Bitesize has changed! We're updating subjects as fast as we can. Visit our new site to find Bitesize guides and clips - and tell us what you think!


The rock cycle


Erosion and transport


Weathering and erosion are often confused, so be careful when answering questions about them.

Weathering is the wearing away of rocks.

Erosion is the movement of the broken pieces away from the site of weathering.

basalt columns

Basalt columns

For example, a basalt cliff may be weathered by freeze-thaw, a type of physical weathering. This means that pieces of the cliff may break away.

Erosion happens when these pieces of rock fall away down the cliff.

In the photograph you can see a basalt cliff. At the bottom there are heaps of rocks, caused by weathering then erosion.


Rivers and streams can move pieces of rock. This is called transport. Fast flowing rivers can transport large rocks, but slow moving rivers can only transport tiny pieces of rock.

As the pieces of rock are carried along by the water, they bash against each other and the river bed. They gradually wear away because of this. They become smaller and more rounded.


Rocks activity

This activity rocks!



Join Questionaut's quest to find his friend's hat.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.