Editing Glacier (section)

=== Classification by size, shape and behavior ===
{{Further|Glacier morphology}}
[[File:Quelccaya Glacier.jpg|left|thumb|The [[Quelccaya Ice Cap]] in Peru is the second-largest glaciated area in the tropics]]
Glaciers are categorized by their morphology, thermal characteristics, and behavior. ''[[Alps|Alpine]] glaciers'' form on the crests and slopes of mountains. A glacier that fills a valley is called a ''valley glacier'', or alternatively, an ''alpine glacier'' or ''mountain glacier''.<ref>{{cite web |url=https://pubs.usgs.gov/of/2004/1216/text.html |title=Glossary of Glacier Terminology |publisher=USGS |access-date=2017-03-13}}</ref> A large body of glacial ice astride a mountain, mountain range, or [[volcano]] is termed an ''[[ice cap]]'' or ''[[ice field]]''.<ref>{{cite web |url=http://www.nichols.edu/departments/glacier/juneau%20icefield.htm |title=Retreat of Alaskan glacier Juneau icefield |publisher=Nichols.edu |access-date=2009-01-05 |archive-date=2017-10-23 |archive-url=https://web.archive.org/web/20171023193102/http://www.nichols.edu/departments/glacier/juneau%20icefield.htm |url-status=dead }}</ref> Ice caps have an area less than {{convert|50,000|km2|sqmi|abbr=on}} by definition.

Glacial bodies larger than {{convert|50,000|km2|sqmi|abbr=on}} are called ''[[ice sheet]]s'' or ''continental glaciers''.<ref>{{cite web |url=http://amsglossary.allenpress.com/glossary/search?id=ice-sheet1 |publisher=American Meteorological Society |title=Glossary of Meteorology |access-date=2013-01-04 |url-status=dead |archive-url=https://web.archive.org/web/20120623093132/http://amsglossary.allenpress.com/glossary/search?id=ice-sheet1 |archive-date=2012-06-23}}</ref> Several kilometers deep, they obscure the underlying topography. Only [[nunatak]]s protrude from their surfaces. The only extant ice sheets are the two that cover most of Antarctica and Greenland.<ref>{{Cite web |url=https://www4.uwsp.edu/geo/faculty/lemke/geol370/activities/02_Morphological_Classification_of_Glaciers.pdf |archive-url=https://web.archive.org/web/20170812133941/https://www4.uwsp.edu/geo/faculty/lemke/geol370/activities/02_Morphological_Classification_of_Glaciers.pdf |archive-date=2017-08-12 |url-status=live |title=Morphological Classification of Glaciers |author=[[University of Wisconsin]], Department of Geography and Geology |date=2015 |website=www.uwsp.edu/Pages/default.aspx}}</ref> They contain vast quantities of freshwater, enough that if both melted, global sea levels would rise by over {{convert|70|m|ft|abbr=on}}.<ref>{{cite web |url=http://pubs.usgs.gov/fs/fs2-00/ |title=Sea Level and Climate |work=USGS FS 002-00 |publisher=[[USGS]] |date=2000-01-31 |access-date=2009-01-05}}</ref> Portions of an ice sheet or cap that extend into water are called [[ice shelves]]; they tend to be thin with limited slopes and reduced velocities.<ref name="NSIDC">{{cite web|publisher=[[National Snow and Ice Data Center]] |website=nsidc.org |title=Types of Glaciers |url=http://www.nsidc.org/glaciers/questions/types.html |url-status=dead |archive-url=https://web.archive.org/web/20100417222017/http://nsidc.org/glaciers/questions/types.html |archive-date=2010-04-17}}</ref> Narrow, fast-moving sections of an ice sheet are called ''[[ice streams]]''.<ref>{{Cite journal |last1=Bindschadler |first1=R.A. |first2=T.A. |last2=Scambos |s2cid=17336434 |title=Satellite-image-derived velocity field of an Antarctic ice stream |journal=[[Science (journal)|Science]] |volume=252 |issue=5003 |pages=242–46 |year=1991 |doi=10.1126/science.252.5003.242 |pmid=17769268|bibcode=1991Sci...252..242B}}</ref><ref name=BAS2009>{{cite web |title=Description of Ice Streams |url=http://www.antarctica.ac.uk/about_antarctica/geography/ice/streams.php |publisher=[[British Antarctic Survey]] |access-date=2009-01-26 |url-status=dead |archive-url=https://web.archive.org/web/20090211004629/http://www.antarctica.ac.uk/about_antarctica/geography/ice/streams.php |archive-date=2009-02-11}}</ref> In Antarctica, many ice streams drain into large [[ice shelf|ice shelves]]. Some drain directly into the sea, often with an [[ice tongue]], like [[Mertz Glacier]].

''[[Tidewater glacier cycle|Tidewater glaciers]]'' are glaciers that terminate in the sea, including most glaciers flowing from Greenland, Antarctica, [[Baffin Island|Baffin]], [[Devon Island|Devon]], and [[Ellesmere Island]]s in Canada, [[Southeast Alaska]], and the [[Northern Patagonian Ice Field|Northern]] and [[Southern Patagonian Ice Field]]s. As the ice reaches the sea, pieces break off or calve, forming [[iceberg]]s. Most tidewater glaciers calve above sea level, which often results in a tremendous impact as the iceberg strikes the water. Tidewater glaciers undergo centuries-long [[tidewater glacier cycle|cycles of advance and retreat]] that are much less affected by climate change than other glaciers.<ref>{{Cite web |url=https://nsidc.org/cryosphere/glaciers/questions/types.html |title=What types of glaciers are there? |publisher=[[National Snow and Ice Data Center]] |website=nsidc.org |access-date=2017-08-12}}</ref>