Rocks can be changed from one type to another and the rock cycle describes how this happens. The figure in the next page show the rock cycle and how the three main rock types are related to each other. The arrows within the circle show how one type of rock may change to a rock of another type. For examples, igneous rock may break down into small pieces of sediment and become sedimentary rock or it may be buried within the earth and become metamorphic rock, or it may change back to molten material and re-cool into a new igneous rock.