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Nunatak

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For other uses, seeNunatak (disambiguation).
Starr Nunatak,on the coast ofVictoria Land,Antarctica
Cântaro Magro,Serra da Estrela,Portugal,formed as anunatakduring thelast ice ageand now exposed.[1]

Anunatak(fromInuitnunataq) is the summit or ridge of a mountain that protrudes from an ice field orglacierthat otherwise covers most of the mountain or ridge. They often form naturalpyramidal peaks.Isolated nunataks are also calledglacial islands,[2]and smaller nunataks rounded by glacial action may be referred to asrognons.[3][4]

The word is ofGreenlandicorigin[5]and has been used in English since the 1870s.

Description

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The term nunatak is typically used in areas where a permanentice sheetis present and the ridge protrudes above the sheet.[6]Nunataks present readily identifiable landmark reference points in glaciers or ice caps and are often named. While some are isolated, they can also form dense clusters, such asQueen Louise Landin Greenland.[7]

Nunataks are generally angular and jagged, hampering the formation of glacial ice on their tops, although snow can accumulate on them. This can contrast strongly with the softer contours of the glacially eroded land after a glacier retreats. They are not greatly affected byfrost weathering,given the low frequency of freeze-thaw cycles in areas of ice caps and ice sheets.[8][page needed]

Typically nunataks are the only places where plant life can survive on ice sheets or ice caps. Lifeforms on nunataks are often isolated by the surrounding ice or glacier, providing unique habitats.[9]

List

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Main article:List of nunataks

See also

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  • Fell– High and barren landscape feature
  • Glacial landform– Landform created by the action of glaciers

References

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  1. ^ Vieira, G.T.; Ferreira, A.B. (1998)."General characteristics of the glacial geomorphology of the Serra da Estrela"(PDF).In G.T. Vieira (ed.).Glacial and Periglacial Geomorphology of the Serra da Estrela. Guidebook for the field-trip IGU Commission on Climate Change and Periglacial Environments, 26–28 August 1998.pp. 37–48.RetrievedOctober 16,2011.
  2. ^Physical Geography: Hydrosphere,2006,ISBN8183561675,p. 114
  3. ^Neuendorf, Klaus K. E.; Institute, American Geological (2005).Glossary of Geology.Springer Science & Business Media.ISBN9780922152766.
  4. ^"Rognon definition and meaning | Collins English Dictionary".collinsdictionary.Retrieved2019-02-06.
  5. ^ "Merriam-Webster: nunatak".RetrievedOctober 16,2011.
  6. ^J. J. Zeeberg,Climate and Glacial History of the Novaya Zemlya Archipelago, Russian Arctic.pp. 82–84
  7. ^"Dronning Louise Land".Mapcarta.Retrieved2 July2016.
  8. ^Tricart, Jean;Cailleux, André(1968).Introduction à la Géomorphologie Climatique(in French).
  9. ^ice cap – National Geographic Society
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