The Big South Fork's most prominent feature is the river gorge cutting through the softer Mississippian age rock beneath the hard Pennsylvanian capstone of the Cumberland Plateau.

Over time water action has left many unique and amazing geologic features ranging from the river gorge with its magnificent bluffs to the natural arches and unusual hoodoos.

[5] Due to the substantial amount of annual rainfall of the region and the action of the Cumberland River and surrounding tributaries the water acts to erode the softer Mississippian rock composed of limestone, shale, and calcareous sandstone from beneath the much harder and erosion resistant capstone composed of Pennsylvanian sandstone.

Where there is hard capstone intact, arches can form creating natural bridges across streams or a dry ravines.

Direct erosion widens a joint and forms a cavity below the more resilient rock thus creating a void between the hard capstone and the area below.