Cycles are sequences of events that repeat themselves over and over again. Some cycles, such as the seasons of the year, move in one direction only. Other cycles, such as the rock cycle, are bit more complicated because the events don't always happen in the same order. Here's how the rock cycle works:
- Heat and pressure as well as weathering and erosion can change a rock's form, recycling it from one rock type to another.
- Each of the rock types - igneous, sedimentary, and metamorphic - can be recycled into the other two.
- Igneous and metamorphic rock can be eroded and weathered into sediments that, over time, are cemented into sedimentary rock.
- Igneous and sedimentary rock break down when exposed to heat and pressure and get recycled into metamorphic rock.
- Sedimentary and metamorphic rock can be melted into magma and, when cooled, form igneous rock.