Continental drift theory definition:-The continental drift is the hypothesis that the continents of the earth have moved away from each other over the geological period.
This theory explained how the continents of the earth change their position on
the surface of the earth. The hypothesis of the continental drift was developed in the early twentieth century.
Alfred Wegener continental
drift: -
The continental drift theory was
proposed by German geophysicist, meteorologist Alfred Wegener in the year of
1912. According to Wegener, all the continents move around on earth’s surface
and they were once joined together as a single supercontinent. The
continents were once united into a single subcontinent called Pangaea. The
meaning of Pangaea is all earth in Greek. Wegener proposed that Pangaea or big
landmass broke up a long time ago, after that the continents moved to their
current positions. This hypothesis is called The Continental Drift.
What causes continental drift:
- Continental
drift is the hypothetical theory that earth’s continents have moved relative to
each other throughout the geological period. In 1912 Alfred Wegener put this
concept to the world, but it was rejected by many geographers due to the lack of
any motive mechanism or mechanism for how it works. Later, the mechanism of the
continental drift was discussed by the plate tectonic theory. It proposed that
the continents move by riding on plates
with the help of the convectional flow of mantle.
Continental drift evidence:-
A. Presence
of same physical features-
1. South America and Africa seem to fit together at
once it is also known as Jig Saw Fit.
2. Based on the characteristics and structure it seems
that the west coast of India, Madagascar, and Africa were connected.
3. North and South America on the one
hand, and Africa and Europe on the other, fit along the mid-oceanic ridge.
B. Rocks of the same age across the oceans-
Using the Radiometric Dating shows that rocks have correlated with different continents of the earth. Such as the belt of ancient rocks of 2000 million years from Brazil coast matches with those from western Africa.
C. Tillite -
Tillite is the sedimentary rocks formed out of
deposits of the glacier. Mostly Tillite is found in cold regions. Gondwanaland
is the southern part of the initial Pangaea landmass which is divided into six different
landmasses (Africa, Falkland Island, Madagascar, India, Antarctica, and
Australia) where Tillite have been found which proved that these six landmasses
have the same history.
D. Magnetic Polarity Evidence –
In this case, two different scenarios are seen one is the magnetic pole on the same continent with different age group rocks and another is the magnetic pole on the different continents with same age group rocks. In simple words, the location of the magnetic north pole constantly changed. Examples are -
Europe's 400 million-year-old magnetite points to a different magnetic north pole than magnetite of the same age in North America.
200 million years ago, positions of the magnetic north poles were also different for the two continents.
E. Placer Deposits –
Placer deposits are reserves of valuable minerals like
diamonds, gold, etc. Placer deposit of gold is found on the Ghana coast,
similarly the same type of gold deposits is found in Brazil. Therefore it is
obvious that the gold deposits of Ghana derived from the Brazil plateau when to
continents are lay side by side.
The lemur is a famous
species in Madagascar but it is also found in India and Africa, which shows the
interrelationship between these three landmasses.
Drawback/Criticisms of the
continental drift theory
1. Wegener presenting the role of forces like
buoyancy, tidal currents, and gravity for continental drift. But these forces (buoyancy,
tidal currents, and gravity) are too weak or not enough to drift continents.
2. Wegener failed to explain that why the continental
drift began only in Mesozoic-era and not before.
3. This theory did not consider the ocean, which is a
big mistake.
4. There is no explanation for the formations of
island arc and oceanic ridge.
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