Did you know that you can find all sorts of ancient rocks in towns and cities?
Next time you go to your local high street, look closely at the different types of rock that buildings are made from. You might find sandy stones that were formed from ancient seas, or glassy rock that was formed when hot liquid rock (magma) first burst through the Earth's surface.
Igneous rocks are formed by magma from Earth's molten interior. Examples of igneous rocks include basalt and granite.
Sedimentary rocks are formed from sediments that have settled at the bottom of a lake, sea or ocean, and have been squashed down 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.
Metamorphic rocks can begin life as either type of rock but have been subjected to heat and/or pressure, causing them to change into another type of rock. Examples of metamorphic rocks include marble, which originates from limestone, and slate, which originates from clay.
Find out more about how different types of rocks formed at Geology for Kids.