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The Coteau des Prairies

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Coteau des Prairies
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The north-pointing, flatiron-shaped Coteau des Prairies in eastern South Dakota is arguably the most conspicuous landform of the U.S. Midcontinent shown on this map. Some 200 miles (320 km) long, the low plateau of thick glacial deposits is underlain by a small ridge of resistant Cretaceous shale. Moving south along pre-glacial stream valleys just to the west and east, respectively, the James River and Des Moines Lobes of the last Pleistocene ice sheet probably parted at the stream divide preexisting the present Coteau ("hill" in French) and further deepened its flanking lowlands- which then drained meltwater as the glaciers retreated to the north.

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Last Modification: 18 Oct 2000 (ebj)
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