Edexcel GCSE Geography

## Rock types and where they are found Rocks are grouped by how they formed, and each group behaves differently when it is attacked by weather, rivers, ice and the sea. | Rock type | How it forms | UK examples | Where they mainly occur | |---|---|---|---| | Sedimentary | Sediment is laid down in layers, then squeezed and cemented over millions of years | Chalk, limestone, sandstone, clay | South and east England, with the Pennines and parts of Wales | | Igneous | Molten rock cools and solidifies, quickly at the surface (basalt, fine crystals) or slowly underground (granite, coarse crystals) | Basalt, granite | Scottish Highlands, Cheviots, Lake District, Dartmoor and Cornwall, Antrim in Northern Ireland | | Metamorphic | Existing rock is changed by heat and pressure without melting | Slate, schist | Scottish Highlands, North Wales, the Lake District | Sedimentary rocks are layered (bedded), often contain fossils and are usually the softest, although they vary a good deal: clay is weak and easily eroded, while chalk and the limestone of the Pennines are more resistant. Igneous and metamorphic rocks are crystalline and generally hard and resistant, because the crystals interlock and there is little water-bearing structure for weathering to exploit. Because the oldest and hardest rocks lie in the north and west, and the youngest and softest in the south and east, the UK is often described as divided by a line from the mouth of the River Tees to the mouth of the River Exe…