1.
Volcanic glass
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Volcanic glass is the amorphous product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the close-packed, highly ordered array of a crystal and the highly disordered array of gas. Volcanic glass can refer to the interstitial, or matrix, material in a volcanic rock or can refer to any of several types of vitreous igneous rocks. Most commonly, it refers to obsidian, a glass with high silica content. Other types of volcanic glass include, Pumice, which is considered a glass because it has no crystal structure, apache tears, a kind of nodular obsidian. Tachylite, a glass with relatively low silica content. Sideromelane, a common form tachylyte. Palagonite, a glass with relatively low silica content. Hyaloclastite, a hydrated tuff-like breccia of sideromelane and palagonite, peles hair, threads or fibers of volcanic glass, usually basaltic. Peles tears, tear-like drops of volcanic glass, usually basaltic, limu o Pele, thin sheets and flakes of brownish-green to near-clear volcanic glass, usually basaltic
2.
Fracture (mineralogy)
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In the field of mineralogy, fracture is the texture and shape of a rocks surface formed when a mineral is fractured. Minerals often have a highly distinctive fracture, making it a feature used in their identification. Fracture differs from cleavage in that the latter involves clean splitting along the planes of the minerals crystal structure. All minerals exhibit fracture, but when very strong cleavage is present, conchoidal fracture breakage that resembles the concentric ripples of a mussel shell. It often occurs in amorphous or fine-grained minerals such as flint, opal or obsidian, subconchoidal fracture is similar to conchoidal fracture, but with less significant curvature. Earthy fracture is reminiscent of freshly broken soil and it is frequently seen in relatively soft, loosely bound minerals, such as limonite, kaolinite and aluminite. Hackly fracture is jagged, sharp and not even and it occurs when metals are torn, and so is often encountered in native metals such as copper and silver. Splintery fracture comprises sharp elongated points and it is particularly seen in fibrous minerals such as chrysotile, but may also occur in non-fibrous minerals such as kyanite. Uneven fracture is a surface or one with random irregularities. It occurs in a range of minerals including arsenopyrite, pyrite and magnetite. Rudolf Duda and Lubos Rejl, Minerals of the World http, //www. galleries. com/minerals/property/fracture. htm
3.
Conchoidal fracture
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Conchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Materials that break in this way include quartz, flint, quartzite, jasper and other fine-grained or amorphous materials with a composition of pure silica, such as obsidian, conchoidal fractures can also occur in other materials under favorable circumstances. This material property was used in the Stone Age to make sharp tools. Conchoidal fractures often result in a curved surface that resembles the rippling, gradual curves of a mussel shell. A swelling appears at the point of impact called the bulb of percussion, shock waves emanating outwards from this point leave their mark on the stone as ripples. Other conchoidal features include small fissures emanating from the bulb of percussion and this property also makes such fractures useful in engineering, since they provide a permanent record of the stress state at the time of failure. As conchoidal fractures can be produced only by mechanical impact, rather than frost cracking for example, the dictionary definition of conchoid at Wiktionary
4.
Mohs scale of mineral hardness
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The Mohs scale of mineral hardness is a qualitative ordinal scale characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. Created in 1812 by German geologist and mineralogist Friedrich Mohs, it is one of several definitions of hardness in materials science, while greatly facilitating the identification of minerals in the field, the Mohs scale does not show how well hard materials perform in an industrial setting. Despite its lack of precision, the Mohs scale is highly relevant for field geologists, the Mohs scale hardness of minerals can be commonly found in reference sheets. Reference materials may be expected to have a uniform Mohs hardness, the Mohs scale of mineral hardness is based on the ability of one natural sample of mineral to scratch another mineral visibly. The samples of matter used by Mohs are all different minerals, Minerals are pure substances found in nature. Rocks are made up of one or more minerals, as the hardest known naturally occurring substance when the scale was designed, diamonds are at the top of the scale. The hardness of a material is measured against the scale by finding the hardest material that the material can scratch. For example, if material is scratched by apatite but not by fluorite. Scratching a material for the purposes of the Mohs scale means creating non-elastic dislocations visible to the naked eye, frequently, materials that are lower on the Mohs scale can create microscopic, non-elastic dislocations on materials that have a higher Mohs number. The Mohs scale is an ordinal scale. For example, corundum is twice as hard as topaz, the table below shows the comparison with the absolute hardness measured by a sclerometer, with pictorial examples. On the Mohs scale, a streak plate has a hardness of 7.0, using these ordinary materials of known hardness can be a simple way to approximate the position of a mineral on the scale. The table below incorporates additional substances that may fall between levels, Comparison between Hardness and Hardness, Mohs hardness of elements is taken from G. V, samsonov in Handbook of the physicochemical properties of the elements, IFI-Plenum, New York, USA,1968. The Hardness of Minerals and Rocks
5.
Lustre (mineralogy)
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Lustre or luster is the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the latin lux, meaning light, a range of terms are used to describe lustre, such as earthy, metallic, greasy, and silky. Similarly, the term refers to a glassy lustre. A list of terms is given below. Lustre varies over a continuum, and so there are no rigid boundaries between the different types of lustre. The terms are frequently combined to describe types of lustre. Some minerals exhibit unusual optical phenomena, such as asterism or chatoyancy, a list of such phenomena is given below. Adamantine minerals possess a superlative lustre, which is most notably seen in diamond, such minerals are transparent or translucent, and have a high refractive index. Minerals with an adamantine lustre are uncommon, with examples being cerussite. Minerals with a degree of lustre are referred to as subadamantine, with some examples being garnet. Dull minerals exhibit little to no lustre, due to coarse granulations which scatter light in all directions, a distinction is sometimes drawn between dull minerals and earthy minerals, with the latter being coarser, and having even less lustre. Greasy minerals resemble fat or grease, a greasy lustre often occurs in minerals containing a great abundance of microscopic inclusions, with examples including opal and cordierite. Many minerals with a greasy lustre also feel greasy to the touch, metallic minerals have the lustre of polished metal, and with ideal surfaces will work as a reflective surface. Examples include galena, pyrite and magnetite, pearly minerals consist of thin transparent co-planar sheets. Light reflecting from these layers give them a lustre reminiscent of pearls, such minerals possess perfect cleavage, with examples including muscovite and stilbite. Resinous minerals have the appearance of resin, chewing gum or plastic, a principal example is amber, which is a form of fossilized resin. Silky minerals have an arrangement of extremely fine fibres, giving them a lustre reminiscent of silk. Examples include asbestos, ulexite and the satin spar variety of gypsum, a fibrous lustre is similar, but has a coarser texture
6.
Specific gravity
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This page is about the measurement using water as a reference. For a general use of gravity, see relative density. See intensive property for the property implied by specific, Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is always water at its densest for liquids. Nonetheless, the temperature and pressure must be specified for both the sample and the reference, pressure is nearly always 1 atm. Temperatures for both sample and reference vary from industry to industry, in British beer brewing, the practice for specific gravity as specified above is to multiply it by 1000. Being a ratio of densities, specific gravity is a dimensionless quantity, Specific gravity varies with temperature and pressure, reference and sample must be compared at the same temperature and pressure or be corrected to a standard reference temperature and pressure. Substances with a gravity of 1 are neutrally buoyant in water. Those with SG greater than 1 are denser than water and will, disregarding surface tension effects and those with an SG less than 1 are less dense than water and will float on it. In scientific work, the relationship of mass to volume is expressed directly in terms of the density of the substance under study. It is in industry where specific gravity finds wide application, often for historical reasons. True specific gravity can be expressed mathematically as, S G true = ρ sample ρ H2 O where ρ sample is the density of the sample, the density of water varies with temperature and pressure as does the density of the sample. So it is necessary to specify the temperatures and pressures at which the densities or weights were determined and it is nearly always the case that measurements are made at 1 nominal atmosphere. For true specific gravity calculations, air pressure must be considered, temperatures are specified by the notation with T s representing the temperature at which the samples density was determined and T r the temperature at which the reference density is specified. For example, SG would be understood to mean that the density of the sample was determined at 20°C and of the water at 4°C. Taking into account different sample and reference temperatures, we note that, while S G H2 O =1.000000, it is also the case that S G H2 O =0.998203 /0.999840 =0.998363. Here, temperature is being specified using the current ITS-90 scale, on the previous IPTS-68 scale, the densities at 20 °C and 4 °C are 0.9982071 and 0.9999720 respectively, resulting in an SG value for water of 0.9982343. For example, in the industry, the Plato table lists sucrose concentration by weight against true SG
7.
