Case Studies from the Dinaric Karst of Slovenia

Andrej Mihevc, Mitja Prelovšek, Nadja Zupan Hajna (Eds.)INTRODUCTION TO THE DINARIC KARSTEditors / Uredniki:Language review / Jezikovni pregled:Photos / Fotografije:Cartography / Kartografija:Design and graphic art / Oblikovanjein grafična ureditev:Published by / Izdal in založil:Represented by / Zanj:Andrej Mihevc, Mitja Prelovšek, Nadja Zupan HajnaCarolyn L. RamseyAuthors of chapters, if not otherwise mentionedMitja PrelovšekMitja PrelovšekInštitut za raziskovanje krasa ZRC SAZU, Postojna /Karst Research Institute at ZRC SAZU, PostojnaTadej SlabePrinted by / Tisk:Printrun / Naklada:Collegium Graphicum d.o.o., Ljubljana300 copies / izvodovPostojna, junij 2010The publication was published within the Karst UndergroundProtection project which is financially supported by the Slovenia-Croatia Operational Programme 2007-2013.Knjiga je bila izdana v okviru projekta Karst UndergorundProtection financiranega iz Operativnega programa IPA Slovenija-Hrvaška 2007-2013.CIP - Kataložni zapis o publikacijiNarodna in univerzitetna knjižnica, Ljubljana911:551.44INTRODUCTION to the Dinaric Karst / edited by Andrej Mihevc,Mitja Prelovšek, Nadja Zupan Hajna ; [photos authors of chapters ;cartography Mitja Prelovšek]. - Postojna : Inštitut za raziskovanjekrasa ZRC SAZU = Karst Research Institute at ZRC SAZU, 2010ISBN 978-961-254-198-91. Mihevc, Andrej, 1952-251366400

Introduction to theDinaric KarstEdited by:Andrej MihevcMitja PrelovšekNadja Zupan HajnaPostojna, junij 2010

ContentsGeographical Position and General Overview(Andrej Mihevc, Mitja Prelovšek)Short History of Research(Andrej Kranjc)Geology(Nadja Zupan Hajna)Climate(Mitja Prelovšek)Hydrology(Mitja Prelovšek)Geomorphology(Andrej Mihevc)Land Use(Nadja Zupan Hajna, Andrej Mihevc, Mitja Prelovšek)Case Studies from the Dinaric Karst of Slovenia(Andrej Mihevc, Nadja Zupan Hajna, Mitja Prelovšek)69142025304449KrasLjubljanica River SystemKarst of Dolenjska and KolpaContac Karst of Matarsko podoljeCavesUnroofed Caves and Surface DenudationUse of Karst and its ProtectionReferences67

Geographical Position and General OverviewAndrej Mihevc, Mitja PrelovšekThe Dinaric karst is the major morphologicaltype of landscape of the Dinarsko gorovje(Dinaric mountains), extending over approximately60,000 km 2 and forming the largestcontinuous karst landscape in Europe.The Dinarsko gorovje are positioned betweenthe Panonian Basin in the northeastand the Adriatic Sea in the southwest, coveringan area over 650 km in length and over 150km wide (Fig. 1). In the north, they border theAlps along the rivers Soča, Idrijca and Dolejnskopodolje (Dolenjska lowland). The inner sideof the mountains is delimited by the river Savavalley. The eastern border of the mountains isin the Kolubara and Morava river basins, theedge of the Kosovo basin and the Prokletijemountains. The transition to the Alps in thenorthwest and the Albanian mountains towardthe southeast is not very distinctive.The Dinarsko gorovje are separated intodifferent natural belts. All have a commondirection (northwest-southeast; the Dinaricdirection), which is the direction of most ofthe relief features. The main geomorphologicdifferences of the mountains are defined bydifferences in lithology. Inland non-carbonaterocks on which fluvial relief has developed prevail.The main parts of the mountains, centralFig. 1: Delimitation of the Dinaric karst toward northeast after Roglić (1965) and after Gams (1974).6

Fig. 2: Coastal part of Dinaric karst experienced severe deforestation which started already in the Neolithoc period(photo: A. Mihevc).Fig. 3: Mountainous Dinaric karst - Popovo polje in Herzegovina (photo: M. Mihevc).8

Short History of ResearchAndrej KranjcDinaric karst is the landscape where thesciences of karstology and speleology tooktheir origin and started to develop thus contributingseveral karstological terms to internationalkarst terminology. In the antiquityalready some of karst phenomena werementioned from the Dinaric karst, but hereare considered published sources mostlyfrom the 16 th century on, when the modernkarst research started. In those times Dinarickarst belonged to different states. Adequatesources were used and and it was a difficulttask yet not completely achieved but it presentsa relatively new approach. For the olderperiod some Venetian and Turkish works areincluded. Emphasized are Austrian and Austro-Hungarian researchers working in Bosnia andHerzegovina as well as Serbian researchers.The contribution which can be no more thanan unpretentious overview mentions earlyphilosopher N. Gučetić discussing karst phenomena,and travellers through the Balkanslike B. Hacquet, B. Kuripečič, E. Čelebija, andA. Fortis, and also well-known geomorphologistsand speleologists A. Penck, E.-A. Martel,J. Cvijić, A. Melik, and J. Roglić.Pre-scientific phaseKarst phenomena or better phenomenawhich we are called nowadays as karst onesare relatively often mentioned by ancientGreek and Roman authors. The groundwaterand its connection with the sea are noted byHomer, Thales of Millet, Anaxagoras, Plato,Aristotle, Lucretius, and Seneca. Among thesedescriptions there are also some from Dinarickarst. Pseudo-Skylax’s Periplous (The Circumnavigationof the Inhabited World) of 4 th centuryBC mentions the springs of Timavo (Herak& Stringfield 1974) which were later studiedby Poseidonios of Apameia (135 – 50 BC). Inconnection with them he mentions also »thechasm« - Škocjanske jame (Škocjan caves;Kranjc 1998). In Virgil’s Aeneida the Timavosprings are called the Mother of the sea andStrabo’s Geography names Lugeon Lacus. Curiouslyall these phenomena are from the northwesternpart of the Dinaric karst. Taking intothe consideration that this is the most distantrelated to Greece, I would say that we do notknow the appropriate references.From the Middle Ages it is not knownmuch more. Tabula Peutingeriana showingthe springs of the Timavus is in fact a Romanmap. Karst phenomena are mentioned in thedocuments from different reasons but withouta notion of karst yet. In 888 the king Berangerdonated the church in the cave Sv. Ivan vČele – San Giovanni d’Antro located in the lastparts of the karst above the plain of Friuli, theCroatian word for the cave Pechice, Pechie orPechine ossia Grotta, that is pećina, figureson the map of the domain of a monastery onthe Ugljan Island in the year 1096 and 1166respectively as shown in many contributionsof late M. Malez (1984). Well known is Byzantine’sEmperor Constantine Porphyrogennetosdescription of his empire De AdministrandoImperio (948 – 952) where many karst sites arementioned like the rivers Pliva and Buna (oneof the biggest karst springs), poljes of Imotskiand Krbava, and the place Vrulja (Bury 1920).The study of this work from the karstologicalpoint of view is still waiting to be done.It can be said that during the 16 th centurythe interest for the karst, future karstol-9

ogy started. In 1531 a lawyer from Ljubljana,Benedikt Kuripečič (Kuripešič) (born 1490)published a diary of his voyage through theBalkans as the interpreter to the Turkish sultanSuleiman to Constantinople (Curipeschitz1531). From the point of view of karst he mentionsjust some karst spring (Kranjc 2008).Equally unimportant is Leonberger’s longpoem about the Lake of Cerknica. Accordingto the description (oral or written) of S. Herberstein,Vienna’s diplomat by the origin fromVipava, G. Wernher (1551) published a descriptionof this lake (in fact seasonally floodedpolje), including the map (Simoniti 2010). Onthe other side of Dinaric karst a philosopherfrom Dubrovnik, Nikola Gučetić (Gozze 1584)published a discussion of the wind in the Caveof Vjetrenica (Wind Cave) and of the speleothemsfrom the cave Šipun. The reputationof the Cerkniško jezero (Cerknica lake) grewwhich can be well seen from the contemporaneousmaps of Lazius, Ortelius or Mercator forexample: the lake is drawn much bigger thanit deserves according to the scale of the map.Evliya Çelebi (Evlija Efendi), his full namewas Evlijā ibn Derviš Mehmed Zillī, travelledthe whole of his life (1611 – 1682), a lot throughBalkans too. In his diaries, discovered littlemore than 100 years ago, are described karstlandscapes, water phenomena, caves (mostlyin connection with fighting guerrilla). Curiouslyhe knows a sort of corrosion: to make theroad through limestone terrain large enoughto pass the canons, soldiers had to pour theacid on the limestone (Kranjc 2008)! This isalso a time when one of the leading scientistsFig. 4: Valvasor’s hydraulic model of Cerkniško jezero (Cerknica lake).10

of his time, a Jesuit Athanasius Kircher (1678),has published his monumental work MundusSubterraneus (1665 the first edition). The bigkarst springs are explained by enormous undergroundreservoirs hydrophillatia and asthe proof of his theory the Cerkniško jezero isused (Fig. 4). Ten years later Valvasor (1689)travelled many times to Cerknica, to explore itby himself (neither Wernher nor Kircher evervisited it). He did not agree with Kircher andmade his own explanation which earned himthe London’s Royal Society membership.The fame of the Dinaric karst phenomena,from Carniola specially, is in great deal due toValvasor’s descriptions; he was not interestedin the Cerkniško polje (Cerknica polje) only, butin other karst phenomena also: sinking rivers,karst springs and caves especially. In 1748 theemperor Franz I. Stephan sent the director ofhis Cabinet of rarities J. A. Nagel (1748) to Carniolato found out what are these unusual phenomena,and to bring some samples for his collection.After returning Nagel wrote a detailedreport; the most important is his explanationof the periodicity of Cerkniško jezero and theobservation of the age of speleothems. F.Steinberg (1758) published the whole book onthe Cerkniško jezero and T. Gruber (1781) wasthe first who published (probably the ideas ofhis brother Gabriel) the accurate explanationof the lake. He even advised a sort of meteorologicalstations to be able to calculate thequantities of in- and output of the water.For the coastal part of Dinaric karst thedescription and exploration even of karst phenomenaby the Abbot Alberto Fortis publishedin 1774 is especially important due to the politicalsituation on the Balkans. He was accompaniedby foreign scholars and even by an Englishbishop so his book was well known. Commentarieswere published about the book (Lovrich1776) but without discussing his views ofkarst phenomena. Just to mention that Fortissupports the collapse theory of foibas (shafts)formation. In the same time another scholartravelled through Dinaric karst too, B. Hacquet(1778). He was a doctor of medicine but by hisown opinion he was a chemist. Some of hisideas about geological development, aboutrocks and the solution of limestone (corrosion)were too early and although they were publishedand despite his relations with learnedsocieties and scholars all round the Europehis ideas were not recognised. Maybe he isthe first to largely use the expression DinaricAlps. In 1785 he has published “The physicalpoliticaltravel from Dinaric through Julian,Carnian, Rhätian and Noric Alps”, including thepanoramic view from the river Zrmanja to themountain Dinara (Hacquet 1785).The first phase of karst geomorphologyresearchDuring the 19 th century the boom of geologicalresearch touched the Dinaric karst too.Vienna was very important scientific centreand Dinaric karst, well developed and largekarst region in its vicinity, became the sourceof main ideas on karst. In 1830 already F. Hohenwartwrites in the preface of a guide book toPostojnska jama (Postojna cave) that the karstis not on the plateau of Karst only, but stretchesfrom the Friuli plain to the Greek Island ofCephalonia.In 1848 A. v. Morlot published the map andthe text about the geology of Istria includingdiscussion of morphological features, especiallydolines. The basic work on speleology of theCarniolian part of Dinaric karst was achievedby A. Schmidl (1854) exploration in the middleof the 19 th century (Fig. 5), helped by Vienna’sAcademy and the Southern Railway Company(the railroad Vienna – Trieste was opened in1857). Western scholars, it is true that few,were interested in the Turkish part of the Balkans,like A. Boué (1840) who published “LaTurquie d’Europe; observations sur la géographie,la géologie, l’histoire naturelle“. Later hewas interested in karst (Karst und Trichterplastikfrom 1861) and in Bosnia specially. Therewere some serious published reports whosetitles imply narrow application but in fact they11

include numerous data and general observationson karst, as are Beyer et al. (1874) andWessely (1876).Following the occupation of Bosnia andHerzegovina (1878) a new and complex approachto karst problems coincided with thebeginning of the geological survey. LeadingVienna’s geologists of the time, E. Mojsisovics,E. Tietze and E. Bittner (1880) gave a scientificexplanation of the karst features genesis,but the discussion between the supporters ofcollapse and of solution theories continued.Leading Vienna’s geomorphologist, A. Penckwas the most prominent protagonist of thenew discipline, karstology. He suggested to hisstudent J. Cvijić for his doctor thesis to studykarst. He got main ideas of karst on the plateauFig. 5: In 1854, A. Schmidl published the basic work on speleologyfor the area of Carniola, Slovenia.of Karst (Kras) and in 1893 he published DasKarstphänomen (Fig. 6), a turning-point and atthe same times the beginning of the intensivestudy of karst morphology, including the useof the term karstification. In 1899 W.M. Daviesjoined Penck and his students at the field tripto Bosnia and Herzegovina. The previous fluvialerosion and the cyclic evolution (dolina –uvala – polje) were introduced into the theoryof karst.In 1903, A. Grund, also the disciple ofPenck, has published a basic work on karsthydrography which is a new milestone alsoin karst morphology, introducing a concept ofkarst groundwater concordant with the cyclictheory too and supported by Penck himself.Speleologists, Knebel and Martel especially,and some geologists (Katzer) and geographers(Kraus 1894) opposed strongly to Grund’skarst groundwater. 1910 Grund has publishedthe work of the relief of the Dinarsko gorovje(Dinaric mountains) based on his observationsin Bosnia and Herzegovina, where his viewson the evolution of poljes and karst plains areexplained. Hungarian geologist H. Terzaghi in1913 introduced a theory of marginal or bordercorrosion to explain limestone plains andflat polje surfaces. Two decades passed beforeit was recognized and later further developedby the most prominent Croatian geomorphologistJ. Roglić (1952). During the 1 st World Warwhen he was teaching at Sorbonne Cvijić hasprepared a synthesis of his views about theevolution of karst relief and has published itin 1918 (Cvijić 1918). He accepts karst groundwaterand distinguishes three hydrographicalzones: permanent inundation, periodical inundation,and a dry zone. He renames Grund’s“Halbkarst” (half-karst) into “merokarst” andintroduces fully developed “holokarst”.The defeat of Austro-Hungarian Monarchyresulted in almost complete lethargy in theViennese centre of karst research. After the1 st World War the investigations of karst reliefstagnated, followers of the respected masterswere few and did not produce worthwhile con-12

tributions. The first phase was rich in generalideas and poor in real analyses (Roglić 1974).The second phase of karst researchThe previous research, including Penck-Grundconcept did not resolve the problem of thewater circulation through fractures, fissures,and joints and its relation to the evolution ofkarst relief. This was explained by Vienna’sgeomorphology group member O. Lehman(1932). According to nearly forgotten Terzaghi’smarginal corrosion Kayser (1934) explainsthe plains at the border of Skadar Lake (Montenegro).Roglić (1938) describes and explainsaccordingly to the theory of a border corrosionsuch terraces of the Dinaric poljes. The newconcept was largely adopted by the authors ofdifferent general or specialised works relatedFig. 6: The book Das Karstphänomen of Jovan Cvijić wasa pioneering monograph and marked the beginning ofmodern karst studies (Shaw 1992).to Dinaric karst. The example is the work ofA. Melik, Slovenia and Sima M. Milojević, Serbia.ConclusionThe second phase was tragically interruptedby the 2 nd World War. Soon after thewar investigations of karst morphology wererevived and increased in volume as well as inintensity in an essentially different way thanthose in the past. In the post-war period thereare global scientific contacts and exchanges.The different countries are easily accessible.Observations and data are multiplying, conceptsare modified and combined, sophisticatedmethods, based on computer and digitaltechnologies are widely used. With more exactobservations and data, the correspondingconclusions have been improved. In the areaof Dinaric karst specially, important practicalwork in the prospection and exploitation ofore deposits has been carried out, as well asthe construction of accumulation basins, hydroelectricpower plants, tunnels, railways,and motorways. Scientific concepts have necessarilybecome adapted to new ideas andfacts. So the Dinaric karst has given a lot ofdata and other material to study, there were agreat number of authors and even much greaternumber of professional and amateur works,there are new centres working on Dinarickarst, there are specialised journals, meetingsfrom the World congresses to local symposia.But the same can be said for the karst all overthe world. New theories and concepts areelaborated on the knowledge of other karsts,not the Dinaric one. So this contribution endssomewhere with the 2 nd World War. On onehand it would require too much work and timeto analyse in detail the imposing investigationsof the Dinaric karst in the last 60 years, and onthe other hand, regarding the investigations ofthe karst worldwide it would be too difficult tofind out the role, the importance and the influenceof the Dinaric karst studies upon thegeneral karstology.13

