At the centre of the earth, is the core. Surrounding this is a layer of molten rock called the mantle. Then on top, is a thinner layer called the crust.
The Earth's crust is made up of seven large tectonic plates and lots of other smaller ones.
There are 2 types of crust:
Continental crust : Thick crust (30km)
Oceanic Crust : More dense, but thinner (5km)
There are three types of plate margins.
DESTRUCTIVE : When plates move together. The denser oceanic crust subducts (gets pushed under) the continental crust.
These types of plates can cause composite volcanoes as magma rises through the breakage.
Energy builds up in the subduction zone and is released as earthquakes. Fold mountains are created due to the collision of plates and ocean trenches are formed.
CONSTRUCTIVE : A constructive plate margin is when plates move apart and magma rises to fill the gap. These are usually found under the sea.
Ridges and shield volcanoes are formed by the build up of magma.
Volcanoes can form inlands if they rise above sea level.
CONSERVATIVE : This is when plates slide past each other. Sometimes the plates are going in the same direction but at different speeds. At times, they stick together, and earthquakes occur when built up pressure forces plates to unstick.