Transparency and translucency
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In the field of optics, transparency is the physical property of allowing light to pass through the material without being scattered. On a macroscopic scale, the photons can be said to follow Snells Law, in other words, a translucent medium allows the transport of light while a transparent medium not only allows the transport of light but allows for image formation. The opposite property of translucency is opacity, transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. When light encounters a material, it can interact with it in different ways. These interactions depend on the wavelength of the light and the nature of the material, photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as glass and clean water, transmit much of the light that falls on them and reflect little of it. Many liquids and aqueous solutions are highly transparent, absence of structural defects and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials which do not transmit light are called opaque, many such substances have a chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of light frequencies. They absorb certain portions of the spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation and this is what gives rise to color. The attenuation of light of all frequencies and wavelengths is due to the mechanisms of absorption. Transparency can provide almost perfect camouflage for animals able to achieve it and this is easier in dimly-lit or turbid seawater than in good illumination. Many marine animals such as jellyfish are highly transparent, at the atomic or molecular level, physical absorption in the infrared portion of the spectrum depends on the frequencies of atomic or molecular vibrations or chemical bonds, and on selection rules. Nitrogen and oxygen are not greenhouse gases because there is no absorption because there is no molecular dipole moment. With regard to the scattering of light, the most critical factor is the scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include, Crystalline structure, whether or not the atoms or molecules exhibit the long-range order evidenced in crystalline solids, glassy structure, scattering centers include fluctuations in density or composition. Microstructure, scattering centers include internal surfaces such as boundaries, crystallographic defects
8.
Glass
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Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are silicate glasses based on the chemical compound silica, the primary constituent of sand. The term glass, in usage, is often used to refer only to this type of material. Many applications of silicate glasses derive from their optical transparency, giving rise to their use as window panes. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels and these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures, because glass can be formed or moulded into any shape, it has been traditionally used for vessels, bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also used for paperweights, marbles. Some objects historically were so commonly made of glass that they are simply called by the name of the material, such as drinking glasses. Porcelains and many polymer thermoplastics familiar from everyday use are glasses and these sorts of glasses can be made of quite different kinds of materials than silica, metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass, silica is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, fused quartz is a glass made from chemically-pure SiO2. It has excellent resistance to shock, being able to survive immersion in water while red hot. However, its high melting-temperature and viscosity make it difficult to work with, normally, other substances are added to simplify processing. One is sodium carbonate, which lowers the transition temperature. The soda makes the glass water-soluble, which is undesirable, so lime, some magnesium oxide. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass, soda-lime glasses account for about 90% of manufactured glass. Most common glass contains other ingredients to change its properties, lead glass or flint glass is more brilliant because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium also increases the refractive index, iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs UV wavelengths
9.
Igneous rock
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Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava, the magma can be derived from partial melts of existing rocks in either a planets mantle or crust. Typically, the melting is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, Igneous and metamorphic rocks make up 90–95% of the top 16 km of the Earths crust by volume. Igneous rocks form about 15% of the Earths current land surface, most of the Earths oceanic crust is made of igneous rock. In terms of modes of occurrence, igneous rocks can be either intrusive or extrusive, the mineral grains in such rocks can generally be identified with the naked eye. Intrusive rocks can also be classified according to the shape and size of the intrusive body, typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes. When the magma solidifies within the earths crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, the central cores of major mountain ranges consist of intrusive igneous rocks, usually granite. When exposed by erosion, these cores may occupy huge areas of the Earths surface, intrusive igneous rocks that form at depth within the crust are termed plutonic rocks and are usually coarse-grained. Intrusive igneous rocks that form near the surface are termed subvolcanic or hypabyssal rocks, hypabyssal rocks are less common than plutonic or volcanic rocks and often form dikes, sills, laccoliths, lopoliths, or phacoliths. Extrusive igneous rocks, also known as rocks, are formed at the crusts surface as a result of the partial melting of rocks within the mantle. Extrusive igneous rocks cool and solidify quicker than intrusive igneous rocks and they are formed by the cooling of molten magma on the earths surface. The magma, which is brought to the surface through fissures or volcanic eruptions, hence such rocks are smooth, crystalline and fine-grained. Basalt is an extrusive igneous rock and forms lava flows, lava sheets. Some kinds of basalt solidify to form long polygonal columns, the Giants Causeway in Antrim, Northern Ireland is an example. The molten rock, with or without suspended crystals and gas bubbles, is called magma and it rises because it is less dense than the rock from which it was created. When magma reaches the surface from beneath water or air, it is called lava, eruptions of volcanoes into air are termed subaerial, whereas those occurring underneath the ocean are termed submarine. Black smokers and mid-ocean ridge basalt are examples of volcanic activity
10.
Felsic
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In geology, felsic refers to igneous rocks that are relatively rich in elements that form feldspar and quartz. It is contrasted with mafic rocks, which are richer in magnesium. It refers to those rocks rich in minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium. They are usually light in color and have specific gravities less than 3, the most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars, in terms of chemistry, felsic minerals and rocks are at the other end of the elemental spectrum from the mafic minerals and rocks. In modern usage, the acid rock, although sometimes used as a synonym, refers to a high-silica-content volcanic rock. The term was used broadly in older geologic literature. It is considered archaic now, as the acidic and basic rock were based on an incorrect idea, dating from the 19th century. The term felsic combines the words feldspar and silica, in order for a rock to be classified as felsic, it generally needs to contain more than 75% felsic minerals, namely quartz, orthoclase and plagioclase. Rocks with greater than 90% felsic minerals can also be called leucocratic, the chemical name of a felsic rock is given according to the TAS classification of Le Maitre. However, this applies to volcanic rocks. If the rock is analyzed and found to be felsic but is metamorphic and has no definite volcanic protolith, there are examples known of highly sheared granites which can be mistaken for rhyolites. For phaneritic felsic rocks, the QAPF diagram should be used, the rock texture thus determines the basic name of a felsic rock. QAPF diagram List of minerals List of rock types Le Maitre, igneous Rocks, A Classification and Glossary of Terms 2nd edition, Cambridge
11.
Lava
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Lava is the molten rock expelled by a volcano during an eruption. The resulting rock after solidification and cooling is called lava. The molten rock is formed in the interior of planets, including Earth. The source of the heat melts the rock within the earth is geothermal energy. When first erupted from a vent, lava is a liquid usually at temperatures from 700 to 1,200 °C. A lava flow is an outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock, the term lava flow is commonly shortened to lava. Although lava can be up to 100,000 times more viscous than water, lava can flow great distances before cooling and solidifying because of its thixotropic, explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word lava comes from Italian, and is derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma was apparently in an account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4,1737. Serao described a flow of lava as an analogy to the flow of water. The composition of almost all lava of the Earths crust is dominated by silicate minerals, mostly feldspars, olivine, pyroxenes, amphiboles, micas, igneous rocks, which form lava flows when erupted, can be classified into three chemical types, felsic, intermediate, and mafic. These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the temperature, its viscosity. Felsic or silicic lavas such as rhyolite and dacite typically form lava spines, most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. Felsic magmas can erupt at temperatures as low as 650 to 750 °C, unusually hot rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States. Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium, intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Poorer in aluminium and silica than felsic lavas, and also commonly hotter, greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C
12.
Volcano
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A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earths volcanoes occur because its crust is broken into 17 major, therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. This type of volcanism falls under the umbrella of plate hypothesis volcanism, Volcanism away from plate boundaries has also been explained as mantle plumes. These so-called hotspots, for example Hawaii, are postulated to arise from upwelling diapirs with magma from the boundary,3,000 km deep in the Earth. Volcanoes are usually not created where two plates slide past one another. Erupting volcanoes can pose hazards, not only in the immediate vicinity of the eruption. Historically, so-called volcanic winters have caused catastrophic famines, the word volcano is derived from the name of Vulcano, a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan, the god of fire in Roman mythology. The study of volcanoes is called volcanology, sometimes spelled vulcanology, at the mid-oceanic ridges, two tectonic plates diverge from one another as new oceanic crust is formed by the cooling and solidifying of hot molten rock. Most divergent plate boundaries are at the bottom of the oceans, therefore, most volcanic activity is submarine, black smokers are evidence of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. In a process called flux melting, water released from the subducting plate lowers the temperature of the overlying mantle wedge. This magma tends to be very viscous due to its high content, so it often does not reach the surface. When it does reach the surface, a volcano is formed, typical examples of this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire. Because tectonic plates move across them, each volcano becomes dormant and is eventually re-formed as the plate advances over the postulated plume and this theory is currently under criticism, however. The most common perception of a volcano is of a mountain, spewing lava and poisonous gases from a crater at its summit, however. The features of volcanoes are more complicated and their structure. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have features such as massive plateaus
13.
