What is Ice sheet?
[[File:Antarctica 6400px from Blue Marble.jpg|thumb|250px| One of Earth's two ice sheets: The [[Antarctic ice sheet]] covers 98% of the [[Antarctic]] [[continent]], and is the largest block of ice in the world, with an average thickness of 2 million kilometers.]] [[File:Greenland-ice_sheet_hg.jpg|thumb|250px|Overview: The [[Greenland ice sheet]] covers 80% of [[Denmark]]'s land area, and is the only permanent ice sheet in the world outside [[Antarctica]].]] In [[glaciology]], an '''ice sheet''' ([[Danish language|Danish]]: «Indlandsis», meaning «inland ice»), usually called '''continental glacier''' and sometimes '''ice shell''' or '''ice layer''', is a large mass of [[glacier]] [[ice]] with an average thickness of over 2 km that covers a large continental area in the polar regions of the [[Earth]]. They're located at extreme [[latitude]]s with a conventional area of more than {{convert|50000|km2|sqmi|lk=off}}.<ref>{{cite web|url=http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm|accessdate=2006-08-22|title=Glossary of Important Terms in Glacial Geology|archive-date=2006-08-29|archive-url=https://web.archive.org/web/20060829001754/http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm|url-status=dead}}</ref><ref>{{Cite web |url=http://amsglossary.allenpress.com/glossary/search?id=ice-sheet1 |title=American Meteorological Society, Glossary of Meteorology |access-date=2013-10-17 |archive-date=2012-06-23 |archive-url=https://web.archive.org/web/20120623093132/http://amsglossary.allenpress.com/glossary/search?id=ice-sheet1 |url-status=dead }}</ref> In other geologic time spans, there was a major number and they were covering an larger area, but currently they only cover [[Antarctica]] and [[Greenland]]. This concept might not be confused with the '''[[sea ice]]''' (the floating layer of ice of variant extension that forms in the polar seas), neither the [[ice shelf]] (barrier of ice of glacier origin that spans from the coast to the inner of the ocean) nor the '''[[polar cap]]'''. Ice sheets are