The Earth's crust is made up of huge floating plates.
Plates are on top of the mantle, which moves very slowly (a few mm per year).
The movement is caused by Convection Currents in the mantle.
The place where plates meet are called plate boudaries or margins.
There are 3 types of plate boundary.
Constructive plate boundary is formed when 2 plates diverge (move apart).
Magama ruses from the gaps created and cools, forming new crustal rocks.
This happen undersea an example is the mid-atlantic ridge.
Destructive plate boundary is when 2 plates push against each other.
This often causes one plate to be forced down and the toher plate to squash up forming fold moutains.
Earthquake and volcanos are commonly caused by this.
Oceanic plates are denser than continental plate so it sinks under the continental plate.
Sometimes this causes friction and builds up the tension as the plates can get stuck.
And when the tension is released it will cause an earthquake.
The denser plate will become magma when it enters the mantle.
Heat and pressure force the magma to the surface to form volcanoes.
Or if 2 plates are the same density this can cause the plates to squash up creating fold mountains.
Conservative plate margins are when plates slide sideways against each other.
Volcanoes are rare…