What is the structure of the Earth?

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