Core and mantle

The mantle makes up the bulk of the Earth's interior. It reaches from about 10-90 km to 2890 km down. As you move through the mantle temperatures climb steadily, until they reach 3000°C.

Mantle rock is so warm that it churns slowly round like very, very thick treacle boiling on a stove. This movement is known as mantle convection currents. Mantle rock moves about 10,000 times more slowly than the hour hand on a kitchen clock. Cooler mantle rock takes about 200 million years to sink all the way to the core.

Near the surface, mantle rock may melt into floods of magma. These may gush through the upper layers like oil that is being squeezed from a sponge.

The boundary between the mantle and the core ( see Earth's interior ) is called the core - mantle boundary ( CMB ) . The CMB is about 250 km thick. Here temperatures jump by 1500°C. The difference in desity between the core and the mantle at the CMB is twice as great as the difference between air and rock