Lake Agassiz
Coordinates: 51°N 98°W / 51°N 98°W
Lake Agassiz was a very large glacial lake located in the middle of the northern part of North America. Fed by glacial meltwater at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined though its mean depth was not as great as that of many major lakes today.
First postulated in 1823 by William H. Keating, it was named by Warren Upham in 1879 after Louis Agassiz, when Upham recognized that the lake was formed by glacial action.
During the last Ice Age, northern North America was covered by a glacier, which alternately advanced and melted with variations in the climate. This continental ice sheet formed during the period now known as the Wisconsin glaciation, and covered much of central North America between 30,000 and 10,000 years ago. As the ice sheet disintegrated, it created at its front an immense proglacial lake, formed from its meltwaters, as the retreat of glacial margins is not caused by a reversal of the glacier's flow, but rather from melting of the ice sheet.
Around 13,000 years ago, the lake came to cover much of Manitoba, northwestern Ontario, northern Minnesota, eastern North Dakota, and Saskatchewan. At its greatest extent, it may have covered as much as 440,000 km2 (170,000 sq mi), larger than any currently existing lake in the world (including the Caspian Sea) and approximately the size of the Black Sea.
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