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Helena Bonici Geography 26/06/2011
12EA2 Plate Tectonics
CONTINENTAL DRIFT THEORY
This is the theory that all the continents and the plates are moving. It stems from belief that all
continents were once joined as one supercontinent called Pangaea, before they all moved apart.
There are several reasons for this belief:
There are many places in the world that all appear to link with
each other due to the similar bands of rock and soil that occur
in these places. However, there appears to be no connection
to the rocks within these continents. It is not until continents
are placed next to each other that the band appears to
continue between the continents, implying that they must've
been once joined.
Much like the bands of rocks, there also appears to be similar
fossils of the same animal on completely different continents.
Many of these creatures, from research, appear not to have
been great swimmers etc. which implies a different way that
they must be linked on these continents. It overall implies that
the continents must've been linked in some way for the animals
to have provinces and territory in both lands. However,
because they are not linked anymore, it means that the
continents must've moved.
A good example of this is the Mesosaurus.
When all the continents are placed together, they all appear to fit
easily with similar outlines. This implies that once they could've all
been connected in a way that the continents would've fitted. It can
then be taken once step further if the continental shelves are used
because they all fit extremely well, like a jigsaw. It means that it
would be completely possible for them to have all been one super
continent at one point because they all fit the same.
As the rocks are formed by the mantle, they develop
magnetism towards the Earth's magnetic poles and thus,
when different rocks move, they will have a magnetism that
faces towards the magnetic pole. If the continent then shifts,
the magnetism will not, so the original facing direction of the
magnetism will not alter. This means that the magnetism is
facing a different way other than to the pole of the Earth