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Type of Plains

Plains

  • Plains usually are the best land of a country & are heavily cultivated & populated
  • Even more at places where rivers transverse the plains
  • For ex: Indo Gangetic Plains, Mississippi Plains & Yang-Tze plain

 

Some of the most extensive temperate plains are Grasslands like Russian Steppes, North American Prairies & Argentinian Pampas. Plains may be grouped into 3 major types based on their mode of formation viz.

Structural Plains

  • Structurally depressed areas of the world that makes up some of the most extensive natural lowlands on the earth’s surface
  • Rock layers on the earth’s crust are aligned almost horizontally
  • They are formed by horizontally bedded rocks, relatively undisturbed by the crustal movements of the earth
  • Examples include Russian Platforms, Great plains of USA & Central lowlands of Australia

Depositional Plains

  • Plains formed by deposition of materials brought by various agents of transportation
  • Comparatively of equal level but rise gently towards adjacent highlands
  • Depositional work by rivers form extensive alluvial plains, flood plains & deltaic plains; that form most productive agricultural plains of the world
  • For ex. Gangetic plain (for rice & jute), Nile delta of Egypt (for rice & cotton) & Hwang ho plain in China

 

Glacial Depositional plains

  • Glaciers & ice sheets may deposit fluvio glacial sands & gravels in outwash plains
  • May also drop boulder clay (mixture of various sizes of boulders & clay) to form till plain or drift plain
  • Outwash plains are usually barren lands but boulder clay may be very valuable for farming

 

Aeolian Depositional plains 

  • Winds may blow Aeolian deposits, very fine particles known as loess, from interior deserts or barren surfaces & deposit them upon hills, valleys or plains forming a loess plateau (ex. in NW China) or a loess plain (Ex. in Pampas of Argentina)
  • The loess help in leveling the undulating plain by filling up groves & depressions
  • Many of the loess covered plains in the world are fertile agricultural regions

 

Erosional Plains

  • These plains are carved by the agents of erosion (Rain, river, ice, and wind)
  • Such plains of denudation are described as Peneplains, which means almost plains.
  • In glaciated regions, glaciers & ice sheets scours & levels the land forming ice scoured plains
  • However scooped out by the ice are now filled by the lakes for ex. in Northern Europe & Northern Canada.
  • Finland is estimated to have 35000 lakes occupying 10 % of total land surface of the country
  • In arid & semi-arid regions, wind erosion lowers the level of the land which are called Reg in Africa
  • Mechanical weathering in arid & semi-arid areas worns mountain slopes leaving a gentle slope, known as Pediplains or Pediments; with remaining steep hills known as Inselbergs
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