There are some exceptions, such as tree trunks surrounded by lava and preserved as casts, but these are rare. Metamorphic rock is formed when existing rock is transformed under high heat and pressure, ...

Sedimentary rocks are formed by small rock pieces which are transported by rivers and laid down in layers. Chalk is a sedimentary rock. Metamorphic rocks are formed when another rock is under heat ...

The last group of rocks is called metamorphic, because these rocks form when a lot of heat and pressure change existing rocks ...

This is a beginner's guide to identifying UK rock types. The guide has two main sections: background information on the structure and forces affecting the Earth in relation to rock formation a more ...