Monday, 25 April 2016

PLATEAUS


·        The plateaus cover about 18% of the earth’s surface.
·        This landform has a large elevated area on its top unlike a mountain and has nearly even surface out there.
·        Very often rivers or streams cut out deep valleys and gorges in a plateau region.
·        In place of its original smooth topography, it then changes into a disected plateau.
·        Though normally 600 metres above sea level, there are plateau of Tibet and Bolivia, more than 3600 metres above sea level.


CLASSIFICATION OF PLATEAUS :
 On the basis of their geographical location and structure of rocks, the plateaus can be classified as:
(a) Intermontane Plateaus
(b) Piedmont Plateaus
(c) Continental Plateaus

(a) Intermontane Plateau :

·        The plateau which are bordering the fold mountain range or are partly or fully enclosed within them are the intermontane plateaus .
·        Vertical movements raise this extensive landforms of nearly horizontal rocks to thousands of metres above sea level.
·        The extensive and over 4500 metres high plateau of Tibet is one such example.
·        It is surrounded by folded mountains like Himalaya, Karakoram, Kunlun, Tien Shah on its two sides.
·        The plateau of Colorado is another well known example, over one km high into which rivers have cut the Grand Canyon and a series of gorges.
·        The plateau of Mexico, Bolivia and Iran are all other examples of this type.


(b) Piedmont Plateau :

·        The plateaus that are situated at the foot of the mountains and are bounded on other sides by a plain or an ocean are called piedmount plateau.
·        The plateau of Malwa in India, those of Patagonia facing the Atlantic ocean and the Appallachian situated between the Appalachian Mountain and the Atlantic Coastal Plain in U.S.A are their examples.
·        In their case, the areas once high have now been reduced by various agents of erosion.
·        For this reason, these are also called the plateaus of denudation.


(c) Continental plateau :

·        These are formed either by an extensive continental uplift or by the spread of horizontal basic lava sheets completely covering the original topography to a great depth.
·        The volcanic lava covered plateau of Maharashtra in India, Snake River Plateau in North West USA are the examples of this type.
·        These are also, called the ptateau of accumulation.
·        All continental plateaus show an abrupt elevation in contrast to the nearby lowland or the sea .
·        As compared to other, these plateaus, cover a vast area like the Great Indian Plateau and those of Arabia, Spain, Greenland, Africa and Australia.
·        They may be tilted on one side without any disturbance in the horizontal nature of underlying rock strata as in the case of Great Indian plateau.
·        Due to continuous erosion of their surface, we observe the prevalence of a patchy or the slow development of agriculture and building of roads on the plateaus.



 Nevertheless plateaus are extremely useful to mankind in the following ways:

(1) Storehouse of Minerals  :
·        Most of the minerals in the world are found in the plateaus.
·        Besides, the extraction of minerals is relatively easier on plateaus.
·        We get gold from the Plateau of Western Australia; copper, diamonds and gold from the Plateaus of Africa and coal, iron, manganese and mica from the Chota Nagpur Plateau in India.

 (2) Generation of Hydel-power :
·        Rivers falling down the edges of plateaus form water-falls.
·        These waterfalls provide ideal sites for generating hydel-power.
     
(3) Cool Climate :
·        The higher parts of the plateaus even in tropical and sub-tropical regions have cool climate.
·        Hence they have attracted Europeans to settle there and develop their economy e.g. South and East Africa.

     
(4) Useful for Animal-rearing and Agriculture :
·        Plateaus have large grassland areas suitable for animal-rearing specially sheep, goat and cattle.
·        They provide a veriety of products such as wool, milk, meat and hides and skin.
·        The lava plateaus as compared to all other plateau are richer in agriculture since their soil is very fertile.


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