GeologyNadja Zupan HajnaThe Dinaric karst is geographically and geologicallypart of the Dinarsko gorovje (Dinaricmountains; Dinarides) and includes all of theExternal Dinarides and some parts of the InternalDinarides (Fig. 7).According to some authors (for instance,Schmid et al. 2004), from a tectonics perspectivethe Dinarides (Dinaric Alps) include theSouthern Limestone Alps, External and InternalDinarides. Other researchers (for instance:Placer 1999, 2008; Tari 2002; Kastelic et al.2008) take the view that only the External andInternal Dinarides are included.The geological evolution of the Dinarides isclosely associated with the history of the TethysOcean, which closed during the Mesozoicand Cenozoic as a result of the convergence ofthe Africa and Eurasian Plates. Intermediatemicroplates played an important role in oceanshortening. The present geological structuresresulted from post-collision processes in theAlpine orogenic system, which started beforeabout 35 Ma (Vrabec & Fodor 2006).The Dinaric karst denotes an area withinthe Dinaric Mountain System, confined mostlyto the External Dinarides, which consists predominantlyof Triassic, Jurassic and Cretaceouslimestones and dolomites; see the Geologicalmap (Fig. 8). Geological data (i.e.,Vlahović etal. 2002) indicate that the External Dinarideswere formed by the destruction of a single,(yet, in morphological terms, highly variable)shallow water carbonate platform. The platformwas very dynamic in some periods becauseof its paleogeographic position duringthe Mesozoic, especially during the Late Creta-Fig. 7: Simplified tectonicmap of Dinaric Mountains(after Schmid et al. 2004;Šumanovac et al. 2009).14

Fig. 8: Geological map of Dinaric karst; modified after Atlas svijeta, 1974).15

ceous. The final disintegration of the platformarea culminated in the formation of flyschtrough(s) in the late Cretaceous and Paleogeneand the subsequent uplift of the Dinarides.There is confusion among the scientific literaturedue to the different names used for thissame shallow water carbonate platform. Probablythe best, although not the ideal, nameis the most frequently used one: the AdriaticCarbonate Platform (Vlahović et al. 2002). Itsduration is estimated to be from the Late Lias(Fig. 9) to the Late Cretaceous, representingthe most important part of a thick carbonatesuccession in the Dinaric karst (ranging fromCarboniferous to Eocene).Fig. 9: Liassic limestone with lithiotides; Rujno abovePaklenica canyon (photo: N. Zupan Hajna).Differing opinions about the geologic evolutionof this system in the northeastern Adriaticregion reflect its complexity (Korbar 2009).After Korbar (2009), the External Dinaridesare a fold-and-thrust belt, part of the Alpineorogenic system, characterized by generallysouthwest-verging structures, and can be consideredas the detached, backthrust and highlydeformed upper crust of the Adria duringsubduction to the northeast. This belt, alongwith the related part of the Adriatic foreland,is geographically situated within the Dinarickarst region.The main tectonostratigraphic units of theDinarides (Tari 2002; Fig. 10) are related to: a)Early and Middle Triassic rifting; b) Late Jurassicto present day compression.Early and Middle Triassic rifting wasmarked by strong magmatism and horst andgraben-related deposition overlying the Variscianbasement. Along the “eastern” Apulianmargin toward the Sava-Vardar, ocean riftingwas followed by subduction-generated extensionfrom the Early Triassic until the Late Jurassic.Subduction-related attenuation of continentalcrust along the eastern margin of Apuliacaused the formation of a back-arc basin in theoceanic crust. The remnants of these activecontinental margin lithologies are found withinthe Eastern thrust belt as the ophiolite melangeof the Central Dinarides Ophiolite Belt.Late Jurassic-to-present day compressiongenerated:• the Eastern thrust belt, foredeep andforeland: the Dinaridic carbonate platformtoward the west presented theforeland of the generally west directedthrusting. During the Early Cretaceous,compressional stresses began to betransmitted westward through the Dinarides,causing the migration of theforedeep basin and regional uplift ofthe Eastern thrust belt.• the Northern Dinarides accretionarywedge: subduction of the oceanicplate along the northern margin of theDinarides resulted in the accumulationof this accretionary wedge from theMaastrichtian to the Eocene.• the Western thrust belt, foredeep andforeland: from the end of the Cretaceousuntil the early Eocene the entirecarbonate platform was uplifted. Duringthe Eocene, the Dinaridic carbonateplatform was finally buried underthe flysch deposits in the broad foredeepbasin of the Western thrust belt.• the Eastern Adria imbricated structures:at the beginning of the Oligo-16

Fig. 10: The main tectonostratigraphicunits of the Dinarides and Adria; afterTari (2002).Legend:1. Eastern thrust belt;2. Dinaridic carbonate platform, forelandof the Eastern thrust belt;2a. Frontal thrust of the Western thrustbelt;3. Maastrichtian-Paleogene accretionarywedge;3a. Maastrichtian- Paleogene retroarcarea, North-Bosnian flysch;4. Slovenian Basin;5. Budva-Cukali Basin;6. Gently tectonised Adriatic carbonateplatform;7. Adriatic Basin;8. Gargano-Sazani-Paxos carbonateplatform;9. Miocene wrenching;10. Miocene tectonic inversion.cene, collision and progressive underthrustingof the Adria below theDinarides created the imbricate structuresof Adria provenience in front ofthe Western thrust belt. The structuralstyle of the Dinaridic thrust belt is aresult of the polyphase tectonic compressionand the competence of thesedimentary units involved. The competentcarbonate rocks are the strongestinfluencing factor on the structuralstyle of the thrust belt. The compressionstarted with ramping along thedeep decollement from the root zonewith a southwestern tectonic transport.In this way, by progressive oversteppingof the thrust faults, variousstructural forms were created alongthe eastern and western thrust belt -fault bend folds, tear fault-related foldsand folded thrust structures reworkedby footwall deformations.• Wrenching and tectonic inversion: thenortheast-southwest striking systemof the dextral strike slip faults duringOligocene - Miocene was followedby northwest-southeast striking andwrenching in the early and middleMiocene, affecting the South PannonianBasin, the Western thrust belt andthe Adriatic foreland. This activity is reflectedin the large flower structures ofthe Dinaridic thrust belt.The main structures of the Dinaric karsthave a strike trend in a northwest - southeastdirection (in the so-called “Dinaric” direction).This structural pre-disposition is visuallyreflected in the directional trend of high plateausand karst poljes from south Slovenia toMontenegro.Mountains above 1,100 m a.s.l. in the Dinarickarst were glaciated during the Pleistocene.Valley glaciers reshaped the original fluvialvalleys into typical U-shaped valleys anddeposited vast amounts of sediments. Thereare a number of characteristic glacial featuressuch as hanging valleys, remains of moraines,fluvioglacial sediments, eratic blocks and17

Fig. 11: Locations of Jelar Breccia and Promina beds; from Perica & Marjanac (2009; afterOluić et al. 1972; cartography: Iztok Sajko).striated cobbles and boulders. The remainsof Pleistocene glaciations are visible fromSnežnik Mountain in Slovenia, Risnjak andVelebit mountains in Croatia to Orjen, Lovčenand Durmitor mountains in Montenegro.Along Dinaric karst, karst features are favoredspecially in massive and thick beddedCretaceous limestones (with rudist shells) andin two characteristic lithological units (Fig. 11)which host an exceptional abundance of welldeveloped karst features. These two are thePromina Beds, Eocene-Oligocene in age, andthe Jelar Breccia, of unknown age - Oligoceneor younger (McCann 2008).The Tertiary Jelar Breccia covers large areasalong the northeastern Adriatic coast on18the southwest rim ofVelebit Mountain (westernCroatia). The largestoutcrop is >100 kmlong, 2–10 km wide, andthicker than 500 m inplaces. The Jelar Brecciawas poorly studiedbecause of its very complexcomposition, unclearstructural positionand intense youngertectonic deformation(Vlahović et al. 2007). Itis usually considered aresult of the disintegrationof frontal parts ofthe major thrusts. TheJelar Breccia is a massive,thick-bedded carbonaterock, comprisedpredominantly of angular,poorly sorted debris(Fig. 12). The brecciahas a carbonate matrix,which is gray- to reddishin color. The lithostratigraphiccompositionof the debris is varied(Bahun 1974). Clasts ofCretaceous limestones and dolomites are themost common, with lesser amounts of Triassiccarbonates and Paleogene limestones. The debrisgrain sizes are highly variable, with clastsin ranging in size from a few mm up to severalmeters.Due to its specific mechanical and petrographicproperties, the Jelar Breccia is characterizedby an abundance of such solutionalkarst features as karren (Perica & Marjanac2009), dolines, conical hills and caves. In theJelar Breccia along the south- and southwestparts of Velebit, ridges of conical hills (named“Kuk” in the local language) are numerous. Betweenthese hills, big and deep karst depressionsare developed. Well known examples

Fig. 12: The Jelar Breccia is a massive, thick-beddedcarbonate rock, comprised predominantly of angular,poorly sorted debris; North Velebit (photo: N. Zupan Hajna).include Hajdučki and Rožanski kukovi nearZavižan (Northern Velebit National Park); Dabarskikukovi next to Baške Oštarije; Bojinac(Fig. 13) above Paklenica Canyon (NationalPark Paklenica) and Tulove grede on the southedge of the Velebit.The deepest explored caves in Croatia aredeveloped in Jelar Breccia (Garašič 2005), andare found north of Velebit. These caves areLukina jama-Trojama (-1,392 m), Slovačka jama(-1,320 m), Velebita cave system (-1,026 m)with a 513 m underground vertical shaft andMeduza (-679 m) (these data are from Lackovićet al. (1999) and the web pages of the CroatianSpeleological Federation (http://www.speleo.hr/deepest.htm); Fig. 30 on page 41).Several significant caves were also discoveredin the Jelar Breccia of Crnopac area (SouthVelebit). Their main morphological characteristicis a network of multiphase cave passages,some of them with very large cross-sectionaldimensions (Bajo et al. 2009). The most importantcaves of Crnopac massif are Munižaba(5,993 m long, -437 m) and Kita Gaćešina(10,603 m long, -456 m).The Promina Beds (Promina Formation)consist of two different lithological parts (Mc-Cann 2008). The lower part is characterized byan alternation of marls, sandstones, conglomerates,limestones and cherts. The upper partsare alluvial sediments– conglomerateswith marlybeds with coaland plant remains.Promina beds areEocene-Oligocenein age (Babić &Zupanič 2007).The Promina Bedscan be seen onPromina Mountain,at Kistanjskiravnik and RavniKotari (the areabetween Velebit,Novigradsko more(Novigrad Sea) andthe River Krka).Fig. 13: Karst in Jelar Breccia; Bojinac at South Velebit. In the distance is Adriatic Sea and levelledsurface around Novigradsko more (Novigrad Sea; photo: N. Zupan Hajna).19

ClimateMitja PrelovšekThe Dinaric karst is situated between42° and 46° N at the northeastern edge of theMediterranean Sea. From a climatic point ofview, this geographic position falls within atemperate climatic zone where mid-latitudewesterly winds (westerlies) prevail throughoutthe year. Nevertheless, the declination of theEarth and its movement around the Sun shiftsthe position of temperate belt 23° northwardduring summer and southward again duringwinter. This means that these latitudes canbe under a strong subtropical zone influenceduring the summer months and under the influenceof polar fronts during winter since thepolar front can move southward of Greece(Kocsis 2007). Westerlies can therefore be verydry during several summer months but alsovery wet during winter.Besides the global atmospheric circulationsystem, the climate of the Dinaric karstis strongly influenced by the Dinarsko gorovje(Dinaric Mountains), which form an orographicbarrier that affects precipitation patterns(Fig. 16) and hinders winter intrusions ofcold polar air flowing from continental regionsin the east toward Adriatic coast. Westerliesusually blow from the Atlantic Ocean over thewarm Mediterranean Sea. If the pressure islow over the Mediterranean Sea, air massesbecome enriched with humidity. When theyhit the Dinarsko gorovje, the result is a highamount of precipitation on the west-facingside (Crkvice, Orjen-5,317 mm/a-the highestamount in Europe; Rodić 1987) and a muchsmaller amount of precipitation on the eastfacingside. Lower amounts of precipitation arealso characteristic for low-lying areas along theAdriatic coast and low islands (e.g., Pula-713mm/a, Vis-676 mm/a; Rodič 1987). In summer,high pressure over the Mediterranean Seahinders uplifting and condensation of the airmasses over the sea, while over the continentprecipitation is possible due to strong convection.In winter, the Dinarsko gorovje preventintrusions of cool air masses that develop overcontinental Eastern Europe. Nevertheless, ifthe pressure difference between marine andcontinental air masses is too high, pockets ofcold air spill over the orographic barrier, causingstrong katabatic winds called “the Bora”,which can exceed even 200 km/h. The mainridge of the Dinarsko gorovje, which rangesin altitude from 612 m to more than 2,500 m,also causes a strong vertical decline of temperature.Average annual temperatures decreasewith height over quite short horizontal distances(80 km) from 15.3 °C (Podgorica; Kovacs& Dobos 2007) to about 2°C (Durmitor). Evensteeper spatial temperature changes are characteristicfor mountain Velebit. At such highaltitudes, snow is present for up to half a year.The Adriatic Sea has a strong moderatinginfluence especially on temperatures alongthe coast and islands. Along the coast, at thesouthwestern boundary of the Dinaric karst,winter temperatures are much higher in comparisonwith places on the northeastern edgeof the Dinaric karst. Along the coast, temperaturesbelow zero are rare even during winterbut very common on the continental edgeof the Dinaric karst at only slightly higher altitudes(~170 m a.s.l.). Consequently, snowat the coast is very rare, but not impossible(when it does occur, it is always related tothe intrusion of cold continental air from thenortheast). In summer, daily temperaturesalong the coast are usually lower than in thecontinental part of the Dinaric karst due to the20

maritime influence of the Adriatic Sea. In somecases, the influence of the Adriatic Sea can extendeven further toward the Dinarsko gorovjethrough wide valleys of rivers such as the Krka,Bojana, Morača, Zeta and the downstreampart of the Neretva.On the continental side of the Dinarsko gorovje,the absence of the maritime influenceresults in more extreme diurnal and seasonaltemperature variations. Snow can persist onthe ground for more than one month on averageduring the winter, and up to severalmonths at higher altitudes. Another differencein comparison with Mediterranean part of Dinarickarst is higher amount of summer precipitation,which is a result of higher daily summertemperatures and more intensive convectionduring the day. Nevertheless, the influence ofthe Mediterranean Sea can be still observed inrelatively high autumn-winter amount of precipitation,which is not characteristic for thepure continental climate (where peak precipitationoccurs in the summer months).While global factors define the frameworkfor general climate conditions, the highest influenceon the Dinaric karst climate is the Dinarskogorovje, which act as an orographic barrier.While latitudinal dependence (in NW-SEdirection) is of minor importance, the greatestdifferences in climate can be observed acrossa southwest-northeast transect, along whichthree different distinct climates with gradualtransitions can be identified:• Mediterranean and Transitional Mediterraneanclimates• Mountainous climate• Transitional Continental climate.The Mediterranean and Transitional Mediterraneanclimates extend along the Adriaticcoast. The extent of these climates into themountainous massif depends on topographicrelief, ranging from 2 km below coastal mountainsup to 120 km along the river Neretva(Rodić 1987). These climates are characterizedby mild wet winters and hot dry summers. Theaverage January temperature of the Mediterraneanclimate (southern Dinaric karst, e.g.Dubrovnik) is higher than 5 °C while that of theTransitional Mediterranean climate (northernDinaric karst) is only slightly above 0 °C. AverageJuly temperatures can be up to 26 °C andthey decrease toward the Dinarsko gorovjeand toward Adriatic Sea (since the sea is somedegrees cooler during summer). Precipitationis highest in the early winter months (December/January;for Transitional Mediterraneanclimate in November), with lesser amounts inApril/May, while the lowest amounts of precipitationoccur during the summer. Amountsof precipitation vary from 600 to 1,500 mm/a(the island of Palagruža receives as little as21

