# Wisconsin glaciation

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Glaciation in North America during the Last Glacial Period

Not to be confused with [Weichselian glaciation](/source/Weichselian_glaciation).

Maximum glaciation of the Northern Hemisphere (black) during the Quaternary climatic cycles

The **Wisconsin glaciation**, also called the **Wisconsin glacial episode**, was the [most recent glacial period](/source/Most_recent_glacial_period) of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the [Cordilleran Ice Sheet](/source/Cordilleran_Ice_Sheet), which nucleated in the northern [North American Cordillera](/source/North_American_Cordillera); the [Innuitian ice sheet](/source/Innuitian_ice_sheet), which extended across the [Canadian Arctic Archipelago](/source/Canadian_Arctic_Archipelago); the [Greenland ice sheet](/source/Greenland_ice_sheet); and the massive [Laurentide Ice Sheet](/source/Laurentide_Ice_Sheet),[1] which covered the high latitudes of central and eastern North America. This advance was synchronous with global glaciation during the last glacial period, including the North American [alpine glacier](/source/Glacier#Classification_by_size,_shape_and_behavior) advance, known as the [Pinedale glaciation](/source/Pinedale_glaciation). The Wisconsin glaciation extended from about 75,000 to 11,000 years ago, between the [Sangamonian Stage](/source/Sangamonian_Stage) and the current interglacial, the [Holocene](/source/Holocene). The maximum ice extent occurred about 25,000–21,000 years ago during the [last glacial maximum](/source/Last_glacial_maximum), also known as the *Late Wisconsin* in North America.

The [Last Glacial Period](/source/Last_Glacial_Period) caused a much lower global sea level

This glaciation radically altered the geography north of the [Ohio River](/source/Ohio_River), creating the [Great Lakes](/source/Great_Lakes). At the height of the Wisconsin Episode glaciation, the [ice sheet](/source/Ice_sheet) covered most of [Canada](/source/Canada), the [Upper Midwest](/source/Upper_Midwest), and [New England](/source/New_England), as well as parts of [Idaho](/source/Idaho), [Montana](/source/Montana), and [Washington](/source/Washington_(state)). On [Kelleys Island](/source/Kelleys_Island) in [Lake Erie](/source/Lake_Erie), northern [New Jersey](/source/New_Jersey) and in [New York City](/source/New_York_City)'s [Central Park](/source/Central_Park),[2] the [grooves left in rock](/source/Glacial_striation) by these glaciers can be easily observed. In southwestern [Saskatchewan](/source/Saskatchewan) and southeastern [Alberta](/source/Alberta) a suture zone between the Laurentide and Cordilleran ice sheets formed the [Cypress Hills](/source/Cypress_Hills_(Canada)), North America's northernmost point that remained south of the continental ice sheets. During much of the glaciation, sea level was low enough to permit land animals, including [humans](/source/Humans), to occupy [Beringia](/source/Beringia) (the [Bering Land Bridge](/source/Bering_Land_Bridge)) and move between [North America](/source/North_America) and [Siberia](/source/Siberia). As the glaciers retreated, glacial lakes were breached in great [glacial lake outburst floods](/source/Glacial_lake_outburst_flood) such as the [Kankakee Torrent](/source/Kankakee_Torrent), which reshaped the landscape south of modern Chicago as far as the Ohio and Mississippi Rivers.

## Timeline

Two related movements have been termed Wisconsin: Early Wisconsin and Late Wisconsin.[3]: 40–75 The Early Wisconsin was the bigger of the two and extended farther west and south. It retreated an unknown distance before halting. During this period of quiet, the glacial deposits were eroded and weathered. This first Wisconsin period erased all the [Illinoian](/source/Illinoian) glacial topography that its glaciers extended over.[3] The Late Wisconsin ice sheet extended more towards the west than the earlier movements. This may have been due to changes in the accumulation center of the ice sheet, topographic changes introduced by the Early phase or by pressure changes in the ice mass in the north.[3]

