Appalachian Plateau Topography

Physiographic provinces

The portion of the Appalachian Plateauin the Southern Appalachians can be subdivided into four sections:

1. The Allegheny Mountains Section is at the northeastern margin of the Plateau. It differs from the Unglaciated Allegheny Plateau to the west in that dissection here is so advanced that the topography no longer resembles a plateau, even a dissected one. It also differs in that mild folding and erosion on anticlines and synclines have produced a topography with linear ridges. The Allegheny Front Escarpment lies along the eastern margin of this section, rising 300 m above the valley floors of the adjacent Ridge and Valley Province.
2. The Unglaciated Allegheny Plateau Section (also referred to as the Kanawha Appalachian Plateau) is the dissected middle portion of the Plateau. Its stratigraphy differs from that of the Allegheny Mountains in that its more abundant shalesresult in slopes that tend to be somewhat smoother than those that occur where sandstone is more common. Altitudes are lowest on the western side of the section in Ohio and Kentucky, where they average 365 to 425 m. From here, they increase eastward and northward, exceeding 1,220 m in West Virginia. Here, the New River Gorge, with the river level lying 600 m below the plateau surface, the most spectacular gorge in the Eastern United States.

Elevation Map of Appalachian Plateau Province
3. The Cumberland Mountain Section represents the southern counterpart of the Allegheny Mountains Section. It occupies a strip about 240 km long and 40 km wide in Virginia, Kentucky, and Tennessee. Its geology is dominated by the Cumberland thrust block, which is 200 km long and 40 km wide, and lies about equally in the States of Virginia, Kentucky, and Tennessee. The block is bounded by four faults: a thrust fault (Pine Mountain) on the northwest, another thrust fault (Hunter Valley-Wallen) on the southeast, and two tear faults on the southwest and northeast. The Cumberland thrust block is divided lengthwise into the Middlesboro syncline on the northwest and the Powell Valley anticline on the southeast; the former is in the Appalachian Plateau and the latter is in the Ridge and Valley Province. The Cumberland Mountain Section is higher than the adjacent Cumberland Plateau because the thrust brought resistant rock (Pottsville) to the surface at a relatively high elevation. An anomalous topographic feature in the Middlesboro syncline is the Middlesboro topographic basin, which has been recognized as the product of a meteorite impact.
   
   Another topographic feature of this section is Cumberland Gap, at the intersection of Virginia, Tennessee, and Kentucky. The wind gap is 180 m deep in the otherwise even-crested Cumberland Mountain. One interpretation is that this wind gap was once a water gap, with drainage through it to the south (Thornbury, 1965).
4. The Cumberland Plateau Section is in a sense the southern counterpart of the Unglaciated Allegheny Plateau Section, but it is much less dissected, and over much of its area, particularly in the southern part, is a true plateau. This difference probably stems from a higher percentage of resistant rocks. The Cumberland Plateau is separated from the Ridge and Valley Province by the eastern Cumberland escarpment, and from the Interior Low Plateau by the western Cumberland escarpment. The eastern escarpment, owing to a fairly steep southeasterly dip of the rocks, is relatively linear. Because of its near-horizontal dip the western escarpment is quite irregular. The deep canyons that penetrate the plateau, particularly on its western side are, locally called "gulfs". From Tennessee to central Alabama the anticline is asymmetrical. It is being overturned to the west and broken by a thrust fault over much of its length. It is included in the Appalachian Plateau rather than the Ridge and Valley because it is separated from the latter by Walden Ridge, part of the Plateau.