Appalachian Mountains

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Appalachian Mountains

(ăpəlā`chən, –chēən, –lăch`–), mountain system of E North America, extending in a broad belt c.1,600 mi (2,570 km) SW from the Gaspé Peninsula in Quebec prov., Canada, to the Gulf coastal plain in Alabama. Main sections in the system are the White Mts., Green Mts., Berkshire Hills, Catskill Mts., Allegheny Plateau, Black Mts., Great Smoky Mts., Blue Ridge, and Cumberland Plateau. To the E is the Piedmont (foothill) region. The Appalachians, much-eroded remnants of a great mass formed by folding (see mountainsmountain,
high land mass projecting conspicuously above its surroundings and usually of limited width at its summit. Although isolated mountains are not unusual, mountains commonly form ranges, comprising either a single complex ridge or a series of related ridges.
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), consist largely of sedimentary rocks. Mt. Mitchell (6,684 ft/2,037 m) in North Carolina's Black Mts. is the highest peak.

The Great Appalachian Valley or Great Valley is a chain of lowlands extending S and W from the Hudson Valley; its main segments are the Lehigh, Lebanon, Cumberland, and Shenandoah valleys; the Valley of Virginia; and the Valley of East Tennessee. Long a major north-south travel and settlement corridor, the Great Valley is one of the most fertile areas in the E United States.

The Appalachians are rich in coal; other resources include iron, petroleum, and natural gas. The scenic ranges also abound in resorts and recreation areas, including Shenandoah and Great Smoky Mts. national parks. The Appalachian TrailAppalachian Trail,
officially Appalachian National Scenic Trail,
hiking path, 2,144 mi (3,450 km) long, passing through 14 states, E United States. Conceived in 1921 by Benton MacKaye, forester and regional planner, and completed in 1937, the trail extends along the
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 winds 2,050 mi (3,299 km) along the ridges of the Appalachians between Mt. Katahdin, Maine, and Springer Mt., Georgia.

Crossed by few passes, the Appalachians were a barrier to early westward expansion and played an important role in U.S. history; major east-west routes like the Cumberland GapCumberland Gap,
natural passage through the Cumberland Mts., near the point where Virginia, Kentucky, and Tennessee meet. The gap was formed by the erosive action of a stream that once flowed there. It was explored and named in 1750 by Dr.
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 and Mohawk TrailMohawk Trail.
1 Old road (c.100 mi/160 km long) in central New York state following the Mohawk River. It was the sole route through the Appalachians by which thousands of settlers emigrated from the Eastern seaboard to the Midwest.
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 followed river valleys or mountain notches. Appalachia is a name applied to parts of the region that were long characterized by marginal economy, isolation of its people from the U.S. mainstream, and distinctive folkways.

Bibliography

See E. Porter, Appalachian Wilderness (1970); H. M. Caudill, My Land is Dying (1971); M. Brooks, The Appalachians (1986); H. D. Shapiro, Appalachia on Our Mind (1986).

Appalachian Mountains

 

a mountain system in eastern North America, in the USA and Canada, forming a belt of ranges and ridges, valleys, plateaus and tableland, from 300 to 500 km in width and extending for 2,600 km southwest to northeast from 33° N lat. to 49° N lat. The principal ranges are the Blue Ridge Mountains, White Mountains, Adirondacks, and Green Mountains. The Appalachian Plateau should also be noted. The dominating altitudes are 1,300–1,600 m (the highest peak is Mount Mitchell, 2,037 m). The Appalachians were uplifted on the site of a géosynclinal system which developed actively in the Paleozoic era on a late Precambrian folded foundation. The mountains were leveled during the Jurassic Paleocene period. Mountains reappeared in the Neocene-Anthropogenic period, when the territory of the modern Appalachians underwent a domed uplift, which resulted in the vigorous breakup of the surface and the formation of the modern terrain. The ranges consist of folded rocks and boulders and are divided by intermontane erosional valleys and basins.

During the Anthropogenic period the northern part of the Appalachians underwent glaciation, while the southern part remained in a warm and humid climate. As a result forests of broad-leaved and evergreen trees were able to survive there and subsequently to spread over a large part of the Appalachians. By structure and development the Appalachians are divided into the northern and southern regions (with the borderline approximately at the latitude of New York City).

The northern Appalachians border on the Canadian Shield in the northwest, along a huge fault (the Logan line). They lack frontal sag and consist of a narrow belt of lower Paleozoic sedimentary deposits in the northwest and a wider belt of igneous, intrusional magmatites and metamor-phic rock in the southeast. The main tectonic periods for the northern Appalachians were the Taconic (at the end of the Ordovician) and the Acadian (at the end of the Devonian). During the Carboniferous-Permian period intermontane sag developed in the interior, filled mainly with continental deposits, first coal-bearing and then red in color.