Table I Table VII – Estimated Age of Glacial Episodes (Leverett) [3]: 74 Age Years before Present (YBP) Culmination of Late Wisconsin 50,000 Culmination of Early Wisconsin 100,000 Beginning of Wisconsin 150,000 Culmination of Illinoian 300,000 Beginning of Illinoian 350,000 Culmination of Pre-Illinoian, i.e., old Nebraskan[4][5] 550,000 Beginning of Pre-Illinoian 1,200,000

## Continental ice sheets

### Laurentide ice sheet

Main article: [Laurentide Ice Sheet](/source/Laurentide_Ice_Sheet)

Table III Laurentide Ice Sheet Glacial lobes and sublobes of the southern Laurentide Ice Sheet during the late Wisconsin Glaciation.[6] Major Lobes Minor Lobes Des Moines Grantsburg St. Louis Rainey Lake Superior[7] Wadena Chippewa[7] Wisconsin Valley[7] Langlade[7] Green Bay[7] Lake Michigan[7] Delavan Harvard-Princeton Peoria Decatur Minor lobes: Milwaukee, Two Rivers; Straits of Mackinac Saginaw Lake Huron[7] East White[7] Miami[7] Scioto[7] Lake Erie[7] Lake Ontario[7] Lake Champlain[7] Hudson River[7] unnamed lobe in Quebec – New England Connecticut Valley[7] Buzzards Bay[7] Cape Cod[7] Georges Bank[7]

### Cordilleran ice sheet

Main article: [Cordilleran ice sheet](/source/Cordilleran_ice_sheet)

The Cordilleran Ice Sheet has left remnants throughout the [Northern Rocky Mountains](/source/Northern_Rocky_Mountains), covering [British Columbia](/source/British_Columbia) and reaching into northern [Washington](/source/Washington_(state)) State and [Montana](/source/Montana). The Cordilleran ice sheet has more of an Alpine style of many glaciers merged into a whole. The striations made by the ice field in moving over the bedrock show that it moved principally to the west through the passes of the coast range.[8]

### Innuitian ice sheet

Main article: [Innuitian ice sheet](/source/Innuitian_ice_sheet)

The Innuitian ice sheet was centered on the [Queen Elizabeth Islands](/source/Queen_Elizabeth_Islands).

## Formation of proglacial and prehistoric lakes

A diagram of the formation of the Great Lakes

See also: [List of prehistoric lakes](/source/List_of_prehistoric_lakes)

Whenever the ice sheet melted from the north at a [moraine](/source/Moraine), water would begin to pond in the divide between a moraine and the ice front. The ice would act as a dam as water could not drain through the ice sheet, which in the Wisconsin period covered most of the proglacial river valleys. Numerous small, isolated water bodies formed between the moraine and the ice front. As the ice sheet would continue to melt and recede northward, these ponds combined into [proglacial lakes](/source/Proglacial_lake). In areas without an available outlet, the water levels would either continue to rise until reaching one or more low spots along the rim of a moraine, or the ice sheet would retreat, opening access to a lower portion of the moraine.[3]: 40–99 Multiple outlets could form through low spots too until one would become dominant after erosion lowered both the outlet and lake surface.

### Meltwater

The [Champlain Sea](/source/Champlain_Sea) - The best evidence of this former sea is the vast clay plain deposited along the [Ottawa](/source/Ottawa_River) and [St. Lawrence Rivers](/source/St._Lawrence_River).[9]

Ice melt and rainfall carried large quantities of [clay](/source/Clay), [sand](/source/Sand), and [gravel](/source/Gravel) from the ice mass. Clays could be moved long distances by moving water, while sand and gravel could not. Thus, sand and gravel [landforms](/source/Landforms) developed along the sides and front of the ice sheet;[3] elongated accumulations of this material are known as [kames](/source/Kame). Mounds along the frontal edge of the ice are called [moraines](/source/Moraines). Wherever a subglacial tunnel began infilling, long winding formations known as [eskers](/source/Eskers) would form. The sweeping plain of sand and gravel beyond the ice margin and a [terminal moraine](/source/Terminal_moraine) is called an [outwash plain](/source/Outwash_plain) .[3] The materials left under the glacier when it melts back is called the [ground moraine](/source/Ground_moraine) or [till plain](/source/Till_plain).[3] Till is highly permeable and creates a large ground reserve for water. This formation is highly desirable for human economic development as a source of water.[3]

