The Rock Cycle is a group of changes. Igneous rock can change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Igneous rock forms when magma cools and makes crystals. Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly.
The rock cycle is a process in which rocks are continuously transformed between the three rock types igneous, sedimentary and metamorphic .Conversion to metamorphic rocks requires conditions of increased temperature and/or increased pressure, conversion to sedimentary rocks occurs via the intermediate stage of sediments, and conversion to igneous rocks occurs via the intermediate stage of magma. Increased temperature and pressure occurs in subduction zones and in areas where two plates of continental lithosphere collide to produce a mountain range, while increased pressure without increased temperature is produced when sedimentary rocks are deeply buried under more sediments. Sediments are produced when rocks are uplifted, weathered and eroded, and the resulting detrital material deposited in marine or terrestrial basins. If the sediments are buried under further layers of sediment, they can become lithified to produce a sedimentary rock. Magma is produced when rocks are melted. This melting can occur when a lithospheric plate descends into the Earth’s crust at a subduction zone, or when a mid-ocean ridge opens up and produces decompression melting in the athenosphere under the ridge. When the magma solidifies, it becomes an igneous rock.
The rock cycle has many alternative pathways. The following diagram illustrates one of these and gives an indication of the plate tectonic setting where it occurs:
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