Copyright © 2007 Dorling Kindersley
The rocks under our feet seem permanent, but they are constantly being changed. This process is called the rock cycle. Rocks exposed on the Earth’s surface are slowly broken down into sediments by water, ice, and wind. Meanwhile, new rocks are being created and recycled by forces in the Earth’s crust and mantle, deep down under the surface.
Older rocks on the surface are destroyed by erosion, or by being pushed down into the crust and melted. New rock is formed as sediments are compressed into sedimentary rocks, erupted magma cools and solidifies into igneous rocks, and heat and pressure changes rocks underground into metamorphic rocks.