Every weekend we present a notable item from our archives. This EPOD was originally published April 16, 2004.
Provided and copyright by: P. RiemerSummary author: P. RiemerThe above photo of this roadside waterfall was taken in early March in southeastern Minnesota. Water seeping out of the high bluffs above the Mississippi River along Highway I-90, across the river from LaCrosse, Wisconsin, has frozen to form this dramatic ice fall, only a few feet from the shoulder of the roadway.
The Mississippi River probably did not occupy its present course before the Pleistocene Epoch. Pleistocene ice advances tied up millions of cubic kilometers of water in the form of glacial ice, but during each ice retreat, the Mississippi River valley was scoured with huge discharges of meltwater. These floods are responsible for the steepness of the bluffs, which consist of Prairie du Chien dolostone and are capped with Cambrian sandstone. Icings such as this are examples of aufeis.
Related Links:
Pleistocene Epoch
Dolostone
The Blufflands Subsection
Aufeis
The Geology of the New Richmond Sandstone
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