Over 70% of the Earth's surface is covered by oceans, with the remaining 29% comprised of continents. Most continents have their bases in the northern hemisphere and extend southward. Alfred Wegener first proposed the continental drift theory in 1912, suggesting that all landmasses were once joined together in a supercontinent called Pangaea, surrounded by a single ocean called Panthalasa. Pangaea later broke apart into separate continents, including Laurasia and Gondwana, as evidenced by matching coastlines, mountain systems, fossils, and plant and animal distributions between separated lands. The theory of plate tectonics later expanded on drift by explaining the Earth's lithospheric plates that move and interact at boundaries

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