Editing Ice age (section)

==Recent glacial and interglacial phases==
{{Main|Timeline of glaciation}}
[[File:Northern icesheet hg.png|thumb|upright=1.25|Northern hemisphere glaciation during the last ice ages. The setup of 3 to 4 kilometer thick ice sheets caused a [[sea level rise|sea level lowering]] of about 120&nbsp;m.]]

The current geological period, the [[Quaternary]], which began about 2.6 million years ago and extends into the present,<ref name="ICSchart2013"/> is marked by warm and cold episodes, cold phases called [[Glacial period|glacials]] ([[Quaternary glaciation|Quaternary ice age]]) lasting about 100,000 years, and warm phases called [[interglacial]]s lasting 10,000–15,000 years. The last cold episode of the [[Last Glacial Period]] ended about 10,000 years ago.<ref>{{cite magazine|url=https://www.nationalgeographic.com/science/prehistoric-world/quaternary|archive-url=https://web.archive.org/web/20170320053318/http://www.nationalgeographic.com/science/prehistoric-world/quaternary/|url-status=dead|archive-date=March 20, 2017|title=Quaternary Period|magazine=National Geographic|date=2017-01-06}}</ref> Earth is currently in an interglacial period of the Quaternary, called the [[Holocene]].

===Glacial stages in North America===
{{See also|Glacial history of Minnesota}}
The major glacial stages of the current ice age in North America are the [[Illinoian (stage)|Illinoian]], [[Eemian]], and [[Wisconsin glaciation]]. The use of the Nebraskan, Afton, Kansan, and Yarmouthian stages to subdivide the ice age in North America has been discontinued by Quaternary geologists and geomorphologists. These stages have all been merged into the [[Pre-Illinoian]] in the 1980s.<ref name="Hallberg1">{{cite journal |author=Hallberg, G.R. |title=Pre-Wisconsin glacial stratigraphy of the Central Plains region in Iowa, Nebraska, Kansas, and Missouri |journal=Quaternary Science Reviews |volume=5 |pages=11–15 |year=1986 |doi=10.1016/0277-3791(86)90169-1 |bibcode = 1986QSRv....5...11H}}</ref><ref name="RichmondOther1">{{cite journal |author1=Richmond, G.M. |author2=Fullerton, D.S. |title=Summation of Quaternary glaciations in the United States of America |journal=Quaternary Science Reviews |volume=5 |pages=183–196 |year=1986 |doi=10.1016/0277-3791(86)90184-8 |bibcode = 1986QSRv....5..183R}}</ref><ref name="GibbardOthers2007">Gibbard, P.L., S. Boreham, K.M. Cohen and A. Moscariello, 2007, [http://www.quaternary.stratigraphy.org.uk/correlation/POSTERSTRAT_v2007b_small.jpg ''Global chronostratigraphical correlation table for the last 2.7 million years v. 2007b.''] {{Webarchive|url=https://web.archive.org/web/20080910122430/http://www.quaternary.stratigraphy.org.uk/correlation/POSTERSTRAT_v2007b_small.jpg |date=2008-09-10 }}, jpg version 844 KB. Subcommission on Quaternary Stratigraphy, Department of Geography, University of Cambridge, Cambridge, England</ref>

During the most recent North American glaciation, during the latter part of the [[Last Glacial Maximum]] (26,000 to 13,300 years ago), ice sheets extended to about [[45th parallel north]]. These sheets were {{convert|3 to 4|km}} thick.<ref name="RichmondOther1"/>
[[File:Glacial lakes.jpg|thumb|right|Stages of [[proglacial lake]] development in the region of the current North American [[Great Lakes]]]]

This Wisconsin glaciation left widespread impacts on the North American landscape. The [[Great Lakes]] and the [[Finger Lakes]] were carved by ice deepening old valleys. Most of the lakes in Minnesota and Wisconsin were gouged out by glaciers and later filled with glacial meltwaters. The old [[Teays River]] drainage system was radically altered and largely reshaped into the [[Ohio River]] drainage system. Other rivers were dammed and diverted to new channels, such as [[Niagara Falls]], which formed a dramatic waterfall and gorge, when the waterflow encountered a limestone escarpment. Another similar waterfall, at the present [[Clark Reservation State Park]] near [[Syracuse, New York]], is now dry.

The area from [[Long Island]] to [[Nantucket, Massachusetts]] was formed from glacial [[till]], and the plethora of lakes on the [[Canadian Shield]] in northern Canada can be almost entirely attributed to the action of the ice. As the ice retreated and the rock dust dried, winds carried the material hundreds of miles, forming beds of [[loess]] many dozens of feet thick in the [[Missouri River|Missouri Valley]]. [[Post-glacial rebound]] continues to reshape the Great Lakes and other areas formerly under the weight of the ice sheets.

