Karst

Karst is a landscape that forms when water dissolves rock that is readily soluble, chiefly limestone, but also dolomite and sometimes gypsum. Rainwater that has absorbed carbon dioxide from the atmosphere and soil becomes weakly acidic and progressively dissolves the limestone, enlarging fissures and opening passages.

The result is land characterized by sinkholes, caves, underground streams, and large cavities. In karst regions, water usually does not flow in surface streams; instead it travels through underground channels. The term 'karst' derives from a geographic region on the eastern shore of the Adriatic Sea, where this landform was first formally described scientifically.

Formation process

Dissolution begins in small cracks and fissures in the rock. As water passes through these channels it widens them, and over time they become large caves. When a cave roof collapses, a sinkhole forms on the surface. The rate of development depends on rainfall amount, temperature, and the concentration of carbon dioxide in the water.

Surface features

Surface features include sinkholes, enclosed depressions with no external drainage, and eroded bare rock. Underground features include caves, water channels, and calcite formations such as stalactites (hanging from cave ceilings) and stalagmites (rising from cave floors). Large cavities often open into springs at the margin of karst areas.

Water and people

Karst regions hold groundwater vital to drinking water supplies for large populations worldwide. However, because water passes rapidly through the rock without full filtering, contamination from agriculture and industry can quickly reach groundwater. Construction and roads in such areas also face the hazard of ground collapse when caves underground fail.