What is the Ridge and Valley region of the Appalachian Mountains?

The Ridge and Valley is a physiographic province within the Appalachian Highlands of the eastern United States. As its name suggests, the region consists of a series of alternating ridges and valleys that stretch for nearly 1,200 miles (1,930 km), ranging from 14 to 80 miles in width.1

Geologically, this region is part of "New" Appalachia, characterized by Paleozoic age sedimentary rocks, such as shales, sandstones, and limestones. These formations were shaped by the Alleghenian orogeny during the Permian Period, a time of intense mountain folding and faulting that buckled the Earth's crust.23

The province extends from the St. Lawrence Valley in New York to central Alabama. Notable features within this region include the Shenandoah Valley in Virginia and Kittatinny Mountain in Pennsylvania. Seismic studies indicate that the southern portion of this region is part of a massive crustal slab that was thrust hundreds of kilometers westward over the former continental margin.13