ROCK CYCLE

ROCK CYCLE

Rocks are the most common material on Earth. Rock divisions occur in three major families based on how they formed: igneous, sedimentary, and metamorphic. The rock cycle is an illustration that is used to explain how the three rock types are related to each other and how Earth processes change a rock from one type to another.

First phase, igneous rock is formed when magma (the molten material found inside Earth) cools and solidifies. This process is called crystallization and can occur beneath the surface or at the surface via a volcanic eruption. When igneous rocks are on the surface of Earth, they are exposed to the different elements of weathering. These are the day to day influences of the atmosphere that slowly disintegrate and decompose the rocks. The resulting material is then picked up, transported and deposited by various erosion agents such as gravity, running water, wind, waves, or glaciers.

Sedimentary rocks are formed from the weathered material of igneous rocks. Once this weather material, called sediment, is deposited (usually as horizontal beds in the ocean) it undergoes a process called lithification which converts the sediment into rock. This occurs when the sediment is compacted by the weight of the overlying layers. Lithification also occurs when the sediment is cemented together as groundwater fills the pores between the sediment with mineral water. The end result in both cases is sedimentary rock.

Metamorphic rock is usually formed from sedimentary rock. When sedimentary rock is exposed to great heat or great pressure the transformation to metamorphic rock occurs. This usually occurs when sedimentary rock is buried deep within Earth or when it is involved in the dynamics of mountain building. When metamorphic rock is subjected to even greater heat and pressure, it melts to create magma, and this completes the rock cycle since eventually this magma will once again be transformed into igneous rock.