflowing together, onecomingfrom up ofmorainedeposits,leftbytwo smallglaciers The areawherethe Andraz Castleisbuilt ismade Mario Panizza Andraz Castle Stop 3.4: transported fromMt.Settsass(Dibona,2000). of Andraz (next stop)standsisanerraticboulder Settsass. The gigantic rockontopofwhichtheCastle Pass andyetanotherfromthesouthernfaces ofMt. from the Valparola Pass, anotherfromtheFalzarego at leastthreedifferent glaciertongues:onecoming narrow valley is characterisedbytilldepositsleft (2405 m). Although covered bythickvegetation, the tion, thatlinksMt.CrodaNegra (2518m)toMt.Pore east) wecanseeasimilarcrest,withthesamedirec- reaches Mt.ColdiLana.Onourleftside(looking that startsfromthesoutherntipofMt.Settsassand our rightside(lookingwest)wecanseeaN-Screst winding roaddown totheRiver Cordevole valley. On After goingbacktotheFalzarego Pass, wefollow the Alessandro Ghinoi From Valparola to Andraz Castle with anironframework andglasspanels. restore theoriginalwooden roof,but tosubstituteit good results,notwithstandingthedecisionnotto start complex restorationworks whichhave produced Region, whichnow owned thestronghold,decidedto winter. In1986thecastlewas derelict,but the Veneto ts foundinthecastletofueltheirfires forawhole of thenew owner usedolddocumentsandparchmen- that madeupthisstronghold.Itissaidthefamily whole roofandsoldoff thetimberandothermaterials in ordertorecuperatethemoney spent,destroyed the Government. In1853itwas soldtoalocalman,who, 1803 thecastlebecamepropertyof Austrian Prince installedtheCaptainofasmalllegion there.In the maledescentbecameextinct in1461,theBishop who gave itasfief tothenobleStückfamily. When in 1350itreturnedtotheBressanoneBishopPrince, In 1331theSchöneckssoldrightsofcastleand and Arnold von Rodenegg-Schöneck asfeudatories. who in1221appointedhistwo nephews Frederich the BressanoneBishopPrinceConradvon Rodenegg, 1200 AD Hartwigevon Puchensteinsoldthecastleto of theRoccaPietoreand Avoscan Castles. Around 1000 AD. Itisthereforecoeval withthenearbyruins as aRoman This castleislikely tohave beenbuilt onthesamesite Figure 15- Andraz Castle(afterLossetal.,1998). of theupperCordevole Valley. The roadrunshigh Starting from Andraz, wetravel alongtheleftside Alessandro Pasuto and theUpperCordevole Valley to Arabba From Andraz mansio , bythePuchensteinfamily around 25-05-2004, 15:39:52 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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above the valley floor near the slopes of Col di Lana, the Autonomous Province of Bolzano (South Tyrol) which, as previously mentioned, witnessed fierce and and is situated in the southernmost sector of the bloody fighting during World War I. Eventually, the Alta Badia district (Upper Badia Valley). Access to village of Livinallongo del Col di Lana is reached. the area of Corvara is possible through the Gardena At a narrow hairpin bend, just before the village, we Pass (2121 m), the Campolongo Pass (1679 m) to the cross a small bridge over Rio Chiesa. This stream is south-west and the narrow gorge of the Gadera stream dry for most of the year, but in the past it has caused to the north, between the villages of Corvara in Badia serious debris flows and overfilling of the underly- and La Villa. ing square used as a parking lot. After Livinallongo, The mountain ridges culminate in the dolomite peaks the road continues along the hillside, across the of Puez-Gardenaccia (3025 m) and Sella (3151 m) Permian-Triassic sequence typical of the Dolomite in the western sector and in the marly pyroclastic environment, as far as Arabba, at the foot of the Sella peaks of Piz la Villa (2078 m), Col Alto (1980 m) and Group relief. This mountain ridge, mainly made up Pralongià (2571 m) in the eastern sector (Figure 16). of Norian-Carnian dolostones, has a roughly circular The main watercourses (T. Pissadù, T. Rutorto and, shape and is surrounded by four mountain passes after their confluence, T. Gadera), flow across the which link the Cordevole Valley with the Fassa, valley floors, which range in altitude between over Gardena and Badia Valleys, respectively. Once in 2000 m near the passes and about 1500 m near the Arabba, we turn right and proceed uphill towards the northern boundary of the study area. The slopes are Campolongo Pass. Later, after passing the administra- usually subvertical in the upper part of the ridge (in tive border between Veneto Region and Alto Adige/ correspondence with the dolomite peaks) and moder- South Tyrol, we go down to the Badia Valley and, ately inclined in the mid-lower part. eventually, to Corvara. Geological setting Corvara in Badia and Upper The area of Corvara in Badia is illustrated by Sheet Badia Valley no. 11 “Monte Marmolada” of the Italian Geological Alessandro Corsini Map at a 1:100,000 scale (Servizio Geologico d’Ita- Introduction lia, 1970) and Sheet no. 028 “La Marmolada” of the The area of Corvara in Badia is located in the cen- Italian Geological Map at a 1:50,000 scale (Servizio tral part of the Dolomites (Eastern Italian Alps), in Geologico d’Italia, 1977). Formations cropping out in the area have been illustrated in the geological setting of the Dolomites and are exhaustively described in literature (Leonardi, 1967; Brondi et al., 1977; De Zanche et al., 1993; Bosellini, 1996): they make up the sedimentary sequence of the Dolomites in the Upper Permian-Norian interval (Servizio Geologico d’Italia, 1977). The mountain groups of Puez-Gardenaccia and Sella are made up of massif or stratified dolostones from the Upper-Middle Triassic (Dolomia Cassiana, Dürrenstein Fm. and Dolomia Principale) and, subordinately, by marls and pelites from the Upper Triassic (Raibl Fm.) (Figure 17). The Pralongià ridge and the upper part of the slopes located beneath the Sella and Gardenaccia dolomite cliffs are made up of lithological complexes, preva- P14 to P36 n° 4 - from Volume lently with ductile mechanical behaviour and made up of alternating sequences of Upper-Middle Triassic calcarenites, marls and pelites (S. Cassiano Fm.) and Middle Triassic pyroclastic arenites and siltites (La Valle Fm.). The crest of the Piz La Villa - Col Alto ridge is made up of Middle Triassic arenites, pyroclastic conglomerates and lavas (Fernazza Fm.; Pillow Figure 16 - Location of the Corvara in Badia area Lavas), which are affected by a dense network of (after Corsini et al., 2001).

