Definitions

jezreel plain

Plain

[pleyn]
In geography, a plain is an area of land with relatively low relief — meaning that it is 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 cse 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. They 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 mechanisation of crop production; or because they support grasslands which provide good grazing for livestock.

Types of terrestrial plains

  • Coastal plain, an area of low-lying land adjacent to a sea coast; the term is used especially where they contrast with hills, mountains or plateaux further inland.
  • Fluvial plains are formed by rivers and streams, and may be one of these overlapping types:
    • Flood plain, adjacent to a stream, river, lake or wetland that experiences occasional or periodic flooding.
    • 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.
    • Scroll plain, a plain through which a river meanders with a very low gradient.
  • Lacustrine plain, a plain that originally formed in a lacustrine environment, that is, as the bed of a lake.
  • Lava plain, formed by sheets of flowing lava.
  • 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 carried.

Other types of plain

The term may also be used for flat areas of the ocean floor or for flat areas on moons and planets.

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

Notes and references

See also

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