Case Studies from the Dinaric Karst of Slovenia

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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
Page 2 and 3: Andrej Mihevc, Mitja Prelovšek, Na
Page 4 and 5: ContentsGeographical Position and G
Page 7 and 8: Fig. 2: Coastal part of Dinaric kar
Page 9 and 10: ogy started. In 1531 a lawyer from
Page 11 and 12: include numerous data and general o
Page 13 and 14: GeologyNadja Zupan HajnaThe Dinaric
Page 15 and 16: ceous. The final disintegration of
Page 17 and 18: Fig. 11: Locations of Jelar Breccia
Page 19 and 20: ClimateMitja PrelovšekThe Dinaric
Page 21 and 22: 311 mm/a; Zaninović 2008) and incr
Page 23 and 24: 24Fig. 16: Spatial distribution of
Page 25 and 26: ocks (such as Eocene flysch, Lower
Page 27 and 28: absent. Downstreamparts of the cany
Page 29 and 30: GeomorphologyAndrej MihevcIn folk l
Page 31 and 32: long. They are smoother especially
Page 33 and 34: is now depositing. Best known are t
Page 35 and 36: Structural poljes are dominated by
Page 37: Fig. 28: Typical dolines of Dinaric
Page 41 and 42: on Northern Velebit, where three ca
Page 43 and 44: Land UseNadja Zupan Hajna, Andrej M
Page 45 and 46: for ‘bare limestone desert’ -th
Page 47 and 48: Fig. 38: Grančarevo dam in the upp
Page 49 and 50: KrasThe Kras is a distinct plateau,
Page 51 and 52: in this part of the Kras (Mihevc 20
Page 53 and 54: dolomite barrier along the Idrija w
Page 55 and 56: of Dolenjska (Gams, 1974; Kranjc, 1
Page 57 and 58: Fig. 44: Blind valleys of Matarsko
Page 59 and 60: ly several dozen meters deep. Shaft
Page 61 and 62: smaller than the higher ones. The r
Page 63 and 64: tion in the Divaški kras (Mihevc 1
Page 65 and 66: Use of Karst and its ProtectionThe
Page 67 and 68: Gams, I., Vrišer, I. (Eds.), 1998:
Page 69 and 70: lems.- Dela 38, Raziskovalni center

Case Studies from the Dinaric Karst of Slovenia

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