Stebbins Gulch Stream Undercutting

Stream undercutting a thin layer of siltstone underlain by shale

The process of erosion that helped form the lower falls is the same one that formed all the cascades and falls in Stebbins Gulch, and for that matter, every waterfall, large or small, in the three-state area bordering the eastern shores of Lake Erie.  We start with water flowing over a resistant siltstone or sandstone with a weaker layer of rock (usually shale) directly underneath it.  The resistant layer is known as a “caprock,” hence the name “caprock falls.”  The flowing, churning water gradually removes the underlying shale, forming a cantilevered overhang in the caprock.  Pieces of the resistant siltstone occasionally break off, either under their own weight or the force of the water, and are swept downstream during storm flow.  This process causes the lip of the waterfall to gradually migrate upstream, one chunk of siltstone at a time. 

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