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 as mentioned.

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