1.
Tektite habitat
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The Tektite habitat was an underwater laboratory which was the home to divers during Tektite I and II programs. The Tektite program was the first scientists-in-the-sea program sponsored nationally, the habitat capsule was placed in Great Lameshur Bay, Saint John, U. S. Virgin Islands in 1969 and again in 1970. The Tektite habitat was designed and built by General Electric Company Space Division at the Valley Forge Space Technology Center in King of Prussia, Pennsylvania, the Program Manager for the Tektite projects was Dr. Theodore Marton at General Electric. The habitat appears as a pair of silos, two metal cylinders 4 m in diameter,6 m high, joined by a flexible tunnel. On February 15,1969, four U. S. Department of Interior scientists descended to the floor in Great Lameshur Bay in the U. S. Virgin Islands to begin an ambitious diving project dubbed Tektite I. By March 18,1969, the four aquanauts had established a new record for saturated diving by a single team. On April 15,1969, the team returned to the surface with over 58 days of marine scientific studies. More than 19 hours of time were needed to accommodate the scientists return to the surface. The United States Office of Naval Research coordinated Tektite I, much of the research for Tektite I centered on humans in this new environment. Topics investigated would include, biology, decompression and decompression sickness, the missions were carried out in May 1970. Tektite II comprised ten missions lasting 10–20 days with four scientists, other scientists participating in the all-female mission included Renate True of Tulane, as well as Sylvia Earle and Alina Szmant, graduate students at Scripps Institute of Oceanography. The fifth member of the crew was Margaret Ann Lucas, a Villanova engineering graduate, the Tektite II missions were the first to undertake in-depth ecological studies. Tektite III was a wholly owned and operated California 501 C Non-Profit Corporation, harold C. Ross was Project Manager. When Tektite II ended General Electric placed the Habitat in storage in Philadelphia, a group of interested parties purchased the Habitat from General Electric for $1.00 with the stipulation it would be removed from the GE storage facility. The Habitat was trucked across the United States to Ft. Mason in San Francisco where it was placed on display, attempts were made to refurbish the Habitat so it could be used in San Francisco Bay as a teaching tool. By 1980 the Habitat was fully restored and certified to be used underwater. § Funds for actually submerging and operating the habitat again were not available. During the more than 10 years the Habitat was on display at Ft Mason, unfortunately lack of funds ended the Project and the Habitat was sold and moved to storage along the Oakland Estuary. The website Tektite Underwater Habitat Museum reports that at the end of display at Fort Mason, the Habitat was dismantled by welding school students, lambertsens Predictive Studies Series that started with Tektite I in 1969 and ended in 1997, researched many aspects of human physiology in extreme environments
2.
Recurring enemies in The Legend of Zelda series
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This article describes several types of fictional enemy creatures encountered in The Legend of Zelda series of video games. While many enemies can be killed solely with Links sword, others require the use of items to eliminate. In addition, starting with The Wind Waker, some enemies wield weapons such as swords or lit torches that can be used by Link after destroying the enemy. These items serve a single use and eliminate other obstacles by means such as smashing open a doorway or burning down a blocked passage, specific enemies also hold key items that can be obtained by either killing the monster or using the grappling hook. Enemies in The Legend of Zelda series first appeared as basic, although initially conveyed as two-dimensional sprites, in the newer games, starting with Ocarina of Time, they are rendered by 3D computer graphics. According to The Minish Cap, they were created to guard the Wind Tribe and they typically pose as statues or suits of armor, but attack when approached. Some Armos statues are inanimate and can be moved like blocks, There is a larger, stronger variety of Armos known as Armos Knights, which first appeared as a collective boss in A Link to the Past. In the The Wind Waker, both the standard Armos and the Armos Knights appear as common enemies, to defeat the standard Armos, an arrow had to be shot into the pink gem that was in the Armos back or slash at it with a sword. After damaging this gem, the Armos will spin around, chasing Link for a few seconds, then explode, to defeat the Armos Knights, a bomb had to be thrown into their open mouth. While the Armos Knight is dying, they, too chase Link for a few seconds before exploding, in Twilight Princess, they are hammer-wielding statues that can only be harmed from behind. There were also enemies called Titan Armos that were supposed to appear in the game, Majoras Mask featured another variety known as Death Armos, which hovered around and attacked by slamming into the floor. Beamos are one of the common enemies in The Legend of Zelda series. The Beamos is typically a type of pillar-mounted mechanical eye that rotates 360 degrees in search of intruders. If the Beamos spots an intruder it will fire a beam while the target is in view, the beam can generally be reflected with the Mirror Shield. In Ocarina of Time, Beamos can fire both a beam that knocks Link back and a beam that inflicts damage. In addition, the organic beamos in Ocarina of Time, Majoras Mask, There are two different variations of the Beetle in the Zelda series. Spiked Beetles have sword-repellent spiked carapaces on their top side to protect their vulnerable undersides and they appear in most handheld Zelda games. Hardhat Beetles have elastic carapaces covering their body that use to knock Link away
3.
