RocksGroup6

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Rocks__ **Rocks** are naturally occurring solids composed of minerals.There are **three** different types of rocks: **Igneous Rocks, Sedimentary Rocks, and Metamorphic Rocks.** The **Rock Cycle** is a fundamental concept in geology that describes the dynamic transitions through geologic time among the three main rock types: sedimentary, metamorphic, and igneous.
 * **Igneous Rocks** form by magma (molten rock) cooling and becoming solid.
 * **Sedimentary Rocks** form by sedimentation of material at the Earth's surface and within bodies of water.
 * **Metamorphic Rocks** are formed from existing rock (sedimentary, igneous, metamorphic) by the action of heat, pressure, and chemicals.

__Igneous Rocks__ **Igneous Rocks** form by magma (molten rock) cooling and becoming solid. There are two kinds of igneous rocks:
 * Intrusive rocks** form below the earth's surface.
 * Extrusive rocks** form on the earth's surface.

Intrusive Rocks
 * Diorite Gabbro Granite Pegmatite**
 * 1) **Diorite** is a coarse-grained, intrusive igneous rock that contains a mixture of feldspar, pyroxene, hornblende and sometimes quartz.
 * 2) **Gabbro** is a coarse-grained, dark colored, intrusive igneous rock that contains feldspar, augite and sometimes olivine.
 * 3) **Granite** is a coarse-grained, light colored, intrusive igneous rock that contains mainly quartz and feldspar minerals.
 * 4) **Pegmatite** is a light-colored, extremely coarse-grained intrusive igneous rock. It forms near the margins of a magma chamber during the final phases of magma chamber crystallization.

Extrusive Rocks
 * Andesite Basalt Rhyolite Scoria**

**Andesite** is a fine-grained, extrusive igneous rock composed mainly of plagioclase with other minerals such as hornblende, pyroxene and biotite.
 * Basalt** is a fine-grained, dark-colored extrusive igneous rock composed mainly of plagioclase and pyroxene.
 * Rhyolite** is a light-colored, fine-grained, extrusive igneous rock that typically contains quartz and feldspar minerals.
 * Scoria** is a dark-colored, vesicular, extrusive igneous rock. The vesicles are a result of trapped gas within the melt at the time of solidification. It often forms as a frothy crust on the top of a lava flow or as material ejected from a volcanic vent and solidifying while airborne.


 * Physical Properties:**
 * **Texture**- size of crystals in an igneous rock
 * **Color**- composed minerals in an igneous rock

__Sedimentary Rocks__ Metamorphic rocks are classified into 3 groups:
 * Metamorphic Rocks **  are formed from existing rock (sedimentary, igneous, metamorphic) by the action of heat, pressure, and chemicals.
 * 1) **Clastic** rocks were formed from rocks that have been broken down into fragments by weathering, which then have been transported and deposited elsewhere.
 * 2) **Organic** rocks contain materials generated by living organisms, and include carbonate minerals created by organisms.
 * 3) **Chemical** rocks form when minerals in solution become undersaturated and precipitate.

**Lithification**- is the cementation and compaction of rock fragments that form sedimentary rocks. 

Examples of Sedimentary Rocks:
 * Breccia Chert Coal Conglomerate**
 * 1) **Breccia** is a clastic sedimentary rock that is composed of large (over two millimeter diameter) angular fragments. The spaces between the large fragments can be filled with a matrix of smaller particles or a mineral cement which binds the rock together.
 * 2) **Chert** is a microcrystalline or cryptocrystalline sedimentary rock material composed of silicon dioxide (SiO2). It occurs as nodules and concretionary masses and less frequently as a layered deposit. It breaks with a conchoidal fracture, often producing very sharp edges.
 * 3) **Coal** is an organic sedimentary rock that forms mainly from plant debris. The plant debris usually accumulates in a swamp environment. Coal is combustible and is often mined for use as a fuel.
 * 4) **Conglomerate** is a clastic sedimentary rock that contains large (greater then two millimeters in diameter) rounded particles. The space between the pebbles is generally filled with smaller particles and/or a chemical cement that binds the rock together.