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati 12) landslide(Lateglacial-Holocene);13)CorvaraandColMaladatlandslides (afterCorsinietal.,2001). 10) screeslopes,fans(Lateglacial-Holocene);11)alluvialorlacustrinedeposit 7) meso-neoalpinefault(Tertiary); 8)meso-neoalpineoverthrust (Tertiary); 9)neotectonicfault(Plio-Quaternary); sandstones andmarls(UpperPermian-Lower Triassic); 6)palaeotectonicline(UpperPermian-Lower Triassic); and siltstones(MiddleTriassic); 4)volcanoclastic arenitesandconglomerates(MiddleTriassic); 5)limestones, Triassic); 2)alternancesofcalcarenites,marlsandclaystones(MiddleUpperTriassic); 3)alternancesofsandstones Figure 17-Geologicalschematic mapoftheCorvarainBadiaarea. Legend:1)dolomitesandmarls(MiddleUpper Permian-Lower Triassic limestones,sandstones and nical behaviour cropout;they are mainlyUpper rock typesdisplayingdifferent kinds ofmecha- and easternslopesofthePuez-Gardenacciaridge, Alto ridge,andinthelower portionof thenorthern In thenorth-westernsectorofPizLa Villa -Col joints withsubstantiallybrittlemechanicalbehaviour. subsidence andfracturing,UpperOligocene-Lower main deformationalphases:UpperPermianbasin The tectonicsettingofthearearesultsfromthree Tectonic setting Conglomerate; ContrinFm.;Livinallongo Fm.). marls (BellerophonFm.; Werfen Fm.;Richthofen 25-05-2004, 15:39:57 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Miocene neoalpine and mesoalpine compressive Pleniglacial deposits or inside landslide bodies. phases and Middle Miocene-Upper Miocene south- These confirm the Austrian provenance of the Last alpine compressive phases (Bosellini, 1965; Leonardi, Glacial Maximum glaciers, which stretched south as 1967; Doglioni, 1987; Doglioni and Bosellini, 1987; far as an altitude of 2300 m, as already hypothesised Doglioni, 1990; Castellarin et al., 1992). Some of the by Penck and Brückner (1909), B. Castiglioni (1936), structures derived from these ancient deformational Sacco (1939) and G.B. Castiglioni (1964). On the phases were reactivated during the Pliocene and the other hand, periglacial features such as the talus and Quaternary. This has been demonstrated for the N-S alluvial fans bordering the base of the Sella and Puez- fault which cuts through the Sella Group along the Gardenaccia Dolomite slopes are also evident. In the Val de Mesdì. This fault is considered active between area of Corvara in Badia the landforms and deposits 5.2-0.7 Ma BP by Carton et al. (1980) and Zanferrari due to slope movements are particularly important. et al. (1982) as well as by Panizza et al. (1978), Slejko Landslides of various types and dimensions affect et al. (1989) and Castaldini and Panizza (1991). Also practically every sector of this area (Figure 17); some the NNW-SSE strike-slip fault, which runs on the of these, in particular those which involve argilla- Col Alto – Pralongià – Passo Incisa lineament, has ceous materials, are at present active. been shown to have been reactivated on the basis of several congruous geomorphological elements Landslide causes (among which also the deep-seated failures affect- The situations favouring landslide processes in the ing the Col Alto – Pralongià slope, among which the area of Corvara in Badia are extremely varied, mainly Corvara landslide). It is thought to have been active, depending on the different rock types involved and with a transcurrent dextral movement during the Plio- stratigraphic and tectonic relations between outcrop- Quaternary (Panizza et al., 1978; Carton et al., 1980; ping formations. The development of numerous slope Zanferrari et al., 1982; Slejko et al., 1989; Castaldini movements in correspondence with the margins of and Panizza, 1991, Corsini and Panizza, 2003). the Sella and Puez-Gardenaccia groups appears to be linked to the overlapping of jointed competent rocks, Geomorphological setting such as dolostones, on materials showing substantial- On the whole, the geomorphological setting of the ly ductile behaviour, such as the S. Cassiano and La Corvara in Badia area is strictly related to the slopes’ Valle formations. In this case, various types of move- geological structure and reflects the different climatic ment combine and take place on different stretches conditions of the Quaternary (Corsini et al., 1997). of the same slope, affecting materials with different From a morpho-structural viewpoint, selective ero- mechanical characteristics, thus giving origin to vast sion processes leading to the exhumation of previ- landslides with a complex and composite movement ously buried geological structures, have played a style. Other complex landslides started because of major role starting from the Miocene-Pliocene, when structural weakness situations, or the presence of the main valleys of the area started to develop, with pelitic rock types which give rise to rotational slides the modelling of the Gardena Pass and Pralongià. accompanied by earth flows. At present the slopes are practically vertical at the margin of the dolomite reliefs, highly inclined in Slope instability correspondence with the Lower-Middle Triassic Many landslides have been identified and mapped in outcrops of limestones and pyroclastic arenites and recent years in Corvara in Badia, and in the Upper mildly inclined and undulated in correspondence with Badia Valley in general. the north-western slope of the Col Alto – Pralongià In order to reconstruct Holocene gravitational relief, where the Late Triassic sedimentary rocks slope dynamics, great importance is assumed by: i) crop out. As regards the landforms and deposits rotational slides–earth flows, involving alternating P14 to P36 n° 4 - from Volume linked to the Würm Pleniglacial and Lateglacial sequences of Upper-Middle Triassic pyroclastic aren- periods, worthy of note are the Pleniglacial moraine ites, siltites, calcarenites, marls and pelites along the ridges near Pralongià and the Gardena Pass, as well north-western slope of the Col Alto – Pralongià ridge; as the cirques, suspended valleys, glacial deposits ii) rotational slides affecting Upper Permian-Lower and moraine arcs which witness the presence and Triassic limestones, sandstones and marls cropping progressive disappearance of valley glaciers which out along the eastern slope of the Puez-Gardenaccia had developed during the Lateglacial and Holocene. Group. Out of 40 radiocarbon age datings, some post- In Pralongià shale clasts are found trapped inside glacial phases of activity were determined in 13 (for

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati volume ofmorethan300millionm slide –earthflow, whichhasanestimatedoverall an active, slow moving, deep-seated rotationalearth Corvara inBadia(Figure19).It canbeclassified as 2.5 km The Corvara landslideaffects anareaofmorethan Alessandro Corsini Corvara landslide Stop 3.5: tions. mass movements aredescribedin thefollowing sec- landslide andthePasso Gardenalandslide. These this areaare:theCorvara landslideunit,theColfosco aspects andriskimplications,themainlandslidesin types. Nevertheless, consideringalsosocio-economic deposits, ascribabletomany different landslide than 80%oftheterritoryiscovered withlandslide As regards onlytheCorvara inBadiaarea,more 18 and Table 2). landslide locationanddatinginformationseeFigure damage topower lines,cablecars and,inparticular, at thesurface andatdepth,cause,onayearlybasis, landslide, rangingfrom0.1tomorethan1m/year al 3) lacustrinedeposits;4)landslidenumberingaccordingtoTable 2(afterSoldatietal.,2004). Figure 18-Geomorphologicalsketch of Alta Badiaarea(heightsaregiven inmetres).Legend:1)bedrock; 2)landslide; ., 1999).Presentdaymovements oftheCorvara 2 locatedimmediatelyuphillofthevillage 3 (Corsini et bon datesthatthelandslidehasexisted sinceatleast are listedin Table 3.Itisknown fromseveral radiocar- rock ridges. The mainmorphometriccharacteristics morphological sectors(S1,S2,S3,S4)separatedby areas (Figure19). The sourceitselfismadeupoffour distinct source(S),track(T)andaccumulation(A) The morphologyoftheCorvara landslide, shows research projects. cies withintheframework ofEuropeanandNational close collaborationwithprovincial andlocalagen- elements atrisk,monitoringhasbeencarriedoutin and thesocio-economicvulnerabilityvalue ofthe relation totheextent andmagnitudeofthelandslide from thissituationispotentiallysignificant, bothin landslide toe.Sincethespecific andtotalriskarising formed ontheriverbeds ofthestreamsflanking lapse ofany ephemerallandslidedamthatcouldbe process orbyflashfloodsoriginatingfromthecol- could beaffected byany advance ofthisgravitational been erectedintheproximityoflandslidetoe,and many ofthebuildings inthevillageofCorvara have centre of Arabba. Moreover, over thepast30years, Campolongo Pass andtotheneighbouringtourist to stateroadno.244,whichconnectsCorvara tothe 25-05-2004, 15:40:01 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Table 2 - Radiocarbon dating in Alta Badia; data calibrated with Calib 4.1 by Stuiver and Reimer (1993), data set by Stuiver et al. (1998) (after Soldati et al., 2004; modiﬁ ed). about 10,000 cal BP, and that it underwent a second has a B1-type lithological and structural complex- major phase of morphological development from ity (A.G.I., 1985). It is made up of a more or less about 5000 to 2500 cal BP (Corsini, 2000; Corsini regular alternation between sub-metre strata of hard

