Veress Márton: A Bakony természettudományi kutatásának eredményei 23. - Covered karst evolution... (Zirc, 2000)

OBJECTIVES

manent dislocation of the cover sediment (only interrupted for short spells). The movement affects highly variable portions of the cover at a particular time. The velocity for the individual particles is low and the surface feature of gentle slopes takes a long time to develop. Alluvial dolines-with-ponors are also defined. In this type a surface depression results from the reworking of cover sediments into the karst by the water-course of the karst passage. Underground karst features may form through corrosion or erosion. Corrosional features usually develop in the zone of flowing karst water. Cavitation is explained in the following way. The infiltrated solvent becomes saturated on the surface or at a shallow depth in the percolation zone and, thus, it is unable to dissolve carbonates. The recurring solution effect in the zone of karst water is due to the mixing of waters of different hardness (Mischungskorrosion). Mixture corrosion occurs when two saturated water masses of different concentration mix. Part of the equilibrium C0

2 (which keeps Ca

2+ ions in solution) appears in surplus. This surplus C0

2 produces carbonic acid and dissolves additional amounts of carbonate. Mixture corrosion in the zone of flowing karst water is caused by the crossing of horizontal flow and downward water percolation routes. Among karst landforms spring caves and closed cavities are distinguished. The former are produced at karst springs, where water is collected from over large surfaces. Large amounts of water are mixing and it makes cavity formation intensive. Open branching caves of several tens of metres dimension develop. Closed cavities are created in the interior of the karst and differ from spring caves as they are closed from the beginning of their evolution. As in such places lesser amounts of water are mixing, their sizes are also smaller than spring cave dimensions. Essentially, in karst interiors groups of cavities develop which are connected into a system of passages of various cross-sections and lengths, usually impassable for humans. Erosional caves are formed in allogenic karsts. The water-courses reaching the interior of the karst through ponors carry along sediment loads from the adjacent non-karstic terrains and erode the corrosional caverns further by corrasion. The caves expanding from the ponors towards the karst interior are called streamsink caves. Erosional caves are through caves if they are so spacious all the way from the ponors to the karst springs that they are passable by humans.