 __Metamorphic Rocks__ <span style="color: #000000; font-family: 'Arial Black',Gadget,sans-serif; font-size: 10pt;"> Metamorphic rocks <span style="color: #000000; font-family: 'Times New Roman',Times,serif; font-size: 12pt;">are formed from existing rock (sedimentary, igneous, metamorphic) by the action of heat, pressure, and chemicals. <span style="font-family: 'Arial Black',Gadget,sans-serif; font-size: 10pt;">Metamorphism <span style="font-family: 'Times New Roman',Times,serif; font-size: 12pt;"> is the process of forming metamorphic rocks within the lithosphere, making the rocks more dense and less porous <span style="font-family: 'Arial Black',Gadget,sans-serif; font-size: 10pt;">Parent Rock <span style="font-family: 'Times New Roman',Times,serif; font-size: 12pt;">is the rock that becomes metamorphosed


 * Examples of changes-**Limestone being changed into marble, Shale turning into slate, Granite being changed into gneiss, Sandstone turning into quartzite <span style="font-family: 'Arial Black',Gadget,sans-serif;">

Physical characteristics- <span style="font-family: 'Times New Roman',Times,serif; font-size: 12pt;">
 * 1) <span style="font-family: 'Comic Sans MS',cursive; font-size: 12pt;">Foliation <span style="font-family: 'Times New Roman',Times,serif; font-size: 12pt;">- gives the appearance of parallel light and dark bands,or is simply a platy or flaky texture
 * 2) <span style="font-family: 'Comic Sans MS',cursive; font-size: 12pt;">Non foliation <span style="font-family: 'Times New Roman',Times,serif; font-size: 12pt;">- display a massive texture, caused by the recrystallization of the crystals that were present in the relatively homogenous parent rock from which they were formed
 * 3) <span style="font-family: 'Comic Sans MS',cursive; font-size: 12pt;">Recrystallization - is the process of changing the mineral composition or increasing the size of the mineral crystals with out melting

__ **<span style="display: block; font-family: 'Comic Sans MS',cursive; font-size: 150%; text-align: left;">Foliated Rocks ** __<span style="display: block; font-family: 'Comic Sans MS',cursive; font-size: 150%; text-align: left;">  **Gneiss Slate Phyllite Schist**


 * 1) **Gneiss** is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. It typically contains abundant quartz or feldspar minerals.
 * 2) **Slate**  is a foliated metamorphic rock that is formed through the metamorphism of shale. It is a low grade metamorphic rock that splits into thin pieces.
 * 3) **Phyllite** is a foliate metamorphic rock that is made up mainly of very fine-grained mica. The surface of phyllite is typically lustrous and sometimes wrinkled. It is intermediate in grade between slate and schist.
 * 4) **Schist** is metamorphic rock with well developed foliation. It often contains significant amounts of mica which allow the rock to split into thin pieces. It is a rock of intermediate metamorphic grade between phyllite and gneiss.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 150%;">**Non Foliated Rocks**
 * Amphibolite Hornfels** **Marble** **Quartzite**


 * 1) **Amphibolite** is a non-foliated metamorphic rock that forms through recrystallization under conditions of high viscosity and directed pressure. It is composed primarily of amphibole and plagioclase, usually with very little quartz.
 * 2) **Hornfels** is a fine-grained nonfoliated metamorphic rock with no specific composition. It is produced by contact metamorphism. Hornfels is a rock that was "baked" while near a heat source such as a magma chamber, sill or dike.
 * 3) **Marble** is a non-foliated metamorphic rock that is produced from the metamorphism of limestone. It is composed primarily of calcium carbonate.
 * 4) **Quartzite** is a non-foliated metamorphic rock that is produced by the metamorphism of sandstone. It is composed primarily of quartz.

Regional Metamorphism Regional or Barrovian metamorphism covers large areas of continental crust typically associated with mountain ranges, particularly subduction zones or the roots of previously eroded mountains. Conditions producing widespread regionally metamorphosed rocks occur during an orogenic event.. The collision of two continental plates or island arcs with continental plates produce the extreme compressional forces required for the metamorphic changes typical of regional metamorphism. These orogenic mountains are later eroded, exposing the intensely deformed rocks typical of their cores. The conditions within the subducting slab as it plunges toward the mantle in a subduction zone also produce regional metamorphic effects. <span style="color: #008000; display: block; font-family: Verdana,Geneva,sans-serif; font-size: 170%; text-align: center;"> Contact Metamorphism Contact metamorphism occurs typically around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock. The area surrounding the intrusion (called **aureoles**) where the contact metamorphism effects are present is called the metamorphic aureole. Contact metamorphic rocks are usually known as hornfels. Rocks formed by contact metamorphism may not present signs of strong deformation and are often fine-grained. <span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 170%; line-height: normal; text-align: center;"> metamorphism Hydrothermal metamorphism is the result of the interaction of a rock with a high-temperature fluid of variable composition. The difference in composition between existing rock and the invading fluid triggers a set of metamorphic and metasomatic reactions. The hydrothermal fluid may be magmatic (originate in an intruding magma), circulating groundwater, or ocean water. Convective circulation of water in the ocean floor basalts produces extensive hydrothermal metamorphism adjacent to spreading centers and other submarine volcanic areas. The patterns of this hydrothermal alteration is used as a guide in the search for deposits of valuable metal ores. <span style="color: #800000; font-family: Impact,Charcoal,sans-serif; font-size: 29px; line-height: 31px;">