The Rock Cycle

geology · earth science · transformation · plate tectonics

Three main types. All rocks on Earth fall into three categories: igneous (formed from melted rock), sedimentary (formed from compressed sediments), and metamorphic (changed by heat and pressure underground).

Endless recycling. Rocks don't stay the same forever. An igneous rock can break down into sediment, get pressed into sedimentary rock, then be pushed deep underground where heat turns it into metamorphic rock.

Water's role. Rain and rivers break down rocks into tiny pieces called sediment. This sediment gets carried away, buried, and eventually becomes new rock layers.

Heat transforms rocks. When rocks get pushed deep into the Earth by plate tectonics, extreme heat and pressure can change their structure completely, creating metamorphic rock without melting them.

Melting completes the cycle. If a rock gets pushed too deep, it melts back into magma, which can cool again to form brand new igneous rock, starting the whole cycle over.