The Continental Drift Theory | With Malayalam Explanation

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THE CONTINENTAL DRIFT THEORY

According to #Wegener , all the continents
formed a single continental mass, a mega ocean
surrounded by the same. The super continent
was named #PANGAEA which meant all earth.
The mega-ocean was called #PANTHALASSA
meaning all water. He argued that, around 200
million years ago, the super continent,
Pangaea, began to split. Pangaea first broke
into two large continental masses as #Laurasia
and #Gondwanaland forming the northern and
southern components respectively. Subsequently, Laurasia and Gondwanaland
continued to break into various smaller
continents that exist today. A variety of evidence
was offered in support of the continental drift.
Some of these are given below.

1. The Matching of Continents ( #Jig-Saw-Fit ):

The shorelines of Africa and South America
facing each other have a remarkable and
unmistakable match. It may be noted that a
map produced using a computer programme
to find the best fit of the Atlantic margin was
presented by #Bullard in 1964. It proved to be
quite perfect. The match was tried at 1,000-
fathom line instead of the present shoreline.

2. Rocks of Same Age Across the Oceans

The radiometric dating methods developed in
the recent period have facilitated correlating the
rock formation from different continents across. the vast ocean. The belt of ancient rocks of
2,000 million years from Brazil coast matches
with those from western Africa. The earliest
marine deposits along the coastline of South
America and Africa are of the #Jurassic age.
This suggests that the ocean did not exist prior
to that time.

Tillite

It is the sedimentary rock formed out of
deposits of glaciers. The Gondawana system
of sediments from India is known to have its
counter parts in six different landmasses of the
Southern Hemisphere. At the base the system
has thick #tillite indicating extensive and
prolonged glaciation. Counter parts of this
succession are found in Africa, #Falkland Island,
#Madagascar , Antarctica and Australia besides
India. Overall resemblance of the Gondawana
type sediments clearly demonstrates that these
landmasses had remarkably similar histories.
The glacial tillite provides unambiguous
evidence of palaeoclimates and also of drifting
of continents.

Placer Deposits

The occurrence of rich placer deposits of gold
in the #Ghana coast and the absolute absence
of source rock in the region is an amazing fact.
The gold bearing veins are in #Brazil and it is
obvious that the gold deposits of the Ghana
are derived from the Brazil plateau when the
two continents lay side by side.

Distribution of Fossils

When identical species of plants and animals
adapted to living on land or in fresh water are
found on either side of the marine barriers, a
problem arises regarding accounting for such
distribution. The observations that Lemurs
occur in India, Madagascar and Africa led some
to consider a contiguous landmass “ #Lemuria ”
linking these three landmasses. Mesosaurus
was a small reptile adapted to shallow brackish
water. The skeletons of these are found only
in two localities : the Southern Cape province
of South Africa and Iraver formations of Brazil.
The two localities presently are 4,800 km apart
with an ocean in between them.

#upsc #psc #hsc #hse #geography #continental #drift