During the Carboniferous period (circa 300 million years before the present), local geological conditions laid down a thick bed of gray sandstone in what is now called Southern Illinois.
The area is geologically located on the south edge of an east-west trough formed by the northward tilt of the bedrock, and has been greatly affected by earthquakes and uplift.
The combined effects of tremors, glacial melt waters, rain, freezing, thawing and wind have naturally sculpted the bluffs into several unusual formations.
[1] Unlike much of Illinois, this plateau was never covered by glaciers; the furthest advance of ice sheets during the Illinoisan glaciation stopped just north of the area.
As a consequence of the reckless clearing, intensive logging, and the local practice of annually burning off the woods, southern Illinois hill-land was severely eroded or badly damaged by 1930.