Rock (geology) - Wikipedia, the free encyclopedia. In geology, rock or stone is a naturally occurring solid aggregate of one or more minerals or mineraloids. For example, the common rock granite is a combination of the quartz, feldspar and biotite minerals. The Earth's outer solid layer, the lithosphere, is made of rock. Rocks have been used by mankind throughout history. From the Stone Age, rocks have been used for tools. The minerals and metals found in rocks have been essential to human civilization. The scientific study of rocks is called petrology, which is an essential component of geology. Classification. At a granular level, rocks are composed of grains of minerals, which, in turn, are homogeneous solids formed from a chemical compound that is arranged in an orderly manner. The aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed. Many rocks contain silica (Si. O2); a compound of silicon and oxygen that forms 7. Earth's crust. This material forms crystals with other compounds in the rock. The proportion of silica in rocks and minerals is a major factor in determining their name and properties. These physical properties are the end result of the processes that formed the rocks. These events produce three general classes of rock: igneous, sedimentary, and metamorphic. The three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks. By increase or decrease in the proportions of their constituent minerals they pass by every gradation into one another, the distinctive structures also of one kind of rock may often be traced gradually merging into those of another. Hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. This magma can be derived from partial melts of pre- existing rocks in either a planet's mantle or crust. Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Igneous rocks are divided into two main categories: plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earth's crust. Shellac - Wikipedia, the free encyclopedia. For the minimalist rock trio, see Shellac (band). 14-08-2016 2/2 Rock Encyclopedia. Other Files Available to Download The Illustrated Encyclopedia of Rock . The Rolling Stone Encyclopedia of Rock & Roll, Third Edition includes all the facts, phenomena, and flukes that make up the history of rock. 8-08-2016 2/2 Rock Encyclopedia. Other Files Available to Download India - Wikipedia, the free encyclopedia. Form 6744 Answers Pdf. Rock Guitar Heroes The Illustrated Encyclopedia Of Artists. 11-09-2016 2/2 Encyclopedia Of Rock. Other Files Available to Download A common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, forming minerals such as pumice or basalt. Most major igneous rocks are found along this scale. Of these, 6. 6% are basalts and gabbros, 1. Only 0. 6% are syenites and 0. In geology, rock or stone is a naturally occurring solid aggregate of one or more minerals or mineraloids. For example, the common rock granite is a combination of.The oceanic crust is 9. Granites and similar rocks, known as meta- granitoids, form much of the continental crust. These have diverse properties, depending on their composition and the temperature and pressure conditions in which they were formed. Sedimentary. Sedimentary rocks are formed at the earth's surface by the accumulation and cementation of fragments of earlier rocks, minerals, and organisms or as chemical precipitates and organic growths in water (sedimentation). This process causes clasticsediments (pieces of rock) or organic particles (detritus) to settle and accumulate, or for minerals to chemically precipitate (evaporite) from a solution. The particulate matter then undergoes compaction and cementation during at moderate temperatures and pressures (diagenesis). Before being deposited, sediments are formed by weathering or earlier rocks by erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers (agents of denudation). Mud rocks comprise 6. Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or strata and may be referred to as stratified rocks. A small fraction of sedimentary rocks deposited on steep slopes will show cross bedding where one layer stops abruptly along an interface where another layer eroded the first as it was laid atop the first. Metamorphic. Metamorphic rocks are formed by subjecting any rock type. This process is called metamorphism; meaning to . The result is a profound change in physical properties and chemistry of the stone. The original rock, known as the protolith, transforms into other mineral types or other forms of the same minerals, by recrystallization. An intrusion of magma that heats the surrounding rock causes contact metamorphism. Pressure metamorphism occurs when sediments are buried deep under the ground; pressure is dominant and temperature plays a smaller role. This is termed burial metamorphism, and it can result in rocks such as jade. Where both heat and pressure play a role, the mechanism is termed regional metamorphism. This is typically found in mountain- building regions. Those that possess a texture are referred to as foliated; the remainder are termed non- foliated. The name of the rock is then determined based on the types of minerals present. Schists are foliated rocks that are primarily composed of lamellar minerals such as micas. A gneiss has visible bands of differing lightness, with a common example being the granite gneiss. Other varieties of foliated rock include slates, phyllites, and mylonite. Familiar examples of non- foliated metamorphic rocks include marble, soapstone, and serpentine. This branch contains quartzite. Rocks have been used by humans and other hominids for at least 2. The mining of rocks for their metalore content has been one of the most important factors of human advancement, which has progressed at different rates in different places in part because of the kind of metals available from the rocks of a region. Mining. Mining is the extraction of valuableminerals or other geological materials from the earth, from an ore body, vein or (coal) seam. This term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock salt and potash. Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory. Mining in a wider sense comprises extraction of any resource (e. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials and finally reclamation of the land to prepare it for other uses once mining ceases. This impact has led to most of the world's nations adopting regulations to manage negative effects of mining operations. Department of Geography, University of California, Santa Barbara. Retrieved 1. 1 November 2. Cambridge University Press. Tracy, Petrology, W. H. Freeman, 2nd ed., 1. ISBN 0- 7. 16. 7- 2. William Haviland, Dana Walrath, Harald Prins, Bunny Mc. Bride, Evolution and Prehistory: The Human Challenge, p. Sustainable Management of Mining Operations. Denver, CO, USA: Society for Mining, Metallurgy, and Exploration. The Living Rock: The Story of Metals Since Earliest Times and Their Impact on Developing Civilization. Cambridge, England: Woodhead Publishing. The Future of strategic Natural Resources. Cambridge, MA, USA: Massachusetts Institute of Technology. Retrieved 1. 0 September 2.
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