Geology And Types Of Rocks: Igneous, Sedimentary Rocks (Essay Sample)

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Types of rocks
Geologists define a rock any coherent, naturally occurring substance generally composed of minerals. Rocks are grouped into three categories that are igneous rocks, Sedimentary rocks, and metamorphic rocks.
Igneous rocks
Igneous rocks are formed by the solidification of magma, a silicate liquid generated by partial melting of the upper mantle or the lower crust. Different environments of formation, and the cooling rates associated with these, create very different textures. There are two main groupings of igneous rocks: volcanic rocks and plutonic rocks.
Volcanic rocks form when magma rises to the surface and erupts, either as lava or pyroclastic material. The rate of cooling of the magma is rapid, and crystal growth is inhibited. Volcanic rocks are characteristically fine-grained. Volcanic rocks at times show structures from their eruption, e.g. molded by shearing the lava as it flowing or banding flow, and exposed voids or cracks that signify bolted gases. Plutonic rocks on the other hand develop when magma cools inside the Earth's crust. The degree at which magma cools is slow thus it allows growing of large crystals. Plutonic rocks are typically coarse-grained. Igneous rocks play a significant role in geology in the following:
Their  HYPERLINK "https://en.wikipedia.org/wiki/Minerals" \o "Minerals" minerals give data and facts about the structure of the mantle, from which several igneous rocks are mined. It helps to know pressure and temperature situations that allow this mining.
Their  HYPERLINK "https://en.wikipedia.org/wiki/Absolute_dating" \o "Absolute dating" actual ages can be acquired from several types of  HYPERLINK "https://en.wikipedia.org/wiki/Radiometric_dating" \o "Radiometric dating" radio dating and thus be related to adjacent geological  HYPERLINK "https://en.wikipedia.org/wiki/Stratum" \o "Stratum" strata, giving a time arrangement of occasions.
Their features are normally characteristic of precise tectonic surroundings, permitting tectonic reconstructions.
They have vital mineral deposits: e.g., tin, uranium and,  HYPERLINK "https://en.wikipedia.org/wiki/Tungsten" \o "Tungsten" tungsten are generally linked with  HYPERLINK "https://en.wikipedia.org/wiki/Diorite" \o "Diorite" diorites and granites, whereas rocks of platinum and  HYPERLINK "https://en.wikipedia.org/wiki/Chromium" \o "Chromium"  are usually linked with  HYPERLINK "https://en.wikipedia.org/wiki/Gabbro" \o "Gabbro" gabbros.
The environment of development generates typical textures which contribute to their identification. These textures are as follows:
Phaneritic where this texture defines a rock with huge, simply observable, linking crystals of numerous minerals. The crystals rocks are casually dispersed. A phaneritic texture is normally created by the sluggish cooling and crystallization of magma liquid trapped inside the Earth's crust and is typical of plutonic rocks.
Porphyritic texture defines a rock that has good crystals observable by the naked eye, established in a precise fine grained, called groundmass. It results when magma has slowly cooled and crystallized inside the Earth's crust and suddenly erupting at the surface, making the remaining uncrystallised magma to cool fast. Most volcanic rocks experience this characteristic...
Aphanitic texture defines very fine grained rock where separate crystals rocks are only visible with the help of a microscope, for instance the rock is generally groundmass. It is normally results when magma comes out of the Earth's surface and then cools too rapidly for huge crystals to develop. This texture is usually revealed by certain volcanic rocks.
Eutaxitic texture defines a rock with a planar material in which compressed  HYPERLINK "javascript:setCookie('pumice','rhyolite.html');" pumice clasts are usually bounded by a fine grained ground mass of the sintered ash. The compressed pumice clasts are lens-shaped in cross-section and are normally known as fiamme. In addition this texture develops when hot, pumice-rich substance explosively erupts and then flattened by overlying plastic plate substance that is still hot.
The chemical structure of the magma decides which  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/index.html" minerals will form and in what sizes they will transpire. Therefore, identification of the minerals present in the rock is a significant stage in being able to properly classify the rock. Magmas that are relatively low in silica crystallize  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/olivine.html" olivine, pyroxene and calcium-rich  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/plagioclase.html" plagioclase, while magmas that are high in SiO2 crystallize  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/quartz.html" quartz, sodium-rich  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/plagioclase.html" plagioclase,  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/orthoclase.html" orthoclase,  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/biotite.html" biotitic and  HYPERLINK "https://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/hornblende.html" hornblende. Thus, igneous rocks can be divided into mafic and felsic types. Mafic rocks are normally darker, and have higher loads of  HYPERLINK "javascript:setCookie('mafic','../minerals/physical.html');" mafic minerals. Felsic rocks are normally lighter in color, having a higher quality or degree of  HYPERLINK "javascript:setCookie('felsic','../minerals/physical.html');" felsic minerals.
Sedimentary rock
Sedimentary rocks are usually the result of the erosion of current rocks. Eroded or worn out material adds as sediment, either in the land or sea, and is then suppressed, compressed and cemented resulting in the formation of sedimentary rock. An element that develops or forms a sedimentary rock by accruing is called  HYPERLINK "https://en.wikipedia.org/wiki/Sediment" \o "Sediment" sediment. Before its deposited, sediment or deposit is developed by erosion and  HYPERLINK "https://en.wikipedia.org/wiki/Weathering" \o "Weathering" weathering in a source area, and then conveyed to the location of deposition by wind, mass glaciers,  HYPERLINK "https://en.wikipedia.org/wiki/Water" \o "Water" water,  HYPERLINK "https://en.wikipedia.org/wiki/Ice" \o "Ice" ice, which are normally referred to as means of  HYPERLINK "https://en.wikipedia.org/wiki/Denudation" \o "Denudation" denudation.
There are two major groupings of sedimentary rocks: Clastic sedimentary r...