The [[Driftless Area]], a portion of western and southwestern Wisconsin along with parts of adjacent [[Minnesota]], [[Iowa]], and [[Illinois]], was not covered by glaciers.

===Last Glacial Period in the semiarid Andes around Aconcagua and Tupungato===
A specially interesting climatic change during glacial times has taken place in the semi-arid Andes. Beside the expected cooling down in comparison with the current climate, a significant precipitation change happened here. So, researches in the presently semiarid subtropic Aconcagua-massif (6,962&nbsp;m) have shown an unexpectedly extensive glacial glaciation of the type "ice stream network".<ref>{{cite journal |author=Kuhle, M. |title=Spuren hocheiszeitlicher Gletscherbedeckung in der Aconcagua-Gruppe (32–33° S) |journal=Zentralblatt für Geologie und Paläontologie, Teil I |volume=11/12 |pages=1635–46 |year=1984 |issn=0340-5109}} Verhandlungsblatt des Südamerika-Symposiums 1984 in Bamberg.</ref><ref>{{cite journal |author=Kuhle, M. |title=Die Vergletscherung Tibets und die Entstehung von Eiszeiten |journal=Spektrum der Wissenschaft |issue=9/86 |pages=42–54 |year=1986 |issn=0170-2971}}</ref><ref>{{cite journal |author=Kuhle, Matthias |title=Subtropical Mountain- and Highland-Glaciation as Ice Age Triggers and the Waning of the Glacial Periods in the Pleistocene |journal=GeoJournal |volume=14 |issue=4 |pages=393–421 |date=June 1987 |jstor=41144132 |doi=10.1007/BF02602717|bibcode=1987GeoJo..14..393M |s2cid=129366521 }}</ref><ref name=Kuhle04>{{cite book |author=Kuhle, M. |chapter=The Last Glacial Maximum (LGM) glacier cover of the Aconcagua group and adjacent massifs in the Mendoza Andes (South America) |chapter-url=https://books.google.com/books?id=2xpIEPH7RW4C&pg=PA75 |editor1=Ehlers, J. |editor2=Gibbard, P.L. |title=Quaternary Glaciations: South America, Asia, Africa, Australasia, Antarctica |publisher=Elsevier |location=Amsterdam |year=2004 |isbn=978-0-444-51593-3 |pages=75–81 |url=https://books.google.com/books?id=2xpIEPH7RW4C |series=Development in Quaternary Science}}</ref><ref name=Kuhle11>{{cite book |author=Kuhle, M. |chapter=Ch 53: The High-Glacial (Last Glacial Maximum) Glacier Cover of the Aconcagua Group and Adjacent Massifs in the Mendoza Andes (South America) with a Closer Look at Further Empirical Evidence |chapter-url=https://books.google.com/books?id=Jv4uA1lHezEC&pg=PA735 |editor1=Ehlers, J. |editor2=Gibbard, P.L. |editor3=Hughes, P.D. |title=Quaternary Glaciations – Extent and Chronology: A Closer Look |publisher=Elsevier |location=Amsterdam |year=2011 |isbn=978-0-444-53447-7 |pages=735–8 |url=https://books.google.com/books?id=Jv4uA1lHezEC |series=Development in Quaternary Science}}</ref> The connected valley glaciers exceeding 100&nbsp;km in length, flowed down on the East-side of this section of the Andes at 32–34°S and 69–71°W as far as a height of 2,060&nbsp;m and on the western luff-side still clearly deeper.<ref name=Kuhle11/><ref>{{cite journal |author=Brüggen, J. |title=Zur Glazialgeologie der chilenischen Anden |journal=Geol. Rundsch. |volume=20 |issue=1 |pages=1–35 |year=1929 |doi=10.1007/BF01805072|bibcode=1929GeoRu..20....1B |s2cid=128436981 }}</ref> Where current glaciers scarcely reach 10&nbsp;km in length, the snowline (ELA) runs at a height of 4,600&nbsp;m and at that time was lowered to 3,200&nbsp;m [[Above sea level|asl]], i.e. about 1,400&nbsp;m. From this follows that—beside of an annual depression of temperature about c. 8.4&nbsp;°C— here was an increase in precipitation. Accordingly, at glacial times the humid climatic belt that today is situated several latitude degrees further to the S, was shifted much further to the N.<ref name=Kuhle04/><ref name=Kuhle11/>