Everything about Lake Agassiz totally explained
Lake Agassiz was an immense
glacial lake located in the center of
North America. Fed by glacial runoff at the end of the
last glacial period, its area was larger than all of the present-day
Great Lakes combined.
Conception
First postulated in 1823 by
William Keating, it was named after
Louis Agassiz in 1879 after he was the first to realize it was formed by glacial action.
Geological progression
Geologists have come to a consensus on the likely geological progression of Lake Agassiz.
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
Minnesota River, a tributary of the
Mississippi River), into the
Great Lakes, or west through the
Yukon Territory and
Alaska. Climatologists believe that a major outbreak of Lake Agassiz in about 11000 BC drained through the Great Lakes and
Saint Lawrence River into the
Atlantic Ocean. This may be the cause of the
Younger Dryas stadial. A return of the ice for some time offered a reprieve, and after retreating north of the Canadian border about 9,900 years ago it refilled. These events had significant impact on climate, sea level and possible early human civilization.
Much of the final drainage of Lake Agassiz may have occurred in a very short time—perhaps as little as one year. Recent studies by British scientist
Chris Turney links this rapid drainage and subsequent global
sea level rise of about one meter to the expansion of agriculture in Europe, as well as the various flood myths of prehistoric cultures including the
biblical flood.
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, draining into
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.
Other
geological and
geomorphological evidence for Lake Agassiz can also be seen today.
Raised beaches, many kilometers from any water, mark the former boundaries of the lake at various times. Several modern river valleys, including the
Red River, the
Assiniboine River and the
Minnesota River, were originally cut by water entering or leaving the lake. The fertile soils of the
Red River Valley agricultural region are Lake Agassiz
silt.
Further Information
Get more info on 'Lake Agassiz'.
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