Impact event
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An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have found to regularly occur in planetary systems, though the most frequent involve asteroids. Impact craters and structures are dominant landforms on many of the Solar Systems solid objects and present the strongest empirical evidence for their frequency, Impact events appear to have played a significant role in the evolution of the Solar System since its formation. Notable impact events include the Chicxulub impact,66 million years ago, throughout recorded history, hundreds of Earth impacts have been reported, with some occurrences causing deaths, injuries, property damage, or other significant localised consequences. One of the best-known recorded impacts in modern times was the Tunguska event, the Comet Shoemaker–Levy 9 impact provided the first direct observation of an extraterrestrial collision of Solar System objects, when the comet broke apart and collided with Jupiter in July 1994. Impact events have been a plot and background element in science fiction, Impact structures are the result of impact events on solid objects and, as the dominant landforms on many of the Systems solid objects, present the most solid evidence of prehistoric events. Small objects frequently collide with Earth, there is an inverse relationship between the size of the object and the frequency of such events. The lunar cratering record shows that the frequency of impacts decreases as approximately the cube of the craters diameter. Asteroids with a 1 km diameter strike Earth every 500,000 years on average, large collisions – with 5 km objects – happen approximately once every twenty million years. The last known impact of an object of 10 km or more in diameter was at the Cretaceous–Paleogene extinction event 66 million years ago, the energy released by an impactor depends on diameter, density, velocity, and angle. The diameter of most near-Earth asteroids that have not been studied by radar or infrared can generally only be estimated within about a factor of 2 based on the asteroid brightness, the density is generally assumed because the diameter and mass are also generally estimates. The minimum impact velocity on Earth is 11 km/s with asteroid impacts averaging around 17 km/s, the most probable impact angle is 45 degrees. Stony asteroids with a diameter of 4 meters enter Earths atmosphere approximately once per year. Asteroids with a diameter of 7 meters enter the atmosphere about every 5 years with as much energy as the atomic bomb dropped on Hiroshima. These ordinarily explode in the atmosphere and most or all of the solids are vaporized. However, asteroids with a diameter of 20 m, and which strike Earth approximately twice every century, the 2013 Chelyabinsk meteor was estimated to be about 20 m in diameter with an airburst of around 500 kilotons, an explosion 30 times the one over Hiroshima. Much larger objects may impact the solid earth and create a crater, objects with a diameter less than 1 m are called meteoroids and seldom make it to the ground to become meteorites. Although no human is known to have been killed directly by an impact, in 2005 it was estimated that the chance of a single person born today dying due to an impact is around 1 in 200,000
4.
Gravel
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Gravel /ˈɡrævəl/ is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel is categorized by the Udden-Wentworth scale into granular gravel and pebble gravel, one cubic metre of gravel typically weighs about 1,800 kg. Gravel is an important commercial product, with a number of applications, many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac, both sand and small gravel are also important for the manufacture of concrete. Large gravel deposits are a geological feature, being formed as a result of the weathering. The action of rivers and waves tends to pile up gravel in large accumulations and this can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called conglomerate. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, quarries where gravel is extracted are known as gravel pits. Southern England possesses particularly large concentrations of them due to the deposition of gravel in the region during the Ice Ages. As of 2006, the United States is the leading producer and consumer of gravel. The word gravel comes from the Breton language, adding the -el suffix in Breton denotes the component parts of something larger. Thus gravel means the stones which make up such a beach on the coast. Many dictionaries ignore the Breton language, citing Old French gravele or gravelle, Gravel often has the meaning a mixture of different size pieces of stone mixed with sand and possibly some clay. American English also allows small stones without sand mixed in also known as crushed stone, types of gravel include, Bank gravel, naturally deposited gravel intermixed with sand or clay found in and next to rivers and streams. Also known as Bank run or River run, bench gravel, a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level. Creek rock, this is rounded, semi-polished stones, potentially of a wide range of types. It is also used as concrete aggregate and less often as a paving surface. Crushed stone, rock crushed and graded by screens and then mixed to a blend of stones and fines and it is widely used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone, dolomite, also known as crusher run, DGA QP, and shoulder stone
5.
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
6.
Eduard Suess
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Eduard Suess was an Austrian geologist who was an expert on the geography of the Alps. He is responsible for hypothesising two major geographical features, the supercontinent Gondwana and the Tethys Ocean. Eduard Suess was born on August 20,1831, in London, England, the oldest son of Adolph Suess, a Lutheran Saxon merchant, when he was three, his family relocated to Prague, and then to Vienna when he was 14. He became interested in geology at a young age, while working as an assistant at the Hofmuseum in Vienna, he published his first paper—on the geology of Carlsbad —when he was 19. In 1855, Suess married Hermine Strauss, the daughter of a prominent physician from Prague and their marriage produced five sons and one daughter. In 1856, he was appointed professor of paleontology at the University of Vienna and he gradually developed views on the connection between Africa and Europe. Eventually, he concluded that the Alps to the north were once at the bottom of an ocean, Suess was not correct in his analysis, which was predicated upon the notion of contractionism—the idea that the Earth is cooling down and, therefore, contracting. Nevertheless, he is credited with postulating the existence of the Tethys Ocean. He claimed in 1885 that land bridges had connected South America, Africa, India, Australia and he named this ancient broken continent Gondwanaland. Suess published a synthesis of his ideas between 1885 and 1901 titled Das Antlitz der Erde, which was a popular textbook for many years. His theory was based upon glossopteris fern fossils occurring in South America, Africa and his explanation was that the three lands were once connected in a supercontinent, which he named Gondwanaland. Again, this is not quite correct, Suess believed that the oceans flooded the spaces currently between those lands, in his work Das Antlitz der Erde, Suess also introduced the concept of the biosphere, which was later extended by Vladimir I. Suess wrote, One thing seems to be foreign on this large body consisting of spheres, namely. But this life is limited to a zone at the surface of the lithosphere. He was elected a member of the Royal Swedish Academy of Sciences in 1895 and he received the Wollaston Medal of the Geological Society of London in 1896 and he won the Copley Medal of the Royal Society in 1903. Suess died on April 26,1914, in Vienna and he is buried in the town of Marz in Burgenland, Austria. Suess is considered one of the practitioners of ecology. The crater Suess on the Moon and a crater on Mars are named after him and his son, Franz Eduard Suess, was superintendent and geologist at the Imperial Geological Institute in Vienna
7.
