The rock cycle describes the processes through which igneous, sedimentary, and metamorphic rocks transform into one another in geological time. The forces that drive the rock cycle are plate tectonics and the water cycle on the surface. These two factors set the earth apart from the other planets in the solar system.

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As tectonic plates are subjected to the forces of thermal convection in the earth’s mantle, divergence, convergence, and subduction occur. The rocks in the plates, in turn, undergo different temperature and pressure conditions that change structure and mineral composition of the rocks. Moreover, the water cycle on the surface erodes rocks into smaller pieces as well as facilitate chemical reactions that affect mineral compositions. It is fair to say that the three major rock types and the rock cycle attest the vitality of the earth.