The Rock Cycle Explained: How Three Main Rock Types Form
The rock cycle explains how rocks change over time. There are three main rock groups: igneous, sedimentary and metamorphic. An andalusite specimen. Photo: Moha112100, CC BY-SA 3.0 , via Wikimedia Commons . Image unchanged. Igneous rocks: cooling from melted rock Magma is melted rock below the surface. When melted rock cools and becomes solid, it forms igneous rock. Sedimentary rocks: pieces become rock Weathering breaks rocks into smaller pieces. Water, wind or ice can move these pieces. Sediment builds up in layers. Compaction and cementation can turn it into sedimentary rock. Metamorphic rocks: change without melting Heat and pressure can change a solid rock into metamorphic rock. Melting is a different process. If rock melts, it becomes magma and may later form igneous rock. Does every rock follow the same path? No. The rock cycle is a model with many possible paths. A rock can be weathered, buried, changed or melted. It does not have to pass through all three groups in a fixed orde...