et al., 2001). The landslide is active at present, with rocks (marls, arenites and/or marly limestone with P14 to P36 n° 4 - from Volume movement rates ranging from about 0.01 to 2 m/year. an uniaxial compressive strength between 50 and 25 The distribution of activity is retrogressive at the MPa) and sub-metre to metre packets of thin strata crown and at the flanks of the source areas, slightly of weak rocks (claystone or clayshales with uniaxial enlarging at the sides of the accumulation area, slight- compressive strength <25 MPa) (Corsini, 2000). The ly advancing at the turn of the landslide into the main ratio between the hard rock component and the weak valley and potentially advancing at the toe. rock component is variable, but is generally higher in From a geomechanical viewpoint, the bedrock can the La Valle Fm. (average hard/weak ~ 1.5 to 2) than be defined as a weak rock (Bieniawski, 1989), that in the S. Cassiano Fm. (average hard/weak ~ 1). On

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati Corvara landslide(afterCorsinietal.,inpress). Table 3-Morphometriccharacteristics ofthe area; T)track zone;S1,S2,S3,S4)sourceareas(afterCorsinietal.,inpress;modiﬁ Fig 19- View oftheCorvaralandslide,illustratinglocationinstrumentedboreholes.Legend: A) accumulation ing canoccuronclayey stratatogetherwith a depthofsometensmetres,whereslid- joints tendtosplitthemass;brittle-plasticat surface, whereconfining loadsarelow and the bedrockcanbedefined asbrittlenearthe 2003). The resultingmechanicalbehaviour of in thisparticularlocation(CorsiniandPanizza, important roleindeterminingslopeinstability tonic compressive stressesthathave playedan and faulting isrelatedtotectonicandneotec- from afew centimetrestodecametres.Jointing affect theserockmasseswithspacingranging sistent discontinuities,besidesstratification, of theS.CassianoFm.).Othermajorper- Fm.) withyellowish marlylimestone(typical coloured volcanic arenites(typicalofLa Valle related totheprogressive substitutionofdark- between thetwo formationsisgradualand the unstableslope,stratigraphicboundary place onalongertermbasis.Boreholesdrilled greater depths,whererockcreepcantake rupture ofthehardstrata;viscous-plasticat ed). 25-05-2004, 15:40:09 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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down to the bedrock starting from axial points in the source, track and accumulation zone of the landslide, have shown that landslide material reaches a maximum thickness of about 50 to 100 m. Similar estimates of the depth of the bedrock have been obtained by some electric resistivity profiles carried out along traces linking or crossing boreholes (Corsini and Arndt, 2003) and refraction/reflection seismic survey. Landslide material consists of clayey silts or silty clay, with mixed gravels and blocks made up of arenites, marly limestone and dolostone. Geotechnical parameters are summarised in Table 4 - Geotechnical characteristics of the landslide material Table 4. From borehole stratig- (after Corsini et al., in press). raphy and radiocarbon dating large diameter TDR cables and electric piezometers on wood remnants found in cores, a system of four (connected to data loggers) have been located in bore- main layers seems to exist, at least on the track and holes on different points of the Corvara landslide. For accumulation zones of the landslide: an uppermost surface movements, a network of 47 benchmarks for layer of landslide material that is relatively loose and measurement with RTK differential GPS technique inconsistent, a lower layer of landslide material that has been installed on the whole Col Alto – Pralongià is more compacted and consistent, a cap of highly slope. weathered bedrock and then the lowermost undis- Results obtained through monitoring with inclinom- turbed bedrock. The two layers of landslide material eters and TDR cables have shown that multiple shear have been correlated to different phases of develop- zones overlap at various depths within the landslide ment of the phenomenon, with the lower one being mass and that the maximum depth of the shear zones the result of a series of landslide events dating back on each individual borehole ranges from 20 to about to the early Holocene and the upper one represent- 50 m (Figure 20). The thickness of these shear zones ing landslide events dating prevalently from 5000 is generally in the order of 1 to 2 m, and it can be cal BP to 2500 cal BP and to the present (Corsini et appreciated that in between two shear zones, the dis- al., 2001). In source area S3 only the most recent and placed material slides as a whole without significant loose layer of landslide material is present, and this evidence of flow-like deformation. seems to indicate that a retrogression of the landslide GPS measurements from September 2001 to scarp of more than 500 m has taken place from about September 2002 have shown that horizontal move- 3000 cal BP. ments have ranged from a few cm to more than one The monitoring network for the Corvara landslide metre, while vertical movements have ranged from a has been designed to accommodate devices capable few centimetres to about ten centimetres (Figure 20). of defining and recording movement rates at the sur- It can be noticed that the maximum displacement rate P14 to P36 n° 4 - from Volume face and underground, as well as groundwater levels occurs in the uppermost part of the accumulation lobe and rainfall (Figure 19). A meteorological station, and in the track zone (from 0.20 to 1.20 m/year). consisting of a rain gauge for rainfall recording, an Piezometers have been used to prove a working air temperature thermometer and an echo-meter for hypothesis that a system of overlapping confined snow depth measurement, was installed in the middle aquifers exists in the landslide body as the result of the landslide in October 1999. As regards under- of horizons of coarser materials occurring in the ground movements and the water table, devices such clayey mass as shown by borehole cores, For this as inclinometers, down-hole wire extensometers, reason, one type of measurement has regarded the

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati eter C4revealed amajorslidingsurface atabout40 sliding surface. Itmustberememberedthatinclinom- landslide anddisplacementdatafromthe29mdepth orological stationspecifically installedintheCorvara together withdailyrainfall recordedinthemete- unsealed inclinometerC4areplottedinFigure21, Groundwater levels recordedform2000to2002in sealed above andbelow. only foratractincludingthemainshearsurface and have beeninstalledinopenpipepiezometersfissured measure thistypeofpressure,electrictransponders horizons, whichprobablyactasconfined aquifers. To data seemstooccurincorrespondencewithcoarser main shearsurfaces, thatonthebasisofborehole of measurementregards thepressureofwater around unsealed piezometersC1,C2andC4. Another type carried outwithelectrictranspondersinstalledin landslide mass. This typeofmeasurementhasbeen aquifers interceptedbytheboreholescrossing water tablegeneratedbythecontribution ofallthe al., inpress;modiﬁ deposits. HorizontalMovements recordedbyGPSmonitoring fromSeptember2001to2002(afterCorsiniet surface; 4)S.CassianoFm.(turbidites);5)La Valle Fm.(turbidites);6)La Valle Fm.(massive sandstones);7) Alluvial surface, revealed byinclinometres orTDR;2)Groundwater level, measuredbypiezometres;3)Interpretedactive shear Figure 20-Crosssectionbasedonboreholes,monitoringdataandgeophysicalinvestigation. Legend:1) Active shear ed). tation patterns. by smallerwater tablefluctuationsrelatedtoprecipi- shallower slidingsurfaces aremore influencedalso continuously beforeandafterthewater tablerise, while thedeeperslidingsurface hasprobablymoved practically dormant. This leads totheconclusionthat of summer2001;sincethenthelandslidehasbeen only intheperiodfollowing thehighprecipitation the 29mdeepslidingsurface hashadanincrease conditions ofsummer2000,displacementratealong 21 shows thatsincethehighstandingwater table ter level andmovement ratesinthislocation.Figure date, thusallowing acomparisonbetweengroundwa- one that,however, hasbeendetectablefrom1997to 29 mindepthshown inFigure21,isthusasecondary of thecasingin August 1999. The sliding surface at m indepthfrom1997to1999,whichledrupture 25-05-2004, 15:40:15 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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DAY 4 From Corvara to the Gardena Pass Alessandro Corsini

