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The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending from northern New Jersey westward into Pennsylvania and southward into Maryland, West Virginia, Virginia, Tennessee, and Alabama. They form a broad arc between the Blue Ridge Mountains and the Appalachian Plateau physiographic province (the Allegheny and Cumberland Plateaus).
These mountains are characterized by long, even ridges, with long, continuous valleys in between. From a great enough altitude, they look almost like corduroy, except that the widths of the valleys are somewhat variable and ridges sometimes meet in a vee.
[edit] Geography
The two great mountain ranges constituting the middle portion of the Ridge and Valley Province are the Alleghenies and the Cumberlands.[citation needed]
The eastern edge 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.
Shaded relief map of Cumberland Plateau and Ridge and Valley Appalachians on the Virginia/West Virginia border
[edit] Geology
These curious formations are the remnants of an ancient fold-and-thrust belt, west of the mountain core that formed in the Alleghenian orogeny (Stanley, 421-2). Here, strata have been folded westward, and forced over massive thrust faults; there is little metamorphism, and no igneous intrusion.(Stanley, 421-2) 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. But a few major rivers, such as the Delaware River, the Susquehanna River, and the Potomac River are evidently older than the present mountains, having cut water gaps that are perpendicular to hard strata ridges. The evidence point to a wearing down of the entire region (the original mountains) to a low level with little relief, so that major rivers were flowing in unconsolidated sediments that were unaffected by the underlying rock structure. Then the region was uplifted slowly enough that the rivers were able to maintain their course, cutting through the ridges as they developed.
Appalachian zones in the US - USGS
Valleys may be synclinal valleys or anticlinal valleys.
These mountains are at their highest development in central Pennsylvania, a phenomenon termed the Pennsylvania climax.
[edit] References
- Stanley, Steven M. Earth System History. New York: W.H. Freeman and Company, 1999. ISBN 0-7167-2882-6
[edit] Significant ridges
[edit] See also
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