1.8 The rock cycle

As you are reading this, rocks are being formed and destroyed on the Earth. Rocks are being heated and squeezed to form new metamorphic rocks; other rocks are melting to form magmas, which eventually cool and solidify as new igneous rocks; and the processes of weathering, erosion, transport and deposition are generating new sediments. The continuous action of rock-forming processes means that (given time) any rock in the Earth's crust will become transformed into new types of rock and that these too may in turn be transformed in to yet other rocks. We call this recycling of rock materials the rock cycle.