The mantle is made of material which differs both from the core and the crust. In the Earth, for example, the core is made of iron and nickel while the crust is made of cold solid rocks.

The mantle, which lies between them, is made of hot, semi-solid rock which flows slowly. It is shown in red on the diagram above.

A mantle is also found in Mercury, Venus, Mars and Pluto.

Because the mantle is made of molten rocks, it is the source of many volcanoes, especially those that form where plates pull apart, such as Iceland, or over hot spots such as Hawaii.