Editing Pyramidal peak (section)

==Formation==
[[File:Cirques mountainmass en.svg|thumb|upright=1.3|Cross-section of cirque erosion over time]]
[[File:Kinnerly Peak.jpg|thumb|left|[[Kinnerly Peak]] in [[Glacier National Park (U.S.)|Glacier National Park]] in the U.S. state of [[Montana]]|alt=]]
[[Glacier]]s, typically forming in drainages on the sides of a mountain, develop bowl-shaped [[depression (geology)|basins]] called [[cirque]]s (sometimes called 'corries' – from [[Scottish Gaelic]] {{lang|gd|coire}} [kʰəɾə] (a bowl) – or {{lang|cy|cwm}}s). Cirque glaciers have rotational sliding that abrades the floor of the basin more than walls and that causes the bowl shape to form. As cirques are formed by glaciation in an alpine environment, the [[headwall]] and ridges between parallel glaciers called [[arête]]s become more steep and defined. This occurs due to [[Frost wedging|freeze/thaw]] and mass wasting beneath the ice surface. It is widely held{{by whom|date=November 2012}} that a common cause for headwall steepening and extension headward is the [[crevasse]]s known as [[bergschrund]] that occur between the moving ice and the headwall. [[Plucking (glaciation)|Plucking]] and shattering can be seen here by those exploring the crevasses. A cirque is exposed when the glacier that created it recedes.{{Citation needed|date=February 2021}}

When three or more of these cirques converge on a central point, they create a pyramid-shaped peak with steep walls. These horns are a common shape for mountain tops in highly glaciated areas. The number of faces of a horn depends on the number of cirques involved in the formation of the peak: three to four is most common. Horns with more than four faces include the [[Weissmies]] and the [[Mönch]].<ref name="embleton">{{cite book | first1=Clifford | title=Glacial and Periglacial Geomorphology | publisher=St. Martin's Press | last2=King | first2=Cuchlaine A. | last1=Embleton | author-link1 = Clifford Embleton| author-link2 = Cuchlaine King| lccn=68-20348 | year=1968 | location=New York | page=193}}</ref> A peak with four symmetrical faces is called a ''Matterhorn'' (after the [[Matterhorn]], a mountain in the Alps).<ref>{{cite web | url=http://pubs.usgs.gov/of/2004/1216/text.html#h | title=Glossary of Glacier Terminology | publisher=[[US Geological Survey]] | access-date=12 October 2012}}</ref>

The peak of a glacial horn will often outlast the arêtes on its flanks.<ref name="embleton" /> As the rock around it erodes, the horn gains in prominence. Eventually, a glacial horn will have near vertical faces on all sides.{{citation needed|date=October 2012}} In the [[Alps]], "horn" is also the name of very exposed peaks with slope inclinations of 45-60° (e.g. [[Kitzbüheler Horn]]).{{citation needed|date=October 2012}}