Crystal growth
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A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. Crystal growth is a stage of a crystallization process, and consists in the addition of new atoms, ions. The growth typically follows a stage of either homogeneous or heterogeneous nucleation, unless a seed crystal. The action of crystal growth yields a crystalline solid whose atoms or molecules are close packed. The crystalline state of matter is characterized by a distinct structural rigidity, most crystalline solids have high values both of Youngs modulus and of the shear modulus of elasticity. This contrasts with most liquids or fluids, which have a low shear modulus, crystalline solids are typically formed by cooling and solidification from the liquid state. According to the Ehrenfest classification of first-order phase transitions, there is a change in volume at the melting point. Within this context, the crystal and melt are distinct phases with an interfacial discontinuity having a surface of tension with a surface energy. Thus, a metastable parent phase is stable with respect to the nucleation of small embryos or droplets from a daughter phase. Such first-order transitions must proceed by the advancement of a region whose structure. The process of nucleation and growth generally occurs in two different stages, in the first nucleation stage, a small nucleus containing the newly forming crystal is created. Nucleation occurs relatively slowly as the initial components must impinge on each other in the correct orientation and placement for them to adhere. After crystal nucleation, the stage of growth rapidly ensues. Crystal growth spreads outwards from the nucleating site, in this faster process, the elements which form the motif add to the growing crystal in a prearranged system, the crystal lattice, started in crystal nucleation. As first pointed out by Frank, perfect crystals would only grow exceedingly slowly, the conditions of a homogeneous environment are often approximated to but rarely ever realized. Crystal growth always involves some form of transport of matter or heat, and homogeneous conditions for the transport process can only exist for spherical, cylindrical, or infinite plane surfaces. A polyhedral crystal cannot grow with uniform levels of supersaturation over its faces, in general, the supersaturation is greatest at its corners. This refutes the assumption that the rate is a function of orientation
14.
Rhyolite
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Rhyolite is an igneous, volcanic rock, of felsic composition. It may have any texture from glassy to aphanitic to porphyritic, the mineral assemblage is usually quartz, sanidine and plagioclase. Biotite and hornblende are common accessory minerals and it is the extrusive equivalent to granite. Rhyolite can be considered as the equivalent to the plutonic granite rock. Due to their content of silica and low iron and magnesium contents, rhyolite melts are highly polymerized. They also occur as breccias or in volcanic plugs and dikes, rhyolites that cool too quickly to grow crystals form a natural glass or vitrophyre, also called obsidian. Slower cooling forms microscopic crystals in the lava and results in such as flow foliations, spherulitic, nodular. Some rhyolite is highly vesicular pumice, many eruptions of rhyolite are highly explosive and the deposits may consist of fallout tephra/tuff or of ignimbrites. Eruptions of rhyolite are relatively rare compared to eruptions of less felsic lavas, etsch Valley Vulcanite Group near Bolzano and the surrounding area Gréixer rhyolitic complex at Moixeró range Vosges Iceland, all active and extinct central volcanoes, e. g. g. Wichita Mountains within the Southern Oklahoma Aulacogen St, in North American pre-historic times, rhyolite was quarried extensively in eastern Pennsylvania in the United States. Among the leading quarries was the Carbaugh Run Rhyolite Quarry Site in Adams County, comendite List of rock types Pantellerite Thunderegg University of North Dakota description of rhyolite Information from rocks-rock. com
15.
Viscosity
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The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the concept of thickness, for example. Viscosity is a property of the fluid which opposes the motion between the two surfaces of the fluid in a fluid that are moving at different velocities. For a given velocity pattern, the stress required is proportional to the fluids viscosity, a fluid that has no resistance to shear stress is known as an ideal or inviscid fluid. Zero viscosity is observed only at low temperatures in superfluids. Otherwise, all fluids have positive viscosity, and are said to be viscous or viscid. A fluid with a high viscosity, such as pitch. The word viscosity is derived from the Latin viscum, meaning mistletoe, the dynamic viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. It can be defined through the situation known as a Couette flow. This fluid has to be homogeneous in the layer and at different shear stresses, if the speed of the top plate is small enough, the fluid particles will move parallel to it, and their speed will vary linearly from zero at the bottom to u at the top. Each layer of fluid will move faster than the one just below it, in particular, the fluid will apply on the top plate a force in the direction opposite to its motion, and an equal but opposite one to the bottom plate. An external force is required in order to keep the top plate moving at constant speed. The magnitude F of this force is found to be proportional to the u and the area A of each plate. The proportionality factor μ in this formula is the viscosity of the fluid, the ratio u/y is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the plates. Isaac Newton expressed the forces by the differential equation τ = μ ∂ u ∂ y, where τ = F/A. This formula assumes that the flow is moving along parallel lines and this equation can be used where the velocity does not vary linearly with y, such as in fluid flowing through a pipe. Use of the Greek letter mu for the dynamic viscosity is common among mechanical and chemical engineers. However, the Greek letter eta is used by chemists, physicists
16.
Polymerization
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In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them, in chemical compounds, polymerization occurs via a variety of reaction mechanisms that vary in complexity due to functional groups present in reacting compounds and their inherent steric effects. Alkanes can also be polymerized, but only with the help of strong acids, further compounds either being referred to as oligomers in smaller molecules. Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous and this phenomenon is known as hazardous polymerization and can cause fires and explosions. Step-growth polymers are defined as polymers formed by the reaction between functional groups of monomers, usually containing heteroatoms such as nitrogen or oxygen. Most step-growth polymers are classified as condensation polymers, but not all step-growth polymers release condensates, in this case. Step-growth polymers increase in weight at a very slow rate at lower conversions. To alleviate inconsistencies in these methods, adjusted definition for condensation and addition polymers have been developed. Chain-growth polymerization involves the linking together of molecules incorporating double or triple carbon-carbon bonds and these unsaturated monomers have extra internal bonds that are able to break and link up with other monomers to form a repeating chain, whose backbone typically contains only carbon atoms. Chain-growth polymerization is involved in the manufacture of such as polyethylene, polypropylene. A special case of chain-growth polymerization leads to living polymerization, in the radical polymerization of ethylene, its π bond is broken, and the two electrons rearrange to create a new propagating center like the one that attacked it. The form this propagating center takes depends on the type of addition mechanism. There are several mechanisms through which this can be initiated, the free radical mechanism is one of the first methods to be used. Free radicals are very reactive atoms or molecules that have unpaired electrons, taking the polymerization of ethylene as an example, the free radical mechanism can be divided into three stages, chain initiation, chain propagation, and chain termination. Free radical addition polymerization of ethylene must take place at temperatures and pressures. While most other free radical polymerizations do not require such extreme temperatures and pressures, one effect of this lack of control is a high degree of branching. Also, as termination occurs randomly, when two chains collide, it is impossible to control the length of individual chains, a newer method of polymerization similar to free radical, but allowing more control involves the Ziegler-Natta catalyst, especially with respect to polymer branching. Other forms of chain growth polymerization include cationic addition polymerization and anionic addition polymerization, cationic and anionic mechanisms are also more ideally suited for living polymerizations, although free radical living polymerizations have also been developed
17.
Brittleness
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A material is brittle if, when subjected to stress, it breaks without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength, breaking is often accompanied by a snapping sound. Brittle materials include most ceramics and glasses and some polymers, such as PMMA, many steels become brittle at low temperatures, depending on their composition and processing. When used in science, it is generally applied to materials that fail when there is little or no evidence of plastic deformation before failure. One proof is to match the broken halves, which should fit exactly since no plastic deformation has occurred, when a material has reached the limit of its strength, it usually has the option of either deformation or fracture. Improving material toughness is therefore a balancing act and this principle generalizes to other classes of material. Naturally brittle materials, such as glass, are not difficult to toughen effectively, the first principle is used in laminated glass where two sheets of glass are separated by an interlayer of polyvinyl butyral, which as a viscoelastic polymer absorbs the growing crack. The second method is used in toughened glass and pre-stressed concrete, a demonstration of glass toughening is provided by Prince Ruperts Drop. Brittle polymers can be toughened by using metal particles to initiate crazes when a sample is stressed, the least brittle structural ceramics are silicon carbide and transformation-toughened zirconia. A different philosophy is used in materials, where brittle glass fibres. When strained, cracks are formed at the interface, but so many are formed that much energy is absorbed. The same principle is used in creating metal matrix composites, generally, the brittle strength of a material can be increased by pressure. Supersonic fracture is crack motion faster than the speed of sound in a brittle material and this phenomenon was first discovered by scientists from the Max Planck Institute for Metals Research in Stuttgart and IBM Almaden Research Center in San Jose, California. Izod impact strength test Charpy impact test Fractography Forensic engineering Ductility Strengthening mechanisms of materials Lewis, Peter Rhys, Reynolds, K, Gagg, rösler, Joachim, Harders, Harald, Bäker, Martin. Mechanical behaviour of engineering materials, metals, ceramics, polymers, and composites
18.
