Useful for Civil Service G S Geography topics

1. CONTINENTS AND
OCEAN BASINS

2. • 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

3. 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

4. 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

5. 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

6. • 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

8. Continental Drift

11. 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 drift
2. The concept of sea floor spreading

12. Lithospheric Plates