Appalachian orogenic belt

Appalachian orogenic belt
Mountain range that extends more than 1,860 mi (3,000 km) along the eastern margin of North America, from Alabama to Newfoundland.

It was formed by the progressive eastward addition of material to the continental margin of North America. The earliest Appalachian sediments were deposited near the start of the Cambrian Period.

* * *

▪ geological region, North America
      an old mountain range that extends for more than 3,000 km (1,860 miles) along the eastern margin of North America from Alabama in the southern United States to Newfoundland, Canada, in the north. The geosynclinal (geosyncline) theory of mountain building was first worked out in the Appalachians by James Dana and James Hall in the late 19th century; today a plate tectonic (plate tectonics) theory is invoked. The earliest Appalachian sediments were deposited near the start of the Cambrian Period (542 million years ago) on the shores of the opening Iapetus Ocean. Subduction of the Iapetus led to its destruction and the collision of different continental blocks and island arcs. Those collisions gave rise to three Appalachian orogenies: the Taconic (Taconic orogeny) in the Middle Ordovician (about 472 million years ago); the Acadian (Acadian orogeny) in the Middle to Late Devonian (at 390 million to 370 million years); and the Alleghenian (Alleghenian orogeny) in the Late Carboniferous to Permian (300 million to 250 million years ago). The age of these orogenies decreases eastward across the orogenic belt, demonstrating that it was formed by the progressive eastward addition of arcs and continental fragments to the continental margin of North America. The Appalachian belt continues to the east in the form of the Caledonian (Caledonian orogenic belt) and Hercynian orogenic belts (Hercynian orogenic belt) in western Europe. The Alleghenian orogeny led to the formation of the Pangaea supercontinent during the Permian Period (299 million to 251 million years ago). Geophysical seismic studies show that the southern Appalachian Mountains comprising the Ridge and Valley region, the Blue Ridge Mountains, and the Piedmont region belong to a crustal slab some 6–15 km (3.7 to 9.3 miles) thick that has been thrust 260 km (162 miles) westwards over the former continental margin.

* * *


Universalium. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • belt — beltless, adj. /belt/, n. 1. a band of flexible material, as leather or cord, for encircling the waist. 2. any encircling or transverse band, strip, or stripe. 3. an elongated region having distinctive properties or characteristics: a belt of… …   Universalium

  • Appalachian — /ap euh lay chee euhn, cheuhn, lach ee euhn, lach euhn/, adj. 1. of or pertaining to the Appalachian Mountains. 2. of or pertaining to the region of Appalachia, its inhabitants, or their culture. 3. Geol. of or pertaining to the orogeny and… …   Universalium

  • North America — North American. the northern continent of the Western Hemisphere, extending from Central America to the Arctic Ocean. Highest point, Mt. McKinley, 20,300 ft. (6187 m); lowest, Death Valley, 276 ft. (84 m) below sea level. 400,000,000 including… …   Universalium

  • Carboniferous Period — Interval of geologic time 354–290 million years ago, marked by great changes in world geography. All the landmasses drew closer together as a result of tectonic plate movements. The supercontinent Gondwana occupied much of the Southern Hemisphere …   Universalium

  • plate tectonics — plate tectonic, adj. Geol. a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past… …   Universalium

  • Geology of North America — The geology of North America, like most topics of scientific study, is undergoing progressive investigation by numerous public and private sector earth scientists, academicians, and students. In that regard, the detailed picture is subject to… …   Wikipedia

  • North America — North American redirects here. For other uses, see North American (disambiguation). North America Area …   Wikipedia

  • Kaskaskia sequence — The Kaskaskia sequence was a cratonic sequence that began in the mid Devonian, peaked early in the Mississippian, and ended by mid Mississippian time. A major unconformity separates it from the lower Tippecanoe sequence.The basal that is, the… …   Wikipedia

  • Environment of the United States — The environment of the United States comprises diverse biotas, climates, and geologies. Environmental regulations and the environmental movement have emerged to respond to the various threats to the environment.BiotaWith habitats ranging from… …   Wikipedia

  • Foreland basin — basins, where accommodation space is generated by lithospheric extension. Types of Foreland BasinForeland basins can be divided into two categories: * Peripheral (Pro) foreland basins, which occur on the plate that is subducted or underthrust… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”