7.1: The Rock Cycle

What Is the Rock Cycle?

The rock cycle is a circular diagram that demonstrates the process by which rocks are continually recycled throughout geologic time. All rocks can be classified into one of three groups: igneous, sedimentary, or metamorphic. This rock classification is based on the origin of each of these rock types, or the processes that form the rock. The Rock Cycle Links to an external site. (Figure 7.1), represents the processes that produce each of the rock types. Igneous rocks Links to an external site. are produced through the melting of rock and eventual cooling of lava or magma. As cooling occurs, crystals may form. Sedimentary rocks Links to an external site. are produced via the processes of weathering (the chemical and physical breakdown of material at Earth’s surface that produces sediments), erosion (the movement and deposition of sediments), and lithification (the compaction and cementation of sediments). Metamorphic rocks Links to an external site. are produced via the agents of change, primarily heat and pressure, which typically result in the recrystallization of minerals. These processes will be explored in greater detail in each of their respective chapters.