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Results for Agassiz, Lake
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A glacial lake of the Pleistocene Epoch extending over present-day northwest Minnesota, northeast North Dakota, southern Manitoba, and southwest Ontario.
Lake Agassiz was an immense lake theorized to be in the center of North America. As such, it was fed by glacial runoff at the end of the last ice age which accumulated into a huge lake that was bigger than all of the present-day Great Lakes combined.
First postulated in 1823 by William Keating, it was
named after
Geologists have come to a consensus on the likely geological progression of Lake Agassiz.
The lake's modern-day remnants, the largest of which is Lake Winnipeg, dominate the geography of Manitoba. Forming around 13,000 calendar years before present (almost 12,000 14C years before present), the lake came to cover much of Manitoba, western Ontario, northern Minnesota, eastern North Dakota, and Saskatchewan. At its greatest extent it may have covered as much as 440,000 square kilometers, larger than any lake currently in the world, or even the Caspian Sea. This is roughly the size of Iraq, the 58th largest country in the world, larger than California, the third largest U.S. state, and smaller than the Yukon, the ninth largest Canadian territory or province.
The lake drained at various times south through the Traverse Gap into Glacial River Warren (parent to the
The last major shift in drainage occurred about 8,400 calendar years before present (about 7,700 14C years before present), when the lake took up its current watershed, that of Hudson Bay. The lake drained nearly completely over the next 1,000 years or so, leaving behind Lake Winnipeg, Lake Winnipegosis, Lake Manitoba, and Lake of the Woods, among others. The outlines and volumes of these lakes are still slowly changing due to differential isostatic rebound. Much of the final drainage of Lake Agassiz may have occurred in a very short time—perhaps as little as one year.
While mostly gone along with the ice sheet that fed it, Lake Agassiz left marks over a large geographic area. Apparent beaches, kilometers or miles from any water, can be found in many locations—these mark the former boundaries of the lake. Several modern river valleys, including the Red River, the Assiniboine River and the aforementioned Minnesota River, were originally cut by water entering or leaving the lake. The Red River Valley agricultural region also exists because of the silt that sank to the bottom of the lake.
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![]() | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more | |
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