Karst processes
Description
Karst landscape is predominated by the high rock solubility and well-developed secondary porosity. This landscape thus has very distinctive hydrology and landforms. The karst landscape is usually associated with carbonate rocks (limestone, marble and dolomite). This landscape can also emerge on the gypsum or rock salt. The karst landscape covers 10% of continental area.
The dominant process that produces karst features is the solution of the rock by rainwater (dissolution/corrosion). The calcium carbonate dissolves in the presence of water and carbon dioxide (that together produce carbonic acid) to yield the more soluble calcium bicarbonate which is transported away in solution. These processes are accelerated in the places where the concentration of soil carbon dioxide and the annual precipitation are higher.
The karst landforms can be divided into two groups: surface landforms and underground forms. The development of the underground systems through which the dissolute rock is carried is necessary for forming the surficial landscape. The dissoluted calcium carbonate is then discharged in the springs where the water emerges cave systems of the karstified rock. The longest karst cave system in the world is more than 530 km long, but is developed in only 100 m vertical stratigraphic thickness. The surface landforms can be divided into input and output and residual landforms (sensu Ford and Williams, 1989). The major input landforms are: blind valleys, karrens, dolines, sinkholes, uvalas, ponors, poljes. The output and residual landforms are: tufa dams, karst springs, and plains with residual hills (mogots). The residues of the karst processes can form new accumulated landforms, e.g. Sabkha marshes or dunes. The main subterranean landforms are caves, tunnels, abimes, cenotes, underground rivers, tunnels.
Many microforms called speleothems are preserved in the karst caves. These are formed by the degassing of the water and calcium carbonate solution due to the lower concentration of carbon dioxide in the caves. The most important types of speleothems are stalagmites, stalactites, soda straws, rimstone dams and draperies.
References:
[1] Goudie, A.S., 2004. Encyclopedia of Geomorphology, Routledge, London, 1156 s.
[2] Strahler A., Strahler, A., 2003. Introducing physical geography, Wiley, New York, 684 s.