311 mm/a; Zaninović 2008) and increase fromthe low islands and coast toward sea-side partof Dinarsko gorovje. Moving from the soutwestto the northwest, the characteristics ofthe typical Mediterranean climate decreases.Mountainous climate extends over themajority of the Dinarsko gorovje. Changesfrom the Mediterranean and TransitionalMediterranean climates are caused by higherelevations and increased distances from Adriaticcoast. The average amount of precipitationcan exceed 3,000 mm/a at the karst plateausTrnovski gozd, Snežnik, Gorski Kotar, Velebitand the wider area of Orjen. Areas near theAdriatic coast have the lowest amounts of precipitationin summer months, while mountainousareas on the northeast side of Dinarskogorovje receive the lowest amounts of precipitationduring winter months. At Zavižan meteorologicalstation (Velebit, 1,594 m a.s.l.),the average annual temperature can be as lowas 3.5 °C, with 1,899 mm/a of rain which onaverage results in almost 6 months of snowcoveredground (Fig. 14) and up to 320 cm ofsnow (Zaninović 2008). Even more severe conditionscan occur at some karst depressions ateven lower elevations.The Transitional Continental climate issimilar to the Continental climate but it ismoderated somewhat by its relatively closeproximity to the Adriatic coast. It is characterizedby higher annual temperature ranges(even more than 20 °C between January andJuly), lower mean annual temperatures (up to11 °C at karst leveled surface between riversKupa/Kolpa and Una; Zaninović 2008), withan average January temperature close or below0 °C. The Transitional Continental climatehas lower July temperatures due to night coolingin comparison with the Mediterraneanclimate but higher maximum daily summertemperatures and lower amounts of annualFig. 14: Several meters high snow cover can be seen at Dinarsko gorovje even in the beginning of summer (exemple fromDurmitor, Montenegro; 11 th June 2006; photo: M. Prelovšek).22

Fig. 15: Temperature and vegetational inversion in the Smrekova draga closed depression (Trnovski gozd, Slovenia;photo: A. Mihevc).precipitation. The lowest amount of precipitationtypically occurs in the winter months.Precipitation amounts peak in the autumnmonths (only close to Panonian basin, e.g. inNovo mesto, in the summer months) and isabove 800 mm/a, which differ slightly for theTransitional Continental climate in comparisonwith the Continental climate. Amounts of precipitationdecrease toward the northeast asdistance from the orographic barrier (Dinarskogorovje) increases.Although these three climates can be easilyobserved, less obvious microlocal changesof climate can be important in several cases,especially in karst areas where the strongestinfluence comes from topography. As a rule,the interiors of karst depressions are colderthan the higher ground surrounding them.This is especially true for karst poljes, whereabsolute minimum temperatures can be aslow as -34.5 °C (Babno polje at Notranjskopodolje (Notranjska lowland) at 756 m a.s.l.)and -41.8 °C (Veliko polje below mountainBjelašnica (Rodič 1987) due to temperatureinversions. Besides lower absolute minimumtemperatures, greater numbers of cold days,and greater amounts of snow cover, fog andfrost are also characteristic for enclosed karstdepressions (Fig. 15).23

24Fig. 16: Spatial distribution of precipitation (modified after Pojatina 1987, Senegačnik 1994, Pinna, 1989), watershed between Adriatic and Black Sea and major karst springs(after Nicod 2003; Burić 2010).

HydrologyMitja PrelovšekThe present day hydrological characteristicsof the Dinaric karst are the result of itscomplex geologic structures and a long andintensive geomorphic evolution. In addition toits varied geology and geomorphology, the hydrologyof the Dinaric karst is one of its mostdistinctive and recognizable elements. The Dinarickarst is an area where hydro-geomorphicphenomena were studied for the first time inthe world in details and where some hydrogeologicalideas were born. It is a place of riversthat sink and reappear several times, a placeof abundant ponors and springs connected byhydrologically active caves, a place where thetypically impressive features of contact karstoccur, and a place where the complex hydrologicalsystems between poljes were modifiedFig. 17: Glavaš is over 115 m deep spring of river Cetina (photo: A. Mihevc).and used for production of hydroelectricity afterthe 2 nd World War.The Dinaric karst is a region that extendsover Dinarsko gorovje (the Dinaric mountains)and comprises both permeable (karstic) andnon-permeable rocks. Due to this mixed geology,two major types of drainage have developed:non-karstic surface drainage and theprevailing subsurface drainage typically associatedwith karst. Even pure and fractured limestonecan support superficial flow if regionalfactors (e.g., hydrological barriers, hydraulicgradients that are too low) do not favor undergroundflow (i.e., as occurs at karst poljes). Nevertheless,fully developed underground drainageis characteristic for areas with very purelimestones (those with less than 1 % of impuritiesare abundant inDinaric karst), withsprings at relativelylow elevation andwithout importantfault zones. At suchplaces, subverticaldrainage whichturns subhorizontalat water leveland drains towardsprings nearby. Verygood examples ofsuch drainage areat the mountainsVelebit, Biokovoand also at somelowland plateaus(e.g. plateau Kras).Aside fromsuperficial drainageon impervious25

ocks (such as Eocene flysch, Lower Mesozoicand Upper Paleozoic rocks), very extensive areasof the Inner Dinarides exhibit the fluviokarstictype of drainage. This type of drainageis especially characteristic for dolomite that isnot able to transfer all the water undergrounddue to rapid superficial weathering, too highfractionation or too slow solubility. In suchcases, a portion of water flows on the surface,especially during heavy rain or intensive meltingof snow in springtime, but the rest can flowunderground toward springs at the sides ofdeep valleys. Fluviokarstic drainage is impressivelydeveloped in the southeastern part ofthe Dinaric karst where dolomites are widelyexposed. Here, the rivers Tara and Piva haveformed canyons exceeding 1,000 m in depth.At the interfaces between permeable andimpermeable rocks, impressive contact karstdeveloped where the superficial rivers encounterpermeable karstic rocks. At these geologicalcontacts, superficial streams stronglyinfluence the characteristics of undergroundFig. 18: Travertine dams are building for impresive waterfalls along Croatian Krka river(photo: A. Mihevc).26hydrology, especially with respect to point recharge,flow regime and high sediment load.During their long history of sinking, these riversand streams have formed big, and still hydrologicallyactive, underground passages, aswell as blind valleys and collapse dolines. Oneof the best examples of such a sinking riveris the Reka, which sinks into Škocjanske jame(Škocjan Caves). Concentration of water isalso characteristic for some sinks at the downstreamends of karst poljes, where long epiphreaticcave systems have been developed(i.e. Postojnska jama, Vjetrenica).Based on described lithological factors,major geomorphic features and hydrologicalcharacteristics, the Dinaric karst is usually hydrologicallydivided into three spatial regions(Gams 1974; Herak et al. 1969; Šarin 1984):low coastal and insular Adriatic karst, continentalmountainous karst and low northeasternand high southeastern inland karst. All ofthese hydrogeological regions are parallel toAdriatic Sea.Low coastal andinsular Adriatic karst,formed mainly in Cretaceous-Tertiaryrocks,is characteristic fornearly all of the islandsalong the Croatiancoast, the northeasterncoastal part of Italy(northwest of Trieste/Trst), the coastal areaof Croatia, Bosnia andHerzegovina and Montenegro.In Slovenia,the coastal area isformed in Eocene flyschrocks and is thereforenon-karstic. Themain characteristic ofthe low coastal andinsular Adriatic karstis the contact of freshwater with seawater.

Fig. 19: Canyon of river Cetina with mountain Mosor in the background (photo: A. Mihevc).Seawater usually underlies fresh water on theislands, resulting in lenses of fresh water belowsurface. The interface between fresh andsalt water along the Adriatic coast is morecomplex due to different patterns of inflow offresh water (superficial or underwater), differentdischarge and different geometry ofconduits. On the western peninsula Istra (Istria),below the mountains Učka, Velebit, Biokovo,in Stonski zaljev (Ston Bay) and in thebay of Boka-Kotorska, examples of submarinesprings, also called “vruljas”, are numerousand efficacious. In some cases water is mixed(i.e., brackish), which presents a problem forwater supply, especially in summer when dischargesare the lowest. A lot of coastal springsare located above sea level and discharge freshwater – the biggest ones are Timavo/Timava(Q min= 9 m 3 /s, Q avg= 30.2 m 3 /s, Q max= 138 m 3 /s;Ford & Williams 2007 after Smart & Worthington2000) and Ombla spring, near Dubrovnik,with a natural average discharge of 33.8 m 3 /s(after 1965, the average discharge was reducedto 29.6 m 3 /s due to the construction of a hydroelectricplant in the hinterland; Milanović2006). Parsts of the hinterland along coast risesteeply to Učka, Velebit, Biokovo and Orjen,but in many cases shallow karst is developedin areas with little topographic relief (e.g., Istra,Sjevernodalmatinska zaravan (North Dalmatianplain), Ravni kotari). A similar situationoccurs on the continental leveled surface betweenrivers Kupa/Kolpa and Una. Homogeneityof such karst is often interrupted with beltsof Eocene flysch rocks trending in a northwestsoutheasterlydirection, which often divert thegeneral southwesterly flow of streams parallelto the Dinaric direction (NW-SE) and stimulatesuperficial drainage, while on the karst rockscanyons are developed. The canyons alongthe rivers Krka, Zrmanja and Cetina (Fig. 19)are up to 180 m deep and were even deeperduring Ice ages, when the sea level was lowerand travertine dams (Fig. 18) were probably27

absent. Downstreamparts of the canyonsare submerged dueto the tufa dams andthe rise in sea level atthe beginning of Holocene.In Istria, thecanyons of the riversMirna and Raša areshallower but alsopartly submergedat the downstreamends.The most characteristichydro-geomorphicphenomenaof the continentalmountainous karstare high plateaus andkarst poljes. The main Fig. 20: Spring of river Buna (photo: M. Prelovšek).ridge of continentalmountainous karst lies above 612 m a.s.l. Thewidth continental mountainous karst rangesbetween 30 to 110 km (Šarin 1984). The transitionfrom the southwestern coastal Adriatickarst can be double this width in places. Insome parts of Adriatic coast, Dinarsko gorovjerise from the coast very steeply without leveledBesides Ljubljanica springs (Q min= 4.3 m 3 /s,Q avg= 39 m 3 /s, Q max= 132 m 3 /s; Gospodarič &Habič 1976), the most efficacious springs inDinaric karst are located in this area (Fig. 16on page 24: Buna spring (Q min= 3.0 m 3 /s,Q avg= 23.7 m 3 /s, Q max= 123 m 3 /s; Fig. 20), Bunicaspring (Q min= 0.7 m 3 /s, Q avg= 20.3 m 3 /s,transition (Učka, Velebit, Biokovo, Orjen, Q max= 207 m 3 /s) and Trebišnjica springLovčen). In such areas, water is drained verticallythrough vadose zones up to 1,350 mdeep and often discharges in vruljas along theAdriatic coast. Behind Istra and Sjevernodalmatinskazaravan, the rise is more gradual. Ineastern Herzegovina, the rise in elevation goesthrough several karst overflow poljes, wherethe lowest are in southwest and the highestin northeast. Water appears and disappearshere several times, from the highest Gatačkopolje and Nevesinjsko polje (Nevesinje polje))through Cerničko (Cernica polje), Fatničko(Fatnica polje), Dabarsko (Dabar polje), Ljubijsko(Ljubinje polje) and Ljubomirsko polje(Ljubomir polje) to Popovo polje and finally tothe spring Ombla at Adriatic coast and springsalong the river Neretva (Milanović 2006).(Q min= 2 m 3 /s, Q avg= 80 m 3 /s, Q max> 800 m 3 /s;Milanović 2006; Ford & Williams 2007 afterMilanović 2000). Similar topography and hydrologicalsystems have developed in westBosnia and Herzegovina. Underground waterflow between karst poljes can be directed eitherperpendicular to the main ridge of Dinarskogorovje (this means also perpendicular tothe smaller ridges and karst poljes –e.g., westernand eastern Herzegovina, the higher partof Slovene Dolenjska) or parallel to it (part ofLjubljanica basin, NE of Velebit). Some tectonicwindows of older (Paleozoic) impervious,or less permeable, rocks enhance superficialrunoff that drains into ponors (e.g., NE of Velebit,central Bosnia), but in very rare cases riverscan flow across Dinarsko gorovje (Neretva,28

Kupa/Kolpa, Morača). The continental mountainousDinaric karst was for many hydrologicalphenomena (polje flooding, complexunderground water flow between poljes, bigponors, springs and estavellas, hydro technicalworks) the first area to be studied or extensivelyused. In recent years, big karst springs arerecognized also due to their surprisingly deepsumps (Fig. 17 on page 25) of Una (-205 m), Divjejezero (-160 m), Sinac (-155 m), Kupa/Kolpa(-154 m; Knab, 2008). Nowadays, at least14 sumps are deeper than -100 m. An evenmore exceptional case is Crvenojezero (Red lake; Fig. 21)with depth -281 m (Knab 2008)and without clear genesis.The low northeastern andhigh southeastern inland karstlies northeast of continentalmountainous karst. The northeasternpart is characterized bylow elevation hills and plains,where both surface and subsurfacedrainage occur. A greatportion of the relief is occupiedby a karst-leveled surface(e.g., Bela Krajina, the leveledsurface between the riversKupa/Kolpa and Una), in whichcanyons are deepened (SloveneKrka, Kupa/Kolpa, Dobra,Mrežnica, Una). The elevationof the rivers is similar and theelevation of subsurface waterbetween them is slightly higher;this prevents from undergroundcirculation betweenrivers. Regarding these characteristics,the low northeasterninland karst is similar to Sjevernodalmatinskazaravan andRavni kotari along the Adriaticcoast. In the northeastern direction,the elevation of inlandkarst decreases until it sinksbeneath young sediments ofthe Panonian basin. Toward the southeast, thesoutheastern inland karst becomes more andmore hilly and karst valleys become deeperdue to a higher portion of Triassic dolomiteand higher elevation. Rivers (e.g., the Tara andPliva) flow in canyons over 1,000 m deep betweendissected karst plateaus with combinedsurface and underground drainage flow. Bigkarst springs are absent, but several of themcan initiate larger rivers (e.g., the Neretva, Vrbas,Miljacka, Željeznica, Usora; Papeš & Srdić1969).Fig. 21: Crveno jezero (Red lake; photo: A. Mihevc).29