Scalpel
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A scalpel, or lancet, is a small and extremely sharp bladed instrument used for surgery, anatomical dissection, and various arts and crafts. Scalpels may be disposable or re-usable. Re-usable scalpels can have permanently attached blades that can be sharpened or, more commonly, disposable scalpels usually have a plastic handle with an extensible blade and are used once, then the entire instrument is discarded. Scalpel blades are usually packed in sterile pouches but are also offered non-sterile. Double-edged scalpels are referred to as lancets, scalpel blades are usually made of hardened and tempered steel, stainless steel, or high carbon steel, in addition, titanium, ceramic, diamond and even obsidian knives are not uncommon. For example, when performing surgery under MRI guidance, steel blades are unusable, historically, the preferred material for surgical scalpels was silver, on account of its antimicrobial properties. Scalpel blades are also offered by manufacturers with a zirconium nitride-coated edge to improve sharpness. Others manufacture blades that are coated to enhance lubricity during a cut. Alternatives to scalpels in surgical applications include electrocautery and lasers, Surgical scalpels consist of two parts, a blade and a handle. The handles are often reusable, with the blades being replaceable, in medical applications, each blade is only used once. The handle is known as a B. P. handle, named after Charles Russell Bard and Morgan Parker. The handle of medical scalpels come in two basic types, the first is a flat handle used in the #3 and #4 handles. The #7 handle is more like a writing pen, rounded at the front. A #4 handle is larger than a #3, blades are manufactured with a corresponding fitment size so that they fit on only one size handle. The following table of blades is incomplete and some blades listed may work with handles not specified here, also called the dinner knife grip. This grip is best for initial incisions and larger cuts, best used for more accurate cuts with smaller blades and the #7 handle. The scalpel is held with the tips of the first and second fingers, care should be taken not to allow the handle to rest too far along the index finger as this promotes an unstable grip and cramped fingers. Graphical and model-making scalpels tend to have handles, with textured grips
19.
Scree
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Scree is a collection of broken rock fragments at the base of crags, mountain cliffs, volcanoes or valley shoulders that has accumulated through periodic rockfall from adjacent cliff faces. Landforms associated with these materials are called talus deposits. Talus deposits typically have a concave form, while the maximum inclination corresponds to the angle of repose of the mean debris size. The term scree comes from the Old Norse term for landslide, skriða, formation of scree or talus deposits the results of physical and chemical weathering and erosion acting on a rock face. During the day, water can flow into joints and discontinuities in the rock wall, if the temperature drops enough, for example in the evening, this water may freeze. Since water expands by 9% when it freezes, it can generate forces that either create new cracks or wedge blocks into an unstable position. Special boundary conditions may be required for this to happen, the efficiency of freeze/thaw processes in scree production is debated by scientists. Many researchers believe that ice formation in large open crack systems cannot generate high pressures, many argue that frost heaving, like that known to act in soil in permafrost areas, may play an important role in cliff degradation in cold places. For example, Lech dl Dragon, in the Sella Group of the Dolomites, derives from the waters of a glacier. The melting process of the glacier is slowed by the protective layer of scree. Eventually a rock slope may be covered by its own scree. The slope is then said to be mantled with debris, fellfield Lava stringer Mass wasting Weathering
20.
Cristobalite
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The mineral cristobalite is a high-temperature polymorph of silica, meaning that it has the same chemical formula as quartz, SiO2, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group, cristobalite occurs as white octahedra or spherulites in acidic volcanic rocks and in converted diatomaceous deposits in the Monterey Formation of the US state of California and similar areas. Cristobalite is stable only above 1470 °C, but can crystallize and it is named after Cerro San Cristóbal in Pachuca Municipality, Hidalgo, Mexico. These frameworks are composed of SiO4 tetrahedra in which every atom is shared with a neighbouring tetrahedron. The breaking of these bonds required to convert cristobalite to tridymite and quartz requires considerable activation energy, framework silicates are also known as tectosilicates. There is more than one form of the cristobalite framework, at high temperatures, the structure is cubic, Fd3m, No.227, Pearson symbol cF104. A tetragonal form of cristobalite occurs on cooling below ca.250 °C at ambient pressure and this transition is variously called the low-high or α − β transition. It may be termed displacive, i. e. it is not generally possible to prevent the cubic β-form from becoming tetragonal by rapid cooling. The exact transition temperature depends on the crystallinity of the cristobalite sample, the cubic β phase consists of dynamically disordered silica tetrahedra. The tetrahedra remain fairly regular and are displaced from their ideal static orientations due to the action of a class of low-frequency phonons called rigid unit modes and it is the freezing of one of these rigid unit modes that is the soft mode for the α–β transition. In the α–β phase transition only one of the three degenerate cubic crystallographic axes retains a fourfold rotational axis in the tetragonal form, the choice of axis is arbitrary, so that various twins can form within the same grain. When devitrifying silica, cristobalite is usually the first phase to form, the dynamically disordered nature of the β-phase is partly responsible for the low enthalpy of fusion of silica. In addition, the presence of water in opal makes it doubtful that opal consists of cristobalite. American Geological Institute Dictionary of Geological Terms, durham, D. L. Monterey Formation, Diagenesis. In, Uranium in the Monterey Formation of California, US Geological Survey Bulletin 1581-A,1987. Reviews in Mineralogy and Geochemistry, vol, silica, behavior, geochemistry and physical applications
21.
Pliny the Elder
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In the latter number will be my uncle, by virtue of his own and of your compositions. Pliny is referring to the fact that Tacitus relied on his uncles now missing work on the History of the German Wars. The wind caused by the sixth and largest pyroclastic surge of the eruption would not allow his ship to leave the shore, and Pliny probably died during this event. Plinys dates are pinned to the eruption of Mount Vesuvius in AD79 and a statement of his nephew that he died in his 56th year, Pliny was the son of an equestrian, Gaius Plinius Celer, and his wife, Marcella. Neither the younger nor the elder Pliny mention the names and their ultimate source is a fragmentary inscription found in a field in Verona and recorded by the 16th century Augustinian monk Onofrio Panvinio at Verona. The reading of the inscription depends on the reconstruction, but in all cases the names come through, whether he was an augur and whether she was named Grania Marcella are less certain. Jean Hardouin presents a statement from a source that he claims was ancient, that Pliny was from Verona. Hardouin also cites the conterraneity of Catullus, additional efforts to connect Celer and Marcella with other gentes are highly speculative. Hardouin is the scholar to use his unknown source. He kept statues of his ancestors there, a statue of Pliny on the facade of the Duomo of Como celebrates him as a native son. He had a sister, Plinia, who married into the Caecilii and was the mother of his nephew, Pliny the Younger, whose letters describe his work and study regimen in detail. In one of his letters to Tacitus, Pliny the Younger details how his uncles breakfasts would be light and simple following the customs of our forefathers. This shows that Pliny the Younger wanted it to be conveyed that Pliny the Elder was a good Roman and this statement would have pleased Tacitus. Two inscriptions identifying the hometown of Pliny the Younger as Como take precedence over the Verona theory, one commemorates the youngers career as imperial magistrate and details his considerable charitable and municipal expenses on behalf of the people of Como. Another identifies his father Lucius village as Fecchio near Como and it is likely therefore that Plinia was a local girl and Pliny the Elder, her brother, was from Como. Gaius was a member of the Plinii gens and he did not take his fathers cognomen, Celer, but assumed his own, Secundus. As his adopted son took the same cognomen, Pliny founded a branch, no earlier instances of the Plinii are known. In 59 BC, only about 82 years before Plinys birth, Julius Caesar founded Novum Comum as a colonia to secure the region against the Alpine tribes, whom he had been unable to defeat
22.
Natural History (Pliny)
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The Natural History is an early encyclopedia in Latin by Pliny the Elder, a Roman author and naval commander who died in 79 AD. It is one of the largest single works to have survived from the Roman Empire to the modern day, the works subject area is thus not limited to what is today understood by natural history, Pliny himself defines his scope as the natural world, or life. The work is divided into 37 books, organised into ten volumes, the Natural History became a model for later encyclopedias and scholarly works as a result of its breadth of subject matter, its referencing of original authors, and its index. The work is dedicated to the emperor Titus, son of Plinys close friend and it is the only work by Pliny to have survived and the last that he published. He began it in 77, and had not made a revision at the time of his death during the AD79 eruption of Vesuvius. Plinys Natural History was written alongside other substantial works, Pliny combined his scholarly activities with a busy career as an imperial administrator for the emperor Vespasian. Pliny claims to be the only Roman ever to have such a work, in his prayer for the blessing of the universal mother, Hail to thee, Nature. And do thou deign to show thy favour unto me, who, alone of all the citizens of Rome, have, in thy every department, the Natural History is encyclopaedic in scope, but its format is unlike a modern encyclopaedia. However, it does have structure, Pliny uses Aristotles division of nature to recreate the world in literary form. The work is unified but varied, My subject is the world of nature, or in other words, life, he tells Titus. Nature for Pliny was divine, a concept inspired by the Stoic philosophy which underlies much of his thought. But the deity in question was a goddess whose main purpose was to serve the human race, nature, that is life is human life in a natural landscape. After an initial survey of cosmology and geography, Pliny starts his treatment of animals with the human race and this teleological view of nature was common in antiquity and is crucial to the understanding of the Natural History. The components of nature are not just described in and for themselves, Pliny devotes a number of the books to plants, with a focus on their medicinal value, the books on minerals include descriptions of their uses in architecture, sculpture, painting and jewellery. Plinys premise is distinct from modern ecological theories, reflecting the sentiment of his time. Pliny repeated Aristotles maxim that Africa was always producing something new, natures variety and versatility were claimed to be infinite, When I have observed nature she has always induced me to deem no statement about her incredible. This led Pliny to recount rumours of strange peoples on the edges of the world and these monstrous races – the Cynocephali or Dog-Heads, the Sciapodae, whose single foot could act as a sunshade, the mouthless Astomi, who lived on scents – were not strictly new. They had been mentioned by the Greek historian Herodotus in the 5th century BC, Pliny had gone to investigate the strange cloud – shaped like an umbrella pine, according to his nephew – rising from the mountain
23.
