Tableland in the U.S. that forms the western section of the Appalachian Mountains and a part of the Allegheny Plateau. It extends southwest for 450 mi (725 km) from southern West Virginia to northeastern Alabama, averages 50 mi (80 km) in width, and is 2,000–4,145 ft (600–1,263 m) high. The roughest and highest portion is a narrow ridge about 140 mi (225 km) long that forms its eastern margin in eastern Kentucky and northeastern Tennessee; the name Cumberland Mountains is generally applied to this area, which includes the Cumberland Gap National Historical Park. The plateau has large deposits of coal, limestone, and sandstone.
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The Cumberland Plateau is a deeply dissected plateau, with topographic relief commonly of about four hundred feet (120 meters), and frequent sandstone outcroppings and bluffs. Many coal seams are present in the area, and the Cumberland Plateau has for many years been heavily mined.
At Kentucky's Pottsville Escarpment, which is the transition from the Cumberland Plateau to the Bluegrass in the north and the Pennyrile in the south, there are many spectacular cliffs, gorges, rockhouses, natural bridges, and waterfalls. In Tennessee, the Cumberland Plateau's western border is the Highland Rim east of the Nashville Basin, and its eastern edge is marked by Walden Ridge, which continues south into Alabama as Sand Mountain. Walden Ridge and Sand Mountain are separated from the main portion of the Cumberland Plateau by the Sequatchie Valley, which extends into central Alabama under other names.
In Kentucky, the height of the plateau's hills increases from northwest to southeast, with the westernmost areas of the plateau having a relief of around 200 feet and an appearance similar to the knobs region, whereas areas near Black Mountain have a relief exceeding 2,500 feet.
The Cumberland Plateau is contiguous with the Allegheny Plateau on the northern side, the only real difference being local naming. The sedimentary rocks that compose both plateaus are of Mississippian and Pennsylvanian geological age, composed of near shore sediments washed westward from the old Appalachian Mountains. Some rock layers were laid down in shallow coastal waters, some, including bituminous coal seams were laid onshore in swampy environments. These are interlaced with delta formations of cross-bedded sandstones and occasionally conglomerate. There are numerous discontinuities in the beds, where they were raised high enough to be eroded, then lowered to have more sediments added on top.