The Earth is divided into four distinct layers: inner core, outer core, mantle and crust.
BBC Bitesize – structure of the Earth 
Inner core: this is the hottest part of the Earth with temperatures of approximately 5,500°C . It is solid and made up of iron and nickel.
Outer core: this is also made up of iron and nickel but it is liquid. It is also extremeley hot with similar temperatures to the inner core.
Mantle: this is the thickest layer (approximately 2,900km thick). It is made up of semi-molten rock (magma). In the upper parts it is more solid than the lower parts where it is more liquid.
Crust: this is the outermost layer of the Earth. It is a thin layer broken up into sections called plates. There are two different types of crust: continental and oceanic.
Oceanic Continental
- Thin (up to 10km thick)
- Heavy
- Sinks into the mantle
- Relatively new (180 million years)
- Forms constantly at constructive plate margins
- Destroyed at destructive plate margins
- Thick
- Light
- Doesn’t sink
- Very old (up to 4 billion years)
- New crust isn’t formed
- Cannot be destroyed
Convection currents make the Earth’s plates move (https://www.youtube.com/watch?v=ryrXAGY1dmE).
Where convection currents diverge (move apart) the plates move apart, where convection currents converge (move together) plates also move together. Plates meet at a plate boundary.
World tectonic plates map