Tektite
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Tektites are gravel-size bodies composed of black, green, brown or gray natural glass formed from terrestrial debris ejected during meteorite impacts. They generally range in size from millimeters to centimeters, millimeters-size tektites are known as microtektites. First, they are completely glassy and lack any microlites or phenocrysts, third, tektites contain virtually no water, unlike terrestrial volcanic glasses. Fourth, the flow-banding within tektites often contains particles and bands of lechatelierite, finally, a few tektites contain partly melted inclusions of shocked and unshocked mineral grains, i. e. quartz, apatite, and zircon, as well as coesite. The difference in water content can be used to distinguish tektites from terrestrial volcanic glasses, when heated to their melting point, terrestrial volcanic glasses will turn into a foamy glass because of their content of water and other volatiles. Unlike terrestrial volcanic glass, a tektite will produce only a few bubbles at most when heated to its melting point, on the basis of morphology and physical characteristics, tektites have traditionally been divided into four groups. The tektites which have found on land have traditionally been subdivided into three groups, splash-form tektites, aerodynamically shaped tektites, and Muong Nong-type tektites. Splash-form and aerodynamically shaped tektites are only differentiated on the basis of their appearance, splash-form tektites are centimeter-sized tektites that are shaped like spheres, ellipsoids, teardrops, dumbbells, and other forms characteristic of isolated molten bodies. They are regarded as having formed from the solidification of rotating liquids, aerodynamically shaped tektites, which are mainly part of the Australasian strewn field, are splash-form tektites which display a secondary ring or flange. The secondary ring or flange is argued as having been produced during the high-speed reentry, Muong Nong tektites are typically larger, greater than 10 cm in size and 24 kg in weight, irregular, and layered tektites. Microtektites, the group of tektites, are tektites that are less than 1 mm in size. They exhibit a variety of shapes ranging from spherical to dumbbell, disc, oval, the color of microtektites ranges from colorless and transparent to yellowish and pale brown. They frequently contain bubbles and lechatelierite inclusions, microtektites are typically found in deep-sea sediments that are of the same ages as those of the four known strewn fields. As summarized by Koeberl, the tektites within each strewn field are related to each other with respect to the criteria of petrological, physical, in addition, three of the four strewn fields have been clearly linked with impact craters using those same criteria. Recognized types of tektites, grouped according to their known strewn fields, their associated craters, Povenmire and others have proposed the existence of an additional tektite strewn field, the Central American strewn field. Evidence for this reported tektite strewn field consists of tektites recovered from western Belize in the area of the villages of Bullet Tree Falls, Santa Familia and Billy White. This area lies about 55 km east-southeast of Tikal where 13 tektites, a limited amount of evidence is interpreted as indicating that the proposed Central American strewn field likely covers Belize, Honduras, Guatemala, Nicaragua and possibly parts of southern Mexico. It is speculated that the hypothesized Pantasma Impact Crater in northern Nicaragua might be the source of these tektites, the ages of tektites from the four strewnfields have been determined using radiometric dating methods
24.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
25.
Hypothesis
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A hypothesis is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the method requires that one can test it. Scientists generally base scientific hypotheses on previous observations that cannot satisfactorily be explained with the scientific theories. Even though the hypothesis and theory are often used synonymously. A working hypothesis is a provisionally accepted hypothesis proposed for further research, P is the assumption in a What If question. Remember, the way that you prove an implication is by assuming the hypothesis, --Philip Wadler In its ancient usage, hypothesis referred to a summary of the plot of a classical drama. The English word hypothesis comes from the ancient Greek ὑπόθεσις word hupothesis, in Platos Meno, Socrates dissects virtue with a method used by mathematicians, that of investigating from a hypothesis. In this sense, hypothesis refers to an idea or to a convenient mathematical approach that simplifies cumbersome calculations. In common usage in the 21st century, a hypothesis refers to an idea whose merit requires evaluation. For proper evaluation, the framer of a hypothesis needs to define specifics in operational terms, a hypothesis requires more work by the researcher in order to either confirm or disprove it. In due course, a hypothesis may become part of a theory or occasionally may grow to become a theory itself. Normally, scientific hypotheses have the form of a mathematical model, in entrepreneurial science, a hypothesis is used to formulate provisional ideas within a business setting. The formulated hypothesis is then evaluated where either the hypothesis is proven to be true or false through a verifiability- or falsifiability-oriented Experiment, any useful hypothesis will enable predictions by reasoning. It might predict the outcome of an experiment in a setting or the observation of a phenomenon in nature. The prediction may also invoke statistics and only talk about probabilities, other philosophers of science have rejected the criterion of falsifiability or supplemented it with other criteria, such as verifiability or coherence. The scientific method involves experimentation, to test the ability of some hypothesis to adequately answer the question under investigation. In contrast, unfettered observation is not as likely to raise unexplained issues or open questions in science, a thought experiment might also be used to test the hypothesis as well. In framing a hypothesis, the investigator must not currently know the outcome of a test or that it remains reasonably under continuing investigation, only in such cases does the experiment, test or study potentially increase the probability of showing the truth of a hypothesis
26.
Mineral
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A mineral is a naturally occurring chemical compound, usually of crystalline form and abiogenic in origin. A mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids, the study of minerals is called mineralogy. There are over 5,300 known mineral species, over 5,070 of these have been approved by the International Mineralogical Association, the silicate minerals compose over 90% of the Earths crust. The diversity and abundance of species is controlled by the Earths chemistry. Silicon and oxygen constitute approximately 75% of the Earths crust, which translates directly into the predominance of silicate minerals, minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Minerals can be described by their various properties, which are related to their chemical structure. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, more specific tests for describing minerals include magnetism, taste or smell, radioactivity and reaction to acid. Minerals are classified by key chemical constituents, the two dominant systems are the Dana classification and the Strunz classification, the silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a unit of a 4− silica tetrahedron—that is, a silicon cation coordinated by four oxygen anions. These tetrahedra can be polymerized to give the subclasses, orthosilicates, disilicates, cyclosilicates, inosilicates, phyllosilicates, other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. The first criterion means that a mineral has to form by a natural process, stability at room temperature, in the simplest sense, is synonymous to the mineral being solid. More specifically, a compound has to be stable or metastable at 25 °C, modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula, many mineral groups and species are composed of a solid solution, pure substances are not usually found because of contamination or chemical substitution. Finally, the requirement of an ordered atomic arrangement is usually synonymous with crystallinity, however, crystals are also periodic, an ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage. There have been recent proposals to amend the definition to consider biogenic or amorphous substances as minerals. The formal definition of an approved by the IMA in 1995, A mineral is an element or chemical compound that is normally crystalline. However, if geological processes were involved in the genesis of the compound, Mineral classification schemes and their definitions are evolving to match recent advances in mineral science
27.
Crystal
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A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, the scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification, the word crystal derives from the Ancient Greek word κρύσταλλος, meaning both ice and rock crystal, from κρύος, icy cold, frost. Examples of large crystals include snowflakes, diamonds, and table salt, most inorganic solids are not crystals but polycrystals, i. e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks, ceramics, a third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass, wax, and many plastics, Crystals are often used in pseudoscientific practices such as crystal therapy, and, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements. The scientific definition of a crystal is based on the arrangement of atoms inside it. A crystal is a solid where the form a periodic arrangement. For example, when liquid water starts freezing, the change begins with small ice crystals that grow until they fuse. Most macroscopic inorganic solids are polycrystalline, including almost all metals, ceramics, ice, rocks, solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids, also called glassy, vitreous, or noncrystalline. These have no periodic order, even microscopically, there are distinct differences between crystalline solids and amorphous solids, most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does. A crystal structure is characterized by its cell, a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal, the symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries, called space groups. These are grouped into 7 crystal systems, such as cubic crystal system or hexagonal crystal system, Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. Euhedral crystals are those with obvious, well-formed flat faces, anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid. The flat faces of a crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal. This occurs because some surface orientations are more stable than others, as a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces
28.
Mafic
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Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, common mafic rocks include basalt, dolerite and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase feldspar, chemically, mafic rocks are on the other side of the rock spectrum from the felsic rocks. The term roughly corresponds to the basic rock class. Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava, water and other volatiles can more easily and gradually escape from mafic lava. As a result, eruptions of volcanoes made of mafic lavas are less violent than felsic-lava eruptions. Most mafic-lava volcanoes are shield volcanoes, like those in Hawaii, QAPF diagram List of minerals List of rock types
29.
