The rock cycle All rocks are made from material that came originally from the Earth's hot interior as molten magma. Once the magma cools to form igneous rock, it is gradually worn away by the weather and the fragments are washed down into the sea. There they settle and form layers of sedimentary rock as they are squeezed and cemented together. When the movement of the Earth's crust thrusts these layers above the sea, they too can be worn away to form new sediments. Igneous rock forms from magma forced up from the Earth's interior.
Weather wears away the rock.
Fragments are washed into the sea and settle on the sea-bed. Sediments are cemented into layers of rock, then lifted up above the sea to be worn away again. Sedimentary rocks usually have clear horizontal layers, made as the sediments settled on the sea-bed. The top of each layer is called the bedding plane, and is often marked by a long crack. Bedding planes may be flat, or they may be tilted where the rock has been crumpled.