Plain

In geography, a plain is a flat expanse of land that generally does not change much in elevation. Plains occur as lowlands along valleys or on the doorsteps of mountains, as coastal plains, and as plateaus or uplands.[1]

For other uses, see Plain (disambiguation) and Plains (disambiguation).
Mount Ararat in the Caucasus, with the Ararat plain in foreground.

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 by cliffs. Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed a gap). Coastal plains would mostly rise from sea level until they run into elevated features such as mountains or plateaus.[2]

Plains are one of the major landforms on earth, where they are present on all continents, and would cover more than one-third of the world's land area.[3] Plains may have been formed from flowing lava, deposited by water, ice, wind, or formed by erosion by these agents from hills and mountains. Plains would generally be under the grassland (temperate or subtropical), steppe (semi-arid), savannah (tropical) or tundra (polar) biomes. In a few instances, deserts and rainforests can also be plains.[4]

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.[5]

Types of plain
A small, incised alluvial plain from Red Rock Canyon State Park (California).
A flood plain in the Isle of Wight.

Depositional plains

The types of depositional plains include:

  • Abyssal plains, flat or very gently sloping areas of the deep ocean basin.[6][7]
  • Planitia, the Latin word for plain, is used in the naming of plains on extraterrestrial objects (planets and moons), such as Hellas Planitia on Mars or Sedna Planitia on Venus.
  • Alluvial plains, which are formed by rivers and which may be one of these overlapping types:
    • Alluvial plains, formed over a long period of time by a river depositing sediment on their flood plains or beds, which become alluvial soil. The difference between a flood plain and an alluvial plain is: a flood plain represents areas experiencing flooding fairly regularly in the present or recently, whereas an alluvial plain includes areas where a flood plain is now and used to be, or areas which only experience flooding a few times a century.[8]
    • Flood plain, adjacent to a lake, river, stream, or wetland that experiences occasional or periodic flooding.
    • Scroll plain, a plain through which a river meanders with a very low gradient.
  • Glacial plains, formed by the movement of glaciers under the force of gravity:
    • Outwash plain (also known as sandur; plural sandar), a glacial out-wash plain formed of sediments deposited by melt-water at the terminus of a glacier. Sandar consist mainly of stratified (layered and sorted) gravel and sand.[9][10]
    • Till plains, plain of glacial till that form 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.
  • Lacustrine plains, plains that originally formed in a lacustrine environment, that is, as the bed of a lake.[11]
  • Lava plains, formed by sheets of flowing lava.[12]

Erosional plains

Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out the rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains.[13]

Structural plains

Structural plains are relatively undisturbed horizontal surfaces of the Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on the Earth's surface.[14]

The Kakanui Range dominates the eastern horizon of the Maniototo Plain
Curry County, eastern New Mexico, on the North American Great Plains

Notable examples
The Llanos, an area of land with relatively high relief in Venezuela
Nineveh Plains (Bozan, Iraq)
A field plain in Liminka, Finland
View of Fields at Biccavolu, Eastern coastal plains, Andhra Pradesh, India
Yilan Plain, Taiwan
View of the South Småland peneplain at Store Mosse National Park in Sweden.
North Somerset Levels taken from Dolebury Warren, England, UK
Terrain near the central German town of Fulda.
The Wallachian Plain, in the southern part of Argeș County.
View of Messara from the hill of Phaestus, Greece.
Cumberland Plain bushland in Western Sydney, Australia.
Looking southeast across the Taieri Plain, Otago, New Zealand.

Caribbean and South America

North America

Eastern Asia

South Asia

Western Asia

Central Europe

Eastern Europe

Northern Europe

Southern Europe

Australia

New Zealand

See also

References
  1. Rood, Stewart B.; Pan, Jason; Gill, Karen M.; Franks, Carmen G.; Samuelson, Glenda M.; Shepherd, Anita (2008-02-01). "Declining summer flows of Rocky Mountain rivers: Changing seasonal hydrology and probable impacts on floodplain forests". Journal of Hydrology. 349 (3–4): 397–410. Bibcode:2008JHyd..349..397R. doi:10.1016/j.jhydrol.2007.11.012.
  2. Whittow, John (1984). Dictionary of Physical Geography. London: Penguin. p. 467. ISBN 978-0-14-051094-2.
  3. Geoff C. Brown; C. J. Hawkesworth; R. C. L. Wilson (1992). Understanding the Earth (2nd ed.). Cambridge University Press. p. 93. ISBN 978-0-521-42740-1. Archived from the original on 2016-06-03.
  4. Gornitz, Vivien (ed.). 2009. Encyclopedia of Paleoclimatology And Ancient Environments. Springer: Dordrecht, p. 665.
  5. Powell, W. Gabe. 2009. Identifying Land Use/Land Cover (LULC) Using National Agriculture Imagery Program (NAIP) Data as a Hydrologic Model Input for Local Flood Plain Management. Applied Research Project, Texas State University.
  6. Goudie, A. S., ed. (2004). "Denudation chronology". Encyclopedia of Geomorphology. pp. 244–248.
  7. Vinogradova, N.G. (1997). "Zoogeography of the Abyssal and Hadal Zones". The Biogeography of the Oceans. Advances in Marine Biology. 32. pp. 325–387. doi:10.1016/S0065-2881(08)60019-X. ISBN 9780120261321.
  8. "Glossary of Landform and Geologic Terms" (PDF). National Soil Survey Handbook—Part 629. National Cooperative Soil Survey. April 2013. Archived from the original on 22 October 2016. Retrieved 17 August 2016.
  9. Magilligan F.J., Gomez B., Mertes L.A.K., Smith, L.C. Smith N.D., Finnegan D., Garvin J.B., Geomorphic effectiveness, sandur development, and the pattern of landscape response during jökulhlaups: Skeiðarársandur, southeastern Iceland, Geomorphology 44 (2002) 95–113
  10. Smith L.C., Sheng Y., Magilligan F.J., Smith N.D., Gomez B., Mertes L., Krabill W.B., Garven J.B., Geomorphic impact and rapid subsequent recovery from the 1996 Skeiðarársandur jökulhlaup, Iceland, measured with multi-year airborne lidar. Geomorphology vol. 75 Is. 1–2 (2006) 65–75
  11. United States. Department of Conservation. Division of Geology. Glacial Sluceways and Lacustrine Plains of Southern Indiana. By William D. Thornburry. Bloomington: n.p., 1950. Web. <"Archived copy" (PDF). Archived (PDF) from the original on 2016-03-03. Retrieved 2015-12-16.CS1 maint: archived copy as title (link)>.
  12. "Lava Plateaus". Archived from the original on 2013-11-14. Retrieved 2014-01-26.
  13. Migoń, Piotr (2004). "Planation surface". In Goudie, A.S. (ed.). Encyclopedia of Geomorphology. pp. 788–792.
  14. "Pediplain". Encyclopedia Britannica.
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