Editing Cirque (section)

{{Short description|Amphitheatre-like valley formed by glacial erosion}}
{{Other uses}}
[[File:Circosabisko.jpg|thumb|Two cirques with semi-permanent snowpatches near [[Abisko National Park]], Sweden]]
[[File:Thornton Lakes 25929.JPG|thumb|Upper Thornton Lake Cirque in [[North Cascades National Park]], U.S.]]

A '''{{Lang|fr|cirque|italic=no}}''' ({{IPA|fr|siʁk|lang}}; from the Latin word {{Lang|la|circus}}) is an [[amphitheatre]]-like [[valley]] formed by [[Glacier#Erosion|glacial erosion]]. Alternative names for this landform are '''corrie''' (from {{langx|gd|coire}}, meaning a pot or [[cauldron]])<ref>{{cite EB1911 |wstitle=Corrie |volume=7 |page=196}}</ref> and {{langnf|cy|'''cwm'''|italic=no|valley|paren=left}}; {{IPA|cy|kʊm|pron}}). A cirque may also be a similarly shaped landform arising from fluvial erosion.

The concave shape of a glacial cirque is open on the downhill side, while the cupped section is generally steep. Cliff-like slopes, down which ice and glaciated debris combine and converge, form the three or more higher sides. The floor of the cirque ends up bowl-shaped, as it is the complex [[convergence zone]] of combining ice flows from multiple directions and their accompanying rock burdens. Hence, it experiences somewhat greater erosion forces and is most often [[overdeepening|overdeepened]] below the level of the cirque's low-side outlet (stage) and its down-slope (backstage) valley. If the cirque is subject to seasonal melting, the floor of the cirque most often forms a [[tarn (lake)|tarn]] (small lake) behind a dam, which marks the downstream limit of the glacial overdeepening. The dam itself can be composed of [[moraine]], [[glacial till]], or a lip of the underlying [[bedrock]].<ref name=Knight2009 />

The fluvial cirque or {{Transliteration|he|[[makhtesh]]}}, found in [[karst]] landscapes, is formed by intermittent river flow cutting through layers of limestone and chalk leaving sheer cliffs. A common feature for all [[fluvial]]-erosion cirques is a terrain which includes erosion resistant upper structures overlying materials which are more easily eroded.