Geology of Minnesota: Minnehaha Falls
N 44° 54.922 W 093° 12.578
15T E 483453 N 4973570
Marker describing the geology of the Minnehaha Falls area.
Waymark Code: WM70NY
Location: Minnesota, United States
Date Posted: 08/15/2009
Views: 22
Geology of Minnesota: Minnehaha Falls
Near Fort Snelling, 10,000 years ago, melt water from the Wisconsin glacier was discharged through the Mississippi River and plunged over a ledge of Platteville limestone into a gorge cut chiefly in the white St. Peter sandstone. The undercutting action in the soft sandstone caused the limestone ledge to break off with a vertical face, thus maintaining the falls, while causing them to retreat upstream. When the falls in the main channel passed the upper end of the island--where the Soldiers Home now stands--the entire flow in the river was diverted to the main gorge and the falls in the west channel were abandoned. This unique and unusual geologic feature, an abandoned waterfall, is located at the north end of the former west channel which lies 200 feet east of this tablet.
The cataract in the Mississippi has migrated to St. Anthony Falls and Minnehaha has retreated from the abandoned channel to its prsent location, where the undercutting action responsible for the migration is apparent.
Erected by the Geological Society of Minnesota in cooperation with the Board of Park Commissioners City of Minneapolis. 1953
(#24 in Minnesota History Along the Highways: A Guide to Historic Markers and Sites, by Sarah P. Rubinstein)