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Earth’s Structure

Plateaus

▬ Plateaus are extensive upland areas characterised by flat and rough top surface and steep walls which rise above the neighbouring ground surface at least for 300 m.

▬ Generally the height of plateau ranges from 300 to 500 feet.



Inter-mountainous Plateaus: Plateaus formed between mountain, Example-Tibetan Plateau.

Mountain-step Plateaus: The flat region between a plain and the base of a mountain.

Continental Plateaus: These are formed when the Lacolith inside the Earth comes to the surface due to weathering. e.g. the Southern Plateau.
Bank Plateaus: These are the plateaus on the banks of the oceans.

Domelike Plateaus: These are formed due to the movement of man and animals on the surface. e.g. Ramgarh Plateau.

Some plateaus having more than average height
Tibetan Plateau 16000 ft
Bolivian Plateau 11800 ft
Columbian Plateau 7800 ft

Plains

Plains can be defined as flat areas with low height (below 500 ft.)

Weathered Plains: The plains formed due to weathering by rivers, glaciers, winds etc.

Loess Plains: These are formed by the soil and sands brought by winds.

Karst Plains : Plains formed due to the weathering of limestone.

Erosional Plains : Plains near the river banks formed by river erosion.
Glacial Plains: Marshy plains formed due to the deposition of ice.

Desert Plains: These are formed as a result of the flow of rivers.

Deposition Plains: Large plains are formed due to the silt brought by the rivers. Such plains are plains of Ganga, Sutlej, Mississipi, Hwang Ho.

Forests

They are of the following types:
(a) Tropical Evergreen Rain Forests: Such forests are found in the equatorial and the tropical regions with more than 200 cms annual rainfall. The leaves of trees in such forests are very wide. Ex-Red wood, palm etc.

(b) Tropical Semi Deciduous Forests: Such forests recieve rainfall less than 150 cms. Saagwan, saal, bamboo etc. are found in such forests.

(c) Temperate mixed Forests: Such forests are a mixture of trees and shrubs, Corks, Oak etc. are the major trees of these forests.

(d) Coniferous Forests or Taiga : These are evergreen forests. The trees.in these forests, have straight trunk, conical shape with relatively short branches and small needlelike leaves. Example Pine, Fir etc.

(e) Tundra Forests: Such forests are covered with snow. Only Mosses, a few sledges and Lichens grow here in the summers. This type of vegetation is chiefly confined to the northern hemisphere (e.g. in Eurasia, North America and Greenland Coast).

(f) Mountainous Forests: Vegetation varies according to altitude.

Pastures (or Grasslands)

▬ They can be divided into two types:
(i) Tropical Pastures and (ii) Temperate Pastures

▬ Tropical Pastures: They have different names in different countries. Savanna in Africa, Campos in Brazil, Lanos in Venezuela and Columbia.

▬ Temperate Pastures: They are known by the following names-Praries in USA and Canada, Pampas in Argentina, Veld in South Africa, Rangelands or Downs in Australia and Newzealand, Steppes in Eurasia (Ukraine, Russia).







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