Volatiles
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In planetary science, volatiles are the group of chemical elements and chemical compounds with low boiling points that are associated with a planets or moons crust or atmosphere. Examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, methane, in astrogeology, these compounds, in their solid state, often comprise large proportions of the crusts of moons and dwarf planets. In contrast with volatiles, elements and compounds with high boiling points are known as refractory substances, the terms gas and ice in this context can apply to compounds that may be solids, liquids or gases. The Moon is very low in volatiles, its crust contains oxygen chemically bound into the rocks, in igneous petrology the term more specifically refers to the volatile components of magma that affect the appearance and explosivity of volcanoes. Volatiles in a magma with a high viscosity, generally felsic with a silica content. Volatiles in a magma with a low viscosity, generally mafic with a silica content, tend to vent. Some volcanic eruptions are explosive because the mixing water and magma reaching the surface, releases energy suddenly. Moreover, in cases, the eruption is caused by volatiles dissolved in the magma. Approaching the surface, pressure decreases and the volatiles evolve creating bubbles that circulate in the liquid, the bubbles are connected together forming a network. This especially increments the fragmentation into small drops or spray or coagulate clots in gas, generally, 95-99% of magma is liquid rock. However, the percentage of gas present, represents a very large volume when it expands on reaching atmospheric pressure. Gas is a preponderant part in a system because it generates explosive eruptions. Magma in the mantle and lower crust have a lot of volatiles within and water, also they leak hydrogen sulfide and sulfur dioxide. Sulfur dioxide is usually possible to find in basaltic and rhyolite rocks, volcanoes also release a high amount of hydrogen chloride and hydrogen fluoride as volatiles. There are three factors that effect the dispersion of volatiles in magma, confining pressure, composition of magma. Pressure and composition are the most important parameters, to understand how the magma behaves rising the surface, the role of solubility within the magma must be known. An empirical law has used for different magma-volatiles combination. For instance, for water in magma the equation is n=0.1078 P where n is the amount of dissolved gas as weight percentage, the value changes for example for water in rhyolite where n=0.4111 P and for the carbon dioxide is n=0.0023 P
8.
Lechatelierite
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Lechatelierite is silica glass, amorphous SiO2, non-crystalline mineraloid. Lechatelierite is a mineraloid as it not have a crystal structure. Although not a mineral, it is often classified in the quartz mineral group. One common way in which forms naturally is by very high temperature melting of quartz sand during a lightning strike. The result is an irregular, branching, often foamy hollow tube of glass called a fulgurite. Lechatelierite also forms as the result of high pressure shock metamorphism during meteorite impact cratering and is a component of a type of glassy ejecta called tektites. High pressure experiments have shown that shock pressures of 85 GPa are needed to produce lechatelierite in quartz grains embedded in granite, lechatelierite was formed during the impact of a meteorite into a layer of Coconino Sandstone at Meteor Crater in Arizona. During the rapid pressure reduction following the impact, steam expanded the newly formed lechatelierite, the shattered and expanded glass has a density less than that of water. Lechatelierite may also form artificially, an example being the trinitite produced by melting of quartz sand at the first nuclear bomb explosion at Trinity Flats, White Sands
9.
Microlite
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Microlite is a pale-yellow, reddish-brown, or black isometric mineral composed of sodium calcium tantalum oxide with a small amount of fluorine 2Ta2O6. Microlite is a mineral in the group that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a specific gravity of 4.2 to 6.4. It occurs as disseminated microscopic subtranslucent to opaque octahedral crystals with an index of 2.0 to 2.2. Microlite occurs as a mineral in lithium-bearing granite pegmatites. Association minerals include, albite, lepidolite, topaz, beryl, tourmaline, spessartine, microlite was first described in 1835 for an occurrence on the Island of Uto, State of Stockholm, Sweden. A type locality is the Clark Ledges pegmatite, Chesterfield, Hampshire County, the name is from Greek mikros for small and lithos for stone. Palache, C. H. Berman, and C, frondel Dana’s system of mineralogy, v. I, 748–757 Webmineral data Mindat with location data Mineral data publishing PDF Atencio, D. Andrade, M. B. Christy, A. G. Gieré, R. & Kartashov, the pyrochlore supergroup of minerals, nomenclature. The Canadian Mineralogist,48, 673-698. doi,10. 3749/canmin.48.3.673 Andrade, Atencio, D. Menezes Filho, L. A. & Ellena, J. The crystal structure of a mineral with a formula near NaCaTa2O6F from the Morro Redondo mine, Coronel Murta, Minas Gerais
10.
Sediment
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For sediment in beverages, see dregs. For example, sand and silt can be carried in suspension in water and on reaching the sea be deposited by sedimentation. Sediments are most often transported by water, but also wind, beach sands and river channel deposits are examples of fluvial transport and deposition, though sediment also often settles out of slow-moving or standing water in lakes and oceans. Desert sand dunes and loess are examples of transport and deposition. Glacial moraine deposits and till are ice-transported sediments, sediment can be classified based on its grain size and/or its composition. Sediment size is measured on a log base 2 scale, called the Phi scale, composition of sediment can be measured in terms of, parent rock lithology mineral composition chemical make-up. This leads to an ambiguity in which clay can be used as both a size-range and a composition, sediment is transported based on the strength of the flow that carries it and its own size, volume, density, and shape. Stronger flows will increase the lift and drag on the particle, causing it to rise, rivers and streams carry sediment in their flows. This sediment can be in a variety of locations within the flow and these relationships are shown in the following table for the Rouse number, which is a ratio of sediment fall velocity to upwards velocity. If the upwards velocity is less than the settling velocity, but still high enough for the sediment to move, it will move along the bed as bed load by rolling, sliding. If the upwards velocity is higher than the velocity, the sediment will be transported high in the flow as wash load. As there are generally a range of different particle sizes in the flow, sediment motion can create self-organized structures such as ripples, dunes, antidunes on the river or stream bed. These bedforms are often preserved in rocks and can be used to estimate the direction. Overland flow can erode soil particles and transport them downslope, the erosion associated with overland flow may occur through different methods depending on meteorological and flow conditions. If the initial impact of rain droplets dislodges soil, the phenomenon is called rainsplash erosion, if overland flow is directly responsible for sediment entrainment but does not form gullies, it is called sheet erosion. If the flow and the substrate permit channelization, gullies may form, glaciers carry a wide range of sediment sizes, and deposit it in moraines. The overall balance between sediment in transport and sediment being deposited on the bed is given by the Exner equation and this expression states that the rate of increase in bed elevation due to deposition is proportional to the amount of sediment that falls out of the flow. This can be localized, and simply due to obstacles, examples are scour holes behind boulders, where flow accelerates
11.
