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Friday, July 6, 2007

Proglacial lakes of Minnesota

Present-day Minnesota, with proglacial lakes added in dark blue.
Present-day Minnesota, with proglacial lakes added in dark blue.

Proglacial lakes of the U.S. state of Minnesota in central North America were lakes created in the wake of the melting and retreat of the Laurentide ice sheet in the waning years of the Wisconsin glaciation, the last ice sheet of the Ice Ages. Evidence for these lakes is provided by topography and sedimentary deposits characteristic of lakebeds, referred to as lacustrine deposits on glaciolacustrine landscapes.[1] Not all contemporaneous, these glacial lakes drained after the retreat of the lobes of the ice sheets that blocked their outlets, or whose meltwaters fed them. There were a number of large lakes, one of which was the largest body of freshwater ever known to have existed on the North American continent; there were also innumerable smaller and more transitory lakes filled from glacial meltwater, which shrank or dried as the ice sheet retreated north.

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