CONTINENTS AND OCEAN BASINS

• About 70.8 percent of the total surface area of the globe is represented by the oceans and the remaining 29.2 percent is represented by the continents

• More than 75 percent of the total land area of the globe is situated in the northern hemisphere

• Contrary to this water bodies dominate in the southern hemisphere

• Most of the continents have their base in the north while their apices are pointed towards south

Continental Drift Theory of Wegner

• Prof.Alfred Wegener propounded his concept of continental drift in the year 1912

• His hypothesis was based on the works and findings of a host of scientists such as geologists, Palaeo climatologists, geophysicists and others

Basic Premise of the theory

• All the land masses united together in the form of one land mass, which he named Pangaea, in carboniferous period

• Which was surrounded by a huge water body named by Wegener as Panthalasa, representing primeval Pacific Ocean

• Pangaea broke up in to Lauratia and Gondwana Land

Evidences in support of the theory

• There is geographical similarity along both the coasts of Atlantic Ocean (Jigsaw fit)

• The mountain systems of the western and the eastern coastal areas of the Atlantic Ocean are similar and identical

• Geologically both the coasts of Atlantic are similar• There is a marked similarity in fossils and

vegetation remains found on the eastern coast of south America and western coast of Africa

• The lemmings of the northern part of the Scandinavia have a tendency to run westward when their population is enormously increased but are foundered in the sea water due to absence of any land beyond Norwegian coast

• The distribution of Glossopteris flora in India, South Africa, Australia, Antarctica etc proves the fact that all the landmasses were previously united and contiguous in the form of Pangaea

• The evidences of carboniferous glaciations of Brazil, Falkland, South Africa, Peninsular India Australia and Antarctica further prove the unification of all land masses

Continental Drift

Plate Tectonic Theory

• The rigid lithospheric slabs or rigid and solid crustal layers are technically called plates

• The whole mechanism of evolution, nature and motion of plates and resultant reaction is called plate tectonics

• It is based on two major scientific concepts 1. Concept of continental drift2. The concept of sea floor spreading

Lithospheric Plates