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Appalachian Mountains

The Appalachian Mountains are a system of North American mountains running from Quebec, Canada to Georgia in the United States. The system is divided into a series of ranges, with the individual mountains averaging around 3000 ft. The highest of the group are Mt. Mitchell (6,684 ft.) and Mt. Washington[?] (6,288 ft.)

The major ranges comprising the Appalachian system include the Notre Dame Mountains[?] in Quebec, the Longfellow Mountains[?] in Maine, the White Mountains in New Hampshire, the Green Mountains[?] in Vermont, the Taconic Mountains[?] in Vermont and Massachusetts, the Berkshire Hills[?] in Massachusetts, the Allegheny Mountains[?] in Pennsylvania, Maryland, West Virginia and Virginia, and the Blue Ridge Mountains[?] that run from South Pennsylvania[?] to North Georgia. The Appalachian Trail is a 2,160 mile hiking trail that runs all the way from Mt. Katahdin in Maine to Springer Mountain[?] in Georgia, passing over or past a large part of the Appalachian system.


The Appalachians are old mountains. A look at rocks exposed in today's Appalachian mountains reveals elongated belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks[?] and slivers of ancient ocean floor, which provides strong evidence that these rocks were deformed during plate collision. The birth of the Appalachian ranges, some 480 million years ago, marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangea with the Appalachians near the center.

During the middle Ordovician Period[?] (about 440-480 million years ago), a change in plate motions set the stage for the first Paleozoic mountain building event (Taconic orogeny) in North America. The once quiet, Appalachian passive margin changed to a very active plate boundary when a neighboring oceanic plate, the Iapetus, collided with and began sinking beneath the North American craton. With the birth of this new subduction zone, the early Appalachians were born. Along the continental margin, volcanoes grew, coincident with the initiation of subduction. Thrust faulting uplifted and warped older sedimentary rock laid down on the passive margin. As mountains rose, erosion began to wear them down. Streams carried rock debris downslope to be deposited in nearby lowlands. The Taconic Orogeny was just the first of a series of mountain building plate collisions that contributed to the formation of the Appalachians.

By the end of the Mesozoic era, the Appalachian Mountains had been eroded to an almost flat plain. It was not until the region was uplifted during the Cenozoic Era[?] that the distinctive topography of the present formed. Uplift rejuvenated the streams, which rapidly responded by cutting downward into the ancient bedrock. Some streams flowed along weak layers that define the folds and faults created many millions of years earlier. Other streams downcut so rapidly that they cut right across the resistant folded rocks of the mountain core, carving canyons across rock layers and geologic structures.

See also: Appalachian Trail

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