Great Falls of the Potomac River, looking north on the Virginia side. The Potomac falls 80 feet across resistant metagraywacke and schist of Neoproterozoic to Early Cambrian age. Downcutting of the Potomac from the bedrock terrace to the current river channel occurred in the last 30,000 years. See field trips 5 and 6.

Photograph by Gary Fleming, Virginia Department of Conservation and Recreation.