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  Wikipedia: Appalachian Mountains

Wikipedia: Appalachian Mountains
Appalachian Mountains
From Wikipedia, the free encyclopedia.

The Appalachian Mountains are a system of North American mountains running from Quebec, Canada to Alabama 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 in North Carolina (2,040m, 6,684 ft), the highest point in the United States east of the Mississippi River, and Mt. Washington (1,920m, 6,288 ft.) in New Hampshire.

Regions

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 southern Pennsylvania to North Georgia. South of New York, the mountains are loosely organized into two large plateau regions, the Allegheny Plateau in western Pennsylvania and northern West Virginia, and the Cumberland Plateau in southern West Virginia, western Virginia, eastern Tennessee and western North Carolina. On the eastern and southeastern fringe of the plateau areas lies a ridge and valley province of elongated, parallel ridges, including the Blue Ridge.

These mountains are a geographical boundary between the eastern seaboard of the U.S. and the Midwestern regions of the country. Before the French and Indian War, the Appalachian Mountains lay on the interdeterminate boundary between Britain's colonies along the Atlantic and French areas centered in the Mississippi.

After the French and Indian War, the Proclamation of 1763 limited settlement for Great Britain's thirteen original colonies in North America to east of the summit line of the mountains (except in the northern regions where the Great Lakes formed the boundary). This was highly disliked by the colonists and formed one of the greivances which led to the American Revolutionary War.

With the formation of the United States of America, an important first phase of westward expansion in the late 18th century and early 19th century consisted of the migration of European-descended settlers westward across the mountains into the Ohio Valley through the Cumberland Gap and other mountain passes.

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.

Geology

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. Because North America and Africa were connected, the Appalachians forms part of the same mountain chain as the Atlas mountains in Morrocco.


Old fault exposed by roadcut
near Harrisburg, Pennsylvania
Such faults are common
in the folded Appalachians

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.

The Appalachian Mountains contain major deposits of coal.

See also: Appalachian Trail, Appalachia\n


  

From Wikipedia, the free encyclopedia. 
Modified by Geona