Restless world - plate tectonics

Plate tectonics

Pangea

 - scientists believed that about 250million years ago there was one super continent called pangea  

 - identical fossils have been found on different continents, sea fossils found on the summit of Mount Everest

 - convection currents moved the continent apart

Crust - old and new

 - continental crust is about 3-4billion years old

 - oceanic crust is about 180million years old

 - new oceanic crust is formed at plate boundaries

 - continental crust is less dense than oceanic crust so it can't be subducted or destroyed

Plate boundaries

 Conservative

 - plates slide past each other

 - violent earthquakes are produced

 - no volcanoes

Collision

 - plates push together and buckle

 - forms mountain ranges

 - violent earthquakes

 - volcanoes are rare

Constructive

 - plates pulled apart

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