## Stages of the Wisconsin episode

Table IV Maxima of the Wisconsin ice sheets[10] Western Ice Eastern Ice Estimated years before present Position of ice border Mankato Valders 25,000 Northern Washington, Idaho, and Montana to the Continental Divide – north of Edmonton – 65 miles east of Edmonton – northwest corner of North Dakota – Des Moines – west end of Lake Superior – Milwaukee – Port Huron – Buffalo – Schuylerville – St. Johnsbury. (Great reduction of ice) Cary 27,500 Minneapolis – north Wisconsin – south of Chicago – Central Ohio – 50 miles south of Buffalo – Binghamton - Northampton Tazewell 40,000 Rockford, Ill. – Peoria – south of Indianapolis – north of Cincinnati – northwestern Pennsylvania – central Long Island Iowan No known ice 65,500 Northern Washington, Idaho, and Montana – northwest North Dakota – east central Iowa - Minneapolis

## Role in human migration

Prehistoric human migration was likely greatly influenced by this last glacial period, as during much of the Wisconsin era, the formation of a [land bridge](/source/Land_bridge) known as [Beringia](/source/Beringia) across the [Bering Strait](/source/Bering_Strait) is believed to have allowed human occupation of this area which provided potential access for some of the first humans to move between North America and [Siberia](/source/Siberia) in [Asia](/source/Asia) (see [Settlement of the Americas](/source/Settlement_of_the_Americas)). Other human migration routes also opened during interglacial periods in both [Europe](/source/Europe) and Asia.[11]

## Flora and fauna

North American flora and fauna species were distributed quite differently during the Wisconsin era, due to altered temperatures, surface water distribution, and in some cases coverage of earth surface by glaciers. A number of scientific studies have been conducted to determine species distribution, particularly during the Late Wisconsin and early to mid-Holocene. An example of findings is from the investigation of flora species using [pollen core](/source/Pollen_core) samples in present-day California. Here in the [Waterman Hills](/source/Waterman_Hills) researchers found that *[Juniperus osteosperma](/source/Juniperus_osteosperma)* and *[Pinus monophylla](/source/Pinus_monophylla)* were early to mid-Holocene dominant trees, while *[Monardella arizonica](/source/Monardella_arizonica)* has been a continuously present understory plant. *[Celtis reticulata](/source/Celtis_reticulata)* is an example of a plant present in the early Holocene following Wisconsin glacial retreat, a species no longer present at the [Waterman Mountains](/source/Waterman_Mountains) site.[12]

## See also

- [Geology portal](https://en.wikipedia.org/wiki/Portal:Geology)
- [North America portal](https://en.wikipedia.org/wiki/Portal:North_America)

- [Driftless Area](/source/Driftless_Area) – Geological region in the Midwestern US

- [Geology of Ontario](/source/Geology_of_Ontario)

- [Glacial history of Minnesota](/source/Glacial_history_of_Minnesota)

- [Glacial Lake Iroquois](/source/Glacial_Lake_Iroquois) – Prehistoric lake that became Lake Ontario

- [Ice Age Trail](/source/Ice_Age_Trail) – Long-distance hiking trail in the United States

- [Ice core](/source/Ice_core) – Cylindrical sample drilled from an ice sheet

- [Last Glacial Period](/source/Last_Glacial_Period) – Period of major glaciations of the Northern Hemisphere (115,000–12,000 years ago)

- [Retreat of glaciers since 1850](/source/Retreat_of_glaciers_since_1850) – Recent shrinking of glaciers due to global warming

- [Timeline of glaciation](/source/Timeline_of_glaciation) – Chronology of the major ice ages of the Earth

- [Younger Dryas](/source/Younger_Dryas) – Time period c. 12,900–11,700 years ago

### Pleistocene historic names

Historical names of the "four major" glacials in four regions. Region Glacial 1 Glacial 2 Glacial 3 Glacial 4 Alps Günz Mindel Riss Würm North Europe Eburonian Elsterian Saalian Weichselian British Isles Beestonian Anglian Wolstonian Devensian Midwest U.S. Nebraskan Kansan Illinoian Wisconsinan

