tarn (lake)

{{short description|Mountain lake or pool in a glacial cirque}}

{{Redirect|Tarns|the hamlet in England|Tarns, Cumbria}}

File:Glacial Tarn Formation EN.svg

A tarn (or corrie loch) is a mountain lake, pond or pool, formed in a cirque (or "corrie") excavated by a glacier. A moraine may form a natural dam below a tarn.{{cite web | title = Illustrated Glossary of Alpine Glacial Landforms | url = http://www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/glossary.html | access-date = 2007-08-05 | url-status = dead | archive-url = https://web.archive.org/web/20070811170134/http://www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/glossary.html | archive-date = 2007-08-11 }}

Etymology

File:Verdi Leak in The Ruby Mountains.JPG in the Ruby Mountains of Nevada]]

The word is derived from the Old Norse word tjörn ("a small mountain lake without tributaries") meaning pond. In parts of Northern England – predominantly Cumberland and Westmorland (where there are 197),{{cite web | url=https://lakelandrambler.wordpress.com/2016/03/15/tarn-dipping-blog-list-of-the-197-tarns-in-the-lake-district-cumbria/ | title=Tarn Dipping blog. List of the 197 Tarns in the Lake District, Cumbria | date=15 March 2016 }} but also areas of North Lancashire and North Yorkshire – 'tarn' is widely used as the name for small lakes or ponds, regardless of their location and origin (e.g. Talkin Tarn, Urswick Tarn, Malham Tarn).{{cite web | title =Fresh Water Tarns | work = Cumbria Wildlife Trust | url = http://www.wildlifetrust.org.uk/cumbria/Surveys/What%20is%20a%20Tarn.htm | access-date = 2007-08-05 |archive-url = https://web.archive.org/web/20070627105447/http://www.wildlifetrust.org.uk/cumbria/Surveys/What%20is%20a%20Tarn.htm |archive-date = 2007-06-27}} Similarly, in Scandinavian languages, a tjern or tjørn (both Norwegian) or tjärn or tärn (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 the Tjörnin in Reykjavik, Iceland is also from a related word.

The specific technical use for a body of water in a glacial corrie comes from the high number of tarns found in corries in the Lake District, an upland area in North-West England.{{cite journal |last1=Evans |first1=Ian |last2=Cox |first2=Nick |title=The form of glacial cirques in the English Lake District, Cumbria |journal=Zeitschrift für Geomorphologie |date=1995 |volume=2 |issue=39 |page=175-202|doi=10.1127/zfg/39/1995/175 |bibcode=1995ZGm....39..175E }} Nonetheless, there are many more bodies of water called 'tarn' in the Lake District than actually fit this technical use.

The Scots language word shon/shun ("a small loch") may too be derived from Old Norse tjørn, perhaps under the influence of sjø ("sea; fresh water lake").{{cite web |title=SND: shon |url=https://www.dsl.ac.uk/entry/snd/shon |website=Dictionaries of the Scots language |access-date=12 February 2025}}

Formation

Tarns are the result of small glaciers called cirque glaciers. Glacial cirques (or 'corries') form as hollows on mountainsides near the firn 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 by plucking. The basin will become deeper as it continues to be eroded by ice segregation and abrasion.{{cite journal|author1=Johnny W. Sanders |author2=Kurt M. Cuffey |author3=Jeffrey R. Moore |author4=Kelly R. MacGregor |author5=Jeffrey L. Kavanaugh |s2cid=128580365 |year=2012|journal= Geology |doi=10.1130/G33330.1 |volume=40|issue=9|title=Periglacial weathering and headwall erosion in cirque glacier bergschrunds |pages= 779–782|bibcode= 2012Geo....40..779S}}{{cite journal|author1=Rempel, A.W. |author2=Wettlaufer, J.S. |author3=Worster, M.G. |s2cid=10308635 |year=2001|journal=Physical Review Letters|doi=10.1103/PhysRevLett.87.088501|volume=87|issue=8|title=Interfacial Premelting and the Thermomolecular Force: Thermodynamic Buoyancy|page= 088501|pmid=11497990|bibcode=2001PhRvL..87h8501R}} A cirque typically will be partially surrounded on three sides by steep cliffs, with a fourth side a form of moraine constructed from glacial till, which forms the lip, threshold or sill,{{cite book|last=Evans|first=I.S.|title=Introduction to fluvial processes|editor=Chorley R.J. & Carson M.A.|publisher=Routledge|year=1971|series=University paperbacks|volume=407|page=218|chapter=8.11(i) The geomorphology and Morphometry of Glacial and Nival Areas|isbn=978-0-416-68820-7 |chapter-url=https://books.google.com/books?id=X_ENAAAAQAAJ&q=cirque+geomorphology&pg=PA157|access-date=2010-01-24}} 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 as supraglacial lakes, or permanent features which form in the hollows left by cirques in formerly glaciated areas.

Gallery

File:Adirondack Mountains, N.Y.- Lake Tear of the Clouds by Stoddard, Seneca Ray.png|Lake Tear of the Clouds (tarn) in the Adirondack Mountains, New York, photo c. 19th century

File:Velke Hincovo pleso.jpg|Veľké Hincovo, Tatra Mts, the largest and deepest tarn in Slovakia

File:Lousy Lake (tarn) N. Cascades Nat. Park, Pickett Range WA.jpg|Lousy Lake (tarn) in North Cascades National Park, Picket Range, Washington, USA

File:Pond at Lakes of the Clouds.JPG|Lakes of the Clouds, below Mount Washington in the White Mountains

File:Banderishki chukar.JPG|Banderishki Chukar seen from the Banderishki Lakes (tarns), Pirin Mountain, Bulgaria

File:Pirin - Gergiysko ezero, vrah Sinanitsa - IMG 4448.jpg|A view to Gergiysko lake (tarn) and Sinanitsa Peak, Pirin Mountain, Bulgaria

File:Страшното езеро.jpg|The Dreadful Lake (tarn), Rila Mountain, Bulgaria

File:Pogled kum ezerata ot biloto.JPG|The Seven Rila Lakes (tarns), Rila Mountain, Bulgaria

Image:Maritsaorigin2.JPG|Marichini lakes (tarns), the origin of the Maritsa river seen from Musala peak, Rila Mountain, Bulgaria

Sea-Lion-Tarn-2.jpg|Sea Lion Tarn on Livingston Island in Antarctica

See also

References