What is a Tectonic Plate?

Look at a map of the world.
Can you see the shapes of Africa and South America?
Does it look as if they will fit together?
Make a jigsaw puzzle of the two shapes and find out if they do.

Early in the 20th century, a German scientist called Alfred Wegener studied fossils in rocks from Africa and South America. Fossils are imprints or remains of plants or animals usually found in rocks. He found that the fossils on both continents were the remains of the same animals and plants.
He introduced the theory that mountains in different countries might once have been joined together. 
The Cape Mountains in South Africa, for example, could have once been joined to mountains south of Buenos Aires, in Argentina.
Wegener believed that, over millions of years, the continents had gradually moved away from each other.
Continents are still moving today. Scientists call this movement the continental drift.

What are tectonic plates?

Many scientists now believe that the crust of the earth is not formed in one huge piece, but is divided up into large sections, called tectonic plates.
These solid plates are floating on the mantle, the thick layer of solid rock that also contains hot, liquid rocks moving underneath the earth's crust.

What causes tectonic plates to move? 

It's so hot inside the earth, that some of the molten rocks in the mantle are pushed upwards.
These rocks break through the crust at the weakest points of the crust, usually where two plates meet.
Then the plates are pushed apart.
In other places, cooler rocks in the mantle are pushed downwards towards the hot inner core.
When the plates that make up the earth's crust are pushed together, one plate is forced below the other and melts in the mantle.

How fast are the tectonic plates moving?

Tectonic plates move from less than one inch (2.5 centimeters) to eight inches (20 centimeters) a year.
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