West of the Carters Dam fault and the Cohutta Mountains, east of the Cumberland Plateau and the main ridges of the Ridge and Valley province, lies a broad, rolling valley. Extending northeast through Tennessee into Virginia, this valley narrows in a cluster of ridges near Roanoke, Virginia. North of Roanoke, the valley widens, passing through New England into Canada. South of the Cohuttas in Georgia and Lookout Mountain in Alabama, the valley's geologic structure continues southwest, but surrounding terrain drops away so that the valley is physiographically less distinct. This great valley has many names, often referent to rivers that run through it; segments are called the Tennessee Valley and the Shenandoah Valley .
The Great Valley's rock is similar to that of the Ridge and Valley and Cumberland Plateau to its west: Paleozoic sandstone, limestone, and shale. Much of the valley's rock is faulted and fractured. Evidently, the valley's form results from erosion -- during 300 million years -- of this fractured rock.