GeomorphologyAndrej MihevcIn folk language, “karst” meant “barrenstony land.” This term often occurred in localtoponyms and could denote an entire landscape.Today, the word “karst” means a landscapewith specific relief, water, and undergroundfeatures that formed in long geologicalperiods on water-soluble rock, mostly limestoneand dolomite (Gams 1973; Kranjc 1998).Relief on impermeable non-karst rock isprimarily sculpted by water that runs on thesurface in river networks. Rivers sculpt fluvialvalleys that dissect the surface into valleys,slopes, and ridges. The valleys are deepenedby the mechanical erosion of rivers, which isgreater where the inclination is steeper andthere is more water. The slopes above valleysare shaped by sheet erosion or denudation.As a rule, closed depressions do not form inthis relief, but if they do, they are immediatelyfilled by water or sediment.On karst, however, relief is formed by waterthat chemically dissolves the limestoneand carries the solution away. Gravel thereforedoes not form on the surface and very littleinsoluble debris remains on the limestone.Gravel and insoluble debris could fill nascentdepressions in the relief, cover the bedrock,and be the basis for the formation of soil. Sincethis is not the case, the karst surface is rockyand hollowed.Pure water can dissolve only a little limestoneor its main component, the mineral calcite.Solubility increases when CO 2from theair or soil is dissolved in the water resultingin weak carbonic acid. Dissolving or corrosionis further accelerated by acids produced byplants or the decomposition of organic matterin the soil.The dissolution of karst rock is strongest onthe surface or a few meters below the surface,but water remains aggressive for a long timeand can form caves underground. Sheet erosionand the lowering of the surface results inkarst denudation. Various methods have determinedthat denudation has amounted tobetween twenty and fifty meters in a millionyears in Slovenia’s karst regions (Gams 1974).This also means that surface denudation hasalready reached individual caves and removedtheir ceilings to create roofless caves (Mihevc2007)Rivers flow onto karst areas and form undergroundstreams. Because they carry largeamounts of water and sediment from impermeableneighbouring areas, they are capableof dissolving a considerable amount of limestone,but their effect is limited only to the vicinityof the watercourse (Gams 1962; Mihevc2001).Karst rock featuresSome dolomites and most of the limestoneare mechanically very resistant types ofrock, but they are all subjected to dissolution.Precipitations start to dissolve them as soonas they get into contact with the karst rocks.Intensity of the corrosion depends on propertiesof the rock, aggressively of the water andthe way in which water flows on the surface ofthe rock. Small corrosion features that form onthe rock make its surface uneven and rough orform different shapes.Karen is common term used for dissolutionfeatures on exposed soluble rock surfaces.(Gines 2009). Two basic processes controltheir formation, the dissolution by thin water30

films flowing down inclined surfaces and thedissolution kinetics of the CO 2-containing rainwater(Dreybrodt & Kaufmann 2007). Some ofthese features and widely spread so they gotspecial names.According to Ford and Williams (2007) themain groups are circular plane forms like micropits,pits, pans, heelprints. Linear formsthat are fracture-controlled are microfisures,splitkarren and grikes. Linear forms that arehydrodynamically controlled are microrills, solutionchanels or rillenkarren, solution runnels,decantation runnels and flutings.Polygenetic formsare mixtures of solutionchannels or assamblages of karren: karenfeld,limestone pavement (clints and grikes),stepped pavements, pinnacle karst, corridorkarst, costal karren.Common features on the bare horizontalrock surfaces exposed to rain are solutionpans. This is circular or irregular depression inthe surface of the rock with flat bottom andoften undercut edges. They are from few cmto 1 m large. Corrosion in them is encouragedby biologic processes like decay of organicmatter where organic acids form. Water fromthem evaporates; crystals of calcite are blownby wind or washed out by rain. Shepards oftenused for watering the animals (Perica 2009).Characteristic form of corrosion is rillenkarren.They are formed by channelled flow ofthe rain water on steep slopes on the tops oflimestone blocks. They are few cm wide anddeep, semi-circulars in cross section and havesharp edges of crests between them. On thelower side they often transform into plat, nondissected surface.Down the slope of the exposed rock largerchannels, runnels form. They are few tens ofcentimeters wide and can be several metersFig. 22: Kamenitza on Velebit mountain (photo: N. Zupan Hajna).31

long. They are smoother especially if theywere formed below the soil.Corrosion dissects karst rocks into clints bycreating grikes along joints or bedding planes.The size of clints depends on the thickness ofthe limestone layers. Clints are larger on limestonewith thicker layers and less joints.Corrosion sculptures the surface of therock also under cover o soil. Soil or even mossthat grows on limestone blocks is soaked withwater and this water slowly and more evenlycorrodes the rock. Surfaces of such rocks aresmoother and more rounded and there is noforms indicating the vertical flow of water.Where soils were eroded the sculpture of therock shows the height to where soil was coveringthe clints.Small corrosion forms on the rock dependon the properties of the rock but also on theclimatic conditions. In the lower positions especiallyin Mediterranean climate with drysummers sharper forms like rillenkarren andkamenitzas are frequent. In higher karst areas,where is more precipitations, long lastingsnow cover and higher air humidity, rocks aremore rounded. Mosses which grow on rocks inforests also make smooth rounded surface ofthe rock.Leveled Corrosion PlainsLeveled surfaces are one of the very distinctrelief features of the Dinaric karst. Theycan be found at different elevations. They arecommon in all the karst regions on the innerside of the Dinarsko gorovje (Dinaric mountains),and especially on the seaward side.They are absent only in the central highestpart of the karst (Roglič 1957).These corrosion plains have been producedover a long period of denudation by corrosionplanation in the level of the karst water.Later uplift connected with regional tectonicscaused entrenchment of major allogenicthrough-rivers. Canyons were formed and theFig. 23: Kras plateau - view toward south (photo: A. Mihevc).32

Fig. 24: Sjevernodalmatinska zaravan (North Dalmatian plan) with canyons of Krka, Cetinja and Čikola (DEM source: ASTERGDEM 1”; figure made by: A. Mihevc).water table dropped beneath the level of theuplifted corrosion plain. Percolating rainwatercould escape vertically and form solutiondolines.An example of such an uplifted and slightlytilted leveled surface is Kras, a plateau on theNW part of the Dinaric karst (Fig. 23). Beforeuplift there were two rivers crossing its surface.Two dry valleys remain there. Only laterdid dolines and collapse dolines dissect thesurface.Elongated remnants of former leveled corrosionplains developed in higher relief arenamed “podolje” or “ravnik” (Gams 1973).They are smaller features, a couple of kilometerswide and several tens of kilometersin length. In some of them, deeper poljes likePlaninsko polje and Fatničko Polje have developed.Larger leveled surfaces are often called“zaravan”. A leveled surface forms the mainpart of Istria. It is slightly tilted and dissectedby large dry valleys, some canyons and numerousdolines. The largest is 40-km long Severnodalmatinskazaravan between Velebit andDinara mountains and the sea (Fig. 24). On thissurface, the 150-m deep canyons of the Zrmanja,Krka and Čikola rivers are entrenched.Large leveled surfaces are also cut by theNeretva and Cetina rivers. In the high leveledsurface at Durmitor Mountain, the River Taracut a 1,000-m deep canyon.On the inner side, toward the PanonianBasin, Kordunska zaravan is developed aroundKolpa, Una and Sana rivers (Roglič, 1952). It islarge - approximately 100 km long and up to30 km wide. This leveled surface is cut by thecanyons of several rivers in which travertine33

is now depositing. Best known are the travertinesat Plitvička Jezera, in the Korana River,which form numerous lakes behind travertinedams.In some cases rivers could not follow theuplift, so canyons became dry and are preservedin such surfaces. The largest dry valleysof the Dinaric karst is the 20-km long and300-m deep dry Čepovanska dolina, cut intoTrnovski gozd plateau. A dry valley in Istria is40 km long and 150 m deep. The dry valley ofBregava is 10 km long and up to 700 m deep.The dry valley Zavala, a former outlet of Popovopolje, is 10 km long and 500 m deep.Closed depressionsThe water that shapes the karst comesmainly from precipitation. Water dissolves therock and carries it through the underground insolution. Dissolution occurs on the surface onbare rock or under the layer of soil and sediment.This direct corrosion sculpts tiny rockrelief forms.Precipitation is dispersed evenly on the surfaceand percolates into the karst via fissuresin the limestone widened by corrosion. Thevarying solubility of the rock and other factorsfoster the formation of an irregular and roughsurface dotted with depressions of all sizes.Depression features can form and preservetheir shape because the water percolates intothe ground carrying the dissolved rock with itor because there is no surface drainage andinsoluble debris is not transported across thesurface to fill them.Closed depressions are a characteristic featureof the Dinaric karst. In some places theyoccur only as topologically lowered surface,while elsewhere depressions with distinctshapes form. The most numerous are corro-Fig. 25: Digital elevation model (DEM) and spatial distribution of Dinaric karst poljes (DEM source: ASTER GDEM 1”, poljesafter Gams, 1974).34

Fig. 26: Fatničko polje (Fatnica polje) in the eastern Herzegovina (DEM source: ASTER GDEM 1”; figure made by: A. Mihevc).sion dolines that form due to locally strongercorrosion. Suffusion dolines form primarily atthe edges of karst poljes due to the washing ofsediments. Some dolines are collapse dolines.Larger features of the Dinaric karst include uvalasand karst poljes.PoljesKarst poljes are the largest flat-floored encloseddepressions in karst (Fig. 26). They differfrom other closed depressions in size and theirlarge flat bottoms which formed as baselevelcorrosion plains. Typical forms have a sinkingriver, steep slopes and a sharp transition betweenthe polje floors and slopes. The bottomof the polje may be covered by sediments.There are about 130 poljes in the Dinaric karst(Gams 1978); about 44 of them are recognizedas outstanding (Fig. 25).Gams (1978) defined some criteria thatmust be met for a depression to be classifiedas a polje. These include a flat floor in the rockor in unconsolidated sediments such as alluvium,a closed basin with steeply rising marginalslope on at least one side, and karstic drainage.Three basic types of poljes have been defined:border poljes, structural poljes andbaselevel poljes (Ford & Williams 2007).Border poljes develop where water tablefluctuations in karst control allogenic fluvialactivity at the surface, so lateral planationdominates valley incision.35

Structural poljes are dominated by bedrockgeological controls. This type of poljes prevailson the Dinaric karst. They are connected withgraben or overthrust structures, or as inliers ofless karstified rocks like dolomite, marl or evenflysch.Baselevel poljes occur where dissolutionhas lowered the karst surface to the regionalepiphreatic zone. Typically these poljes developin lower parts of the karst, but they alsooccur in higher parts of the Dinaric mountainswhere impermeable formations may act as hydrologicalbarriers.Dinaric poljes are polygenetic features.They are generally elongated along the strikeof the Dinarsko gorovje (i.e. in a northwest—southeast direction). Poljes are developed atall elevations, between 1,200 and 20 m abovesea level. A complex suite of processes governstheir genesis. They develop along regionalfaults, graben structures and overthrust. Thehighest is Trebistovo polje, (1,278 m a.s.l.) andthe lowest are Bokanjačko polje and Vrgoračkojezero (Vrgorac lake; only 20–25 m a.s.l.).The largest poljes are Liško polje (460 km 2 )and Livanjsko Polje (65 km long and 6 km,402 km 2 ), but the majority of poljes are smaller,covering only few 10 km 2 .In natural conditions floods are normalphenomena for many poljes. In some poljeslike Cerkniško polje and Buško blato they lastedabout half a year. The flooding of 60 kmlong Popovo polje under natural conditionsreached a height of 40 m in the lowest sectionof the polje, and the average yearly flood durationwas 253 days.Poljes are very important for human settlement.In them the best, and often only, arableland in the Dinaric karst is available. There isalways some water available and floods areregular and limited to lower parts of poljes, soall of the largest settlements are located there.Fig. 27: Klekovača and Materniča uvala are two large closed depressions northern of Livanjsko polje in Bosnia. Note that thebottom of large uvala is dotted with dolines (DEM source: ASTER GDEM 1”, figure made by: A. Mihevc).36

UvalasUvalas are large, km-scale closed karst depressionsof elongated or irregular plan form.Their bottoms are undulating or pitted withdolines, seldom flattened by colluvial sediments.Uvalas are always situated above thekarst water table. They are polygenetic featuresand are strongly guided by geological structureand tectonics (Čalić 2009). The word “uvala” iscommon toponym in the Dinaric karst, alwaysdenoting a large depression. In folk language ithas a morphological meaning only.The term was introduced into literature byJovan Cvijić (1893) for dolines with huge diameters,but unfortunately with an erroneousexplanation of their genesis – that the uvalasare transitional evolutional elements betweendolines and poljes, formed by the coalescenceof several dolines which have enlargedand merged towards each other (Cvijić 1901,1960). Because of this erroneous explanation,the term “uvala” is mostly abandoned in professionalliterature outside the Dinaric karst.There is considerable variety among thedimensions, and also the shapes, of the uvalas,but there are also some common generalcharacteristics (Čalić 2009). In most cases theuvalas are developed along tectonically brokenzones of regional extension. Their perimetersare of irregular shape, the plan dimensionsvary from approximately 1 km up toseveral kilometers along the longer axis, whilethe depths below the highest closed contoursare at least 40-50 m, and sometimes exceed200 m. Uvalas are not present on karst leveledsurfaces, but only in areas with more orless dissected relief, so the bottoms are alwaysabove the karst water table.Uvalas have internal karstic drainage; occurrencesof small seasonal surface flows arean exception. Sediments in the bottoms arescarce; their origin is from denudation fromthe slopes. Infill is not threatening to fill up adepression. The inclinations of the slopes aregenerally smaller than those of dolines. Uvalasare formed because of differences in solubilityof the karstified rock, structural elementsand recent tectonics. Formation of such topologicallyclosed areas within larger karst areasneeds only sufficient time and favorable climaticconditions.Uvalas can be found in all of the Dinarickarst except in low positions and on leveledsurfaces. In many uvalas, because of some colluvium,small settlements developed. Someuvalas were affected by glaciation; in some,glacial tongues ended and fluvioglacial till wasdeposited. In them, the lowest temperaturesin the area were observed because of temperatureinversions.DolinesDolines are the most frequent karst depressions.They are centric and mostly roundrelief forms. Dolines commonly have circularto sub circular plan geometry, and a bowl- orfunnel-shaped concave profile. Their depthsrange from a few decameters to a few hundredmeters, and their inner slopes vary from subhorizontal to nearly vertical. Dolines up to tenmeters deep and 100 meters wide dominate.Their genetic definition is difficult becausealthough they formed in very diverse conditions,all the processes led to the same funnelor bowl shape. Morphologically, the same orsimilar dolines can therefore have differentorigins. In order to understand how dolinesand other, closed karst depressions develop, itis necessary to examine their morphology andsize, their relationships with the topographicand geomorphologic settings, their structures,their hydrological behaviour and related solutionprocesses, examples of evolution, and peculiarmorphologies that occur under specificenvironmental conditions (Sauro 2005).Corrosion dolines occurred where verticalpercolation into the karst was possible anddissolution of rock was stronger than in thesurrounding area. The round shape with onelowest point indicates a spatially limited andactive process of rock mass removal. In mostcases, the soil plays a major role due to the37

