Tectonic Plates and Pangea

​Tectonic Plates

Some slide  past each other.  These plates are called transform plates.  The plates are found under the land and the ocean.  The plates under the land are called continental plates.  The plates under the ocean are called oceanic plates.  Plates move all of the time.  Big changes only happen to the Earth over millions of years. 

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​Tectonic Plates continued

The idea that plates form and move is called plate tectonics.  The word tectonic comes from a Greek word that means “to build”.  The phrase plate tectonics means that the Earth is built from plates of rock. 

Pangea

A long time ago, all of the continental plates were together as a large plate.  There was only one continent.  It was called Pangaea.  The picture (next slide) shows the movement of the continental plates from the time of Pangaea until now.  Over many hundreds of millions of years the continental plates separated. 

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Ocean Ridges and Trenches

Scientists have found a group of mountains in the middle of the ocean!  As they discovered more, they found these mountains are between all of the continents of the Earth.  The mountains are called the Mid-Ocean Ridge.  

Ocean Ridges and Trenches

Magma flows next to the  Mid-Ocean Ridge.  Magma is hot liquid from inside the Earth.  The magma spreads out along the ocean floor and cools.  Adding magma makes the oceanic plates grow.  As they grow, they push other plates away. 

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