Mesdì Valley and its extinct glacier The N-S directed Val Mesdì, which cuts the Sella Group almost in half has developed in correspondence with a normal fault ascribable to the Neogene (Tertiary Alpine compressive phases, Leonardi, 1967; Doglioni and Bosellini, 1987; Castellarin et al., 1992; Doglioni, 1990; Bosellini, 1996). This is the principal fault among a sub-parallel set of normal faults affecting the whole eastern portion of the Sella Group that, as a consequence, has assumed a marked and characteristic step- like morphology. The Val Mesdì fault line has been considered as having been active between 5.2- 0.7 Ma BP by Carton et al. (1980) and Zanferrari et al. (1982) as well as by Panizza et al. (1978), Slejko et al. (1989) and Castaldini and Panizza (1991). During the Holocene glaciers progressively withdrew into high mountain cirques and, at times – such as probably during the climatic optimum (hypsithermal) – they completely disappeared. The Little Ice Age of the 19th century caused the formation of new small glaciers in many narrow valleys and cirques that progressively

Figure 21 - Relationships between groundwater P14 to P36 n° 4 - from Volume table ﬂ uctuations in C4 (A), precipitation records from 2000 to 2002 from the meteorological station installed in the Corvara landslide (B) and displacements (C) (after Corsini et al., in press).

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati large rockfalls have detachedeven inrecenttimes. Puez-Gardenaccia Group,fromwhereotherquite rock walls ofSassdiCampacciopeak,withinthe detachment areacanbeidentified inthesub-vertical borehole coresdrilledupstreamofthelandslide. The sediments (typicalofdamlake deposition)foundin age ofabout7000calBPobtainedfromorganic events occurredeven earlier, assuggestedbythe accumulation zone.However, otherrock-avalanche dolomite boulders,whichmake upthelandslide was foundburied atadepth of7mamonglarge a treetrunk,withdiameterexceeding 1m,which 0.14 km residual extension oftheglacieratthattimeabout the headof Val Mesdì.Marinelli(1910)indicatesa Val Badiawas the“Dlaciade Val Mesdì”,locatedat well preserved ruralbuildings ofthe16 ments in Alta Badia,andstillcomprisessomequite The villageofColfoscoisamongtheoldestsettle- Colfosco landslide melted inthe20 years BP(Corsini This event isbelieved tohave taken placeabout5000 ably ascribabletoarockfall –rockavalanche event. blocks sealedbyasiltymatrix,whoseoriginisprob- village liesonavast accumulationoflarge dolomite 2 . th century. The lastknown glacierin et al ., 2000). This dateresults from Figure 22-Sketch mapofthePasso Gardenalandslide. th century. The the debrisflow channel. and destroyed afew buildings locatedinproximityof a debrisflow event in1918thatreachedthevillage from theStella Alpina valley. Localinhabitantsreport up andreshapedbyvast debrisflows runningdown and especiallyitsapicalportion,hasalsobeenbuilt to spreadingandtoppling. The Colfoscolandslide, sing therocktobedivided intolarge prismssubject In thiszone,threefault systemscrosseachother, cau- of theearthslide–flow portionranges from a geophysicalsurvey have shown thatthethickness movements isdepictedinFigure23.Boreholesand A sketched crosssectionshowing this sequence of 22). 1.4 km style massmovement extending over anareaofabout The Passo Gardenalandslideisacomplex-composite- Alessandro Corsini Passo Gardenalandslide Stop 4.1: flow ofsomemillionm formations, andthenbecomesanearthslide– weak clayey rocksof the S.CassianoandLa Valle boulders –itevolves intoarotationalslideaffecting spiky outcrops)–thatinturnhave fallen intocoarse dolomite rocktypes(makingupcleanrocky and 2 . Itstartsoff asarockblockslideaffecting 3 ofclay-richmaterial(Figure 25-05-2004, 15:40:21 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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Figure 23 - Sketch section of the Passo Gardena landslide.

45 to 70 m. As regards present day movements, the (2001) and Borgatti and Soldati (2002). uppermost rock block slide does not show evidence For the Dolomites, an effort has been made to assess of ongoing activity, whereas large sectors of the which of the numerous radiocarbon dates collected flow-like processes are active, damaging a strategic in the study areas of Cortina d’Ampezzo (see Table roadway connecting the Alta Badia Valley with the 1) and Corvara in Badia (see Table 2) are related to adjacent valley. events of a type or magnitude that might be indicators Recent monitoring data from inclinometers have of Holocene climatic changes (Soldati et al., 2004). shown that movements in the earth flow portion take The degree of paleoclimatic significance of each of place on sliding surfaces located at about 20 m in the dated landslides has been assessed on the basis of depth. Downslope, movements are negligible, so at the following criteria: geomorphological context in present the landslide is to be considered active-sus- which the landslide has taken place; type of landslide; pended or dormant. Seismic data have also shown material involved in the landslide; size/magnitude of that underneath the toe of the landslide, a 30 to 50 m the landslide; type of dated material; depth at which thick level of glacial or fluvial-glacial gravel exists; the dated material has been found (either from exca- this level probably acts as a natural drainage system, vations or drillings); borehole stratigraphy when preventing the steeper portions of the earth flows dated material is collected from drill holes. from being active with higher displacement rates. The first phase of marked slope instability (Figure 24), is observed in the Preboreal and Boreal (about 11,500 Synthesis of the relationships between to 8500 cal BP) and includes, on the one hand, large landslide occurrence and climate translational rock slides, which affected the Dolomite changes in the Dolomites since the slopes following the withdrawal of the Lateglacial Lateglacial glaciers and the consequent decompression of slopes

Alessandro Corsini, Alessandro Pasuto and, on the other hand, complex movements (rota- P14 to P36 n° 4 - from Volume and Mauro Soldati tional slides and flows) which affected the underly- Several investigations on landslide recurrence and ing pelitic formations and were probably favoured by climatic implications have been described in literature high groundwater levels resulting from an increase of for various European regions among which, in par- precipitation and/or permafrost meltdown. A second ticular, Austria, Great Britain, Italy, Norway, Poland, concentration of landslide events is found during the Spain and Switzerland. For a wider review aiming at Sub-boreal (about 5800 to 2000 cal BP), when slope illustrating the state of the art of these topics, with processes, mainly rotational slides and/or flows, took particular attention paid to Europe, see Borgatti et al. place in both the study areas. These slides may be