Strewn field
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The term strewnfield indicates the area where meteorites from a single fall are dispersed. It is also used with tektites produced by large meteorite impact. This mid-air explosion causes the dispersion of the material over a large oval-shaped area, the orientation of this oval is determined by the flight path of the meteoroid. When multiple-explosions occur, the material can be found in several overlapping ovals, impact fragmentation, when there is almost no mid-air fragmentation the fragmentation can occur upon impact. In this case the shape can be different, usually circular. In the case of mid-air fragmentation, smaller fragments tend to fall shorter and that is why the biggest fragment is usually found at one end of the oval. In order to get an idea of the flight direction it is necessary to analyze the size pattern of the material over the strewnfield. Fragments of about 1 to 5 grams can be picked up on radar as they fall at terminal velocity
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.
Obsidian
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Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth, Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition induces a high viscosity and polymerization degree of the lava. The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth. Obsidian is hard and brittle, it therefore fractures with very sharp edges, which were used in the past in cutting and piercing tools, among the various forms of glass we may reckon Obsidian glass, a substance very similar to the stone found by Obsidius in Ethiopia. Obsidian is the rock formed as a result of quickly cooled lava, tektites were once thought by many to be obsidian produced by lunar volcanic eruptions, though few scientists now adhere to this hypothesis. Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline, in addition and it is sometimes classified as a mineraloid. Though obsidian is usually dark in color similar to mafic rocks such as basalt, Obsidian consists mainly of SiO2, usually 70% or more. Crystalline rocks with obsidians composition include granite and rhyolite, because obsidian is metastable at the Earths surface, no obsidian has been found that is older than Cretaceous age. This breakdown of obsidian is accelerated by the presence of water, having a low water content when newly formed, typically less than 1% water by weight, obsidian becomes progressively hydrated when exposed to groundwater, forming perlite. Pure obsidian is usually dark in appearance, though the color varies depending on the presence of impurities, iron and other transition elements may give the obsidian a dark brown to black color. Very few samples are nearly colorless, in some stones, the inclusion of small, white, radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern. Obsidian may contain patterns of gas bubbles remaining from the lava flow and these bubbles can produce interesting effects such as a golden sheen. An iridescent, rainbow-like sheen is caused by inclusions of magnetite nanoparticles, Obsidian can be found in locations which have experienced rhyolitic eruptions. Obsidian can also be found in the eastern U. S. states of Virginia, as well as Pennsylvania, there are only four major deposit areas in the central Mediterranean, Lipari, Pantelleria, Palmarola and Monte Arci. Ancient sources in the Aegean were Milos and Gyali, acıgöl town and the Göllü Dağ volcano were the most important sources in central Anatolia, one of the more important source areas in the prehistoric Near East. Use of obsidian in pottery of the Neolithic in the area around Lipari was found to be less at a distance representing two weeks journeying. Anatolian sources of obsidian are known to have been the used in the Levant. The first attested civilized use is from excavations at Tell Brak dated the late fifth millennia, Obsidian was valued in Stone Age cultures because, like flint, it could be fractured to produce sharp blades or arrowheads
14.
Phenocryst
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A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a difference in the size of the crystals are called porphyries. Phenocrysts often have euhedral forms, either due to growth within a magma. Normally the term phenocryst is not used unless the crystals are directly observable, phenocrysts below this level, but still larger than the groundmass crystals, are termed microphenocrysts. Very large phenocrysts are termed megaphenocrysts, some rocks contain both microphenocrysts and megaphenocrysts. In metamorphic rocks, crystals similar to phenocrysts are called porphyroblasts, phenocrysts are more often found in the lighter igneous rocks such as felsites and andesites, although they occur throughout the igneous spectrum including in the ultramafics. The largest crystals found in some pegmatites are often phenocrysts being significantly larger than the other minerals, rocks can be classified according to the nature, size and abundance of phenocrysts, and the presence or absence of phenocrysts is often noted when a rock name is determined. Porphyritic rocks are named using mineral name modifiers, normally in decreasing order of abundance. Thus when olivine forms the primary phenocrysts in a basalt, the name may be refined from basalt to porphyritic olivine basalt or olivine phyric basalt. Similarly, a basalt with olivine as the dominate phenocrysts, but with lesser amounts of plagioclase phenocrysts, categorizing a rock as aphyric or as sparsely phyric is often a question of whether a significant number of crystals exceed the minimum size. Geologists use phenocrysts to help determine rock origins and transformations, as when and whether crystals form depends on pressure, fumiko Shido first applied this technique to oceanic basalts, further development came from Tsugio Shibata, and from W. B. Plagioclase phenocrysts often exhibit zoning with a more calcic core surrounded by progressively more sodic rinds and this zoning reflects the change in magma composition as crystallization progresses. In rapakivi granites, phenocrysts of orthoclase are enveloped within rinds of sodic plagioclase such as oligoclase, in shallow intrusives or volcanic flows phenocrysts which formed before eruption or shallow emplacement are surrounded by a fine-grained to glassy matrix. These volcanic phenocrysts often show flow banding, an arrangement of lath-shaped crystals. These characteristics provide clues to the rocks origins, similarly, intragranular microfractures and any intergrowth among crystals provide additional clues. Williams, Howel, Turner, Francis J. & Gilbert, Charlse M. Petrography, proceedings of the Ocean Drilling Program, Vol.187 Initial Reports
15.
