This printable PDF explains how volcanoes erupt. It also gives step by step instructions on how to build a volcano of your very own
The lava that erupts from a volcano is in fact really hot rock. It is rock that has been heated so much that it has become runny. When this runny rock is underground, it is called magma.
Volcanoes form where the surface crust of the earth is weak. This means that the magma can creep up through cracks in the weak crust. When it gets to the surface: BOOM!
A volcanic eruption happens when the magma forces through the surface (like the way that a fizzy drink will spray everywhere if you shake it up before you open it!). The way that a volcano erupts depends on how runny the magma is and much pressure has built up before the magma breaks through the surface.
When a volcano erupts, we call the magma a new name: Lava.
Lava quickly cools down in the open air or sometimes, in water. When it cools down, the lava becomes hard again and turns back into rock.