Fig. 28: Typical dolines of Dinaric karst, Smoljana near Bosanski Petrovac (photo: A. Mihevc).production of biological CO 2that locally amplifiesthe corrosion of the limestone. Dolines arefound everywhere in Dinaric karst, but mostare located on karst plains where, if small theirnumber can exceed one hundred per squarekilometer. The number of dolines is muchsmaller on slopes and there are none at all onsteep slopes. Larger dolines are found on higherkarst plateaus, some of them up to a hundredmeters wide (Gams 2000; Faivre 2002).Dolines are a very important relief formof the Dinaric karst. Because soil is only foundat their bottoms, they are used for fields orgardens. In the past, rocks were carefully removedfrom the slopes and the bottoms werelevelled. Some of the rocks were buried underthe soil at the bottom while the rest of wereused to build dry stone walls (Gams 1991, Mihevc2005).The bottoms of dolines were often usedas water reservoirs. Soil was removed fromselected dolines and cattle were driven acrossthe clay to compact it and make the bottomsimpermeable enough to hold water well intoa dry summer.More than any other karst form, dolinesreflect man’s changed relationship to the environment,as the fact that villagers have transformednumerous cow ponds and dolines intodump sites demonstrates.A special type of doline is formed by thewashing, subsiding, and settling of sedimentson karst. In the past they formed only wherelayers of sediment piled up, for example, onkarst poljes, but in current conditions the sedimentis washed as particles into the karst underground.Collapse dolinesIn the Dinaric karst, collapse dolines arequite common relief features. The term “collapsedoline” presumes the formation of a38

doline by collapse into a karst cave situatedbeneath. Expert literature understands collapsedolines as dolines with exceptional dimensionsand steep or vertical walls (Gams2004). Smaller collapse forms are frequentlyleft aside because of lack of signs of collapseprocesses. In practice, it is often difficult to distinguisha real collapse doline from other typesof depression. It is even more difficult to do soin the case of the older features, which havebeen modified by corrosion and other surfaceprocesses, and where the primary origin is nolonger clear (Šušteršič 1974; Stepišnik 2006).The cave roof collapse is a slow processthat proceeds by the breaking of the walls andceiling until equilibrium is established on theslopes of the doline. The volume of the newlyformed feature (i.e., the collapse doline)should be smaller, since the collapsed rock occupiesa larger volume than the solid rock.With respect to genesis and dimensions,there are two distinctive types of collapsedolines on the Dinaric karst. One of thesetypes is dolines formed by the collapse of relictcaves, usually when denudation thins the ceilingabove the underground chamber. As mostof the known cave chambers within the areahave dimensions of up to some 10,000 m 3 , weshould expect the dimensions of collapses tobe smaller than that. These collapse dolinesdiffer from other dolines because they havevertical walls or slopes’.The second type of dolines of collapseorigin is often several hundreds of m in diameter,with steep or vertical walls and volumesof to several million m 3 . The formation oflarge chambers by collapsing, and of collapsedolines, is a result of a combination of severalfactors and not just simple collapse because ofrock failure in the cave ceiling (Habič 1982). Itcannot be treated as the decay of caves, butas a distinct speleologenetic and geomorphicprocess (Mihevc 2009). Their immense dimensionsare mainly the result of the removal ofFig. 29: Divača karst is thebest Dinaric example ofthe interrelation betweencontact karst features- ponor caves, collapsedolines and unroofedcaves (DEM source: ASTERGDEM 1”; figure made by:A. Mihevc).Legend:1. hydrologicaly activecaves;2. dry caves;3. unroofed caves;4. terrain elevation;5. water level;6. surface water flow.39

the disintegrated collapsed rock at depth bysolution of the underground flow. Therefore,the volumes of these collapse dolines aremuch larger than the volumes of the pre-existingcavities.Usually these dolines are connected withmain underground watercourses, and aremore abundant in levelled surfaces near sinksor springs of the rivers. In Slovenia, there is aconcentration of dolines on the Kras plateauabove the underground course of the Rekariver. More than 16 large dolines are situatedhere. The largest has a volume of 9 m 3 (Mihevc2001). There are numerous dolines in theLjubljanica river basin above cave Postojnskajama, between Cerkniško and Planinsko poljes.On the edge of Imotsko polje, there are severallarge collapse dolines. One of them is Crvenojezero, which is the deepest collapse doline ofthe Dinaric karst. Its maximum depth is 528 m,and it is filled with water 287 m deep. Recentdiving explorations have found large openingsin the submerged walls of the doline and caveentrances at its floor (Garašić 2000).There are groups of large colapse dolinesaround Liško polje, Lušci polje, above springsof Pliva, springs of Zeta, between Duvanjskopolje and Buško bato, and on Nevesinjskopolje. Many others scattered on the karst surfaces.Karst on dolomiteDolomite is a type of rock that dissolves andis karstified similarly as limestone. Dolomitesare rarely pure; they are formed of differentmixture of mineral dolomite and calciumcarbonate. There are important differencesbetween karst landscape on dolomite andthose on limestone. Jurassic or cretaceousdolomites are resistant, but they disintegrateon the surface into fine sand. Triassic dolomiteswhich prevail are less resistant against frostshattering and they easily disintegrate intogravel and sand. This is sometimes so intensive,that whole surface is covered with dolomitegravel. Precipitations infiltrates trough thismaterial into the undamaged and karstifieddolomite.The sediment on the surface and the smallerpermeability of the dolomite can slow downthe infiltration, therefore after rains watersoften flow across the surface. Because of limitedpermeability a mixture of fluvial and karstfeatures can develop on dolomite. This typeof karst was named fluviokarst (Gams 2004).On the dolomites there are less caves, they areusually shorter and smaller.Characteristic features of dolomite areasare dells, dolines and large surfaces with undergrounddrainage but no distinct karst orfluvial relief features. Where rock is more resistantto weathering tors develop. In steeperrelief or in high mountains fluvial features likegullies and erosion valleys divided with ridgesand develop. On smaller slopes most commonfeature is dells and on smaller even doline(Komac 2004).Dell is a shallow valley with steep slopesand lesser gradient of the bottom. There areno traces of erosion and the bottoms andslopes are covered with soil. Sometimes theyopen out on a plain on lover end; sometimesthey end blindly in a doline.Typical for the dolomite areas is soft landscapewith no rocks exposed. In past these areaswere used for agriculture, pastures, meadowsand even field are located on dolomite.Also they are favourable for settlements. Theyare widely used in quarries for sand for buildingand road constructing.Dolomites are more common on inner sideof Dinaric karst. There are large areas of dolomitekarst or fluviokarst in eastern side of Dinarickarst in Slovenia, around Plitvička jezeraand Lika in Croatia, around Una river, uppervalley of Neretva river in Bosnia and north ofOrjen in Montenegro.Contact karstOne of the possible classifications of thekarst is by the dominant morphological process.Karst formed by the influence surface40

iver flow could be designated by the term ofcontact karst. The term grows familiar in Sloveniaand Croatia where the karst contacts noncarbonate rocks and specific relief forms andphenomena developed (Roglič 1957, Gams1973). The term is reasonable, because suchkarst essentially differs from the karst whichsurface and underground was formed by precipitationwater only. In the international karstologicalliterature these forms and phenomenaare usually named as karst influenced byallogenic inputs (Ford &Williams 2007).Contact karst develops where water flowsfrom fluvial relief onto karst. The distributionof contact karst is preconditioned to spatialdistribution of karstic and non-karstic rock orless karstified rocks like some dolomites. Becausehere is more water available dissolutionof limestone is faster than on other karst surfacewhere only precipitations shape the relief.Surface waters also transport and deposit sedimentsbefore they sink into sinks or ponorsand caves (Gams 1962). That is because theunderground channels are shaped by low oraverage water and can not transfer the highwaters, which causes short but regular floodingand precipitation of sediments in front ofponors. Corrosion is faster also because of thesediments are accelerating the corrosion beneaththem because of organic CO 2producedin sediment or soil. The results of these areoften widened bottoms of blind valleys beforesinks.Contact karst features are limited only tothe area influenced by sinking rivers. They aremostly depressions, most common are blindvalleys. These are valleys, which from nonkarst fluvial valley protrude some distance tokarst and end above the sinks. His relief hassome characteristics of fluvial relief, but thefeatures are karstic. The sinking into the karstis controlled by the gradient and the morphologyin the whole karst area between sink anda spring. If this is changing due to tectonicmovements, evolution of the caves also thecontact karst forms change. So we have often aset of evolutionary stages in the contact zone,reflecting the changes trough whole evolutionof karst (Mihevc 2007).We must differentiate between sinking riverson poljes and allogenic sinking rivers. Differenceis that the flooding in contact karst isbecause of surface inflow, while in the karstpoljes because of oscillation or rise of the levelof karst water.Areas of contact karst with developed reliefof blind valleys and similar border depressionsin Dinaric karst are in the inner side ofthe mountains where older noncarbonaterocks and Triassic dolomite are in contactwith limestone. On the Mediterranean sideof the karst main supply for allogenic sinkingrivers are Eocene flysch rocks. Best examplesare blind valleys in Matarsko podolje (Mihevc1993) and blind valleys in Istra peninsula.Largest sinking rivers are Reka with meandischarge 8 m 3 /s (max over 200 m 3 /s) thatsinks on the edge of Kras in Škocjanske jamecaves (Fig. 29). Large sinking rivers of contactkarst are also Pivka river (4 m 3 /s), Pazinska rekain Istra sinking in Foiba cave, Dobra which sinksnear Ogulin. Large sinking river is Zalomskareka that sinks in Biogradski ponor on Nevesinjskopolje with capacity over 110 m 3 /s.CavesCaves are one ob the most remarkablekarst features. We can find them from the highestkarst mountain to the lowest parts alongthe sea, and some of them are submerged belowthe recent sea level. Caves are active orrelict parts of the karst drainage system. Mostaccessible or known caves however are justsmall fractions of old relict cave systems. Activecaves are often flooded or obstructed withsediments. The cave distribution, morphologyand sediments give us information about evolutionof the whole karst.On the high karst mountains vertical shaftsand deep caves without horizontal passagesprevail. They were formed by vertical percolationof precipitations. The deepest caves are41

on Northern Velebit, where three caves aredeeper than 1,000 m (Fig. 30). The deepestLukina jama 1,355 m ends only 83 m abovethe sea level which is only 10 km away (Bakšič2000).Horizontal caves are common on the levelledsurfaces and lower karst plateaus. Theyare formed by more horizontal flow of watertowards the springs. The longest like Postojnskajama (20.5 km), Đulin ponor - Medvedica(16,396 m), and many others were formed bysinking rivers. These caves have also large passages.One profile in Škocjanske jame the passageis in general 20 m wide and about 80 mhigh. The sinking rivers like Reka in Škocjanskejame can take more than 270 m³ at flood.Biogradski ponori of river Zalomska rijeka dischargeis 110 m³ (Milanović 2000).In Slovenia only on 7,000 km 2 10,000 cavesis known, but that number shows only actualknowledge. These caves together are longerthan 700 km.Caves are important archaeological historicalreligious and cultural sites. They are importantscientific localities and also great subjectto be explored or visit by cavers.Today Postojnska jama, Škocjanske jame,Cerovačke pečine, Vjetrenica, and many smallercaves are managed. They are importanttourist attraction and are visited by nearly onemillion visitors per a year.The age of the Dinaric karstThe age of the karst can be defined as thetime when the karst rocks were uplifted out ofthe sea. For the most of central part of Dinarickarst this occurred after the Eocene, becausethere is no evidence of younger marine sediments,on the inner part however marine sedimentationlasted till Neogene. As soon as thecarbonate rocks were exposed, we can expectthat the karst start to form, but there are noremnants of karst features from that time. Denudationhas already destroyed them.The other view on the age of karst is to definethe age of karst features that are presenton the surface and underground. We know theconditions in which features form. If these conditionschanged in past, features may still beunchanged or only slightly changed by generalkarst denudation. Such features are levellednow dissected surfaces high above the groundFig. 30: Cross-section through Velebit mountain with outstanding caves (published with permision of the author-D. Bakšić).42

Fig. 31: The oldest caves are found on the surface where they are incorporatedinto the karst surface. Example of unroofed cave by Povir at Kras plateu, Slovenia(photo: J. Hajna).water level, dry and blind valleys and cavesthat are now exposed to the surface due tokarst denudation. This tells us about the genesisof the landscape trough different phasesbut not the age of a karst features itself.Measurements show, that denudation islowering surface of karst with rate between30-50 m/Ma (Gams 1963; Gabrovšek 2009). Ifwe consider, that the then we understand thatmost of the surface karst features can not beolder than maybe 3-6 Ma.The oldest elements in karstare probably the caves thatformed deep below the surfaceand are now exposedas unroofed caves (Mihevc1996, 1998, 2001; Fig. 31).Real datation of karst ispossible only from the sedimentsthat were depositedin karst features, caves orkarst depressions. Differentmethods are used and theycan date only the time of thesedimentation.Datation of flowstoneusing different U/Th methodswe can date only about500,000 years old sediments,that is the limit ofthe method. Paleomagneticanalyses can give us paleomagneticrecord in sediments,but method is relative,so the data has to becalibrated by some othermethod, like palaeontology(Zupan et. al. 2008). Thismethod is basing on comparisonof animals remainsthat preserve in caves.The oldest cave profilesare in Račiška pečina, wherewith combination of paleomagneticmethod and palaeontology methoda sedimentary profile was dated to 3.2 Ma.In unroofed cave cut in Črnotiče quarry sedimentswith same methods were about 4 Maold. They were covering remains of cave animalMarifugia cavatica, which was living inthat at the time water cave. This is also theoldest known remnant of the cave animal andwith it we can also reconstruct the paleoenvironmentof that time (Mihevc 2001).43

Land UseNadja Zupan Hajna, Andrej Mihevc, Mitja PrelovšekThe lack of soil cover on the stones and thedisappearance of water under the surface arethe main characteristics of the Dinaric karst.In the past, when most of the people madea living from farming, these characteristicswere the main limiting factors for populatingand developing settlements in the area. Manystudies (Gams 1974, 1991, 2003; Gams et al.1993; Gams & Gabrovec 1999) show that themanagement phases have been in relationwith the historical conditions and changes.The largest problem was the soil. The inhabitantscleaned the surface of the stonesand piled them into walls and heaps which alsoprotected the arable land against strong borawind. In this way, they created thin patches ofsoil that were connected and thus made somefarming possible. Thicker layers of soil emergedat the bottom of dolines (Fig. 32, Fig. 34). Smallfields were created there, where the droughtwas not so devastating. Other more stony surfacesof the plateau were used for pastures,which replaced the natural forests.To illustrate the amount of the work involved,and also man’s impact, three villageswere studied by Mihevc (2005). Village Divačahas 7.9 km 2 of land in its cadastral unit. Thekarst surface was cleaned of rock that waspiled to dry walls. There are 69.5 km of drywalls, which gives 11.3 km, or 2,825 m³, ofstones removed from one square kilometer. Inthis way they gained 99 hectares of field sur-Fig. 32: Thicker soil in dolines was often used for fields and later replaced by grassland. Example fromLovčen, mountainous part of Dinaric karst (photo: A. Mihevc).44

Fig. 33: Island Kornat. Especially along the Adriatic coast, deforestation led to bare rocky country (photo: A. Mihevc).faces. Out of that, 24.6 ha are fields in the bottomsof 261 dolines. The rest of the surfaceswere used as pastures.At Račice village, 11.9 km² of theland is mostly covered by forest. There are1,395 dolines. While cleaning the land, thestones were piled into 23.2 km of dry walls.The volume of the removed stones is about5,815 m³, or 488 m³ per km 2 . On some Adriaticislands, quantity of removed stones is similar;at Krk island, more than 1,000 kg of stoneswere removed from one m 2 of the surface(Gams 1987). During long history of cleaningthe land, width and length of walls increasedtogether with fragmentation, while the area ofarable land decreased.Volčji Grad village is in the central part ofthe Kras plateau. It has 4.8 km² of land. Cleaningstarted in Bronze Age and by this meansthey gained 38.6 ha of fields. All of the dolineswere cultivated too, and there are 20 ha of cultivatedland in the 162 dolines.Even with such long and intensive land use,there was no more than about 10 cm of soilerosion on the slopes of dolines.One of the main parts of the Dinaric karst- the Kras, the islands and low plateaus of theDalmatian coast - present the types of land usetypical of Mediterranean countries. These landuse activities produce changes in the surface(Nicod 2003) like stone clearing, the buildingof dry walls and hill slope terraces and managementin the dolines, uvalas and poljes.From historical data, it is known (Kranjc2008) that a great part of the Dinaric karstwas deforested and that the landscape transformedinto a bare rocky country, a real stonedesert. Human deforestation began during theNeolithic period (6,500-6,000 BC). There wereseveral reasons for deforestation, mostly requirementsof new land for pasture and timberuse.The Dinaric karst became more and morebarren and a great part of it became synonym45

for ‘bare limestone desert’ –the karst (Fig. 33). Reforestationis mentioned earlier insome of the areas, but successfulreforestation did notbegin until the 1850s. Subsequently,large parts of theDinaric karst were artificiallyreforested, and eventuallythe process continued by itselfas the trees propagatednaturally. However, insteadof ‘natural’ forest with anoptimal tree association,monoculture forests, dominatedmainly by black pine,have resulted (Gams & Gabrovec1999). Nowadays,the great part of arable landFig. 34: Dry wals and small field above uvala Kruščica on the southern side of Orjen(photo: A. Mihevc).between dry walls is no longer cultivated dueto fragmentation and social changes (depopulationand deagrarization); box-like countrysideslowly vanishes in dense bushes and degradedforests. Nowadays dense natural forests, extensiveforest plantations, dry karst shrublandsand also completely barren karst areas can allbe found on the Dinaric karst (Kranjc 2008).Inland, because of a more humid climate anddifferent land use, the forests remained.Fig. 35: Water reservoir built in the bottom of small doline in Boljuni, near Stolac in Herzegovina. This water wasused for animals only (photo: A. Mihevc).46

