Eroded sandstone formation. This is Corbin Sandstone Member, a sandstone of the Lee Formation. It formed over 300 million years ago during the Pennsylvanian Age (a portion of the Carboniferous Period) in the Paleozoic Era. Erosion due to weathering has formed outcrops (overhanging rock), which makes the formation a popular site for climbing. It contains layers of quartz, sand and gravel that were deposited by rivers from the ancestral Appalachian Mountains in Pennsylvania. Photographed in the Red River Gorge, Daniel Boone National Forest, Menifee County, Kentucky, USA.