Earth's Structure

Planet Earth has layers made of different materials: an outer crust, a mantle and a core at its centre.

The crust is a very thin layer of rock – basalt below the oceans (10 km thick), and granite and sedimentary rocks on the continents (up to 70 km thick). Under the crust is the mantle, a semi-solid layer 2830 km thick. It is composed mainly of silicate minerals such as olivine. We get clues about its composition when molten rock from this layer comes to the surface during volcanic eruptions.

Below the mantle, the outer core is a layer of slow-moving liquid metal. It generates electrical currents as it flows and these create Earth’s magnetic field. Right in the centre of the Earth, the inner core is a solid mass of hot metal reaching over 5000 °C.