THE ROCK CYCLE

THE ROCK CYCLE IS A GROUP OF CHANGES IN WHICH: 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 Igneous rock is formed 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.

SEDIMENTARY ROCK Sedimentary rocks form at or near the earth's surface at relatively low temperatures and pressures primarily by: deposition by water, wind or ice precipitation from solution (may be biologically mediated) growth in position by organic processes (e.g., carbonate reefs )

METAMORPHIC ROCK Metamorphic Rock is formed when rocky material experiences intense heat and pressure in the crust of the earth. Through the metamorphic process, both igneous rocks and sedimentary rocks can change into metamorphic rocks, and a metamorphic rock can change into another type of metamorphic rock. Heat and pressure do not change the chemical makeup of the parent rocks but they do change the mineral structure and physical properties of those rocks.

SEDIMENT Sediment can either be: Material, originally suspended in a liquid, that settles at the bottom of the liquid when it is left standing for a long time Material eroded from preexisting rocks that is transported by water, wind, or ice and deposited elsewhere

PLUTONIC AND VOLCANIC ROCK Volcanic rocks, or extrusive rocks or lava rocks, crystallize when the magma reaches the earth’s surface cooling quickly. Plutonic or intrusive rocks crystallize within the crust of the earth, and as a result plutonic rocks cool at a much slower pace then volcanic rocks

Melting Melting is the result of continued heating Leads to production of magma and new igneous rocks which are formed when the the magma cools. This process depends on the size of the reservoir that it drains and the relative intensity or activity of plate tectonics.

HEAT AND PRESSURE Metamorphic rocks trapped underground are still subject to enormous heat from rising magma, or heated water, and pressure. Sometimes the heat can get so intense the rocks actually melt. Pressure comes from the incredible weight of material surrounding the rock on all sides. The pressure pushes new minerals into the rock and drives other minerals out; the result, of course, is that the rock is chemically changed.

WEATHERING The process in which rocks are broken down by chemical and/or physical mechanisms into smaller particles. There are three types of weathering Physical weathering: physical action which breaks up rocks. An example of this is freethaw weathering Chemical Weathering: when the rock is attacked by chemicals. An example of this is how acid rain breaks down limestone. Biological weathering: occurs when rocks are weakened and broken down by animals and plants. A tree root system that is slowly splitting rocks is an example of this type of weathering..

EROSION Erosion is the wearing away of exposed surfaces by agents such as wind, moving water and ice. These agents usually contain weathered rock debris. Rock fall under gravity is also erosion. Erosion influences orogenesis by changing the topography and hence the thickness of the deforming orogen, which, in turn results in modification of the gravitational force relative to the tectonic driving force. Whereas efficient erosion tends to localize deformation within a relatively narrow belt, decrease in erosional efficiency causes deformation to propagate toward more distal sites.

Subduction A rock that gets caught up in the subduction zone may get dragged down with the oceanic plate. As the rock gets dragged down, they undergo metamorphism. Some parts of the rocks get taken all the way down to the mantle where they slowly mix with the rest of the mantle. – this is the only way that rocks formed on the continent get recycled with the mantle.

COMPACTION The result of this pressure is a compaction of the sediment it is squeezed together causing a reduction in pore space and a sticking together of the grains. Under pressure, some chemical sediments, like halite, may recrystallize into a solid state.

CEMENTATION Most sediments are deposited in water containing dissolved minerals. The water flows through the sediment and some of these minerals precipitate on the grain surfaces. With time, this intergranular material effectively glues the sediment together into a cohesive solid- a sedimentary rock.

UPLIFTING Because certain rocks are created under the Earth ’ s surface A process called uplifting occurs through orogeny and volcanic process, which then bring rocks to the surface. The rock is eventually becomes recycled again.

TRANSPORTATION This process occurs when the particles created by weathering are carried by ice, air, or water to a region of lower energy known as a sedimentary basin.

DECOMPOSITION Decomposition takes place when a lowering of hydraulic energy, organic biochemical activity, or chemical changes occur.

CRYSTALLIZATION When hot conditions that caused magma to melt will cool, either because the source of heat subsides or the magma moves into cooler regions of the Earth. When it gets cool enough the minerals that will make up the rock begin to crystallize and form an intergrown mass of crystals. If the crystals begin to form deep in the Earth where it is relatively warm the magma cools slowly allowing the crystals to grow relatively large. If the magma reaches the surface, the lava cools quickly and the crystals do not have time to grow very large. If the crystals cannot grow at all and volcanic glass is formed.