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Concept
Periglaciation
Résumé
Periglaciation (adjective: "periglacial", referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing and freezing, very often in areas of permafrost. The meltwater may refreeze in ice wedges and other structures. "Periglacial" originally suggested an environment located on the margin of past glaciers. However, freeze and thaw cycles influence landscapes also outside areas of past glaciation. Therefore, periglacial environments are anywhere when freezing and thawing modify the landscape in a significant manner.
Periglaciation became a distinct subject within the study of geology after Walery Łoziński, a Polish geologist, introduced the term in 1909. Łoziński drew upon the early work of Johan Gunnar Andersson. According to Alfred Jahn, his introduction of his work at the 1910 International Geological Congress held in Stockholm caused significant discussion. In the field trip to Svalbard that followed the congress participants were able to observe the phenomena reported by Łoziński, directly. Łoziński published his contribution to the congress in 1912. From 1950 to 1970, periglacial geomorphology developed chiefly as a subdiscipline of climatic geomorphology that was current in Europe at the time. The journal Biuletyn Peryglacjalny, established in 1954 by Jan Dylik, was important for the consolidation of the discipline.
Climatic geomorphology
Albeit the definition of what a periglacial zone is not clear-cut, a conservative estimate is that a quarter of Earth's land surface has periglacial conditions. Beyond this quarter an additional quarter or fifth of Earth's land surface had periglacial conditions at some time during the Pleistocene. In the northern hemisphere larger swathes of northern Asia and northern North America are periglaciated. In Europe parts of Fennoscandia, Iceland, northern European Russia and Svalbard. In addition Alpine areas in the non-arctic northern hemisphere might also be subject to periglaciation.
Source officielle
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