Evidence for plate tectonic theory

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  • Created on: 12-08-14 10:59
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Plate tectonics
How do we know that the earth is divided into
plates?
-The main evidence to show that the earth used to be all part of the same landmass is that most of
the continents fit together like a puzzle; the West African coastline fits into the east coast of South
America and the Caribbean sea; and a similar fit appears across the Pacific. In 1912 Alfred
Wegener(1880-1930) noticed the same thing and concluded that all the continents used to be part of
a pro-continent called Pangaea: meaning "all lands". Over time they had drifted apart due to
convection currents beneath the plates. Wegener's theory was based on the form of the continents,
similarities in fossils and contemporary life on different continents.
-We know that the earth has been divided into plates and was once a full landmass because
scientists have discovered that there are animals either of the same species or that are very similar
to each other on the edges of West Africa and Northeast South America. West Africa is where the
landmass curves in and south American is the corner, this means they fit together like a puzzle.
-Similar rock formations and fossilized plants were found on different continents.
-Scientists believe that the earth's crust is split into different plates, because of mountains,
volcanoes, earthquakes etc that are all moving really slowly.
-New sea floor is constantly being created along spreading centres because the plates are pulling
apart at boundaries like the Mid-Atlantic Ridge. This means that the sea floor near these ridges
should be very young geologically. The sea floor which is slowly going away, occurs in trenches, called
subduction zones. Trenches occur along the boundary between two plates that are moving towards
each other.

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