Case Studies from the Dinaric Karst of Slovenia

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