Rocks come in many shapes, textures and colours. But they are all formed in one of three ways. Some is spewed out by volcanoes to form extrusive igneous rock. Some is forced up beneath the surface, forming intrusive igneous rock.
Molten magma is incredibly hot as it nears the surface, but it soon starts to cool.
As it cools, more and more crystals appear, until eventually all the magma becomes a solid mass of hard, crystalline rock. Sedimentary rock forms in thin layers from debris that settles on the sea-bed and then is squeezed and cemented over millions of years into solid rock. Some, like limestone, are made largely from plant and animal remains, or from chemicals settling out of the water. Most, however, are clastic - made from fragments of rock worn away by the weather and washed down into the sea by rivers. Metamorphic rock is made when rock is crushed by the huge forces that build mountains or seared by the ferocious heat of magma.