The Rock Cycle.

The rock cycle is a basic concept in geology that describes transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous. Each rock type is altered when it is forced out of its equilibrium conditions. The three main rock types are igneous, metamorphic and sedimentary. The three processes that change one rock to another are crystallization, metamorphism, and erosion and sedimentation. Any rock can transform into any other rock by passing through one or more of these processes. This creates the rock cycle. It can melt into magma, erode into sediment, or be pressed tightly together to become metamorphic.

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