Plateau
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In geology and earth science, a plateau (/[invalid input: 'icon']pləˈtoʊ/ or /ˈplætoʊ/; plural plateaus or rarely plateaux), also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain.
Formation
Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, and erosion by water and glaciers. Magma rises from the mantle causing the ground to swell upward, in this way large, flat areas of rock are uplifted. Plateaus can also be built up by lava spreading outward from cracks and weak areas in the crust. Plateaus can also be formed by the erosional processes of glaciers on mountain ranges, leaving them sitting between the mountain ranges. Water can also erode mountains and other landforms down into plateaus.
Classification
Plateaus are classified according to their surrounding environment.
- Intermontane plateaus are the highest in the world, bordered by mountains. The Tibetan Plateau is one such plateau.
- Piedmont plateaus are bordered on one side by mountains and on the other by a plain or sea.
- Continental plateaus are bordered on all sides by the plains or seas, forming away from mountains.
- Volcanic plateaus are produced by volcanic activity. The Columbia Plateau in the northwestern United States of America is one such plateau.
- Dissected plateaus are highly eroded plateaus cut by rivers and broken by deep narrow valleys.
Major plateaus of the world
The largest and highest plateau in the world is the Tibetan Plateau, called the "roof of the world", which is still being formed by the collisions of the Indo-Australian and Eurasian tectonic plates. In all, the Tibetan plateau covers an area of some 2.5 million square kilometres, approximately 5000 m above sea level. The height of this plateau is such that it is enough to reverse the Hadley cell convection cycles and to drive the monsoons of India towards the south.
The second-largest current plateau in the world is the Antarctic Plateau, which covers most of the central part of Antarctica. In that region of Antarctica, there are no known mountains, but rather 3000 meters or more of ice - which very slowly spreads toward the coastline via enormous glaciers. This ice cap is so massive that echo location sound measurements of the thickness of the ice have shown that large parts of the "dry land" surface of Antarctica have been pressed below sea level. Thus, if the icecap were somehow removed, large areas of Antarctica would be flooded by the oceans. On the other hand - more realistically - were the icecap to gradually melt away, the surface of the land beneath it would gradually rebound away from the center of the Earth, and that land would ultimately rise above sea level.
The third-largest plateau in the world is probably the one in South America that lies in the middle of the Andes Mountains. This Andean Plateau covers most of Bolivia, central Ecuador, central Peru, northern Chile and northern Argentina.
Major plateaus of North America
In North America, the largest plateau is the Colorado Plateau covering an area of about 337,000 square kilometres (130,000 sq mi) in Colorado, Utah, Arizona and New Mexico.[1]
The Colorado Plateau in northern Arizona and southern Utah is bisected by the valley of the Colorado River and the Grand Canyon. How this came to be is that over 10 million years ago, a river was already there, though not necessarily on exactly the same course. Then, subterranean geological forces caused the land in that part of North America to gradually rise by about a centimeter per year for millions of years. An unusual balance occurred: the river that would become the Colorado River was able to erode into the crust of the Earth at a nearly equal rate to the uplift of the plateau. Now, millions of years later, the North Rim of the Grand Canyon is at an elevation of about 2450 meters (9800 ft) above sea level, and the South Rim of the Grand Canyon is about 2150 meters (8200 ft) above sea level. At its deepest, the Colorado River is about 1830 meters (6000 ft) below the level of the North Rim.
The southern edge of the plateau in northern Arizona is called the Mogollon Rim, where the elevation of the land declines steeply into central Arizona. This Mogollon Rim is located about 20 kilometers south Flagstaff, Holbrook, Winslow, and Williams, Arizona. Because of the snowy plateau and the San Francisco Mountains to its north, the Mogollon Rim area is noted for its many natural springs and artesian wells.
See also
- Oceanic plateau for submarine or undersea plateaux
- Altiplano
- Mesa
- Potrero
- Tuya
- Butte
- Atherton Tableland
- Chapada
- Tepuis
References
- ^ Leighty, Dr. Robert D. (2001). "Colorado Plateau Physiographic Province". Contract Report. Defense Advanced Research Projects Agency (DOD) Information Sciences Office. Retrieved 2007-12-25.
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