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Nunatak

From Wikipedia, the free encyclopedia
For other uses, see Nunatak (disambiguation).
Nunataks in Antarctica
Cântaro Magro, Serra da Estrela, Portugal, formed as a nunatak during the last ice age and now exposed[1]

A nunatak (from Inuit nunataq) is the summit or ridge of a mountain that protrudes from an ice field or glacier that otherwise covers most of the mountain or ridge. They often form natural pyramidal peaks. Isolated nunataks are also called glacial islands,[2] and smaller nunataks rounded by glacial action may be referred to as rognons.[3][4]

The word is of Greenlandic origin[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 permanent ice sheet is 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 as Queen Louise Land in 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 by frost 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. Retrieved October 16, 2011.
  2. ^ Physical Geography: Hydrosphere, 2006, ISBN 8183561675, p. 114
  3. ^ Neuendorf, Klaus K. E.; Institute, American Geological (2005). Glossary of Geology. Springer Science & Business Media. ISBN 9780922152766.
  4. ^ "Rognon definition and meaning | Collins English Dictionary". www.collinsdictionary.com. Retrieved 2019-02-06.
  5. ^ "Merriam-Webster: nunatak". Retrieved October 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. Retrieved 2 July 2016.
  8. ^ Tricart, Jean; Cailleux, André (1968). Introduction à la Géomorphologie Climatique (in French).
  9. ^ ice cap – National Geographic Society
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