The other problem of karst is water, especiallyalong Adriatic coast where the highestlack of water occurs during summer. Thisis a result of low amount or precipitation andhigh evapotranspiration. For the water supply,some aqueducts were made in antiquity (Bonacci1987). More common are wells, whichwere often built in closed depresions (Fig. 35).Fig. 36: During Austro-Hungarian Empire and Yugoslaviakingdom surface streams were regulated, ponors were widenedand screens were installed in front of them to holdback deposits, all in order to shorten the flood time in karstpoljes. Example from Šica ponor at Radensko polje (Račnapolje; Slovenia; photo: M. Prelovšek).A greater impact was made by the irrigationof some poljes to avoid long lasting floods.They enlarged ponors on poljes and even dugsome tunnels for the floodwaters. None theless, enlargement of ponors successfully reducedthe length of floods only at places,where a restristions were close to the ponors.At places with regional rise of water level, enlargementof ponors brought only minor success.However, the main impact on the karst wasmade by the use of waters in power stations.Especially high mountainous karst has beenvery interesting from the hydroenergeticsaspect due to a high amount of precipitation,high runoff coefficient (about 0.7), high reliefamplitude and relief suitability. Especiallyduring the 1950s and 1960s, big hydroenergeticprojects were initiated on Dinaric karst poljesin Croatia, Bosnia and Herzegovina. Largeworks were done in the Trebišnjica river karstby flooding part of the karst (Fig. 37 and 38),by diverting water to other catchment areas(Fig. 39) and stopping regular flooding of thePopovo polje (Milanovič 2006). Importanthydroenergetic objects were placed also inCetina, Lika-Gacka and Zeta river basins. Inthe present day situation, hydroelectric powerplants in the Dinaric karst have a total installpower of over 2,727 MW. Nevertheless, thelevel of environmental concern about someareas (e.g., Planinsko polje, Cerkniško polje,Pivka basin, Reka valley, and the Kupa/KolpaRiver) was so high that these areas remainhydroenergetically untouched.Fig. 37: Hutovo accumulation lake at the downstream end of Popovo polje (on the right), Herzegovina (photo: M. Prelovšek).47

Fig. 38: Grančarevo dam in the upper part of Trebišnjica valley. Behind the dam, Bileća lake withstarage capacity of 1,28 billion m 3 (Milanović 2004) was formed and flooded spring of Trebišnjica(photo: A. Mihevc).Fig. 39: Canalized Trebišnica river on Popovo polje. On the right bank, remnants of one of the 43 flourmills (Lučić 2007) that were built along Trebišnica river are located (photo: A. Mihevc).48

Case Studies from the Dinaric Karst of SloveniaAndrej Mihevc, Nadja Zupan Hajna, Mitja PrelovšekThe Dinaric karst (Dinarski kras) is themajor karst area of Slovenia. In past centuries,the Dinarski kras of Slovenia represented oneof the world’s prime sites of early scientificexploration of karst phenomena (Kranjc1997; Shaw 1992) due to the large number ofoutstanding karst features such as caves, largesinking rivers and flooded poljes. Speleology,karst hydrology and biospeleology were bornhere. The most prominent phenomena aresituated in the north-western part on theplateau named Kras. In Slovene language, krasmeans a rocky, barren surface. The name isoften used as toponym (Kranjc 1994, 1997). Krasplateau became a textbook example for thiskind of landscape because of the extraordinarykarst phenomena, and explorations done inthe 19 th Century. The name Kras in the Germanform of the word (der Karst) became aninternational scientific term. The area wherethese early explorations took place is calledthe Classical Karst (term introduced by Radinja1966, also 1972 as Matični Kras; which shouldnot be confused with the misinterpretation byŠušteršič 2000).The dominant relief features are ratherextensive levelled surfaces at differentelevations, large closed depressions (e.g.,poljes), and conical hills. Fluviokarst featureslike dells are common on dolomites. Karstrivers appear only in the bottoms of poljes,where they result from a high level of karstwater. Allogenic rivers flowing from noncarbonateregions either sink at the karstboundary, forming blind valleys, or cross thekarst through deep karst valleys and canyons.There are numerous extensive and complicatedcave systems formed by sinking rivers andconnected with the surface also by numerousvadose shafts. The surface karst morphology istypified by the abundance of karren, dolinesof various diameters and depths, sometimesextensive collapse dolines, cave entrances,unroofed caves, etc.For the Dinaric karst of Slovenia, twotypes of relief are characteristic: High Dinarickarst (high karst plateaus: Javorniki, Hrušica,Nanos, Trnovski gozd, Banjščice and Snežnik)and Low Dinaric karst (karst in the lowerparts: Notranjsko podolje, Pivka basin, Kras).There are presented limestones and dolomitesof Permian, Triassic, Jurassic, Cretaceous andPaleogene, cut by faults in the dominant Dinaricdirection (i.e., NW-SE). The most dominantkarst forms in the area are dolines, collapsedolines, karst poljes and high plateaus (Mihevc1997). The main factor in relief developmenthas been the dissolution process; others(fluvial erosion, slope processes, etc.) have asubordinate role. Along Idrija Fault the mainkarst poljes in Slovenia are developed: Loškopolje (Lož polje), Cerkniško polje (Cerknicapolje), Planinsko polje (Planina polje). Thereare many caves developed, among which is theoutstanding Postojna caves system with about20 km of known passages.49

KrasThe Kras is a distinct plateau, especiallywhen viewed from the seaward side. The Krastrends NW–SE between Trieste Bay, the northernmostpart of the Adriatic Sea, Vipava valleyin north-east, and the Friuli–Venezia Giulialowlands and river Soča in northwest (Fig. 40).The 45°45´´N and 14°00´´E lines of latitudeand longitude cross the Kras near Divača village.There are steep limestone slopes a fewhundred meters high rising directly from thesea or from the neighbouring lowlands to thenorthwest. Higher relief on flysch in the eastseparates the Kras from the Pivka region. Inthe southeast, the border of Kras is again welldefined by contact with the non-carbonateflysch of the Brkini hills and the valley of theReka river. Toward the south, the transition tokarst ridges and Matarsko podolje karst plateauis less obvious. The climate is sub-Mediterraneanwith warm dry summers. Cold winters,with most of the precipitation, show thestrong influence of the continent.The Kras belongs to the Adriatic–DinaricCarbonate Platform of the External Dinarides,composed of shallow marine fossil-bearingCretaceous and Palaeogene carbonates. Eoceneflysch rocks encircle the carbonate plateau.Kras and Matarsko podolje tectonicallybelong to Komen thrust sheet (Placer 1999),which is thrust over Eocene flysch and Palaeocene/Eocenelimestone of the Podgorski kras,a part of Kras imbricated structure (beforeknown as Čičarija imbricated structure; Placer2007). The whole structure is sub-thrust by theIstria unit.The main part of the plateau is essentiallylevelled, inclined slightly towards the northwest,with numerous dolines, caves and otherkarst features. There is a belt of slightly higherrelief in the central part of the plateau, formedby conical hills-like Grmada (324 m a.s.l.), Volnik(545 m a.s.l.) and Stari tabor (603 m a.s.l.), anddissected by large depressions. The higherrelief divides the Kras into two separatedlevelled surfaces. The southern one is namedNabrežinsko podolje. In the northwestern part,the plateau descends to below 50 m a.s.l. onthe edge of the Friuli Plain; on its south-easternedge altitudes are about 500 m a.s.l There areabout 300 m of accessible vadose zone withcaves formed at all altitudes from the surfaceto the sea level and below it. No superficialstreams occur on the Kras surface because allrainwater immediately infiltrates to carbonaterocks. There are two dry valleys crossing theplateau and some NW–SE-trending belts oflower relief which were believed to representprimary river valleys also because they containremnants of fluvial sediments dated to a prekarstificationphase (Melik 1955; Radinja1985).Geomorphologic and speleogenetic studiesand especially new interpretations of fluvialsediments from the Kras surface as the fluvialfill of now unroofed caves have enabled a newexplanation of the evolution of the Kras (Mihevc1996, 1998, 1999a-c, 2001b, 2007; ZupanHajna et al. 2008a).Nabrežinski krasNabrežinski kras (Nabrežina Karst) is thenorth-western part of the Kras around thevillage of Nabrežina (Aurisina in Italian). It isonly about 150–180 m a.s.l. There are severalold collapse dolines on the surface, morethan 300 m wide and to 50 m deep. Smallersolution dolines are less abundant, most ofthe surface having plain or slightly undulatingrelief. Toward the north-east, the surface ofthe Nabrežinski kras gradually transforms intothe slopes of the Volnik (545 m a.s.l.) hills andGrmada (324 m a.s.l.). An abrupt change of50

the surface occurs in the south-west, wherethe surface drops from about 160 m a.s.l. tothe sea level on the distance of 300 m only.There are numerous caves, some of them areover 100 m deep, but they do not reach theunderground karst water level or the main flowof the underground Reka river that appearsin springs at sea level only about 7 km to thenorth-west.Divaški krasDivaški kras (Divača Karst) is the karstsurface above Škocjanske jame; it is sometimescalled also the Škocjanski kras. The Divaškikras is situated in the south-eastern edge ofthe Kras between ponors of the river Rekaand Divača village. It is composed chiefly ofCretaceous and Palaeogene limestones. Thesurface is levelled at altitudes between 420 and450 m a.s.l., inclined slightly north-westwardsand dissected by karst denudation. There areoutstanding karst features covering an areaof 32 km 2 , including ponors of the Reka riverand two smaller streams, 15 large collapsedolines, 64 caves, among them Škocjanskejame, Kačna jama, Divaška jama and Trhlovca,plus hundreds of dolines. The Reka river sinksin Škocjanske jame and flows into Kačnajama. Explored passages of Divaška jamaand Trhlovca are situated some 200 m abovethe underground water course and containa lot of fluvial sediments. A number of fossilcaves completely filled with sediments wereuncovered during the highway constructionin the area. A comparison of the proportionof area of smooth relief and the area coveredwith dolines and collapse dolines shows thatlevelling is a dominant geomorphologic processFig. 40: Digital elevation model of Kras plateau (DEM source: DMV 12.5 m, Geodetska uprava Republike Slovenije; figuremade by: A. Mihevc).51

in this part of the Kras (Mihevc 2001). Theproportional area of dolines is low, despite thegreat vertical gradient in karst. In comparisonwith doline surfaces, the speleologicalelements (collapse dolines, unroofed caves andcave entrances) are an important part of therelief. Even more important is the proportionof speleological elements in karstic relief ifwe compare volumes of ordinary dolines andcollapse dolines. Even though the areas ofthe dolines are only twice those of collapsedolines, the volumes of collapse dolines arefive times larger than those of collapse dolines.Ljubljanica River SystemThe karst area along underground Ljubljanicariver is important from a historicalpoint of view because karst hydrology studiesbegun here in the 16 th century and numerouskarst features were first described hereand are the reference features for the similarfeatures elsewhere. Important features of theLjubljanica karst are: poljes (Cerkniško polje,Planinsko polje); high karst plateaus (Hrušicaplateau), dolines, collapse dolines, cave systems(Postojnska jama – Planinska jama cavesystem, Križna jama, Rakov Škocjan) and karsthydrology (sinking rivers, ponors, springs,floods; Fig. 41).Ljubljanica River collects the water fromsouthwest part of the Dinaric karst in Sloveniaand belongs as right Sava affluent to Danubepart of Black Sea water basin. The real watershedis placed somewhere in the underground,and the waters from karst plateauare flowing to all sides. The Ljubljanica waterbasin is about 1,100-1,200 km 2 . The mean annualprecipitation in the basin is 1,300-3,000mm, during 100 to 150 rainy days. The one-daymaximal amount to 100 mm, in extreme caseseven 300 mm.Most of the river basin is formed on Mesozoicrocks, mostly limestone. On these rocksthe precipitation infiltrates directly into thekarst and there are no surface rivers. Triassicdolomite is important, allowing some surfaceflow, forming bottoms of some karst poljes orforming hydrologic barriers.The highest parts of the basin are highkarst plateaus Hrušica, Javorniki and Snežnikand Racna gora. On the poljes among them,surface rivers appear only, but they have differentnames: Trbuhovica, Obrh, Stržen, Rak,Pivka, Unica and finally after the springs at Vrhnikathe name Ljubljanica. The highest lying isthe karst polje near Prezid (770 m), followedby Babno polje (750 m), Loško polje (580 m),Cerkniško polje (550 m), Rakov Škocjan andUnško polje (520 m), Planinsko polje (450m),Logaško polje (470 m) and finally LjubljanskoBarje (300 m), where the Ljubljanica springsare at 300 m a.s.l. There are several largesprings are dispersed along the edge of theLjubljana Moor, which is connected with thegradual tectonic subsidence of the area. Meanannual discharge of the Ljubljanica River at thesprings is 38.6 m 3 .There are about 1,540 caves, accessiblefragments of underground drainage systemknown in the catchment area of the Ljubljanica.Almost fifty kilometres of cave passages areknown to exist along significant undergroundwatercourses. The average length of the caveis 48 m and the depth 18 m. However, thelargest caves are the ponor or spring caves;in them we can follow the 71 km of passagesof the main rivers, tributaries of Ljubljanica.Larger caves found in this area include the Karlovice,Zelške jame, Tkalca jama, and Planinacaves. In Planina Cave these waters are joinedby the Pivka River from Postojna Cave. From52

the Planinsko polje, the underground LjubljanicaRiver flows through Logarček, the Najdenajama cave, and the Vetrovna jama cave. Thesecaves provide a habitat for the Proteus anguinussalamander (the “human fish”) and othersubterranean water animals.Logaško polje (Logatec polje)The Logaško polje developed on the contactof dolomite and limestone between 470-480 m a.s.l. A number of small streams flowonto in it, the largest being the Logaščica,which collects run-off from an area of 19 km 2 .The mean flow is 0.3 m 3 /s. Short lasting floodsoccur at the swallow-holes Jačka on theLogaško polje when the flow exceeds 30 m 3 /s.The bottom of the polje is covered by a thinsediment cover of sinking streams that flowfrom Triassic dolomites and marls and Palaeozoicrocks. Sediments deposited on levelledsurface reveal the catchment area of the depositingstreams. At the present the washingof sediments into the ponors is main processfrom which subsidence connected with pipingof sediments appears, and there is also someerosion of the river banks.Planinsko polje (Planina polje)Planina polje is an overflow polje, of rectangularshape, 6 km long, 2 km wide, with twonarrow pocket valleys on SW part, 50 m deep,with a 16 km 2 flat surface at height of 450 m.Its wider surrounding area is built by Upper Triassicdolomite, Jurassic and Cretaceous limestone.The development of the closed karstdepression is result of accelerated corrosion,controlled by geological structures.It presents the most important water confluencein the river basin of Ljubljanica. A tectonicallycrushed and almost impermeableFig. 41: Digital elevation model of Planinsko polje (Planina polje) with the most important springs, ponors and cave passages(DEM source: DMV 12.5 m, Geodetska uprava Republike Slovenije; figure made by: A. Mihevc).53

dolomite barrier along the Idrija wrench faultzone, which crosses the polje, forces the karstwaters to overflow from higher karstified limestonebackground to the surface, and aftercrossing Planinsko polje toward the northeastthey can sink into the underground again. Theprincipal Unica springs, with mean annual discharge24 m 3 /s (min. 0.3 m 3 /s, max. 100 m 3 /s),are situated in the southern polje’s part in Cretaceouslimestone, where the confluence ofwaters from Cerknica, Javorniki Mt. and Pivkais located. Main spring is 6,656 m long cavePlaninska jama.The principal Unica swallow-holes are disposedat the northern edge, where mostlymedium and high waters are sinking. At lowwaters the whole Unica is disappearing inswallow-holes at eastern polje’s border. Upto 160 m long ponor caves are known, butthere are several horizontal caves in vicinityof the polje, where water oscillations canbe observed. Larger caves behind the ponorsare over 5,110 m long Najdena jama cave andLogarček.Rakov ŠkocjanRakov Škocjan is a karst depression about1,5 km long and 200 m wide. It is situatedbelow the N side of Javorniki Mountain at elevationabout 500 m between Planinsko andCerkniško polje. Through the depression flowsthe permanent river Rak. The Rak springsfrom Zelške jame cave, bringing water fromCerkniško polje. Zelške jame are about 5 kmlong; the end of the cave is in huge collapsedoline Velika Šujca, where from the other sidethe Karlovica cave system ends. In Karlovicasystem is the main outflow from Cerkniškopolje. Numerous collapse dolines are situatedaround the entrance of Zelške jame. In oneof them the small natural bridge is present.Downstream, the valley widens and severalsprings bring additional water to the Rak River.The valley narrows at the Great Natural Bridgeand afterwards the Rak sinks into Tkalca jamacave, from where the water flows towardsthe cave Planinska jama at Planinsko polje.The connections of the Rak with water fromCerkniško polje and with the Unica springs atPlaninsko polje were proved by water tracing.From 1949 Rakov Škocjan has been a LandscapePark.Cerkniško polje (Cerknica polje)Cerkniško polje (Cerknica polje; Fig. 42) isthe biggest karst polje in Slovenia. Often it iscalled just Cerkniško jezero (Lake of Cerknica),because of its regular floods, or intermittentlake. The intermittent lake covers 26 km 2 whenis full; it is 10.5 km long and almost 5 km wide.Its hydrological properties caused that alreadyin the beginning of New Age scholars from allround Europe were attracted to it. The lake becomesstill more known through the Valvasor’sdescription in 1689. Bottom of Cerkniško poljecovers 38 km 2 in elevation of about 550 m. Inflowsare on E, S, and partly on W polje’s side.The largest tributary to polje is Cerkniščica,drained about 45 km 2 large mostly dolomitecatchment area. The important karst springsare Žerovnica, Šteberščica and Stržen. Strženflows on the W side of polje towards theponors in the middle of the polje, from wherewater flows directly to Ljubljanica springs, andtowards NW side of polje, from where the waterflows to Rakov Škocjan. From the foot ofJavorniki mountain to the contact with dolomitein the polje bottom are 12 ponor caves.They are connected to Karlovica cave system,to which also the highest waters from poljeflows. The system there is more the 7 km ofpassages. Passages are generally low, becausethey are filled by alluvia. Thickness of alluviain Jamski zaliv, before the caves entrances, isabout 8 –15 m.Cerkniško polje is a karst polje developed inthe important regional fault zone – Idrija fault.Idrija fault has the “Dinaric” direction (NW-SE);in the same fault zone are developed: Planinskopolje, Loško polje and Babno polje. Bottomof polje is formed on Upper Triasic dolomite,which is presented also on the N, E and SE side54

