Karst

A karst spring in the Jura mountains near Ouhans in eastern France at the source of the river Loue

The Devil's Hole sinkhole near Hawthorne, Florida, USA.

The karst limestone, after surface rock has weathered away, makes a ground surface which is almost imposssibly difficult for humans. Velebit in Croatia.

From a World Heritage Site in Madagascar, the Tsingy de Bemaraha Strict Nature Reserve. Gradual erosion has produced vast fields of limestone spires known locally as tsingy, interspersed with dry forests, lakes and mangrove swamps inhabited by numerous endemic and threatened lemur and bird species.

Karst is a geological system of rocks where water has eroded (dissolved) the bedrock. If very extensive, karst can be a geographical or topographical feature.

Almost always, karst is formed in carbonate rocks, such as limestone or dolomite. Since carbonate sedimentary rocks are very common, karst areas occur all over the world.

Many karst regions display distinctive surface features, with sinkholes being the most common. However, karst surface features may be absent where the soluble rock is mantled (covered), such as by a non-soluble rock strata on top of the carbonate strata. Some karst regions include thousands of caves, and the water is generally underground.