Shale
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Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable, shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. Mudstones, on the hand, are similar in composition. Before the mid 19th century, the slate, shale. In the context of underground mining, shale was frequently referred to as slate well into the 20th century. Non-fissile rocks of similar composition but made of smaller than 0.06 mm are described as mudstones or claystone. Rocks with similar sizes but with less clay and therefore grittier are siltstones. Shale is the most common sedimentary rock, shales are typically composed of variable amounts of clay minerals and quartz grains and the typical color is gray. Addition of variable amounts of minor constituents alters the color of the rock, black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment. Black shale can also be referred to as black metal, red, brown and green colors are indicative of ferric oxide, iron hydroxide, or micaceous minerals. Clays are the constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite, clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid- to early Paleozoic shales illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and these released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor minerals found in shales and other mudrocks. Shales and mudrocks contain roughly 95 percent of the matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale, black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron and sulfur. Pyrite and amorphous iron sulfide along with carbon produce the black coloration, the process in the rock cycle which forms shale is called compaction. The fine particles that compose shale can remain suspended in long after the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are found in lakes and lagoonal deposits, in river deltas, on floodplains
16.
Sedimentary rock
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Sedimentary rocks are types of rock that are formed by the deposition and subsequent cementation of that material at the Earths surface and within bodies of water. Sedimentation is the name for processes that cause mineral and/or organic particles to settle in place. The particles that form a rock by accumulating are called sediment. Sedimentation may also occur as minerals precipitate from solution or shells of aquatic creatures settle out of suspension. The sedimentary rock cover of the continents of the Earths crust is extensive, sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks. Sedimentary rocks are deposited in layers as strata, forming a structure called bedding, sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores. The study of the sequence of rock strata is the main source for an understanding of the Earths history, including palaeogeography, paleoclimatology. The scientific discipline that studies the properties and origin of rocks is called sedimentology. Sedimentology is part of both geology and physical geography and overlaps partly with other disciplines in the Earth sciences, such as pedology, geomorphology, geochemistry, sedimentary rocks have also been found on Mars. Clastic sedimentary rocks are composed of rock fragments that were cemented by silicate minerals. Clastic rocks are composed largely of quartz, feldspar, rock fragments, clay minerals, and mica, any type of mineral may be present, clastic sedimentary rocks, are subdivided according to the dominant particle size. Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions, gravel, sand, and mud and this tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature. The subdivision of these three categories is based on differences in clast shape, conglomerates and breccias), composition. Conglomerates are dominantly composed of rounded gravel, while breccias are composed of dominantly angular gravel, composition of framework grains The relative abundance of sand-sized framework grains determines the first word in a sandstone name. Naming depends on the dominance of the three most abundant components quartz, feldspar, or the lithic fragments that originated from other rocks, all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance. Clean sandstones with open space are called arenites. Muddy sandstones with abundant muddy matrix are called wackes, six sandstone names are possible using the descriptors for grain composition and the amount of matrix. Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles and these relatively fine-grained particles are commonly transported by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension
17.
Shocked quartz
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Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure, the structure of quartz is deformed along planes inside the crystal. These planes, which show up as lines under a microscope, are called planar deformation features, Shocked quartz was discovered after underground nuclear bomb testing, which caused the intense pressures required to form it. Eugene Shoemaker showed that shocked quartz is found inside craters created by meteor impact, such as the Barringer Crater. The presence of shocked quartz proves that these craters were formed by an impact, Shocked quartz is found worldwide, in the thin Cretaceous–Paleogene boundary layer, which occurs at the contact between Cretaceous and Paleogene rocks. This is further evidence that the transition between the two periods was caused by a large impact. Though shocked quartz is only recognized, Eugene Shoemaker discovered it in building stones in the Bavarian town of Nördlingen. Shocked quartz is associated with two high-pressure polymorphs of silicon dioxide, coesite and stishovite and these polymorphs have a crystal structure different from standard quartz. This structure can be formed only by pressure, but at moderate temperatures. High temperatures would anneal the quartz back to its standard form, Coesite and stishovite are also indicative of impact events. Breccia Lechatelierite Shatter cone Shock metamorphism Shocked quartz page Coesite page Stishovite page
18.
Quartz
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Quartz is the second most abundant mineral in Earths continental crust, behind feldspar. There are many different varieties of quartz, several of which are semi-precious gemstones, since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. The word quartz is derived from the German word Quarz and its Middle High German ancestor twarc, the Ancient Greeks referred to quartz as κρύσταλλος derived from the Ancient Greek κρύος meaning icy cold, because some philosophers apparently believed the mineral to be a form of supercooled ice. Today, the rock crystal is sometimes used as an alternative name for the purest form of quartz. Quartz belongs to the crystal system. The ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end, well-formed crystals typically form in a bed that has unconstrained growth into a void, usually the crystals are attached at the other end to a matrix and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, a quartz geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward. α-quartz crystallizes in the crystal system, space group P3121 and P3221 respectively. β-quartz belongs to the system, space group P6222 and P6422. These space groups are truly chiral, both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks. The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is an identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent, common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others. The most important distinction between types of quartz is that of macrocrystalline and the microcrystalline or cryptocrystalline varieties, the cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline. Chalcedony is a form of silica consisting of fine intergrowths of both quartz, and its monoclinic polymorph moganite. Other opaque gemstone varieties of quartz, or mixed rocks including quartz, often including contrasting bands or patterns of color, are agate, carnelian or sard, onyx, heliotrope, amethyst is a form of quartz that ranges from a bright to dark or dull purple color. The worlds largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia, sometimes amethyst and citrine are found growing in the same crystal. It is then referred to as ametrine, an amethyst is formed when there is iron in the area where it was formed
19.
