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Climatic Geomorphology
5. Thermokarst or cryokarst
These terms refer to the landforms created by subsidence caused by the thawing of
the upper part of the permafrost (Figure 8.36). These phenomena may give place to a very
irregular topography. The word thermokarst is not widely accepted since the resulting
landforms do not have much resemblance to the exokarstic features occurring in
karst terranes (Pissart, 2004). The thermokarst depressions are mainly found in low-relief
areas like alluvial plains, because their persistence is unlikely in zones with rugged
topography (Williams and Smith, 1989; K~i~ib and Haeberli, 2001). The subsidence due
to thawing of ground ice may be very active and consequently these periglacial
landscapes change very rapidly (Harry, 1988).
The causes of the thawing are highly varied. A climate change towards milder
temperatures may affect the thermal equilibrium of the permafrost in extensive areas.
Figure 8.36. Small collapse affecting slope deposits resulting from the thawing of ground ice during the
summer. James Ross Island. east of the Antarctic Peninsula. Photo: A. Mart~n-Serrano.