Thermokarst

Thermokarst is a type of terrain marked by irregular marshy hollows and small hummocks that form when ice-rich permafrost thaws. It occurs mainly in Arctic regions and, on a smaller scale, in mountain ranges such as the Himalayas and the Swiss Alps. The pitted ground resembles the sinkhole-dotted landscape produced by limestone dissolution in true karst terrain, which is how thermokarst got its name even though no limestone is involved; its development often includes frost-heaved domes and pingos that eventually collapse into the depressions characteristic of the terrain.