Atarn(orcorrie loch) is a mountainlake,pond or pool, formed in acirque(or "corrie" ) excavated by aglacier.Amorainemay form a naturaldambelow a tarn.[1]
Etymology
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The word isderivedfrom theOld Norsewordtjörn( "a small mountain lake without tributaries" ) meaning pond. In parts ofNorthern England– predominantlyCumberlandandWestmorland(where there are 197),[2]but also areas of NorthLancashireandNorth Yorkshire– 'tarn' is widely used as the name for small lakes orponds,regardless of their location and origin (e.g.Talkin Tarn,Urswick Tarn,Malham Tarn).[3]Similarly, inScandinavian languages,atjernortjørn(both Norwegian) ortjärnortärn(both Swedish) is a small natural lake, often in a forest or with vegetation closely surrounding it or growing into the tarn. The name of theTjörnininReykjavik,Iceland is also from a related word.
The specific technical use for a body of water in a glacial corrie comes from high number of tarns found in corries in theLake District,an upland area in North-West England.[4]Nonetheless, there are many more bodies of water called 'tarn' in the Lake District than actually fit this technical use.
Formation
editTarns are the result of small glaciers calledcirqueglaciers. Glacial cirques (or 'corries') form as hollows on mountainsides near thefirn line.Eventually, the hollow in which a cirque glacier develops may become a large bowl shape in the side of the mountain, caused by weathering, by ice segregation, and as well as being eroded byplucking.The basin will become deeper as it continues to be eroded by ice segregation and abrasion.[5][6]A cirque typically will be partially surrounded on three sides by steepcliffs,with a fourth side a form ofmoraineconstructed fromglacial till,which forms thelip,thresholdorsill,[7]from which either a stream or glacier will flow away from the cirque.
Tarns form from the melting of the cirque glacier. They may either be seasonal features assupraglacial lakes,or permanent features which form in the hollows left by cirques in formerly glaciated areas.[4]
Gallery
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Lousy Lake (tarn) inNorth Cascades National Park,Picket Range,Washington, USA -
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The Dreadful Lake (tarn),Rila Mountain,Bulgaria -
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Sea Lion TarnonLivingston Islandin Antarctica
See also
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References
edit- ^"Illustrated Glossary of Alpine Glacial Landforms".Archived fromthe originalon 2007-08-11.Retrieved2007-08-05.
- ^"Tarn Dipping blog. List of the 197 Tarns in the Lake District, Cumbria".15 March 2016.
- ^"Fresh Water Tarns".Cumbria Wildlife Trust.Archived fromthe originalon 2007-06-27.Retrieved2007-08-05.
- ^abEvans, Ian; Cox, Nick (1995). "The form of glacial cirques in the English Lake District, Cumbria".Zeitschrift für Geomorphologie.2(39): 175-202.Bibcode:1995ZGm....39..175E.doi:10.1127/zfg/39/1995/175.
- ^Johnny W. Sanders; Kurt M. Cuffey; Jeffrey R. Moore; Kelly R. MacGregor; Jeffrey L. Kavanaugh (2012). "Periglacial weathering and headwall erosion in cirque glacier bergschrunds".Geology.40(9): 779–782.Bibcode:2012Geo....40..779S.doi:10.1130/G33330.1.S2CID128580365.
- ^Rempel, A.W.; Wettlaufer, J.S.; Worster, M.G. (2001). "Interfacial Premelting and the Thermomolecular Force: Thermodynamic Buoyancy".Physical Review Letters.87(8): 088501.Bibcode:2001PhRvL..87h8501R.doi:10.1103/PhysRevLett.87.088501.PMID11497990.S2CID10308635.
- ^Evans, I.S. (1971)."8.11(i) The geomorphology and Morphometry of Glacial and Nival Areas".In Chorley R.J. & Carson M.A. (ed.).Introduction to fluvial processes.University paperbacks. Vol. 407. Routledge. p. 218.ISBN978-0-416-68820-7.Retrieved2010-01-24.
External links
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Media related toTarn (lake)at Wikimedia Commons
The dictionary definition oftarnat Wiktionary