Fig. 42: Cerkniško polje with meandering river Stržen and ponoring places Rešeto and Vodonos (photo: A. Mihevc).of the polje; there are some Jurassic dolomitesin the area. On W and NW the Cretaceouslimestone are presented.During the last centuries, a lot of plansfor the hydro melioration of polje have beenmade, but not any of them were realized. In1965 it was proposed to make Cerknica poljea permanent lake; in the years 1968 and 1969,entrances to the caves Velika and Mala Karlovicawere closed by concrete walls and 30 mlong tunnel was made to connect Karlovicawith the surface, but small effect of retentionin dry period and less moistened years wereassessed.The flattened bottom of Cerkniško poljeis regularly flooded for several months in autumnwinter and springtime; at floods it altersto spacious karst lake. Lower waters are sinkingmostly in marginal swallow holes and innumerous ground swallow holes and estavellas,which are disposed in central polje’s bottom.Principal ponor caves and swallow holesare disposed at the polje’s northwest border.Outflow from the polje was not orientedto one channel, rather to a mesh of channels,which about 200 m from the edge of poljecombine into a couple of larger galleries. Theyare generally low, because the bottom is filledwith alluvia. Alluvium at altitude of 550 m isdistinctive in all ponor caves; its thickness ispossibly the same as a thickness of alluvia inJamski zaliv.Karst of Dolenjska and KolpaThe karst of Dolenjska (Lower Carniola)occupies an area between the Ljubljanskobarje (Ljubljana moor), the eastern edge ofthe Bloška planota (Bloke plateau), the riverKupa/Kolpa, the mountains Gorjanci, thesettlement Krško and the southern of theDolenjsko podolje (Dolenjska lowland). It isalso described as the covered lowland karst55

of Dolenjska (Gams, 1974; Kranjc, 1990), andoccupies the northeastern part of the Dinarickarst region.Tectonically the area corresponds to theeastern part of the Hrušica thrust sheet, whichis the part of the northeastern External Dinarides(Placer, 1999). The rocks are Triassic dolomites,Jurassic carbonates (dolomites andlimestones) and Cretaceous shallow marinecarbonates (mainly limestones) overlain byPliocene-Quaternary deposits and soils up toa few meters thick in places (Pleničar et al.,1977). Dolomites are widespread especiallyalong the northern, northwestern and easternedges of Dolenjska.The highest part of the karst of Dolenjska(up to 1,289 m a.s.l.) is located in the west andis similar to the karst of Notranjska (i.e., highkarst plateaus, uvalas and karst poljes). Towardthe east, the elevation generally decreases tothe flood plain of the river Krka and the levelledsurface of Bela Krajina (both at ~170 ma.s.l.). Bela Krajina is the northern part of theplateau between rivers Kupa/Kolpa and Unaseparated by the canyon of the river Kolpa. Betweenthe Krka flood plain and Bela Krajina arethe mountains Gorjanci (1,178 m a.s.l.). Whilethe western part of Dolenjska shows featuresand hydrogeological conditions characteristicof deep karst, the eastern part is more fluviokarsticdue to low spatial differences in elevationand, in some areas, dolomites. Water isclose to the surface, and the surface is coveredwith a thick layer of red karst soil due to thelow elevation and consequently low erosion.The red soils above dolomites are thicker andmore cohesive than those above limestones(Gams & Vrišer 1998). Wide linear and conicaldepressions and rounded hills predominate inthe relief although some karst poljes are alsodeveloped in this area (e.g. Radensko polje,Globodol). The biggest morphological featureis the Dolenjsko podolje – a 48 km-long valleylikefeature running in a northwest-southeast-Fig. 43: Middle course of the river Kupa/Kolpa where it crosses levelled surface along Rajhenav tectonic block. Due tosubsidence of this block, canyon bottom is relatively wide (photo: M. Prelovšek).56

erly direction between Ljubljansko barje andthe Krka flood plain near Novo mesto. Belowthe thick soil cover, subcutaneous stone teethup to 8 m high are developed (Knez & Slabe2006).The central surface stream of Dolenjskais the river Krka, which cuts a shallow canyoninto the karst surface. It is situated in the centralpart of the Dolenjska karst and thereforeattracts underground waters from the majorpart of Dolenjska karst. Its catchment area(2,250 km 2 ) is 19 % larger than that of the riverbasin of Ljubljanica (1,884 km 2 ) but due to alower amount of precipitation it has a practicallyidentical average annual discharge (54m 3 /s; data from http://www.arso.gov.si/vode).The river Krka is characterized by travertinedams, which are the result of the higher hardnessof the water in comparison with the karstof Notranjska (Gams 2003). Due to a higheramount of precipitation and a larger drainagebasin that covers southern Dolenjska karst andextends also to Croatia, the river Kolpa hashigher discharge (Q avg= 72 m 3 /s). The deepsump (more than -154 m) of the river Kolpain Croatia (Knab 2008) is situated only 23 kmfrom the Adriatic coast (Fig. 16 on page 24),but it belongs to the catchment of the BlackSea. Its upper watercourse is cut between highplateaus and high leveled surfaces, while thedownstream flow is situated in a canyon (upto 40 m deep; Fig. 43) cut into the leveled surfacebetween rivers Kupa/Kolpa and Una. Avery small, but hydrologically very interesting,stream is the river Temenica (Q avg= 4.3 m 3 /s),which emerges as springs at the northern edgeof the Dinaric karst near Trebnje and flowssoutheast toward the river Krka. Along its42 km-long superficial streams, two separateunderground courses of the river Temenica arelocated, with a combined length of more than3.5 km.Contact Karst of Matarsko podoljeThe Matarsko podolje (Fig. 44) is 20 kmlong and 2 - 5 km wide levelled karst surfacesouth of Brkini hills. The surface probably developedas a base-levelled plain; later it wasdissected by the dolines. It gently rises fromabout 490 m on NW to 650 m on the SE side.The lowered surface continues towards southeastbut from the highest point near the blindvalley Račiška dana blind valley it lowers onthe distance of 2 km for 200 m towards southeastto surface of Brgudsko podolje. This bendis most likely result of neotectonic shifting.Along the contact series of 17 brooks sinksin the karst edge of Matarsko podolje. The allogenicdischarge into the karst is responsible forthe creation of several large blind valleys andcaves and lot of allogenic sediments depositedon the surface and underground (Mihevc1993, 1994). Most of the brooks developedblind valleys bottom widened by corrosionbottom. The bottoms of these valleys are situatedbetween 490 to 510 m. As the valleys areincised in the border of the karst, uplifted towardsSE, the blind valleys lying more to thesouth are deeper. The first, Brezovica blind valleyis cut for 50 m only while the deepest is thelast Račiška and Brdanska blind valleys. Theyare deepened into border limestone for 250 mand its bottom lies 120 m below the surface ofthe Matarsko podolje.More than hundred vadose caves areknown in the karst plain. Great oscillation ofkarst ground water was observed. Water tracingshowed that the sinking streams flow tothree groups of springs: (1) submarine springsalong the coast in the Kvarner Bay on the57

Fig. 44: Blind valleys of Matarsko podolje (DEM source: DMV 12.5 m, Geodetska uprava Republike Slovenije; figure made by:A. Mihevc).south, (2) springs in Istria on the south-west,and (3) the Rižana springs at 70 m a.s.l. on thewest (Krivic et al. 1987).The contact karst of Matarsko podolje atthe foot of Brkini hills was explained withinthe frame of cyclic and later climatic geomorphologictheory. The period of fluvial reliefdevelopment should be followed by the karstificationwhen the impermeable cover wasremoved. At the karstification beginning thesuperficial streams shortened and the last remainsof this pre-karstic phase should be theblind valleys (Melik 1955). Various forms ofthe blind valleys were later contributed to theclimatic changes (Gams 1962). Now we understandthe contact karst features as a type ofinteraction of two systems of drainage, fluvialand karstic and that has also geomorphic expression.Allogenic sediments are very importantfor the formation.The surface of the Matarsko podolje probablydeveloped as a base-levelled plain; laterit was dissected by the dolines and blind valleys.Stronger tectonic uplift in the southeastpart upraised the lowered surface, and due tostronger uplift incomparable deep blind valleysdeveloped there (Mihevc 1993). The deepeningand the contemporaneous widening ofthe valleys followed the lowering of the karstwater to the altitudes about 500 m. Becausethe bottoms of the blind valleys practically remainon the same altitude were probably controlledby the piezometric level. The blind valleysstarted to cut into the corrosion plain withsmall transverse and longitudinal gradient asin the contrary case the fluvial valleys shoulddevelop in them. They should be preserved onkarst as dry valleys. Bad permeability or lowgradient of the karst caused the deposition ofthe sediments on the edge of the karst in front58

of ponors and the deposits affected the planationand corrosion of the bottom of the blindvalleys. The sedimentation was especially intensivein the cold periods of the Quaternaryand these deposits are preserved on the bottomof most of the blind valleys. Due to lackof sediments the sequence of the events couldnot be temporally defined.In actual conditions the karst water tablestays deep under the altitude of the blind valleybottoms. The bottoms of the blind valleysare out of reach of the floods of the sinkingstreams in front of ponors and the gradient inthe karst is so big that the old deposits fromthe surface are washed off into the karst by thesuffosion processes.Fossil blind valleys developed in uppersoutheast part of the lowered surface onlyand according to altitude, preservation of sedimentsor size they are no more comparableamong themselves. The characteristic of thiscontact where are the most of the fossil blindvalleys on higher position in comparison toimpermeable flysch where the water basinsof sinking streams developed and sink in theblind valleys.Caves in blind valleys have been often refilledwith allogenic sediments, originatingfrom the impermeable surroundings. On thesediments of last infill stalagmites are growing,and some of them have been dated.CavesIn 2010, almost ten thousand caves wereregistered in the Cadastre of Caves maintainedby the Scientific Research Center ofthe Slovenian Academy of Sciences and Artsand the Speleological Association of Slovenia.The longest cave system in the Dinaric karst isPostojnska jama system with 20.570 km, followedby Jama pod predjamskim gradom with13,092 km, and Kačna jama with 13,250 km.Slovenia’s oldest tourist cave is Vilenica, wherethe first tourist visit was recorded in the early17 th century (Gams 2003). The best knownand most visited cave in Slovenia is Postojnskajama, where tourism flourished after the discoveryof the interior parts of the cave in 1818.The Škocjanske jame system with its undergroundcanyon is also very attractive and popularwith tourists; since 1986, the Škocjanskejame have been on the UNESCO List of WorldNatural Heritage Sites (Kranjc 1997). Theirgeomorphological, geological, hydrological,zoological, and botanical features make thesecaves a very important part of Slovenia’s naturalheritage (Institute of the Republic of Sloveniafor Nature Conservation 2000).Water arrives on the karst as precipitationor in rivers from the non-karst surroundings.Due to gravity, the water seeps through fissures,widening them in the process and formingvertical shafts. It trickles downward until itreaches the level of the karst water table. Thekarst aquifer inclines toward springs. The waterflows along the lowest cave passages thatin some places are completely filled with waterand run as much as a hundred meters or morebelow the top of the water table. In these passagesthe water can even flow upwards. Thecross sections of these caves are often roundor oval. One example is the cave Gabrancanear Neverke where low water periods allowa 214-meter descent into the cave, but heavyrains cause the water to erupt from the caveand from the spring of the Sušica river with adischarge of several cubic meters per second.Vertical shafts formed by rainwater are usuallyfissures widened by corrosion and are normal-59

ly several dozen meters deep. Shafts that canreach great depths in steps often occur on highplateaus. A typical example is the 218 m deepStrmadna shaft on the Nanos plateau.High karst water tables that remainedstable over a long period enabled the formationof large horizontal caves. This is how largeponors and spring caves such as the Postojnskajama and Planinska jama and the caves inRakov Škocjan park formed in the karst riverbasin of the Ljubljanica river and caves such asthe Škocjanske jame and Kačna jama along theunderground flow of the Reka river.The greater part of Dinaric karst territoryin Slovenia is drained by the Reka river in theKras region and by the Ljubljanica river in theNotranjska region. These rivers formed largecave systems that are partly accessible. TheReka sinks into the Škocjanske jame and canbe followed as far as the siphon. After a shortbreak, we can follow its course again in thecave Kačna jama, then in the Jama v Kanjeducah,and finally in Jama v Stršinkini dolini. Altogetheralmost twenty kilometres of cave passagesare accessible along the undergroundcourse of the Reka river.Due to denudation, cave passages get evercloser to the surface. Finally they are left withoutceilings and roofless caves become part ofthe morphology of the karst surface. As thesurface continues lowering, the remains ofcave passages and sediments disappear completely.The evolution of the caves in Slovenia(from the start up to their total destruction bydenudation) took part within one karstificationperiod, which began with the regressionof Eocene sea and exposing of limestones atthe surface within complicated overthrustedstructure, which formed principally during theOligocene to early Miocene. The interpretationof palaeomagnetic data (Zupan Hajna etal. 2008a), with some support from palaeontologicalfinds, indicates that karst developedin pulses tightly linked with tectonic evolutionand changes of the geodynamic regime. Individualpulses were not sharply limited, however,and therefore cannot be tied to preciselydefined karst phases. Moreover, the complicatedgeological structure and tectonic/geomorphicevolution makes the picture less cleardue to the differing tectonic evolution of individualmorpho-structural units, which oftenhave also quite different histories of evolutionof the relief and karst.Postojnska jamaPostojnska jama is developed in Postojnskikras where the surface is at 600 to 650 m a.s.l.The evolution of the Pivka basin (Eocene flyschrocks) is defined by the altitudes of the ponorsof Pivka River that drain into this cave. Thegentle fluvial surface of the basin itself standsout in sharp contrast to the karst lands abovethe cave and to other higher karst plateaus,where there are no traces of fluvial valleys orother elements of the early fluvial relief today.These surfaces are dissected with numerousdolines. Sixteen large collapse dolines developedabove some parts of Postojnska jama,blocking certain passages. The thickness ofbedrock overburden above the cave is 60 to120 m.The cave was formed by the Pivka river. Itsmodern ponor is at 511 m a.s.l. and the terminalsump in Pivka jama is at 477 m a.s.l. Thereare still more than 2,200 m of unexplored galleriesbefore the river re-appears in Planinskajama at 460 m a.s.l.The historical entrance at 529 m a.s.l. islocated above the modern ponor. Other entrancesand parts of the system, i.e. Otoškajama, Magdalena jama, Črna jama and Pivkajama, are scattered on the surface above thecave. All these caves are interconnected andform a cave system 20.5 km in length, the longestin Slovenia.The entrance to Postojnska jama is situatednear the contact between the Eoceneflysch and the Upper Cretaceous limestones(Buser et al. 1967). The entire cave system isdeveloped in an 800 m thick sequence of the60

