Old Appalachia was an ancient, Paleozoic Era land mass of igneous and metamorphic rock located where the North American Atlantic sea coast and its borderlands now lie. About 600 million years ago, Old Appalachia began a geologic history of mountain building and reduction of which Appalachia’s Blue Ridge and Piedmont physiographic regions are the modern remnants.
Throughout most of the Paleozoic, Old Appalachia was bordered on the west by an inland sea that extended across the present middle part of the United States to the modern Rocky Mountains. The deepest part of the inland sea was a geosyncline trough that filled with sediments washed down from the flanks of Old Appalachia. As the sediments accumulated in the trough the coast of the inland sea gradually sank but Old Appalachia’s borderland was maintained by uplifts.
The igneous and metamorphic rock of Old Appalachia and the newer sedimentary formations in the geosyncline trough were uplifted during the later mountain-building period called the Appalachian Orogeny. After being eroded to a near featureless plain in the Mesozoic Era, the Appalachian land mass was again uplifted. Each time the land mass was re-elevated the rocks were warped, buckled, folded, and broken, and the rejuvenated streams resumed their erosive cutting power.
South of New England and the Adirondacks, the differences in deformation and resistance of the bedrock to erosion have resulted in the current Appalachian Highlands of four physiographic regions: On the eastward side of Old Appalachia is the non-mountainous Piedmont Region. The westward side of Old Appalachia is the mountainous Blue Ridge Region that marks the boundary of West Virginia in eastern Jefferson County. The other two regions, the Plateau and the Ridge and Valley, make up the remainder of our state.
This Article was written by Howard G. Adkins
Last Revised on October 22, 2010
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