Historical names of interglacials. Region Interglacial 1 Interglacial 2 Interglacial 3 Alps Günz-Mindel Mindel-Riss Riss-Würm North Europe Waalian Holsteinian Eemian British Isles Cromerian Hoxnian Ipswichian Midwest U.S. Aftonian Yarmouthian Sangamonian

## References

1. **[^](#cite_ref-Harris1997_1-0)** Ann G. Harris, Esther Tuttle, Sherwood D. Tuttle. 1997. *Geology of National Parks: Fifth Edition*, Iowa, Kendall/Hunt Publishing [ISBN](/source/ISBN_(identifier)) [0-7872-5353-7](https://en.wikipedia.org/wiki/Special:BookSources/0-7872-5353-7)

1. **[^](#cite_ref-2)** SERC Media; Glacial Grooves, Central Park; Image 14884 is a 208 by 173 pixel JPEG; Uploaded: Apr5 09; Wayne Powell, CUNY Brooklyn College; [http://serc.carleton.edu/details/images/14884.html](http://serc.carleton.edu/details/images/14884.html)

1. ^ [***a***](#cite_ref-Sherzer_3-0) [***b***](#cite_ref-Sherzer_3-1) [***c***](#cite_ref-Sherzer_3-2) [***d***](#cite_ref-Sherzer_3-3) [***e***](#cite_ref-Sherzer_3-4) [***f***](#cite_ref-Sherzer_3-5) [***g***](#cite_ref-Sherzer_3-6) [***h***](#cite_ref-Sherzer_3-7) [***i***](#cite_ref-Sherzer_3-8) Chapter II. Glacial History of the Huron-Erie Basin; Geological Report on Wayne County; W.H. Sherzer; Michigan Geological and Biological Survey, Publication 12, Geological Series 9; Lansing, Michigan; Wynkoop Hallenbeck Crawford Co., State Printers; 1913

1. **[^](#cite_ref-Attig_4-0)** Attig, John W.; Mickelson, David M. (1999). Glacial processes past and present. Boulder, Colo: The Geological Society of America, Inc. [ISBN](/source/ISBN_(identifier)) [0-8137-2337-X](https://en.wikipedia.org/wiki/Special:BookSources/0-8137-2337-X)

1. **[^](#cite_ref-5)** Boellstorff, J (1978). "Chronology of some Late Cenozoic deposits from the central United States and the Ice Ages"(pdf). Transactions of the Nebraska Academy of Science 6: 35–49. Retrieved 2012-04-04.

1. **[^](#cite_ref-6)** The southern Laurentide Ice Sheet; Cavid M. Mickelson and Patrick M. Colgan; Department of Geology, University of Wisconsin Madison; Madison, Wisconsin; 2003

1. ^ [***a***](#cite_ref-Hill_7-0) [***b***](#cite_ref-Hill_7-1) [***c***](#cite_ref-Hill_7-2) [***d***](#cite_ref-Hill_7-3) [***e***](#cite_ref-Hill_7-4) [***f***](#cite_ref-Hill_7-5) [***g***](#cite_ref-Hill_7-6) [***h***](#cite_ref-Hill_7-7) [***i***](#cite_ref-Hill_7-8) [***j***](#cite_ref-Hill_7-9) [***k***](#cite_ref-Hill_7-10) [***l***](#cite_ref-Hill_7-11) [***m***](#cite_ref-Hill_7-12) [***n***](#cite_ref-Hill_7-13) [***o***](#cite_ref-Hill_7-14) [***p***](#cite_ref-Hill_7-15) [***q***](#cite_ref-Hill_7-16) [***r***](#cite_ref-Hill_7-17) Geological Framework and Glaciation of the Eastern Area; Christopher L. Hill; pg 82-98

1. **[^](#cite_ref-C&S3_8-0)** Chamberlin, Thomas C. and Salisbury, Rollin T., Geology, 3 Vols. 1906, Vol III., pp. 330-333.

1. **[^](#cite_ref-9)** Chapman, L.J. and D.F. Putnam. 1984. *The Physiography of Southern Ontario*. Third edition. Ontario Geological Survey, Special Volume No.2. Government of Ontario, Toronto.