Apatite
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Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the four most common endmembers is written as Ca1062, apatite is a mineral that is often mistaken for other minerals. This tendency is reflected in the name, which is derived from the Greek word απατείν. Apatite is one of a few minerals produced and used by biological micro-environmental systems, apatite is the defining mineral for 5 on the Mohs scale. Hydroxyapatite, also known as hydroxylapatite, is the component of tooth enamel. A relatively rare form of apatite in which most of the OH groups are absent and containing many carbonate, fluoridated water allows exchange in the teeth of fluoride ions for hydroxyl groups in apatite. Similarly, toothpaste typically contains a source of fluoride anions, too much fluoride results in dental fluorosis and/or skeletal fluorosis. Fission tracks in apatite are commonly used to determine the history of orogenic belts. /He dating of apatite is also established for use in determining thermal histories and other. Phosphorite is a sedimentary rock, that contains between 18% and 40% P2O5. The apatite in phosphorite is present as cryptocrystalline masses referred to as collophane, the primary use of apatite is in the manufacture of fertilizer – it is a source of phosphorus. It is occasionally used as a gemstone, green and blue varieties, in finely divided form, are pigments with excellent covering power. During digestion of apatite with sulfuric acid to phosphoric acid. This byproduct is an industrial source of hydrofluoric acid. Fluoro-chloro apatite forms the basis of the now obsolete Halophosphor fluorescent tube phosphor system and this system has been almost entirely replaced by the Tri-Phosphor system. In the United States, apatite-derived fertilizers are used to supplement the nutrition of many agricultural crops by providing a source of phosphate. Apatites are also a proposed host material for storage of nuclear waste, apatite is infrequently used as a gemstone. Transparent stones of clean color have been faceted, and chatoyant specimens have been cabochon-cut, chatoyant stones are known as cats-eye apatite, transparent green stones are known as asparagus stone, and blue stones have been called moroxite
20.
Zircon
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Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y, Zircon forms in silicate melts with large proportions of high field strength incompatible elements. For example, hafnium is almost always present in quantities ranging from 1 to 4%, the crystal structure of zircon is tetragonal crystal system. The natural color of zircon varies between colorless, yellow-golden, red, brown, blue, and green, colorless specimens that show gem quality are a popular substitute for diamond and are also known as Matura diamond. The name derives from the Persian zargun meaning gold-hued and this word is corrupted into jargoon, a term applied to light-colored zircons. The English word zircon is derived from Zirkon, which is the German adaptation of this word, yellow, orange and red zircon is also known as hyacinth, from the flower hyacinthus, whose name is of Ancient Greek origin. Zircon is ubiquitous in the crust of Earth and it occurs as a common accessory mineral in igneous rocks, in metamorphic rocks and as detrital grains in sedimentary rocks. Their average size in granite rocks is about 0. 1–0.3 mm, Zircon is also very resistant to heat and corrosion. Because of their uranium and thorium content, some zircons undergo metamictization, connected to internal radiation damage, these processes partially disrupt the crystal structure and partly explain the highly variable properties of zircon. As zircon becomes more and more modified by internal radiation damage, the density decreases, the structure is compromised. Zircon occurs in many colors, including brown, yellow, green, blue, gray. The color of zircons can sometimes be changed by heat treatment, common brown zircons can be transformed into colorless and blue zircons by heating to 800 to 1000 °C. In geological settings, the development of pink, red, and purple zircon occurs after hundreds of millions of years, color in this red or pink series is annealed in geological conditions above the temperature about 350 °C. Zircon is mainly consumed as an opacifier, and has known to be used in the decorative ceramics industry. Zircon is one of the key used by geologists for geochronology. Zircon is a part of the ZTR index to classify highly-weathered sediments, Zircon is a common accessory to trace mineral constituent of most granite and felsic igneous rocks. Due to its hardness, durability and chemical inertness, zircon persists in sedimentary deposits and is a constituent of most sands
21.
Coesite
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Coesite is a form of silicon dioxide SiO2 that is formed when very high pressure, and moderately high temperature, are applied to quartz. Coesite was first synthesized by Loring Coes Jr. a chemist at the Norton Company, after this report, the presence of coesite in unmetamorphosed rocks was taken as evidence of a meteorite impact event or of an atomic bomb explosion. It was not expected that coesite would survive in high pressure metamorphic rocks, in metamorphic rocks, coesite is now recognized as one of the best mineral indicators of metamorphism at very high pressures. Such UHP metamorphic rocks record subduction or continental collisions in which rocks are carried to depths of 70 km or more. Coesite is formed at pressures above about 2.5 GPa and this corresponds to a depth of about 70 km in the Earth. As a result, the grains have a texture of a polycrystalline quartz rim. Coesite is a tectosilicate with each silicon atom surrounded by four oxygen atoms in a tetrahedron, each oxygen atom is then bonded to two Si atoms to form a framework. There are two crystallographically distinct Si atoms and five different oxygen positions in the unit cell, although the unit cell is close to being hexagonal in shape, it is inherently monoclinic and cannot be hexagonal. The crystal structure of coesite is similar to that of feldspar and consists of four silicon dioxide tetrahedra arranged in Si4O8, the rings are further arranged into chains. The crystal symmetry is monoclinic C2/c, No.15, Pearson symbol mS48, seifertite, forming at higher pressure than stishovite Stishovite, a higher-pressure polymorph Coesite page Barringer Meteor Crater science education page
22.
Baddeleyite
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Baddeleyite is a rare zirconium oxide mineral, occurring in a variety of monoclinic prismatic crystal forms. It is transparent to translucent, has high indices of refraction, and ranges from colorless to yellow, green, Baddeleyite is a refractory mineral, with a melting point of 2700 °C. Hafnium is an impurity and may be present in quantities ranging from 0.1 to several percent. It can be found in rocks containing potassium feldspar and plagioclase. Baddeleyite is commonly found with zircon, yet it forms in places with lower silica content and this is because baddeleyite tends to become zircon where there is higher silica content, hence why both minerals can be found together. It belongs to the class, of the P21/c crystal system. It has been used for geochronology, Baddeleyite was first found in Sri Lanka in 1892. It can be found in terrestrial and lunar rocks. Some of these rocks are carbonatite, kimberlite, alkaline syenite, some rocks of layered mafic intrusions, diabase dikes, gabbroid sills. Some examples of rocks are tektites, meteorites and lunar basalt. Studies have shown that zircon and baddeleyite can be recovered from some rocks in Proterozoic anorthosite complexes. Baddeleyite forms in igneous rocks low in silica, it can be found in rocks containing potassium feldspar and it has been observed in thin section that baddeleyite forms within plagioclase grains. Associated minerals include ilmenite, zirkelite, apatite, magnetite, perovskite, fluorite, nepheline, pyrochlore, because of their refractory nature and stability under diverse conditions, baddeleyite grains, along with zircon, are used for uranium-lead radiometric age determinations. There has been dispute in the structure of baddeleyite. Originally, the mineral was assigned to the 8-fold coordination by Naray Szabo and this structure was ruled out due to the inaccuracy of the data used to establish it. Baddeleyite has the group symmetry P21/c with four ZrO2 in the unit cell and it has unit cell dimensions of, a =5.169 b =5.232 c =5.341 Å, β = 99˚15ˊ ± 10ˊ. The coordination number for ZrO2 has been found to be 7, the mineral has two types of separations. The first being the seven shortest Zr-O, ranging from 2.04 to 2.26 Å, because of this, the coordination of baddeleyite was determined to be sevenfold
23.
