palsa
Link: http://w3id.org/permafrost/v/ipaglossary/t0228
Within: IPA Permafrost Glossary
Definition: A peaty permafrost mound possessing a core of alternating layers of segregated ice and peat or mineral soil material (see Figures 14 and 15a).
| Term |
palse
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palsa en |
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| Comment |
Palsas are typically between 1 and 7 m in height and a few metres to 100 m in diameter. The term is of Fennoscandian origin, originally meaning ". a hummock rising out of a bog with a core of ice" (Seppälä, 1972). Implicit in this definition are their constructional nature, their origin in wetlands (fens or peat bogs), and that ice segregation in mineral soil beneath peat is the process responsible for growth. Most, but not all, palsas occur in the discontinuous permafrost zone. A more general definition has been proposed by Washburn (1983) in which the term is applied in a descriptive sense to a broader range of permafrost mounds that may include intrusive as well as segregated ice: "Palsas are peaty permafrost mounds, ranging from about 0.5 to about 10 m in height and exceeding about 2 m in average diameter, comprising (1) aggradation forms due to permafrost aggradation at an active-layer/permafrost contact zone, and (2) similar-appearing degradation forms due to disintegration of an extensive peaty deposit". The disadvantage of this broader definition is that mounds of entirely different origins (e.g., those including intrusive ice) are grouped under one term. It is proposed, therefore, that the term "palsa" be restricted to those features where the internal structure shows the presence of segregated ice and where the environment lacks high hydraulic potentials, provided that other parameters (size, shape, location in wetlands) are also satisfied. The term "frost mound" should be used as a non- genetic term to describe the range of morphologically similar, but genetically different, features that occur in permafrost terrain.
en
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| dcterms:source |
https://doi.org/10.4224/20386561
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| skos:hiddenLabel |
peat hummock
en
peat mound en |