The falls were a series of rapids formed by the relatively recent erosion of the Ohio River operating on 386-million-year-old Devonian hard limestone rock shelves.

The taming of the Ohio River at the falls, with the attendant reduction in local flow velocity, has of late led to the covering over of the fossil beds by large and increasing quantities of low-velocity effluvia: although an impediment to viewing the fossils, this action serves to protect the portions of the falls covered over by sediment and therefore temporarily immune to direct weathering.

However, a significant area of the fossil-rich Devonian limestone rock is still left exposed, and is accessible to visitors today.

Native Americans and early European explorers heard the crisp roar of the Ohio River crashing down the cascade falls more than 10 miles away.

During the Devonian Period, the region lay at the bottom of a shallow inland sea about ten degrees north of the equator in the supercontinent of Euramerica.