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 ...

Igneous rock is formed by the cooling of molten rock, either at the surface (lava), or underground (as granite or other similar rocks). The heat of molten rock usually incinerates organisms rather ...

It depends on what the rocks are made of – and that’s related to how they were formed. There are three main rock types: ...