ekalawya/?p=1633 Continental Drift Theory The theory of continetal drift expounded by Alfred Wegener in 1915, holds that portions of the original continent which comprised the entire landmass of the world underwent a series of horizontal displacement before the present continents were formed. According to this theory, about 280 million years ago, the entire landmass formed one super continent, called Pangea. According to Wegener, after the breaking of the super continent Pangea, the movement of the continents took place in two directions- one towards the equator due to centrifugal force of the earth which gace rise to fold mountains like the Himalaya, the Alps, etc and another towards west due to tidal force of Sun and the Moon which gave rise to Andes and Rockies. Various evidences show that the continents or the land areas of the globe have been the same in the geological past as they are today. Latest geological investigations show that the crust of the earth consisting of plates are drifting away along the mid oceanic ridges. A glace at the world map shows that S.America particularly Brazil can be fitted into the gulf of Guinea of Africa, Antartica can roughly be fitted into S.Australian coast and S.E.African coast. Similarly NW Australian coast and E Indian coast are liable to fit. After the drifts some water bodies developed between them. Geological evidences said that S.America and Africa were probably joined together till the Upper Triassic. Biological history of certain animals like marsupials and placental mammals also throw significant light on the continental drift. The rate of drift ranges from one centimetre per year in N.Atlantic to about two centimetre per year in central Atlantic. It varies from 16cm. per year in East Central Pacific to about two centimetre per year in S.Pacific. in the Indian ocean, the drift varies from 1.5 centimetre per year in Arabia in 0.3 centimetre per year in south Indian ocean.
Posted on: Tue, 21 Jan 2014 15:56:27 +0000
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