Basalt
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Basalt is a common extrusive igneous rock formed from the rapid cooling of basaltic lava exposed at or very near the surface of a planet or moon. Flood basalt describes the formation in a series of basalt flows. By definition, basalt is an igneous rock with generally 45-55% silica and less than 10% feldspathoid by volume. Basalt commonly features a very fine-grained or glassy matrix interspersed with visible mineral grains, the average density is 3.0 gm/cm3. Basalt is defined by its content and texture, and physical descriptions without mineralogical context may be unreliable in some circumstances. Basalt is usually grey to black in colour, but rapidly weathers to brown or rust-red due to oxidation of its mafic minerals into hematite, although usually characterized as dark, basaltic rocks exhibit a wide range of shading due to regional geochemical processes. Due to weathering or high concentrations of plagioclase, some basalts can be quite light-coloured and these phenocrysts usually are of olivine or a calcium-rich plagioclase, which have the highest melting temperatures of the typical minerals that can crystallize from the melt. Basalt with a texture is called vesicular basalt, when the bulk of the rock is mostly solid. Gabbro is often marketed commercially as black granite and these ultramafic volcanic rocks, with silica contents below 45% are usually classified as komatiites. Agricola applied basalt to the black rock of the Schloßberg at Stolpen. Tholeiitic basalt is relatively rich in silica and poor in sodium, included in this category are most basalts of the ocean floor, most large oceanic islands, and continental flood basalts such as the Columbia River Plateau. Basalt rocks are in some cases classified after their content in High-Ti and Low-Ti varieties. High-Ti and Low-Ti basalts have been distinguished in the Paraná and Etendeka traps and it has greater than 17% alumina and is intermediate in composition between tholeiite and alkali basalt, the relatively alumina-rich composition is based on rocks without phenocrysts of plagioclase. Alkali basalt is relatively poor in silica and rich in sodium and it is silica-undersaturated and may contain feldspathoids, alkali feldspar and phlogopite. Boninite is a form of basalt that is erupted generally in back-arc basins. Ocean island basalt Lunar basalt On Earth, most basalt magmas have formed by melting of the mantle. Basalt commonly erupts on Io, the third largest moon of Jupiter, and has formed on the Moon, Mars, Venus. The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below, the mineralogy of basalt is characterized by a preponderance of calcic plagioclase feldspar and pyroxene
30.
Granite
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Granite is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Granites can be white, pink, or gray in color. The word granite comes from the Latin granum, a grain, in reference to the structure of such a holocrystalline rock. By definition, granite is a rock with at least 20% quartz. The term granitic means granite-like and is applied to granite and a group of igneous rocks with similar textures and slight variations in composition. Occasionally some individual crystals are larger than the groundmass, in case the texture is known as porphyritic. A granitic rock with a texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks, petrographic examination is required for identification of specific types of granitoids. The extrusive igneous rock equivalent of granite is rhyolite, Granite is nearly always massive, hard and tough, and therefore it has gained widespread use throughout human history, and more recently as a construction stone. The average density of granite is between 2.65 and 2.75 g/cm3, its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6 •1019 Pa·s. The melting temperature of dry granite at ambient pressure is 1215–1260 °C, it is reduced in the presence of water. Granite has poor primary permeability, but strong secondary permeability, true granite according to modern petrologic convention contains both plagioclase and alkali feldspars. When a granitoid is devoid or nearly devoid of plagioclase, the rock is referred to as alkali feldspar granite, when a granitoid contains less than 10% orthoclase, it is called tonalite, pyroxene and amphibole are common in tonalite. A granite containing both muscovite and biotite micas is called a binary or two-mica granite, two-mica granites are typically high in potassium and low in plagioclase, and are usually S-type granites or A-type granites. A worldwide average of the composition of granite, by weight percent, based on 2485 analyses. Much of it was intruded during the Precambrian age, it is the most abundant basement rock that underlies the relatively thin veneer of the continents. Outcrops of granite tend to form tors and rounded massifs, granites sometimes occur in circular depressions surrounded by a range of hills, formed by the metamorphic aureole or hornfels. Granite often occurs as small, less than 100 km² stock masses
31.
Metastability
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In physics, metastability denotes the phenomenon when a dynamical system spends an extended time in a configuration other than the systems state of least energy. During a metastable state of finite lifetime, all state-describing parameters reach, a conceptual analogy may be drawn with a ball resting in a hollow on a slope. Small perturbations will result in the ball settling back into its current hollow, isomerisation is another common example of metastability. Higher energy isomers are long lived as they are prevented from rearranging to their ground state by barriers in the potential energy. The metastability concept originated in the physics of first-order phase transitions and it then acquired new meaning in the study of aggregated subatomic particles or in molecules, macromolecules or clusters of atoms and molecules. Later, it was borrowed for the study of decision-making and information transmission systems, many complex natural and man-made systems can demonstrate metastability. Metastability is common in physics and chemistry – from an atom to statistical ensembles of molecules at molecular levels or as a whole, the abundance of states is more prevalent as the systems grow larger and/or if the forces of their mutual interaction are spatially less uniform or more diverse. In these systems, the equivalent of thermal fluctuations in molecular systems is the noise that affects signal propagation. Non-equilibrium thermodynamics is a branch of physics that studies the dynamics of statistical ensembles of molecules via unstable states, being stuck in a thermodynamic trough without being at the lowest energy state is known as having kinetic stability or being kinetically persistent. The particular motion or kinetics of the atoms involved has resulted in getting stuck, metastable states of matter range from melting solids, boiling liquids and sublimating solids to supercooled liquids or superheated liquid-gas mixtures. Extremely pure, supercooled water stays liquid below 0 °C and remains so until applied vibrations or condensing seed doping initiates crystallization centers and this is a common situation for the droplets of atmospheric clouds. Metastable phases are common in condensed matter, for example, diamond is a metastable form of carbon at standard temperature and pressure. It can be converted to graphite, but only after overcoming an activation energy – an intervening hill, martensite is a metastable phase used to control the hardness of most steel. The bonds between the blocks of polymers such as DNA, RNA and proteins are also metastable. Metastable polymorphs of silica are commonly observed, in some cases, such as in the allotropes of solid boron, acquiring a sample of the stable phase is difficult. Generally speaking, emulsions/colloidal systems and glasses are metastable, sandpiles are one system which can exhibit metastability if a steep slope or tunnel is present. Sand grains form a pile due to friction and it is possible for an entire large sand pile to reach a point where it is stable, but the addition of a single grain causes large parts of it to collapse. The avalanche is a problem with large piles of snow
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Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
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Groundwater
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Groundwater is the water present beneath Earths surface in soil pore spaces and in the fractures of rock formations. A unit of rock or a deposit is called an aquifer when it can yield a usable quantity of water. The depth at which pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the naturally, natural discharge often occurs at springs and seeps. Groundwater is also withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of Earths subsurface contains some water, Groundwater may not be confined only to Earth. The formation of some of the landforms observed on Mars may have influenced by groundwater. There is also evidence that water may also exist in the subsurface of Jupiters moon Europa. Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water, therefore, it is commonly used for public water supplies. For example, groundwater provides the largest source of water storage in the United States. Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, many municipal water supplies are derived solely from groundwater. Polluted groundwater is less visible, but more difficult to clean up, than pollution in rivers, Groundwater pollution most often results from improper disposal of wastes on land. An aquifer is a layer of substrate that contains and transmits groundwater. When water can flow directly between the surface and the zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are more saturated since gravity causes water to flow downward. The upper level of this layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone, substrate with low porosity that permits limited transmission of groundwater is known as an aquitard
34.
Perlite
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Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the property of greatly expanding when heated sufficiently. It is a mineral and a commercial product useful for its low density after processing. Perlite softens when it reaches temperatures of 850–900 °C, water trapped in the structure of the material vaporises and escapes, and this causes the expansion of the material to 7–16 times its original volume. The expanded material is a brilliant white, due to the reflectivity of the trapped bubbles, unexpanded perlite has a bulk density around 1100 kg/m3, while typical expanded perlite has a bulk density of about 30–150 kg/m3. The world reserves of perlite are estimated at 700 million tonnes, in 2011,1.7 million tonnes were produced, mostly by Greece, United States and Turkey. However, no information for China – a leading producer – was available, because of its low density and relatively low price, many commercial applications for perlite have developed. In the construction and manufacturing fields, it is used in lightweight plasters, concrete and mortar, insulation, in horticulture, perlite can be used as a soil amendment or alone as a medium for hydroponics or for starting cuttings. When used as an amendment it has high permeability / low water retention, perlite is an excellent filtration aid and is used extensively as an alternative to diatomaceous earth. The popularity of usage as a filter medium is growing considerably worldwide. Perlite filters are commonplace in filtering beer before it is bottled. Small quantities of perlite are also used in foundries, cryogenic insulation and it is also used by the explosives industry. Due to thermal and mechanical stability, non-toxicity, and high resistance against microbial attacks and organic solvents, perlite was found to be an excellent support for immobilization of biocatalysts such as enzymes for bioremediation and sensing applications. Perlite can be substituted for all of its uses, substitutes include, Diatomite Expanded clay Shale Pumice Slag Vermiculite People can be exposed to perlite in the workplace by breathing in dust, skin contact, and eye contact. The Occupational Safety and Health Administration has set the limit for perlite exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health has set a recommended limit of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. Popular Mechanics, December 1954, p.136, CDC - NIOSH Pocket Guide to Chemical Hazards
35.
