Description of the Rock Cycle

Volcanic Eruption

• Although an explanation of the rock cycle can start at any stage, this one will begin with the eruption of a volcano.

Igneous Rock

• When magma erupts from a volcano, it cools to become igneous rock. Igneous rock can also be formed underground and then slowly push to the surface. Common forms of igneous rock include granite, obsidian and basalt.

Sediment and Lava

• Igneous rock can then undergo several changes. If it melts, it turns back into lava. If it receive heat and pressure, it changes to metamorphic rock. If it is eroded, it becomes sediment.

Sedimentary Rock

• When sediment is compacted and cemented together, it turns into sedimentary rock. The most well known types of sedimentary rock are limestone, sandstone and conglomerate rock.

Metamorphic Rock

• The sedimentary rock will then either erode and become sediment again, or will undergo heat and pressure and become metamorphic rock, commonly known as gneiss, marble, or quartzite. Metamorphic rock is then either eroded and turned into sediment, or melted and turned to lava.