Agassiz(redirected from Agassiz, Jean Louis Rodolphe)
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freshwater, glacier-formed lake which existed around 10,000–12,000 years ago along the edge of the retreating glacial mantle in North America. It extended 1,100 km from north to south and 400 km from west to east, with a maximum depth of more than 200 m. Lake Agassiz drained into the Mississippi River through the valleys of the Warren and Minnesota rivers. It existed for about 1,000 years and then was drained by the Nelson River, which formed a valley to the Hudson Bay. Remaining on the site of Lake Agassiz are Lake Winnipeg, Lake Manitoba, Lake Winnipegosis, Lake of the Woods, and others, as well as a broad belt of flat plains composed of varved clays, with fertile, gray forest gley (clay) soils. Farming is widely developed in these plains. The lake was named in honor of the Swiss naturalist J. Agassiz.