Inclusion (mineral)
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In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation. In gemology, an inclusion is a characteristic enclosed within a gemstone, according to Huttons law of inclusions, fragments included in a host rock are older than the host rock itself. Inclusions are usually other minerals or rocks, but may also be water, liquid or vapor inclusions are known as fluid inclusions. In the case of amber it is possible to find insects and plants as inclusions, the analysis of atmospheric gas bubbles as inclusions in ice cores is an important tool in the study of climate change. A xenolith is a rock which has been picked up by a lava flow. Melt inclusions form when bits of melt become trapped inside crystals as they form in the melt, inclusions are one of the most important factors when it comes to gem valuation. In many gemstones, such as diamonds, inclusions affect the clarity of the gem, in some gems, however, such as star sapphires, the inclusion actually increases the value of the gem. Many colored gemstones, such as amethyst, emerald, and sapphire, are expected to have inclusions, colored gemstones are categorized into three types as follows, Type I colored gems include gems with very little or no inclusions. They include aquamarines, topaz and zircon, Type II colored gems include those that often have a few inclusions. They include sapphire, ruby, garnet and spinel, Type III colored gems include those that almost always have inclusions. Gems in this category include emerald and tourmaline, the term inclusion is also used in the context of metallurgy and metals processing. During the melt stage of processing hard particles such as oxides can enter or form in the metal which are subsequently trapped when the melt solidifies. The term is used negatively such as when the particle could act as a fatigue crack nucleator or as an area of high stress intensity
36.
Iridescence
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Iridescence is the phenomenon of certain surfaces that appear to gradually change colour as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, butterfly wings and sea shells and it is often created by structural coloration. The word iridescence is derived in part from the Greek word ἶρις îris, meaning rainbow, Iris in turn derives from the goddess Iris of Greek mythology, who is the personification of the rainbow and acted as a messenger of the gods. Goniochromism is derived from the Greek words gonia, meaning angle, iridescence is an optical phenomenon of surfaces in which hue changes with the angle of observation and the angle of illumination. It is often caused by reflections from two or more semi-transparent surfaces in which phase shift and interference of the reflections modulates the incidental light. The thickness of the layers of the material determines the interference pattern, iridescence is also found in plants, animals and many other items. The range of colours of natural iridescent objects can be narrow, iridescence can also be created by diffraction. This is found in items like CDs, DVDs, or cloud iridescence, in the case of diffraction, the entire rainbow of colours will typically be observed as the viewing angle changes. In biology, this type of results from the formation of diffraction gratings on the surface. In biological uses, colours produced other than with pigments or dyes are called structural coloration and it was later found that iridescence in the peacock is due to a complex photonic crystal. The feathers of birds such as kingfishers, Birds-of-paradise, hummingbirds, parrots, starlings, grackles, ducks, the lateral line on the Neon tetra is also iridescent. A single iridescent species of gecko, Cnemaspis kolhapurensis, was identified in India in 2009, the tapetum lucidum, present in the eyes of many vertebrates, is also iridescent. Many groups of plants have developed iridescence as an adaptation to use light in dark environments such as the lower levels of tropical forests. Nanocellulose is sometimes iridescent, as are films of gasoline and some other hydrocarbons. Iridescent products in the cosmetic and clothing industries are often referred as being holographic
37.
Magnetite
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Magnetite is a mineral and one of the main iron ores. With the chemical formula Fe3O4, it is one of the oxides of iron, Magnetite is ferrimagnetic, it is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is the most magnetic of all the minerals on Earth. Naturally-magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, today it is mined as iron ore. Small grains of magnetite occur in almost all igneous and metamorphic rocks, Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak. The chemical IUPAC name is iron oxide and the chemical name is ferrous-ferric oxide. In addition to rocks, magnetite also occurs in sedimentary rocks, including banded iron formations and in lake. Magnetite nanoparticles are also thought to form in soils, where they probably oxidize rapidly to maghemite, Magnetite has an inverse spinel crystal structure. As a member of the group, it can form solid solutions with similarly structured minerals, including ulvospinel. Titanomagnetite, also known as titaniferous magnetite, is a solution between magnetite and ulvospinel that crystallizes in many mafic igneous rocks. Titanomagnetite may undergo oxyexsolution during cooling, resulting in ingrowths of magnetite and ilmenite, Magnetite has been important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite, and the pair forms a buffer that can control oxygen fugacity. Commonly, igneous rocks contain solid solutions of both titanomagnetite and hemoilmenite or titanohematite, Magnetite also is produced from peridotites and dunites by serpentinization. Lodestones were used as a form of magnetic compass. At low temperatures, magnetite undergoes a crystal structure phase transition from a structure to a cubic structure known as the Verwey transition. The Verwey transition occurs around 121 K and is dependent on size, domain state. An isotropic point also occurs near the Verwey transition around 130 K, the Curie temperature of magnetite is 858 K. Magnetite is sometimes found in large quantities in beach sand. Such black sands are found in places, such as Lung Kwu Tan of Hong Kong, California of the United States
38.
Nanoparticle
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Nanoparticles are particles between 1 and 100 nanometers in size. In nanotechnology, a particle is defined as an object that behaves as a whole unit with respect to its transport. Particles are further classified according to diameter, scientific research on nanoparticles is intense as they have many potential applications in medicine, physics, optics, and electronics. The U. S. National Nanotechnology Initiative offers government funding focused on nanoparticle research, the term nanoparticle is not usually applied to individual molecules, it usually refers to inorganic materials. However, during the 1990s before the National Nanotechnology Initiative was launched in the USA, nanoparticles can exhibit size-related properties significantly different from those of either fine particles or bulk materials. Nanoclusters have at least one dimension between 1 and 10 nanometers and a size distribution. Nanopowders are agglomerates of ultrafine particles, nanoparticles, or nanoclusters, nanometer-sized single crystals, or single-domain ultrafine particles, are often referred to as nanocrystals. Although nanoparticles are associated with science, they have a long history. In modern times, pottery from the Middle Ages and Renaissance often retains a distinct gold- or copper-colored metallic glitter and this luster is caused by a metallic film that was applied to the transparent surface of a glazing. The luster can still be visible if the film has resisted atmospheric oxidation, the luster originates within the film itself, which contains silver and copper nanoparticles dispersed homogeneously in the glassy matrix of the ceramic glaze. These nanoparticles are created by the artisans by adding copper and silver salts and oxides together with vinegar, ochre, the object is then placed into a kiln and heated to about 600 °C in a reducing atmosphere. In the heat the glaze softens, causing the copper and silver ions to migrate into the layers of the glaze. There the reducing atmosphere reduced the ions back to metals, which came together forming the nanoparticles that give the color. Luster technique showed that ancient craftsmen had an empirical knowledge of materials. The technique originated in the Muslim world, as Muslims were not allowed to use gold in artistic representations, they sought a way to create a similar effect without using real gold. The solution they found was using luster, michael Faraday provided the first description, in scientific terms, of the optical properties of nanometer-scale metals in his classic 1857 paper. The result is white light is now freely transmitted, reflection is correspondingly diminished. Uncontrolled agglomeration of powders due to van der Waals forces can also give rise to microstructural heterogeneity
39.
