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The Appalachian Mountains are a system of North American mountains running from Newfoundland and Labrador, Canada to Alabama in the United States, although the northernmost mainland portion ends at the Gaspé Peninsula of Quebec. The system is divided into a series of ranges, with the individual mountains averaging around 3000 ft. The highest of the group is Mt. Mitchell in North Carolina (2,040m, 6,684 ft.), which is the highest point in the United States east of the Mississippi River as well as the highest point in eastern North America.
The major ranges comprising the Appalachian system include the Long Range Mountains and Annieopsquotch Mountains in Newfoundland, the Notre Dame Mountains in New Brunswick and 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 and West Virginia, the Ridge-and-valley Appalachians in Pennsylvania, Maryland, West Virginia and Virginia, and the Blue Ridge Mountains that run from southern Pennsylvania to North Georgia.
In addition to the true folded mountains, known as the ridge and valley province, the area of dissected plateau to the north and west of the mountains is usually grouped with them. This includes the Catskill Mountains of southeastern New York, and the Allegheny Plateau of southwestern New York, western Pennsylvania, eastern Ohio and northern West Virginia. The plateau does not change character but changes name to the Cumberland Plateau in southern West Virginia, eastern Kentucky, western Virginia, eastern Tennessee.
The dissected plateau area is popularly called mountains, especially in eastern Kentucky and West Virginia, and while the ridges are not high, the terrain is extremely rugged. In Ohio and New York, some of the plateau has been glaciated, which has rounded off the sharp ridges, and filled the valleys to some extent. The glaciated regions are usually referred to as hill country rather than mountains.
The Appalachian region is generally considered the geographical dividing line between the eastern seaboard of the United States and the Midwest region of the country. Before the French and Indian War, the Appalachian Mountains lay on the indeterminate boundary between Britain's colonies along the Atlantic and French areas centered in the Mississippi basin.
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 grievances 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 Erie Canal, finished in 1825, formed the first route through the Appalachians that was capable of large amounts of commerce.
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 680 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 Morocco.
During the middle Ordovician Period (about 495-440 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 (see Appalachian orogeny).
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. In the folded mountains the coal is in metamorphosed form as anthracite represented by the coal fields of northeastern Pennsylvania. The coal fields of eastern Kentucky and West Virginia are bituminous coal, which is the sedimentary form.
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