Two types of sedimentary rock: limey shale overlaid by limestone. Cumberland Plateau, Tennessee.

Red sandstone: Wirral, England

Sedimentary rock: Karnataka, India

Pressure solution at work in a clastic rock. While material dissolves at places where grains are in contact, material crystallizes from the solution (as cement) in open pore spaces. This makes a net flow of material from areas under high stress to those under low stress. As a result, the rock becomes more compact and harder. Loose sand can become sandstone in this way.

Fossil in shale: Grube Messel, Germany

Sedimentary rocks are rocks formed from sediment. They are deposited over time, and often show layers which can be seen in cliffs. Other types of rock are igneous rock and metamorphic rock.

Sediments are usually formed from matter which falls to the bottom of oceans and lakes. The matter includes tiny pieces of other rocks, and dead animals, plants and microorganisms. Also, inorganic chemicals may be precipitated from solution in the water. The three most common sedimentary rocks are limestone, sandstone and shale.