Medicine Lake Volcano
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Medicine Lake Volcano is a large shield volcano in northeastern California about 30 miles northeast of Mount Shasta. The volcano is located in a zone of east-west crustal extension east of the axis of the Cascade Volcanic Arc. The 0. 6-mile thick shield is 22 miles from east to west and 28 to 31 miles from north to south, the underlying rock has downwarped by 0.3 miles under the center of the volcano. The volcano is composed of basalt and basaltic andesite lava flows. The Medicine Lake shield rises about 3,900 feet above the Modoc Plateau to an elevation of 7,795 feet. Lavas from Medicine Lake Volcano are estimated to be at least 140 cubic miles in volume, Lava Beds National Monument lies on the northeast flank of the volcano. Medicine Lake Volcano has been active for 500,000 years, the eruptions were gentle rather than explosive like Mount St. Helens, coating the volcanos sides with flow after flow of basaltic lava. Medicine Lake is part of the old caldera, a depression in the mountain. It is believed that the Medicine Lake volcano is unique, having many small magma chambers rather than one large one, Medicine Lake is in the caldera of the volcano, which measures 4.3 by 7.5 miles. The caldera may have formed by collapse after a volume of andesite was erupted from vents along the caldera rim. The distribution of late Pleistocene vents, mostly concentrated along the rim, no single large eruption has been related to caldera formation. The only eruption recognized to have produced ash flow tuff occurred in late Pleistocene time, later conclusions were that Medicine Lake caldera formed by collapse in response to repeated extrusions of mostly mafic lava beginning early in the history of the volcano. Several small differentiated magma bodies may have fed by and interspersed among a plexus of dikes. Late Holocene andesitic to rhyolitic lavas were derived by fractionation, assimilation, the small lake from which Medicine Lake volcano derives its name lies within the central caldera. Medicine Lake Volcano began to grow about one years ago in Pleistocene time. Similar high-alumina basalt has continued to erupt around the volcano throughout its history, although mafic lavas predominate on the volcanos flanks, all lava compositions from basalt to rhyolite have erupted during Pleistocene time. The lower flanks consist of basaltic and some andesitic lavas. Basalt is mostly absent at higher elevation, where andesite dominates and rhyolite, during the past 11,000 years, eruptive activity at Medicine Lake Volcano has been episodic
40.
Argentina
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Argentina, officially the Argentine Republic, is a federal republic in the southern half of South America. With a mainland area of 2,780,400 km2, Argentina is the eighth-largest country in the world, the second largest in Latin America, and the largest Spanish-speaking one. The country is subdivided into provinces and one autonomous city, Buenos Aires. The provinces and the capital have their own constitutions, but exist under a federal system, Argentina claims sovereignty over part of Antarctica, the Falkland Islands, and South Georgia and the South Sandwich Islands. The earliest recorded presence in the area of modern-day Argentina dates back to the Paleolithic period. The country has its roots in Spanish colonization of the region during the 16th century, Argentina rose as the successor state of the Viceroyalty of the Río de la Plata, a Spanish overseas viceroyalty founded in 1776. The country thereafter enjoyed relative peace and stability, with waves of European immigration radically reshaping its cultural. The almost-unparalleled increase in prosperity led to Argentina becoming the seventh wealthiest developed nation in the world by the early 20th century, Argentina retains its historic status as a middle power in international affairs, and is a prominent regional power in the Southern Cone and Latin America. Argentina has the second largest economy in South America, the third-largest in Latin America and is a member of the G-15 and it is the country with the second highest Human Development Index in Latin America with a rating of very high. Because of its stability, market size and growing high-tech sector, the description of the country by the word Argentina has to be found on a Venice map in 1536. In English the name Argentina probably comes from the Spanish language, however the naming itself is not Spanish, Argentina means in Italian of silver, silver coloured, probably borrowed from the Old French adjective argentine of silver > silver coloured already mentioned in the 12th century. The French word argentine is the form of argentin and derives of argent silver with the suffix -in. The Italian naming Argentina for the country implies Argentina Terra land of silver or Argentina costa coast of silver, in Italian, the adjective or the proper noun is often used in an autonomous way as a substantive and replaces it and it is said lArgentina. The name Argentina was probably first given by the Venitian and Genoese navigators, in Spanish and Portuguese, the words for silver are respectively plata and prata and of silver is said plateado and prateado. Argentina was first associated with the silver mountains legend, widespread among the first European explorers of the La Plata Basin. The first written use of the name in Spanish can be traced to La Argentina, a 1602 poem by Martín del Barco Centenera describing the region, the 1826 constitution included the first use of the name Argentine Republic in legal documents. The name Argentine Confederation was also used and was formalized in the Argentine Constitution of 1853. In 1860 a presidential decree settled the name as Argentine Republic
41.
Armenia
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Armenia, officially the Republic of Armenia, is a sovereign state in the South Caucasus region of Eurasia. The Republic of Armenia constitutes only one-tenth of historical Armenia, Armenia is a unitary, multi-party, democratic nation-state with an ancient cultural heritage. Urartu was established in 860 BC and by the 6th century BC it was replaced by the Satrapy of Armenia, in the 1st century BC the Kingdom of Armenia reached its height under Tigranes the Great. Armenia became the first state in the world to adopt Christianity as its official religion, in between the late 3rd century to early years of the 4th century, the state became the first Christian nation. The official date of adoption of Christianity is 301 AD. The ancient Armenian kingdom was split between the Byzantine and Sasanian Empires around the early 5th century, under the Bagratuni dynasty, the Bagratid Kingdom of Armenia was restored in the 9th century. Declining due to the wars against the Byzantines, the fell in 1045. An Armenian principality and later a kingdom Cilician Armenia was located on the coast of the Mediterranean Sea between the 11th and 14th centuries. By the 19th century, Eastern Armenia had been conquered by the Russian Empire, during World War I, Armenians living in their ancestral lands in the Ottoman Empire were systematically exterminated in the Armenian Genocide. By 1920, the state was incorporated into the Transcaucasian Socialist Federative Soviet Republic, in 1936, the Transcaucasian state was dissolved, transforming its constituent states, including the Armenian Soviet Socialist Republic, into full Union republics. The modern Republic of Armenia became independent in 1991 during the dissolution of the Soviet Union, the Republic of Armenia recognises the Armenian Apostolic Church, the worlds oldest national church, as the countrys primary religious establishment. The unique Armenian alphabet was invented by Mesrop Mashtots in 405 AD, Armenia is a member of the Eurasian Economic Union, the Council of Europe and the Collective Security Treaty Organization. Armenia supports the de facto independent Nagorno-Karabakh Republic, which was proclaimed in 1991, the native Armenian name for the country is Հայք. The name in the Middle Ages was extended to Հայաստան, by addition of the Persian suffix -stan, the further origin of the name is uncertain. It is also postulated that the name Hay comes from one of the two confederated, Hittite vassal states—the Ḫayaša-Azzi. The exonym Armenia is attested in the Old Persian Behistun Inscription as Armina, the ancient Greek terms Ἀρμενία and Ἀρμένιοι are first mentioned by Hecataeus of Miletus. Xenophon, a Greek general serving in some of the Persian expeditions, describes many aspects of Armenian village life and he relates that the people spoke a language that to his ear sounded like the language of the Persians. According to the histories of both Moses of Chorene and Michael Chamchian, Armenia derives from the name of Aram, a descendant of Hayk
42.
Azerbaijan
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Azerbaijan, officially the Republic of Azerbaijan, is a country in the South Caucasus region, situated at the crossroads of Southwest Asia and Southeastern Europe. It is bound by the Caspian Sea to the east, Russia to the north, Georgia to the northwest, Armenia to the west and Iran to the south. The exclave of Nakhchivan is bound by Armenia to the north and east, Iran to the south and west, the Azerbaijan Democratic Republic proclaimed its independence in 1918 and became the first democratic state in the Muslim orient world. The country was incorporated into the Soviet Union in 1920 as the Azerbaijan Soviet Socialist Republic, the modern Republic of Azerbaijan proclaimed its independence on 30 August 1991, prior to the official dissolution of the USSR in December 1991. In September 1991, the Armenian majority of the disputed Nagorno-Karabakh region seceded to form the Nagorno-Karabakh Republic, the region and seven adjacent districts outside it became de facto independent with the end of the Nagorno-Karabakh War in 1994. These regions are recognized as part of Azerbaijan pending a solution to the status of the Nagorno-Karabakh. Azerbaijan is a unitary semi-presidential republic, the country is a member state of the Council of Europe, the OSCE and the NATO Partnership for Peace program. It is one of six independent Turkic states, a member of the Turkic Council. Azerbaijan has diplomatic relations with 158 countries and holds membership in 38 international organizations and it is one of the founding members of GUAM, the Commonwealth of Independent States and the Organization for the Prohibition of Chemical Weapons. Its term of office began on 19 June 2006, Azerbaijan is also a member state of the Non-Aligned Movement, holds observer status in World Trade Organization and is a correspondent at the International Telecommunication Union. The Constitution of Azerbaijan does not declare an official religion and all political forces in the country are secularist. However, the majority of the population are of a Shiite Muslim background, Azerbaijan has a high level of human development which ranks on par with most Eastern European countries. It has a rate of economic development and literacy, as well as a low rate of unemployment. According to the Davos World Economic Forum, Azerbaijans economy has scored 37th place within 138 countries in 2016, Global Competitiveness Index 2015 indicates that Azerbaijan scores highest in its region. ASAN services, established with Presidential Decree, are known for eliminating bribery. ASAN Service has been awarded with United Nations Public Service Award 2015, the ruling party, the New Azerbaijan Party, has been accused of authoritarianism and human rights abuses. The original etymology of name is thought to have its roots in the once-dominant Zoroastrianism. In the Avesta, Frawardin Yasht, there is a mention of âterepâtahe ashaonô fravashîm ýazamaide, the name Atropates itself is the Greek transliteration of an Old Iranian, probably Median, compounded name with the meaning Protected by the Fire or The Land of the Fire
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