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati (e.g. Provansal, 1995;Dapples other Alpine areasatleastsincethemid-Holocene activity, whichisproved tohave beencrucialfor matic factors. Among these,theinfluenceofhuman Lateglacial was certainlyalsoinfluenced bynon-cli- The recurrenceintimeoflandslideactivity sincethe quency oflandslidesto be detected. in thestudyareasdoesnotenableanincreasedfre- Little Ice Age, thescarcenumberoflandslidesdated mid-Holocene period.Ontheotherhand,during documented inseveral Europeanregions duringthe the phaseofprecipitationincrease,whichhasbeen considered asreactivations ofolderevents linked to (after Soldatietal.,2004;modiﬁ Figure 24-Temporal distribution of to bealmostirrelevant inthestudyareaswhereonly ed). et al. “ climatically signiﬁ , 2002),seems cant ” landslideevents intheDolomitesandEurope dating ofmassmovements bymeansofradiocarbon esses andclimaticchanges.Furthermore,sincedirect relationships betweenrecurrenceofinstabilityproc- in thepastcancontribute totheassessmentof only aportionoftheslopemovements takingplace tified afterhundredsorthousandsofyears. Therefore, have suchapersistenceinthelandscapeastobeiden- In any case,oneshould consider thatonlylarge events matic signalidentifiable inthelandslidesstudied. climatic causes,whichmighthave “disturbed”thecli- the degree ofinfluencethisandotherpossiblenon- the investigations doesnotallow theassessmentof the Middle Ages. Nevertheless, thepresentstateof seasonal orisolatedsettlementswerepresentbefore 21-06-2004, 9:28:37 GEOMORPHOLOGY AND SLOPE INSTABILITY IN THE DOLOMITES (NORTHERN ITALY): FROM LATEGLACIAL TO RECENT GEOMORPHOLOGICAL EVIDENCE

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strictly depends on the presence of organic remains Once in the River Isarco Valley, we take the A22 in landslide deposits, only the events which affected Brenner motorway and, just south of Bolzano, follow stable vegetation-covered areas – or landslide bodies the main valley where the R. Adige flows. This wide which had previously been dormant long enough for Alpine valley stretches in a NNE-SSW direction from new vegetation to grow – can be dated. It is therefore Bolzano to its outlet into the Po Plain, following an particularly difficult to obtain data ascribable to slope important fault and tectonic lineament system called instability for the periods closest to glaciation, such the “Sistema Giudicariense”. This system divides as, for example, the Lateglacial, considering the lack the Southern Alps of the Lombardy basin from the or scantiness of tree cover in that epoch. Venetian basin. In its terminal stretch, this valley is Notwithstanding this, in the light of the results so far parallel to Lake Garda, from which it is divided by obtained, many landslide events previously described the ridge of Mt. Baldo. might be considered as indicators of climatic changes. The Adige Valley is characterised by a flat bottom due For this purpose, the comparison with bibliographic to fluvioglacial and fluvial sedimentation principally data on other European mountain areas seems to be occurring from the LGM to the Lower Holocene. In significant (Figure 24). In fact, concentrations of the northern part, a Permian large porphyric plat- landslides during periods similar to those of the areas form marginally outcrops. Whereas, the geological studied were reported in various European regions, formations cropping out in the lower Adige Valley such as the United Kingdom, the Iberian Peninsula, and in the basins of its tributaries are Mesozoic and the Alps and Eastern Europe. Cainozoic in age and the most representative terrains In the light of these remarks, some analogies in are calcareous and dolomitic formations (Dolomia the temporal distribution of landslides in vari- Principale Fm., Noriglio Grey Limestone Fm., San ous European regions and in the Italian Dolomites Vigilio Oolitic Limestone Fm.). seem quite evident. Indeed, all the cases previously The valley originated during an intense erosional phase described can be fixed, more or less precisely, in the that can be dated to the Late Miocene (Messinian), two periods of greatest activity identified. In Europe, when the Mediterranean basin was isolated from the the Preboreal period coincides with the oldest period Atlantic Ocean (Bini et al., 1977; Finckh, 1978). The of frequent postglacial slope movements, which has Messinian fluvial erosion of the River Adige took been identified by various Authors, whereas a sec- place in a pre-existing valley, which was tectonically ond period coincides with an increase of precipita- controlled by structures belonging to the Giudicarie tion reported in literature (Figure 24). However, the System. During the Pleistocene glacial phases the hypothesis of a direct influence of this climate change valley was affected by the action of glaciers, with on landslides, partially confirmed by the European consequent glacial remodelling. During the LGM case studies above mentioned, still needs further the glacier thickness reached 1700 m near Trento and verification. In fact, this trend of landslide recur- 1500 m a little to the south. Other extremely active rence, which inevitably shows differences among the processes acting on the slopes and valley floor are European regions considered, is influenced not only linked to karst dissolution, fluvial dynamics of the by geographic, and therefore climatic, diversity but River Adige and anthropogenetic activity. also by the amount and climatic significance of the Near the road junction of Rovereto Sud with the A22 data available. Moreover, non-climatic factors, in par- motorway, the vast, impressive complex of “Lavini ticular human influence, need to be analysed in detail, di Marco” is visible. This is an extensive landslide also in collaboration with other experts (i.e. archae- accumulation with various minor gravitational ologists), and through comparison with other sites. deposits. The landslide has long been famous, mainly because of a reference made to it by Dante Alighieri From Gardena Pass to Verona in his “Divine Comedy”. The main landslide occupies P14 to P36 n° 4 - from Volume Mauro Marchetti a surface of about 6 km2, with a maximum length of After the Gardena Pass, we proceed along Gardena about 5 km, a maximum width of 1800 m and a dif- Valley towards the River Isarco Valley. Travelling ference in altitude of 1030 m (Orombelli and Sauro, across Gardena Valley, the complete stratigraphic 1988). The zone of detachment coincides with bed- sequence is exposed: from the Dolomia Principale to ding planes and affects a modest thickness of the the Permian volcanites cropping out near Ortisei (see calcareous sequence (up to some tens of metres). stratigraphic column, Figure 4). Within the zone of accumulation it is possible to

