Rocks are not permanent; they transform from one type to another over geologic time. The rock cycle describes these continuous transformations among igneous, sedimentary, and metamorphic rocks driven by Earth’s internal heat and surface processes.

Magma cools to form igneous rock. Weathering and erosion produce sediment that lithifies into sedimentary rock. Burial and heating convert both into metamorphic rock, which may eventually melt to form new magma. Uplift and erosion expose deep rocks at the surface, restarting the cycle.

Any rock type can in principle be converted into any other. The cycle links plate tectonics, climate, and surface processes into a single conceptual framework. It emphasizes that the materials of the crust are constantly recycled rather than created or destroyed in bulk.

• Continuous transformation among rock types
• Driven by internal heat and surface processes
• Links igneous, sedimentary, and metamorphic rocks
• Central concept of physical geology