Plain

Plain From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about the geographical feature. For other uses, see Plain (disambiguation).

A small mirage on the road, Western plains, New South Wales, Australia

Los llanos (it is an area of land with relatively high relief) in Venezuela In geography, a plain is an area of land with relatively high relief, as well as flat. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or vegetation may be absent in the case of sandy or stony plains in hot deserts. Types of flatlands for which the term is not generally used include those covered entirely and permanently by swamps, marshes, playas, or ice sheets. Plains occur as lowlands and at the bottoms of valleys but also on plateaus at high elevations. In a valley, a plain is enclosed on two sides but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains or cliffs. Where a geological region contains more than one plain, they may be connected by a pass (sometime termed a gap). Plains may have been formed from flowing lava, deposited by water, ice or wind, or formed by erosion by these agents from hills and mountains.

Plains in many areas are important for agriculture, because where the soils were deposited as sediments they may be deep and fertile, and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock.

Contents [hide] •

1 Types of terrestrial plains

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2 Other types

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3 See also

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4 References

[edit] Types of terrestrial plains

Part of the plain that surrounds Lightning Ridge, New South Wales, Australia •

Coastal plain, an area of low-lying land adjacent to a sea; the term is used especially where they contrast with hills, mountains or plateaux further inland.

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Fluvial plains are formed by rivers, and may be one of these overlapping types: ○

Flood plain, adjacent to a stream, river, lake or wetland that experiences occasional or periodic flooding.

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Alluvial plain, formed over a long period of time by a river depositing sediment on its floodplain or bed which becomes alluvial soil. The difference between a floodplain and an alluvial plain is that the floodplain represents the area experiencing flooding fairly regularly in the present or recently, whereas an alluvial plain includes areas where the floodplain is now and used to be, or areas which only experience flooding a few times a century.

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Scroll plain, a plain through which a river meanders with a very low gradient.

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Lacustrine plain, a plain that originally formed in a lacustrine environment, that is, as the bed of a lake.

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Lava plain, formed by sheets of flowing lava.

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Glacial plains are formed by the movement of glaciers under the force of gravity:

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Till plain, a plain of glacial till that forms when a sheet of ice becomes detached from the main body of a glacier and melts in place depositing the sediments it carries. Till plains are composed of unsorted material (till) of all sizes.

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Sandur (plural sandar), a glacial outwash plain formed of sediments deposited by meltwater at the terminus of a glacier. Sandar consist mainly of stratified (layered and sorted) gravel and sand.

[edit] Other types The term may also be used for flat areas of the ocean floor or for flat areas on moons and planets. •

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Abyssal plain, a flat or very gently sloping area of the deep ocean basin floor.

Plains

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Plains are broad, nearly level stretches of land that have no great changes in elevation. Plains are generally lower than the land around them; they may be found along a coast or inland. Coastal plains generally rise from sea level until they meet higher landforms such as mountains or plateaus. Inland plains may be found at high altitudes. Plant life on plains is controlled by the climate. Thick forests usually

thrive on plains in humid climates, grasslands cover fairly dry plains such as the Great Plains in the United States. Plains are usually well populated because the soil and terrain are good for farming, and roads and railways are easily built between rural towns and cities. A coastal plain is a stretch of lowland along a seacoast which slopes toward the sea. In most cases, such a plain may be an elevated part of the ocean floor. Solid materials are carried off by rivers or waves from other coastal plains; these materials are deposited along the shore extending the coast seaward. The Atlantic Coastal Plain is a good example of a fertile and well populated coastal plain. It lies along the eastern shore of North America from Nova Scotia to Florida. The sharp upward slope of the land along the plain's inland edge is called the fall line. Coastal plains generally have a few poor harbors, but the mouth of rivers along the Atlantic seacoast have produced some fine harbors. A flood plain is the floor of a river valley beyond the riverbed. A flood plain is formed of mud, sand, and silt that are left behind when the river overflows its banks. These materials are carried off by the river as it erodes the land upstream. A river in flood conditions can carry a large amount of eroded material, which the overflow waters deposit onto the flood plain.