Upper Cenomanian and Turonian to Senonianlimestones. The cave passages are formed inthe Postojna anticline, which is oriented NW–SE (Gospodarič 1976), most of channels beingin its steeper south-western flank. The cavesystem is in the tectonic block confined by twodistinctive dextral strike-slip fault zones in theDinaric trend, the Idrija and Predjama faults(Buser et al. 1967; Placer 1996). Habič (1982)explained different features, such as collapsesand sumps in the cave, as the results of neotectonicmovements. A geological survey ofthe cave passages was made by Gospodarič(1964, 1976) and Šebela (1994, 1998a, b) addedstructural mapping in detail. The cave andthe Pivka underground river have a generalN–S trend.The known passages were formed attwo main levels. The upper level is between529 m a.s.l., at the main entrance to the caveand 520 m a.s.l. in the Črna jama. This levelis composed of large passages, generally up to10 m high and wide. Their profiles are morerounded and show also traces of paragenesis(levelled ceilings, side notches on the walls andscallops on the walls and ceiling). There arealso remnants of cave fills indicating repeatedfillings of the cave and successive erosion ofthe sediments. Speleothems were depositedin different phases above clastic sediments.The natural floor of the cave was modified forthe construction of a railway during openingfor tourists.The second level is about 18 m below theupper one, where the modern undergroundPivka river flows from its entrance. The riverbed has a low gradient and, except for somecollapses and sumps, there are no natural barriers.It leaves the system through a terminalsump. The active river passages are mostlyFig. 45: Postojnska jama - the longest and the most touristic cave of Dinaric karst (photo: N. Zupan Hajna).61

smaller than the higher ones. The river bed iscomposed mostly of gravels derived from theEocene flysch. The mean annual discharge ofthe river is 5.2 m 3 /s. The water level can rise10 m during floods.Cave fill was originally expected not tobe older than Middle Quaternary (i.e. about0.4 Ma). Pleistocene large mammal fauna suchas hippopotamus, cave lion and cave bear,were found here (Rakovec 1954) as well as Paleolithicstone tools from the last glacial (Brodar1969). Later numerical dating (Th/U andESR) indicated ages older than 0.53 ka. Newpalaeomagnetic data from selected sedimentaryprofiles within the cave system detectednormal polarization in prevalent amount ofstudy profiles. Reverse polarized magnetozones,interpreted mostly as short-livedexcursions of magnetic field, were detectedonly in places. Therefore we (Zupan Hajna etal. 2008a, b) interpreted most of studied sedimentsas younger than 0.78 Ma, belonging todifferent depositional phases within the Brunheschron. Palaeomagnetic properties on twoprofiles in the caves intersected by artificialtunnel between Postojnska jama and Črnajama with reverse polarized magnetozones,and sediments in Zguba jama, can indicate agedeeply below 0.78 Ma.The cave system shows long evolution governedby the function of the Planinsko poljein the relation to the evolution of resurgencearea in Ljubljana Moor farther on the east. Thegeneral stabilization of the hydrological systemwith low hydraulic head led to evolutionof caves in epiphreatic and paragenetic conditionsfor a long time-span. Individual cavesegments or passages were fully filled andexhumed several times during the cave evolution.The alternation of depositional and erosionphases may be connected with changingconditions within the cave system, functionsof the resurgence area, collapses, climaticchanges, tectonic movements and the intrinsicmechanisms of the contact karst.Škocjanske jameŠkocjanske jame are 5.8 km long cave. TheReka River enters the cave at an altitude of317 m; in the Martelova dvorana room, it is214 m above sea level (i.e. 103 m lower). TheReka can also sink before it enters the cave.Floods usually reach up to 30 m, higher floodsare common too, and the largest known floodin the 19 th century raised the water table levelfor 132 m. Caves are developed in a contactarea of Cretaceous thick-bedded rudistic limestoneand Palaeocene thin-bedded dark limestone.The cave is composed of phreatic tunnels,and gravitational or paragenetic reshapedgalleries. The proto-channels developedin phreatic conditions along tectonisedbedding-planes. The water flow demanded ahigh degree of phreatic rising and falling betweenindividual bedding-planes which, in thearea of the chambers Svetinova dvorana andMüllerjeva dvorana, is approximately 175 m.Large quantities of water could flow throughall these tunnels, but meanwhile, rubble wastransported through water table caves abovethem. Such a cave is the unroofed cave in Lipovedoline at an altitude of around 450 m.A long period followed when the piezometricwater table was 340-300 m above sea leveland the gradient was in a southwest direction.In it Reka formed new or adopted old passagesby paragenesis and bypassing. These large gallerieswere Mahorčičeva and Mariničeva jama,Tominčeva jama, Schmidlova dvorana in Tihajama. The largest chambers are Martelovadvorana, with a volume of 2,100,000 m 3 , andŠumeča jama (870,000 m 3 ). Some of big chamberscollapsed forming the big collapse dolineslike Velika and Mala dolina.In the further development of Škocjanskejame, potent entrenchment prevailed. Cuttingoccurred in inner parts of the cave, in Hankejevchannel for about 80 m, much less, about10 m, in the eastern, entrance part of the cave.The first paths in the cave area were madein 1823, but the construction of paths for ex-62

ploration and for the visitors started in 1884.Cave exploration and construction of the pathwayswere done by cavers of DÖAV from Trieste.The most important explorer was AntonHanke. In 1891 they reached the final sump inthe cave.Because of their extraordinary significancefor the world’s natural heritage, in 1986 theŠkocjanske jame were included in UNESCO’sWorld Heritage List. The Republic of Sloveniapledged to ensure the protection of theŠkocjanske jame area and therefore adoptedthe Škocjanske jame Regional Park Act. TheŠkocjan Caves were entered also on the RamsarList of Wetlands of International Importancein 1999. Together with the underground RekaRiver, they represent one of the longest karstunderground wetlands in Europe.Križna jamaKrižna jama is large river cave 8,273 m long.It is situated in the area between Loško, Bloškoand Cerkniško poljes. The relief above the caveis characterized by conical hills and closed depressions,dolines, uvalas and small, polje-likelevelled surfaces. The entrance of the cave islocated in an elongated karst depression to theeast of Križna gora (856 m a.s.l.).The cave is developed in the light greymicritic Liass/Dogger limestones, with lensesof dolomite (Gospodarič 1974; Buser, Grad &Pleničar 1967). The cave was formed in ratherstable conditions between the Cerkniškoand Loško polje, as indicated by the mostlyepiphreatic conditions of passage evolution.A small river with autogenic catchment areaflows in the cave and continues through at least124 m deep terminal sump towards the westinto the cave, Križna jama II, and to springs atCerkniško polje. The active water passages arelocated at about 610 m a.s.l. The older passagesare slightly higher, between 620 and640 m a.s.l. Remains of fluvial sediments arepreserved throughout the entire cave, indicatingthat it was filled by more sediments in thepast (Gospodarič 1974). The remains of Ursusspelaeus in clay inter-beds among flowstonesheets are important in the Medvedji rov. Theywere studied by Hochstetter (1881), Rabeder& Withalm (2001), Pohar et al. (2002) and theothers. The most detailed study of fluvial sedimentswas done by Gospodarič (1974), whoconcluded that the cave was much more filledby sediment in the past and less open than it isat the present time.Unroofed Caves and Surface DenudationOn several places on Kras allogenic sediments,quartz sands and pebbles can be foundon the surface. Their appearance was explainedas remains fluvial deposits of surfacerivers. These sediments were the basis for thepresumption of pre-karstification period andseveral karst forms were described as remainsfrom that period (Radinja 1969; Melik 1962).New interpretation of these localities togetherwith geomorphologic and sedimentary studiesreveal (Mihevc 1996; Mihevc & Zupan Hajna1996; Mihevc 2001) that these are the cavesediments exposed to the surface because thedenudation removed the rock above the caves.The appearance of old unroofed caves andtheir fills resulted from denudation, erosionand chemical dissolution of limestone abovethe cavities. Fills exposed on the present surfaceinclude speleothems and cave fluvial deposits.The ancient directions of flow, differentcatchment areas of sinking rivers and differentorganisation of the ancient undergrounddrainage were reconstructed from several unroofedcaves opened during highway construc-63

tion in the Divaški kras (Mihevc 1996; Mihevc& Zupan Hajna 1996). The thickness of rockoverburden removed above cavities was establishedto have been 50–100 m. The age ofcave fills was calculated from denudation ratesand the expected thickness of missing overburdento 0.7–5 Ma (Mihevc 1996, 2001). Thislarge time range resulted from the expectedminimum (20 m/Ma) and maximum denudationrates (50 m/Ma) calculated or measuredin the area (Gams 1962; Cucchi et al. 1994).Unroofed caves were also described by Šebela& Mihevc (1995), Šebela (1995, 1999), Mihevc,Slabe & Šebela (1998), Šušteršič (1998), Knez& Slabe (1999a, b).The study (Zupan Hajna et al. 2008a) ofcave deposits in unroofed caves of the Krasprovided entirely new insights into the age ofcave and karst sediments and introduced newideas concerning the development of karst.Geomorphic comparative method used fordating of processes and landforms showedthat many accessible caves in the Kras are ofPliocene age at least or even older (Mihevc1996, 2000, 2001).The shape of unroofed caves depends on(1) the morphology of the present surface; (2)size, type and original arrangement of caves,and (3) the cave fill. Unroofed caves are usuallyaltered by surface processes. They representan important element of the epikarst zone. Onthe surface, they are expressed as narrow andoften meandering shallow trenches, shallowoblong depressions, doline-like forms in rowsand collapsed dolines. Mihevc (1999a) offeredmodels of their origin and their relation to thepresently accessible caves.Lipove dolineUnroofed caves are an important part ofthe surface morphology of Divaški kras where2,900 m of the unroofed caves were mapped(Mihevc 2001). In such features, flowstone,allochtonous sediments and morphology aretestifying their cave origin. The proportion ofdenuded caves is small in area (only approximately0.16 % of the total area). The largestsuch denuded or unroofed cave of the Divaškikras is located on the surface northeast ofŠkocjanske jame, named after great number ofdolines Lipove doline. The mapping of the surfaceshowed a 1800-m long series of dolinesand elongated dolina-like depressions 450 mabove sea level and interconnected withouthigher thresholds. The bottoms of the dolinesare 5 m to 10 m below the level of the rest ofthe surface; the depressions are 20 m to 30 mwide. Chert pebbles, yellowish red sandy loamand massive flowstone were found at the bottomof the dolines. The denuded cave passageforks in a number of places. In the westernpart of this roofless cave, in one of the Lipovedolines, quartz sand was exploited, duringwhich a large amount of flowstone and a largestalagmite were exposed. The stalagmite andthe sediments were first described by Pleničar(1954), who interpreted the cave as small cavewith a collapsed roof located near the surface.The unroofed cave in Lipove doline is similarto Škocjanske jame in its dimensions, as thewidth of the tunnel was in some places likelyto be more than 20 m. Anticipation from themassive stalagmite, the ceiling of the cave wasat least 10 m thick and at least 500 m abovesea level during the time when flowstone wasdeposited.The unroofed cave Ulica and Ulica pečinacaveThe unroofed cave Ulica and Ulica pečinacave (Fig. 46) are situated in the southeastpart of the Matarsko podolje (SW Slovenia),near the Croatian border. They are presumablyremains of the same cave system as Račiškapečina (Mihevc 2004). The passages of Račiškapečina are in elevation between 598-589 m.The 1,200 m distant Ulica pečina cave has itsparagenetic ceiling in elevation 585-589 m,while sediments at the bottom of the passageare between 585-562 m. In similar height, 580-585 m, is also the floor of the unroofed caveUlica.64

Ulica pečina is 125 m long, 10-15 m widecave with two entrances. Cave is developedin Lower Cretaceous thick-bedded limestone.The cave represents relict of old cave system,which was opened by denudation to the recentsurface. The bottom of the cave is composedof clastic sediments, clays, rocks andgravel. There is evidence of fast sliding of sedimentinto the lowest part of the passage as aresult of periglacial processes in the cave. Thethickness of roof above the cave is about 10 m.On the south side, the cave opens on theslope of the hill, while on the north side cavewas continues in unroofed cave Ulica. Theunroofed cave Ulica is a 250-m long series ofelongated depressions. The unroofed cave isabout 10 m deep and 20-30 m wide. The wallsof the unroofed cave are mostly steep, thefloor of it are composed of sediments, on onespot with massive flowstone. Continuation ofthe unroofed cave is not clear, possibly is towardsnorhwest, where are some large boulders,the remnants of collapsed cave ceiling.Even if the caves are not of the same system,they were most likely developed at thesame time, and were probably connected withthe sinking rivers from the flysch. Dating ofRačiška pečina sediments shows their ages upto 3.4 Ma. After the presumed lowering of thesurface with denudation rate of about 50 m/Ma with this age there was about 100 m of therock above the caves removed since de depositionof the dated sediments.Fig. 46: Plan and cross-section of cave Ulica pečina and unfoofed cave (figure made by: A. Mihevc).65

Use of Karst and its ProtectionThe Nature Conservation Act in Sloveniaprovided a basis for the overall conservationof biodiversity and protection of valuablenatural features (included karst surface andunderground) as part of Slovenia’s naturalheritage. Nature conservation legislationand the Cave Conservation Act (from 2000)regulate the protection and conservationof caves. This Act governs the protectionand use of underground caves, protectionarrangements, protective measures and otherrules of conduct, including the restoration ofpolluted or damaged caves.The conservation of caves is often difficultto implement because important segments oflife on karst take place above them. Becauselarge caves along underground rivers areimportant economically as tourist caves, as asource of water supplies, and for science, itis necessary to protect them or exploit themwithout devaluating them in the process.Unnecessary activities that often take placeabove the caves could easily be avoidedthrough more reasonable planning. Forinstance the entire Kačna jama cave lies belowthe town of Divača. While it is impossible tomove settlements, the sewage treatmentplant and its discharge could easily be installedfarther away from the cave. It is also notnecessary to build an industrial zone directlyabove the cave passage that connects theKačna jama cave and Škocjan Caves, a worldclassphenomenon. The industrial zone couldbe built one kilometer further north and notthreaten the underground world. This is notjust about the conservation of the two cavesbut about the tourist exploitation of the cavesas well; the situation will be much worseif the surface above the caves is built up.Along the underground Reka River is anotherproblem with the Sežana sewage treatmentplant in Kanjeduce, which is located abovethe underground passages of the cave and itsdischarges are far from achieving the requiredstandards. The entrances to Postojna Cave,Planina Cave, and the caves in Rakov ŠkocjanPark face similar problems. Thoughtlessencroachments are destroying importantassets and society will benefit from themmuch less in the future.There is a problem with tourist visits tocaves. For example two hundred years oftourism have left a number of negative tracesin Postojna Cave. Some have damaged thenatural condition of the cave, while othersthreaten the tourist exploitation of the caveand have reduced the value of the cave. Whilethese changes are negative, they could beminimized if we are aware of them. Stalactiteshave been removed, the floor of the cave hasbeen changed excessively, and large amountsof dust have accumulated in the entranceparts of the cave. Other activities in the vicinityof the cave may present an even greater threatto the cave than tourist exploitation: the poorcondition of the sinking Pivka River due to theinefficient treatment plant, the construction ofindustrial buildings in the immediate vicinity,for example, on the site of former militarybarracks near Veliki Otok, abandoned militaryfacilities above the cave, and a car dump sitebeside the old road toward Planina. Suchactivities should be moved farther from thecave since they present a serious threat andare certainly not examples of good practice.66

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