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.