The southern Appalachians border on the midcontinental plate of the North American platform via the cis-Appalachian sag, comprising Upper Paleozoic deposits, with which important deposits of coal, oil, and gas are linked. The external, wider zone of the southern Appalachians (Valley and Ridge Province) consists of folds pointing northwest and accumulations of Lower and Middle Paleozoic rocks. The interior zone (the Blue Ridge Mountains) is made up of metamorphic sedimentary igneous Lower and Middle Paleozoic and Upper Precambrian rocks and granites. The final uplift and folding of the southern Appalachians occurred toward the end of the Paleozoic era.

In the late Triassic period the structure of the Appalachians was complicated by grabens that were filled with red continental deposits and basalt extrusions.

The climate of the Appalachians is modified by the influence of the Atlantic Ocean and especially of the Gulf of Mexico. It is temperate in the north and subtropical in the south. The average temperature in January ranges from - 12°C in the north to 8°C in the south; in July the average ranges from 18°C to 26°C. Annual precipitation is from 1,000 to 1,300 mm. In the winter there are heavy frosts in the upper zone of the mountains, and much snow falls. The valleys are drier and warmer. The summers are humid and cloudy; rainfall is abundant, especially on the western slopes. The clearest and sunniest weather comes at the end of summer and beginning of autumn.

The rivers flow in deep valleys; the flow is abundant all year round, providing considerable reserves of hydro-power. Drainage altitude ranges from 30 cm in the north to 40 cm in the south. The largest rivers are the Connecticut, Hudson, Susquehanna, and Tennessee. They overflow their banks frequently because of melting snow in the spring and heavy rainfall in the summer. The major rivers of the northern Appalachians are navigable. As they fall from the eastern edge of the Piedmont, most of the rivers form rapids and waterfalls (the so-called fall line), which are used in part for power production.

The Appalachians may be divided into two sections according to geomorphological characteristics. The northern Appalachians (as far as New York City) are a leveled-off plateau, 400 to 600 m high, with rocky massifs and ridges or ranges rising above it—the Adirondacks (1,628 m), the Green Mountains (1,338 m), the White Mountains (1,916 m), and others. The mountains have flattened tops, slanting slopes, and occasional dissected cirques. The massifs are divided by tectonic valleys, which have been transformed into troughs (the largest are along the Hudson-Mohawk-Connecticut rivers and Lake Champlain). The depressed sections, especially along the Atlantic coast, are hilly and covered with glacial deposits. The soils are mountainous, podzolic, and turf-podzolic. The vegetation consists of coniferous and mixed forests of fir, silver fir, thuja, hemlock, maple, elm, beech, yellow birch, hickory, and basswood. The southern Appalachians have a more varied terrain. Their eastern foothills are made up of flat, poorly separated valleys of the Piedmont plateau (altitude from 40–80 m in the east and up to 400 m in the west). Rising sharply above the plateau are the Blue Ridge Mountains with steep slopes and undulating or domed peaks (altitude 2,037 m—Mount Mitchell). The western slope of the range falls steeply to a long depression, the so-called Great Valley. The western foothills of the Appalachians form the Appalachian Plateau, criss-crossed by narrow and deep valleys and sloping gently from 1,500 m in the east down to 500 m in the west. The predominating soils are mountain dark brown forest soils; in the foothills, the soils are red and yellow earth. Up to an altitude of around 1,000 m there are broad-leafed forests consisting of numerous species of oak, maple, ash, and many endemic and relic species (tulip tree, magnolia, planer tree, white acacia, and others); above 1,000 m the forests are mixed and coniferous, characteristic for the northern Appalachians. Subalpine vegetation is widespread in the upper belt of the mountains (rhododendron, alders). The forests have been badly depleted.

The most characteristic fauna of the Appalachians includes numerous endemic species: whitetail deer, Virginian opossum, and several species of bats; there are also tree porcupines, American black bears, lynxes, raccoon, skunks, otters, and others.

The Appalachians are a very important area for hiking, skiing, water sports, and hunting. The Shenandoah and Great Smoky Mountains national parks, the Blue Ridge Parkway, and other features are well known.

REFERENCES

Baulig, H. Severnaia Amerika. Moscow, 1948. (Translated from French.)
Ignatyev, G. M. Severnaia Amerika. Moscow, 1965.
King, Lester. Morfologiia Zemli. Moscow, 1967. (Translated from English. Rel’ef Zemli. Moscow, 1967.
King, P. B. Geologicheskoe razvitie Severnoi Ameriki. Moscow, 1961. (Translated from English.)
Rogers, J. “Nekotorye voprosy tectoniki Appalachei.” Geotektonika, 1968, no. 3.
Fardley, A. J. Structural Geology of North America,2nd ed. New York, 1962.

G. M. IGNATYEV and V. E. KHAIN

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