Geology Along the Lewis & Clark Trail

Geologic Points of Interest

Diversion of the Missouri's Course

Prior to the Ice Age, the Missouri River flowed northward around the Bear Paw Mountains into Canada and the Hudson Bay (A). Ice and end moraines dammed the river during the glacial maximas, creating Glacial Lake Great Falls (B). As the ice retreated, the Missouri flowed down tributaries of the Musselshell and thus created its current course. The concurrent change in gradient product the nip points currently known as the Great Falls. The Milk River now flows through the ancestral Missouri's channel (C) (data from Alden, 1932, base from USGS I-2206).

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