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati Dolomites. (1999). Fieldobservation ofadebris flow event inthe Berti, M.,Genevois, R.,Simoni, A. and Tecca, P.R. Geology d’Ampezzo, Italy. for slopeanalysisappliedtoamudslideinCortina A. andSilvano, S.(1996). A visco-plasticmodel Angeli, M.-G.,Gasparetto,P., Menotti,R.M., Pasuto, L. Chiovini, Roma. Engineering inItaly”(A.G.I.,Ed.),pp.159-184. Tip. Plain, andwillbeconcludedin Verona. The excursion continuesdownstream, towards thePo They areallascribedtotheEarlyPleistocene. the northreliefsofCaprino Veronese, arealsofound. eroded andterracedglacialdeposits,pushedagainst Middle Pleistoceneerodedmorainesandhighly Outside theUpperPleistocenemainmoraineridge, the wholeamphitheatretoUpperPleistocene. and theirstratigraphicnature,Cremaschi(1990)dated Considering thestateofconservation ofthemoraines and fluvioglacialterraceshave alsobeenpreserved. the Adige Valley, wherethick loesscovers, redsoils, ridges depositedbytheglaciersdescendingalong but isawellpreserved systemoffrontalmoraine of amoraineridgesmallerthantheGardasystem Rivoli Veronese glacialamphitheatre.Itconsists the A22 motorway, thetripwillproceedalong the Southwards, neartheroadjunctionof Affi with documented. 1984). Nevertheless, thisattribution isnotsufficiently (Sacco, 1940;Fuganti,1969;EisbacherandClague, ascribed totheearlyMiddle Ages byseveral Authors the basisofhistoricalevidence, thelandslidewas have separatedthedisplacedmaterialintotwo. On located inthefailure surface (CostaStenda)could of asingleevent duringwhicharesistantrocky ridge been generatedatdifferent timesorbetheoutcome vegetation cover. These two lobescouldeitherhave made upoflarge rockblocksandismostlylackingin lesser lobeliesonthebulging partoftheslopeandis sions ontheflat,cultivated portionoftheplain. The vegetation andischaracterisedbyseveral depres- of over 1km;itismostlycovered byspontaneous fan-like expansion onthevalley floorforadistance observe two different lobes. The majorlobeshows a example ofsometypicalformations. features onthegeotechnicalcharacterization Geological outlineofItaly:bearingthegeological A.G.I. - Associazione GeotecnicaItaliana,1985. References 29,233-240. Geomorphology Quarterly Journal ofEngineering 29,265-274. In “Geotechnical ed totheMessinianentrenchment. Alpine Lakes: hypothesisofanerosionaloriginrelat- Bini, A., Cita,B.M.andGaetani,M.(1977).Southern Classification. Wiley IntersciencePubl.,New York. Bieniawski, Z.T. (1989).EngineeringRockMass Bertoglio, G.andDeSimoni,(1979). delle Alpi in220gruppi. Guida allaEscursioneGenerale). Geologia delleDolomiti(IntroduzioneGeologica, Bosellini, A., Neri,C.andStefani, M.(1996). Reg. 2. Vai, Eds.),pp.273-278.Soc.Geol.It.,Guide del sudalpinocentro-orientale”(A.CastellarineG.B. geologia delPasso Falzarego. Bosellini, A., Masetti,D.andNeri,C.(1982).La Geol. Overthrust (Southern Alps, NorthernItaly). structures inthehanging-wall ofthe Valsugana Bosellini, A. andDoglioni,C.(1986).Inherited Athesia, Bolzano. Bosellini, A. (1996).GeologiadelleDolomiti. in Europe. Holocene climaticchangesonlandslideoccurrence Borgatti, L.andSoldati,M.(2002). The influenceof pezzo. sul PiccoloLagazuoi.PrintHouse,Cortinad’Am- Bobbio, L.andIlling,S.(1997).LaGrandeGuerra 27, 217-288. Intensive Courseon Applied Geomorphology– features oftheDolomites(Italy). Carton, A. andSoldati,M.(1993).Geomorphological Brückner, Eds.),pp.954-1042. Tauchnitz, Lipsia. In Brückner, E.(1909).Dievenezianischen Gletscher. d’Italia, Roma. 50.000, F°028“LaMarmolada”.ServizioGeologico esplicative dellaCartaGeologicad’Italiaallascala1: D., Sommavilla, E. Vuillermin, F. (1977).Note Brondi, A., Mittempergher, M.,Panizza, M.,Rossi, Lincei Trias post-erciniconelle Alpi Meridionali. Bosellini, A. (1965).SchemastrutturaledelPermo- Nat. Ven.Trid. Meridionali duranteilPermo-Trias. Bosellini, A. (1965).LineamentiStrutturalidelle Alpi Quaternario bibliografia ragionata relativa alterritorioeuropeo. Rapporti trafraneevariazioni climatiche:una Borgatti, L.,Soldati,M.andSurian,N.(2001). Publishers, Lisse. and P. Wagner, Eds.),pp.111-116. A.A. Balkema “Die Alpen imEiszeitalter”(A.PenckandE. 8,581-583.

sc. ff. mm.nn. In 14(2),137-166. “Landslides”(J.Rybár, J.Stemberk, 15(3),1-72. 8, 2. Boll. A.I.C. In “Guidaallageologia Soc. Geo.It. In Mem. Mus.Stud. “FirstEuropean Marine Geology XVI46,7-17.

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Proceedings”. (M. Panizza, M. Soldati and D. Barani, Corsini, A., Pasuto, A. and Soldati, M. (1999). Eds.), pp. 13-29. Istituto di Geologia - Università Geomorphological investigation and management of degli Studi di Modena. the Corvara landslide (Dolomites, Italy). Transactions Carloni, G.C. and Mazzanti, R. (1964). Aspetti geo- Japanese Geomorphological Union 20(3), 169-186. morfologici della frana del Vajont. Rivista Geografica Corsini, A., Pasuto, A. and Soldati, M. (2000). Italiana, 71 (3), 201-231. Landslides and climate change in the Alps since the Carton, A., Castaldini, D. and Panizza, M. (1980). Late-glacial: evidence of case studies in the Dolomites Schema neotettonico riassuntivo dell’area fra Trento (Italy). In “Landslides in research, theory and prac- e Cortina d’Ampezzo (Fogli P.P. Bolzano (10), M. tice” (E. Bromhead, N. Nixon and M.-L. Ibsen, Eds.), Marmolada (11), Cortina d’Ampezzo (12), Trento pp. 329-334. Thomas Telford Publishing, London. (21) e Feltre (22). In “Contributi alla realizzazio- Corsini, A., Marchetti, M. and Soldati, M. (2001). ne della Carta Neotettonica d’Italia”, pp. 621-641. Holocene slope dynamics in the area of Corvara in Progetto Finalizzato Geodinamica, Pubbl. 356. Badia (Dolomites, Italy). Geogr. Fis. Dinam. Quat Castaldini, D. and Panizza, M. (1991). Inventario 24(2), 127-139. delle faglie attive tra i fiumi Po e Piave e il Lago Corsini, A., Pasuto, A., Soldati, M. and Zannoni, A. di Como (Italia Settentrionale). Il Quaternario 4(2), (in press). Field monitoring of the Corvara landslide 333-410. (Dolomites, Italy) and its relevance for hazard assess- Castellarin, A. (1982). La scarpata tettonica mesozoi- ment. Geomorphology. ca Ballino-Garda tra Riva e il Gruppo di Brenta. In Corsini, A., Panizza, M., Pasuto, A., Silvano, S., “Guida alla Geologia del Sudalpino centroorientale” Siorpaes, C. and Soldati, M. (1997). Indagini preli- (A. Castellarin and G.B. Vai, Eds.), pp. 79-95. Soc. minari per la definizione della pericolosità da frana Geol. It., Guide Geol. Reg. 2. nella conca di Corvara in Badia (Dolomiti). Mem. Castellarin, A., Cantelli, L., Fesce, A.M., Mercier, J., Soc. Geol. It. 53, 207-224. Picotti, V., Pini, G.A., Prosser, G. and Selli L. (1992). Cremaschi, M. (1990). The loess in Northern and Alpine compressional tectonic in the Southern Central Italy: a loess basin between the Alps and the Alps: Relationships with the Apennines. Annales Mediterranean Region. Quaderni di Geodinamica Tectonicae 6, 62-94. Alpina e Quaternaria n°1. Castiglioni, B. (1936). Sugli stadi post-würmiani Dal Piaz, G. (1912). Studi geotettonici sulle Alpi nelle Alpi orientali. Verhandl. der III Intern. Quartär. orientali. Regione fra il Brenta e i dintorni del Lago di Konferenz, Wien, 106-109. Santa Croce. Mem. Ist. Geol. Univ. Padova 1, 1-195. Castiglioni, G.B. (1964). Sul morenico stadiale delle Dapples, F., Lotter, A.F., van Leeuwen, J.F.N., van Dolomiti. Mem. Ist. Geol. e Min. Univ. di Padova 24, der Knaap, W.O., Dimitriadis, S. and Oswald, D. 1-16. (2002). Paleolimnological evidence for increased Corsini, A. (2000). L’influenza dei fenomeni franosi landslide activity due to forest clearing and land-use sull’evoluzione geomorfologica post-glaciale del- since 3600 cal BP in the western Swiss Alps. Journal l’Alta Val Badia e della Valparola (Dolomiti). PhD of Paleolimnology 27, 239-248. Thesis. Università di Bologna. De Zanche, V. (1990). A review of Triassic Corsini, A. and Arndt, R. (2003). Resistivity profiles stratigraphy and paleogeography in the Eastern of a deep-seated rotational earthslide - earthflow in Southern Alps. Boll. Soc. Geol. It. 109, 59-71. Corvara in Badia (Dolomites, Italy): data processing De Zanche, V., Gianolla, P., Mietto, P., Siorpaes, C. and geological interpretation. In “Atti I° Congresso and Vail, P.R. (1993). Triassic sequence stratigraphy Nazionale Associazione Nazionale Geologia in the Dolomites (Italy). Mem. Sci. Geol. 45, 1-27. Applicata (AIGA)” (N. Sciarra, M. Calista and M. Dibona, D. (2000). Guida insolita ai misteri, ai Mangifesta, Eds.), pp. 233-244. Rendina Editori, segreti, alle leggende e alle curiosità delle Dolomiti. P14 to P36 n° 4 - from Volume Roma. Newton and Compton Editori, Roma. Corsini, A. and Panizza, M. (2003). Conseguenze Doglioni, C. (1984). Tettonica triassica transpressiva geomorfologiche di una faglia neotettonica nell’Alta nelle Dolomiti. Giorn. Geol. 3, 47-60. Val Badia (Dolomiti). In “Risposta dei processi geo- Doglioni, C. (1985). The overthrust in the Dolomites: morfologici alle variazioni ambientali” (A. Biancotti ramp-flat systems. Eclog. Geol. Helv. 78, 335-350. and M. Motta, Eds.), pp. 163-176. Glauco Brigati Doglioni, C. (1987). Tectonics of the Dolomites Editore, Genova. (Southern Alps - Northern Italy). J. Struct. Geol. 9,

