River Warren Falls

[1] These layers were the result of an Ordovician Period sea which covered east-central Minnesota 500 million years ago.

About 20,000 years ago, the area was covered by the Superior Lobe of the Laurentide Ice Sheet, which left the St. Croix moraine on the Twin Cities as it receded.

[3] The result was a series of troughs in the limestone, which were filled by glacial till and outwash deposit as the glaciers receded.

[3][4] Connecting the city lakes in several north-south arteries are gorges cut through the bedrock, but filled with sand and sediment.

When the river reached present-day St. Paul, the massive volume of water quickly washed out the till, sand, gravel, and sedimentary rock that had filled one of the troughs.

One branch of the river coming from the west, Minnehaha Creek receded only a few hundred yards from one of the channels of the Mississippi.

Relief map showing glacial River Warren valley - flowing northwest to southeast, then northeast, then southeast. Falls were in present downtown St. Paul
Limestone cap over soft sandstone base as seen in Minnehaha Park