Chromite
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Chromite is an iron chromium oxide, FeCr2O4. It is a mineral belonging to the spinel group. Magnesium can substitute for iron in variable amounts as it forms a solution with magnesiochromite. It is by far the most industrially important mineral for the production of chromium, used as an alloying ingredient in stainless. Chromite is found as orthocumulate lenses of chromitite in peridotite from the Earths mantle and it also occurs in layered ultramafic intrusive rocks. In addition, it is found in rocks such as some serpentinites. Ore deposits of chromite form as early magmatic differentiates and it is commonly associated with olivine, magnetite, serpentine, and corundum. The vast Bushveld igneous complex of South Africa is a layered mafic to ultramafic igneous body with some layers consisting of 90% chromite making the rare rock type. The Stillwater igneous complex in Montana also contains significant chromite, the only ores of chromium are the minerals chromite and magnesiochromite. Most of the time, economic geology names chromite the whole chromite-magnesiochromite series, the two main products of chromite refining are ferrochromium and metallic chromium, for those products the ore smelter process differs considerably. Chromite is also used as a material, because it has a high heat stability. The chromium extracted from chromite is used in plating and alloying for production of corrosion resistant superalloys, nichrome. Chromium is used as a pigment for glass, glazes, and paint and it is also sometimes used as a gemstone. In 200214,600,000 metric tons of chromite were mined, the largest producers were South Africa, India, Kazakhstan, Zimbabwe, Finland, Iran, and Brazil with several other countries producing the rest of less than 10% of the world production. Afghanistan has significant deposits of high grade ore, which is mined illegally in Khost Province. In Pakistan, chromite is mined from the rocks in mainly the Muslimbagh killa Saifullah District. Most of the chromite is of metallurgical grade with Cr2O3 averaging 54%, recently, the biggest user of chromite ore has been China, importing large quantities from South Africa, Pakistan, and other countries. The concentrate is used to make ferrochrome, which is in used to make stainless steel
24.
Rutile
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Rutile is a mineral composed primarily of titanium dioxide, TiO2. Rutile is the most common form of TiO2. Three rarer polymorphs of TiO2 are known, Anatase, a metastable tetragonal mineral of pseudo-octahedral habit Brookite, an orthorhombic mineral TiO2, rutile has among the highest refractive indices at visible wavelengths of any known crystal, and also exhibits a particularly large birefringence and high dispersion. Owing to these properties, it is useful for the manufacture of optical elements, especially polarization optics, for longer visible. Natural rutile may contain up to 10% iron and significant amounts of niobium and tantalum, rutile derives its name from the Latin rutilus, red, in reference to the deep red color observed in some specimens when viewed by transmitted light. Rutile is an accessory mineral in high-temperature and high-pressure metamorphic rocks. Thermodynamically, rutile is the most stable polymorph of TiO2 at all temperatures, consequently, the transformation of the metastable TiO2 polymorphs to rutile is irreversible. As it has the lowest molecular volume of the three polymorphs, it is generally the primary titanium bearing phase in most high-pressure metamorphic rocks. The occurrence of large specimen crystals is most common in pegmatites, skarns, rutile is found as an accessory mineral in some altered igneous rocks, and in certain gneisses and schists. In groups of acicular crystals it is frequently seen penetrating quartz as in the fléches damour from Graubünden, in 2005 the Republic of Sierra Leone in West Africa had a production capacity of 23% of the worlds annual rutile supply, which rose to approximately 30% in 2008. The reserves, lasting for about 19 years, are estimated at 259,000,000 metric tons, rutile has a body-centred tetragonal unit cell, with unit cell parameters a=b=4.584 Å, and c=2.953 Å. The titanium cations have a number of 6 meaning they are surrounded by an octahedron of 6 oxygen atoms. The oxygen anions have a number of 3 resulting in a trigonal planar co-ordination. Rutile also shows a screw axis when its octahedra are viewed sequentially, rutile crystals are most commonly observed to exhibit a prsimatic or acicular growth habit with preferential orientation along their c-axis, the direction. This growth habit is favored as the facets of rutile exhibit the lowest surface free energy and are therefore thermodynamically most stable, the c-axis oriented growth of rutile appears clearly in nanorods, nanowires and Abnormal grain growth phenomena of this phase. In large enough quantities in beach sands, rutile forms an important constituent of heavy minerals, miners extract and separate the valuable minerals—e. g. The main uses for rutile are the manufacture of ceramic, as a pigment. Finely powdered rutile is a brilliant white pigment and is used in paints, plastics, paper, foods, titanium dioxide pigment is the single greatest use of titanium worldwide
25.