1. **[^](#cite_ref-10)** Correlation of Wisconsin Glacial Maxima; Ernst Antevs; ca 1943; The Quaternary Geology of Southeastern Wisconsin with a Chapter on the Older Rock Formations, Professional Paper 106; William C. Alden; United States Geological Survey; Government Printing Office, Washington, D.C.; 1918

1. **[^](#cite_ref-Harm2005_11-0)** Harm J. De Blij. 2005. *Why geography matters: three challenges facing America*, 308 pages, p.69

1. **[^](#cite_ref-Hogan2009_12-0)** [C. Michael Hogan, 2009. *Elephant Tree: Bursera microphylla*, GlobalTwitcher.com, ed. N. Stromberg](http://www.globaltwitcher.com/artspec_information.asp?thingid=90792)

## External links and references

- [Wisconsin Glacial Stage](https://www.britannica.com/science/Wisconsin-Glacial-Stage) at the [Encyclopædia Britannica](/source/Encyclop%C3%A6dia_Britannica)

v t e Continental glaciations General Post-glacial rebound Glacial lake outburst flood Time periods Glacial period Timeline of glaciation Quaternary glaciation Illinoian Stage Interglacial Interstadial Penultimate Glacial Period Last Glacial Period Last Glacial Maximum Mousterian Pluvial Holocene glacial retreat Oldest Dryas Older Dryas Pleistocene Pre-Illinoian Stage Quaternary glaciation Sangamonian Stage Wisconsin glaciation Bølling–Allerød warming Late Glacial Interstadial Huelmo–Mascardi Cold Reversal Younger Dryas 8.2 kiloyear event 4.2 kiloyear event Piora Oscillation Little Ice Age Landforms Erosional Fjord Glacial striae Roche moutonnée Tunnel valley U-shaped valley Glacial lake Proglacial lake Subglacial lake Supraglacial lake Ribbon lake List of prehistoric lakes Depositional Drumlin Erratic block Moraine Pulju moraine Rogen moraine Terminal moraine Till plain Veiki moraine Glacifluvial Diluvium Esker Giant current ripples Kame Kame delta Kettle hole Outwash fan Sandur North America Greenland ice sheet Canadian Shield Cordilleran ice sheet Laurentide ice sheet Lake Agassiz Lake Chicago Lake Tight Canada Arrowhead Provincial Park, Ontario Big Rock (glacial erratic), Alberta Cypress Hills (Canada), Saskatchewan Eramosa River, Ontario Eskers Provincial Park, British Columbia Foothills Erratics Train, Alberta Lion's Head Provincial Park, Ontario Origin of the Oak Ridges Moraine, Ontario Ovayok Territorial Park, Nunavut United States Lake Bonneville, Utah Lake Lahontan, Nevada Lake Missoula, Montana Glacial Lake Wisconsin, Wisconsin Chippewa Moraine State Recreation Area, Wisconsin Coteau des Prairies, South Dakota Devil's Lake State Park, Wisconsin Glacial Lakes State Park, Minnesota Glacial history of Minnesota Horicon Marsh State Wildlife Area, Wisconsin Ice Age Floods National Geologic Trail, Idaho, Oregon and Washington Ice Age National Scientific Reserve, Wisconsin Ice Age Trail, Wisconsin Interstate State Park, Minnesota and Wisconsin Kelleys Island, Ohio Teays River, Ohio Kettle Moraine State Forest, Wisconsin Mill Bluff State Park, Wisconsin Oneida Lake, New York Two Creeks Buried Forest State Natural Area, Wisconsin Withrow Moraine and Jameson Lake Drumlin Field, Washington Yosemite National Park, California Eurasia Hardangerfjord Killary Harbour Monte Rosa Svalbard Antarctica Antarctic Glaciation Antarctic ice sheet (East, West) Lambert Glacier Ross Ice Shelf Category

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Adapted from the Wikipedia article [Wisconsin glaciation](https://en.wikipedia.org/wiki/Wisconsin_glaciation) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Wisconsin_glaciation?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.