Ridge-and-Valley Appalachians

The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a

The eastern head of the Ridge and Valley region is marked by the Great Appalachian Valley, which lies just west of the Blue Ridge. The western side of the Ridge and Valley region is marked by steep escarpments such as the Allegheny Front, the Cumberland Mountains, and Walden Ridge. The Valley and Ridge is located on the west side of the Blue Ridge Mountains.

The Province extends from southeastern New York in the north through northwestern New Jersey, westward into Pennsylvania through the Lehigh Valley, and southward into Maryland, West Virginia, Virginia, Kentucky, Tennessee, Georgia, and Alabama. They form a broad arc between the Blue Ridge Mountains and the Appalachian Plateau physiographic province, which includes the Allegheny and Cumberland plateaus. They are characterized by long, even ridges, with long, continuous valleys in between.

The Valley and Ridge Province was formed during the Alleghanian orogeny, a mountain-building event that occurred between 325 and 260 million years ago.^[2] The rocks in the region were subjected to immense pressure and heat, causing them to deform and fold. The softer parts of these rock units (chiefly shale and limestone) were eroded to form the valleys and the harder parts of the folds (quartzites) formed the mountain tops and ridges.^[3] The ridges represent the edges of the erosion-resistant strata, and the valleys portray the absence of the more erodible strata. Smaller streams have developed their valleys following the lines of the more easily eroded strata.^[4][5]