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati (Dolomiti - Alpi meridionali). con ilclimadegli Altopiani diFanes, SenneseFosses lazioni frontalitardiglacialiepostglacialirelazioni Masini, M.(1998).Limitedellenevi perenni, oscil- Geograf. It. Memorie Geografiche G.Dainelli, Marinelli O.(1910).Ighiacciaidelle Alpi Venete. 1589-1656. morfologia, nivopluviometria. Boll.Soc.Geol.It.,95, S. (1976).L’Alpago (Prealpibellunesi)geologia,geo- Mantovani, F., Panizza, M.Semenza,E.andPiacente, 200. castello di Andraz eleminieredelFursil.Dolomiti Loss, G.,Pallabazzer, V. andChizzali,F. (1998).Il tra IsarcoePiave. Ed.Manfrini,Rovereto. Leonardi, P. (1967).LeDolomiti.Geologiadeimonti d’Ampezzo, Italy). (1996). The mobilityofthe Alverà landslide(Cortina Gasparetto, P., Mosselman,M.and Van Asch, T.W.J. Mem. Museo Trident. Sc.Nat. frane diroccianellaRegione Trentino-Alto Adige. Fuganti, A. (1969).Studiogeologicodiseigrandi Geol. glacial erosioninthesouthernalpinelakes. messinian canyons? -Geophysicalevidence forpre- Finckh, P.G. (1978). Are southernalpinelakes former management. Geol.Survey Canada,Paper 84/16. mass movements inthehighmountains:hazardand Eisbacher, G.H.andClague,J.J.(1984).Destructive 204. in thePasso Rolle Area. Doglioni, C.andNeri,(1988). Anisian tectonics Rundschau mesoalpine tectonicsintheSouthern Alps. Doglioni, C.andBosellini, A. (1987).Eoalpineand Annales Tectonicae Doglioni, C.(1990). Anatomy ofanoverthrust. 181-193. Anteil). geomorphologische Studien.DasPustertal(Rienz- Klebesberg, R.V. (1956).Sudtiroler Publ. Inc.,Edison(NJ). Dolomites ofItaly. A &CBlack,London; Hunter Goldsmith, J.and A. (1989). The del serbatoio Vajont. SADEUnpublishedreport. Giudici, F. andSemenza,E.(1960).Studiogeologico Geol. It. (Dolomiti, Belluno):un’ipotesidilavoro successione terrigenaladino-carnicadiPasso Duran Gianolla, P., Prosser, G.andSiorpaes,C.(1988).La 335 . 27,289-302. Schlern -Schriften 11, 217-220. 76,735-754. 11,1-289. 4(1),68-82. Geomorphology Rend. Soc.Geol.It. 151. 17-3,63-129. Studi Trentinidi 15(3-4),327- Suppl. Riv. .

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Pasuto, A., Siorpaes,C.and Soldati, M.(1997).I Italia). frane: casidistudionella Valle delBoite(Dolomiti, Deformazioni gravitative profondediversante e Pasuto, A., Silvano, S.andSoldati,M.(1997). (in press). debris flow intheItalianDolomites. approach forhazardassessmentandmitigation ofa Pasuto, A. andSoldati,M.(2004). An integrated Soc. Geol.It. Borca diCadore(Belluno)del7 Agosto 1996. Toffoletto, F. andBozzo,G.P. (1998).Lafranadi Panizza, M.,Piacente,S.,Silvano, S.,Siorpaes,C., pezzo (Dolomites,Italy). Panizza, M.(1990). The landslidesinCortinad’Am- Idrol. production oflandslideintheDolomiticarea. Panizza, M.(1973).Glacialpressureimplicationin Suppl. Geogr. Fis. Dinam.Quat morfotettonico dell’Alta Val Lagarina(Trentino). Marco: ungruppodifraneolocenichenelcontesto Orombelli, G.andSauro,U.(1988).ILavini di Speleologica Veneta -Regione del Veneto. Paesaggi carsiciegrottedel Veneto. Federazione Mietto, P. andSauro,U.(1989).Grottedel Veneto. Geografia G.Morandini, 11-18. Università degli studidiPadova. Dipartimentodi Pordoi. ScrittiinricordodiGiovanna Brunetta. della valle delCordevole tra Arabba edilPasso Meneghel, M.andCarton, A. (2002).Morfologia Scienze Naturali - Acta Geologica Italy). slides intheareaofCortinad’Ampezzo(Dolomites, (1996). Temporal occurrenceandactivity ofland- Panizza, M.,Pasuto, A., Silvano, S.andSoldati,M. se. nelle Dolomitioccidentalienell’Appenninomodene- F. andSpina,R.(1978).Esempidimorfoneotettonica Panizza, M.,Carton, A., Castaldini,D.,Mantovani, Sci. Geol. sorge Cortina d’Ampezzo (Dolomiti,Italia). Panizza, M.andZardini,R.(1986).Lafranasucui Pieve d’Alpago,Belluno. - Somadida(Auronzo),Nuove Edizioni Dolomiti, S.Vito diCadore-Rif.S.MarcoCadindelDoge – SettsassCastellodi Andraz, Itinerarion.5: Dolomiti venete, Itinerarion.4:Rifugio Valparola Panizza, M.(Ed.)(1991).Guidenaturalistichedelle 63, Università degli StudidiMilano. Conference Proceedings”(A.Cancelli,Ed.),pp.55- 12th, Switzerland-Austria-Italy,31st-Sept. Aug. Geogr. Fis. Dinam.Quat. 8,289-297. Geomorphology Geogr. Fis. Dinam.Quat. 38,415-426. 53,465-478. 15(3-4),311-326. In 1(1),28-54. “ALPS 90-6thICFL, . I,107-116. 20,107-111. 73,107-117. Geomorphology 25-05-2004, 15:40:34 Mem. Mem. Geol.

