Rock is a solid material and only exists as a shell around the outside of the Earth. Inside the Earth is molten.

Rock is made from chemicals called minerals. Minerals form regular shapes called crystals which can lock together to give the rock its strength. This is the kind of rock that forms when lava from volcanoes cools and becomes solid. Basalt and granite are the names of two kinds of rock that began as molten material.

All other kinds of rock are made when volcanic rock is worn down by rivers and glaciers. It is broken down into small particles which are carried to the sea where they settle out in layers. If the fragments are sandy, the material gradually turns into sandstone; if the material settling out is fine, the rock that forms is called shale. Sometimes the shells of animals also gather in large enough amounts to make rock. This is called limestone or chalk.

Many rocks contain important materials that we can use to make things. These include metals, such as copper. The video below shows what a rock with copper looks like. A rock with important amounts of metal in it is called an ore.