Cryoplanation

Cryoplanation (also known as cryoplanation terraces) is the alteration of a terrestrial surface by intense frost action that effectively reduces slope steepness and lowers mountain and hill peaks. Cryoplanation is a variant of pediplanation that is restricted to cold climates. All the cryoplanation surfaces that exists at present date to the Quaternary.

The term cryoplanation was introduced by Kirk Bryan in 1946 and it is a type of frost weathering that often modifies the landscape into terraces. These terraces are called cryoplanation terraces. Czudek described cryoplanation terraces as gently inclined or nearly horizontal bedrock-cut benches on slopes, spurs and on broad interfluves that are formed by the parallel retreat of steeper slope segments under periglacial conditions. Additionally, with the effect of cryoplanation on the landscape, the vegetation on these frost-altered terraces is also reshaped. The vegetation tends to be uniquely uniform both laterally and vertically. The results of this unique freeze-thaw cycle are customarily found in Arctic periglacial regions of Eastern Siberia and Alaska. They may also be found in areas that currently or have sometime in the past experienced intense seasonal freezing or permafrost. Some terraces developed on flood basalt in eastern Lesotho Highlands, Southern Africa, have been suggested to fit the criteria to be cryoplanation terraces.

The concept has been questioned. According to geomorpholigists Kevin Hall and Marie-Françoise André the theory has caused confusion because of “the almost complete absence of actual data from active cryoplanation terraces”. It is considered unlikely that cryoplanation can produce any large surfaces.

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