Igneous:
Igneous rocks are formed by magma from the molten interior of the Earth. When magma erupts it cools to form volcanic landforms. If magma cools inside the Earth it forms intrusive rock, which may later be exposed by erosion and weathering.
Examples of igneous rocks include basalt and granite.
Metamorphic:
Metamorphic rocks have been subjected to tremendous heat and/or pressure, causing them to change into another type of rock. They are usually resistant to weathering and erosion and are therefore very hard-wearing.
Examples of metamorphic rocks include marble and quartzite.
Sedimentary:
Sedimentary rocks are formed from sediments that have settled at the bottom of a lake, sea or ocean, and have been compressed over millions of years. The sediment comes from eroded rocks carried there by rivers or ice, and from the skeletons of sea creatures.
Examples of sedimentary rocks include sandstone, limestone, chalk and clay.