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fenomeni franosi nel quadro geologico e geomorfo- Alps: a review. Boll. Geof. Teor. ed Appl 31(122), logico della conca di Cortina d’Ampezzo (Dolomiti, 109-136. Italia). Il Quaternario 10(1), 75-92. Soldati, M. (1989). Studio sul crioclastismo dell’alta Pasuto, A., Silvano, S., Soldati, M. and Tecca, Valle di S. Pellegrino (Dolomiti): indagini sul terreno P.R. (1994). Research on deep-seated gravitational e sperimentazioni in laboratorio. Il Quaternario 2(1), deformations in North-eastern Italy. In “Deep-seated 79-98. gravitational deformations and large-scale landslides Soldati, M. (1999). Landslide Hazard Investigations in Italy” (U. Crescenti, F. Dramis, A. Prestininzi and in the Dolomites (Italy): The Case Study of Cortina M. Sorriso-Valvo, Eds.), pp. 23-27. Special volume d’Ampezzo. In “Floods and Landslides: Integrated for the International Congress IAEG, Lisboa (sept. Risk Assessment” (R. Casale and C. Margottini Eds.), 1994), Dipartimento di Scienze, Storia dell’Architet- pp. 281-294. Springer-Verlag, Berlin. tura e Restauro - Univ. Pescara. Soldati, M. and Pasuto, A. (1991). Some cases of Pellegrini, G.B. and Surian, N. (1996). deep-seated gravitational deformations in the area Geomorphological study of the Fadalto landslide, of Cortina d’Ampezzo (Dolomites). Implications Venetian Prealps, Italy. Geomorphology 15, 337-350. in environmental risk assessment. In “European Pellegrini, G.B., Surian, N. and Urbinati, C. (2004). Experimental Corse on Applied Geomorphology, Dating and explanation of Late Glacial – Holocene Vol.2 - Proceedings” (M. Panizza, M. Soldati and landslides: a case study from the Southern Alps, Italy. M.M. Coltellacci, Eds.), pp. 91-104. Istituto di Zeitschrift für Geomorphologie, in press. Geologia, Università degli Studi di Modena. Pellegrini, G.B. and Zambrano, R. (1979). Il corso Soldati, M., Corsini, A. and Pasuto, A. (2004). del Piave a Ponte nelle Alpi nel Quaternario. Studi Landslides and climate change in the Italian Trentini di Scienze Naturali 56, 69-100. Dolomites since the Lateglacial. Catena (in press). Penck, A. and Brückner, E. (1909). Die Alpen im Stuiver, M. and Reimer, P.J. (1993). Extended 14C Eiszeitalter. 3 Vols. Tauchnitz, Leipzig. data base and revised CALIB 3.0 14C age calibration Picotti, V. and Prosser, G. (1987). Studio geologico program. Radiocarbon 35, 215-230. dell‘area compresa tra Lozzo di Cadore e il Gruppo Stuiver, M., Reimer, P.J., Bard, E., Beck, J.W., Burr, delle Marmarole Dolomiti, Alpi Meridionali. Gior. G.S., Hughen, K.A., Kromer, B., McCormac, F.G., Geol. Ser. 3 49, 33-50. v. d. Plicht, J., and Spurk, M., 1998. INTCAL98 Pisa, G., Marinelli, M. and Viel, G. (1980). Infraraibl Radiocarbon age calibration 24,000 - 0 cal BP. Group: a proposal (Southern Calcareous Alps, Italy). Radiocarbon 40, 1041-1083. Riv. It. Paleont. Strat. 85, 807-828. Surian, N. and Pellegrini, G.B. (2000). Paraglacial Provansal, M. (1995). The role of climate in landscape sedimentation in the Piave valley (Eastern Alps, morphogenesis since the Bronze Age in Provence, Italy): an example of fluvial processes conditioned Southeastern France. The Holocene 5, 348-353. by glaciation. Geogr. Fis. Dinam. Quat. 23, 87-92. Sacco, F. (1939). L’alta Italia durante l’Era Venzo, S. (1939). Osservazioni geotettoniche e geo- Quaternaria. L’Universo 20(2-3), 3-32. morfologiche sul rilevamento del Foglio Belluno. Sacco, F. (1940). Le marocche del Veneto. L’Universo Boll. Soc. Geol. It. 58, 433-451. 21, 763-782. Viel, G. (1979). Litostratigrafia ladinica: una revisio- Sauro, U. and Meneghel, M. (Eds.) (1995). Altopiani ne. Ricostruzione paleogeografica e paleostrutturale Ampezzani: geologia, geomorfologia, speleologia. La dell’area Dolomitico-Cadorina (Alpi Meridionali). Grafica Editrice, Verona. Riv. It. Paleont. Strat. 85, 85-125 (Parte I), 279-352 Servizio Geologico d’Italia (1970). Foglio 11 “M. (Parte II). Marmolada”. Carta Geologica d’Italia a scala 1: Von Lichem, H. (1993). La guerra in montagna, 100.000, 2ª edizione. 1915-1918 (Volume 2), il fronte dolomitico. Athesia, P14 to P36 n° 4 - from Volume Servizio Geologico d’Italia (1977). Foglio 028 “La Bolzano. Marmolada”. Carta Geologica d’Italia alla scala 1: Winterer, E.L. and Bosellini, A. (1981). Subsidence 50.000. and sedimentation on Jurassic passive continental Slejko, D., Carulli, G.B., Nicolich, R., Rebez, A., margin, Southern Alps, Italy. AAPG Bull. 65, 394- Zanferrari, A., Cavallin, A., Doglioni, C., Carraro, F., 421. Castaldini, D., Iliceto, V., Semenza, E. and Zanolla Zanferrari, A., Bollettinari, G., Carobene, L., Carton, C. (1989). Seismotectonics of the eastern Southern- A., Carulli, G.B., Castaldini, D., Cavallin, A.,

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Volume n° 4 - from P14 to P36 P22 - P22 Leader: M.Soldati 1976. Zardini, R.(1979).LafranainlocalitàCinque Torri: Orientale. U. (1982).Evoluzione neotettonicadell’ItaliaNord- Panizza, M.,Pellegrini, G.B.,Pianetti,F. andSauro, Le DolomitiBellunesi Mem. Sci.Geol. 35,355-376. 3,51. d’Ampezzo. d’Ampezzo). CassaRuraleed Artigiana, Cortina vazioni geomorfologichesulColDrusciè(Cortina Reperto arboreodi9000annifa aRoncoeosser- Zardini, R.,Panizza, M.andSpampani,(1984). 25-05-2004, 15:40:38 Back Cover: ﬁ eld trip itinerary

P22 copertina_R_OK E 25-05-2004, 15:28:32 FIELD TRIP MAP INTERNATIONAL GEOLOGICAL CONGRESS nd 32

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