The earth

Structure: Crust - hard, rigid, it's the earths outmost and thinnest layer, 5 km deep under oceans, 30 km deep under continents.

Lithosphere - made from crust and tiny bits of the upper mantle. This layer is divided into several very slowly moving plates of solid rock.

Asthenosphere - Malleable semi-liquid zone in the upper mantle, directly under the lithosphere.

Mantle - subdivided into two parts, upper and lower mantle.

Outer core - The only liquid layer of the earth. A sea of mostly iron and nickel. It is roughly 2,890 - 5,150 km below the surface and roughly 2,300 km thick.

Inner core - Extremely hot, it is a solid sphere of mostly iron and nickel at the centre of the earth. It is 5,150 - 6,378 km below the surface, and about 1,200 km in diameter.

What are planets made of and why? By Madeleine