The three rock types are introduced. Granite is named as an example of igneous rock. Igneous rock can be formed underground from molten rock, or magma. It cools slowly, resulting in large grained rock. Igneous rock can also be formed above ground from lava. It cools quickly, resulting in small grained rock.

First broadcast:
25 March 2003

This clip could be used as an introduction to modelling of the rock cycle or to a practical using the cooling of salol to show the size of crystals formed during intrusive and extrusive processes.