Corundum
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Corundum is a crystalline form of aluminium oxide typically containing traces of iron, titanium, vanadium and chromium. It is a transparent material, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red, all other colors are called sapphire, e. g. green sapphire for a green specimen. The name corundum is derived from the Tamil word Kurundam which originates from the Sanskrit word Kuruvinda meaning ruby, because of corundums hardness, it can scratch almost every other mineral. It is commonly used as an abrasive on everything from sandpaper to large machines used in machining metals, plastics, some emery is a mix of corundum and other substances, and the mix is less abrasive, with an average Mohs hardness of 8.0. In addition to its hardness, corundum is unusual for its density of 4.02 g/cm3, corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. It also occurs in low silica igneous syenite and nepheline syenite intrusives, other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals in pegmatites. It commonly occurs as a mineral in stream and beach sands because of its hardness. The largest documented crystal of corundum measured about 65×40×40 cm. The record has since surpassed by certain synthetic boules. Corundum for abrasives is mined in Zimbabwe, Russia, Sri Lanka, historically it was mined from deposits associated with dunites in North Carolina, US and from a nepheline syenite in Craigmont, Ontario. Emery-grade corundum is found on the Greek island of Naxos and near Peekskill, New York, abrasive corundum is synthetically manufactured from bauxite. Four corundum axes dating back to 2500 BCE from the Liangzhou culture have been discovered in China, in 1837, Marc Antoine Gaudin made the first synthetic rubies by fusing alumina at a high temperature with a small amount of chromium as a pigment. In 1847, Ebelmen made white synthetic sapphires by fusing alumina in boric acid, in 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF2, in 1903, Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process. The Verneuil process allows the production of flawless single-crystal sapphires, rubies and it is also possible to grow gem-quality synthetic corundum by flux-growth and hydrothermal synthesis. Corundum crystallizes with trigonal symmetry in the space group R3c and has the lattice parameters a =4.75 Å and c =12.982 Å at standard conditions, the unit cell contains six formula units. In the lattice of corundum, the atoms form a slightly distorted hexagonal close packing
26.
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
27.
Australasian strewnfield
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The Australasian strewnfield is the youngest and largest of the tektite strewnfields, with recent estimates suggesting it may cover 10%-30% of the Earths surface. 790, 000-year-old strewnfield includes most of Southeast Asia, the material from the impact stretches across the ocean to include the Philippines, Indonesia, Malaysia, and Java. It also reaches far west out into the Indian Ocean, since the 1960s, it has been accepted that the strewn field included Hainan in southern China to Australia or about 10% of the Earths surface. This was later extended by finds in Africa and Tasmania to 20%, recent additional finds in northern Tibet and Guangxi increased the strewnfield to about 30% of the Earths surface, or almost 150 million km2. The Earth Impact Database lists about 25 known craters less than a years old. The notable exception is the 14-km Zhamanshin crater in Kazakhstan which at one time was proposed as the source of the Australasian strewn field. However, due to the size of the Australasian strewn field. Glass also suggested southern Laos or an adjacent area as a possible source, more recently, Lee and Wei gave its size as 90 to 116 km and P. Ma et al. using beryllium-10 postulated the crater as between southern Laos and Hainan, possibly within the Gulf of Tonkin, the Wilkes Land crater in Antarctica has also been proposed as a possible source. It has been suggested that the impact may have triggered the Brunhes–Matuyama reversal, archeological artifacts found with these tektites in Baise, Guangxi in southern China indicates that a Homo erectus population was living in the area during and after the impact. Stone tools have been found within the field along with a charcoal layer likely caused by fires from the impact. It has been suggested that the subsequent local deforestation after the fires allowed this population easier access to stones useful for tool-making, australite List of unconfirmed impact craters on Earth
28.
Australite
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Australites are tektites found in Australia. They are mostly dark or black, and have shapes including discs, NASA used the shape of flanged button australites in designing re-entry modules for the Apollo program in the 1960s. Indigenous Australians termed australites ooga, and they were used as sacred objects or as cutting tools, europeans found out about australites in 1857, when explorer Thomas Mitchell gave naturalist Charles Darwin a mysteriously shaped piece of natural black glass. Darwin thought that australites were of volcanic origin due to their similarity to obsidian, later, australites were called blackfellows buttons and obsidian bombs. One of the first scientists to seriously study australites was Charles Fenner and he believed that australites were glass meteorites. Early theories about the source of australites included volcanoes, the bushfires that are common in Australia, some scientists believed them to be meteorites, possibly lunar meteorites ejected from the Moon in impacts. Although different theories about the origin of australites are still circulating, the impact ejected myriads of small rocks right out of the atmosphere. The australites acquired their streamlined, aerodynamic forms when they re-entered the Earths atmosphere while molten, most australites are found in Southern Australia, below 25 degrees latitude. Based on similar ages and compositions, they represent the edge of the vast Australasian tektite strewnfield that stretches from southern China to Australia. The Australasian strewnfield has an age of 0.8 million years and is the result of an impact in Indochina, the primary forms of australites are sphere, oval, boat, dumbbell and teardrop. Australites are smaller than other tektites and different in shape and their initial velocity was higher than other tektites, enough to propel them just out of the Earths atmosphere, so they then re-entered the atmosphere and underwent a rare secondary melting. One of the most famous australite shapes is the flanged button, flanged buttons are rare, but the most unusual and rarest australites are discs, bowls, plates and other small forms. George Baker called them flying flanges, the result of distortion of small primary forms by aerodynamic frictional heating. Well preserved shapes are found near Port Campbell in western Victoria, chapman and Larson experimented on the ablation of australites. At first they seemed to prove their origin, but later in repeated studies they claimed that the australites could not have come from outside the Earth-Moon system. They were able to reproduce the shapes, flanges and the network of the rings on the front face in great detail
29.
Australia
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Australia, officially the Commonwealth of Australia, is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the worlds sixth-largest country by total area, the neighbouring countries are Papua New Guinea, Indonesia and East Timor to the north, the Solomon Islands and Vanuatu to the north-east, and New Zealand to the south-east. Australias capital is Canberra, and its largest urban area is Sydney, for about 50,000 years before the first British settlement in the late 18th century, Australia was inhabited by indigenous Australians, who spoke languages classifiable into roughly 250 groups. The population grew steadily in subsequent decades, and by the 1850s most of the continent had been explored, on 1 January 1901, the six colonies federated, forming the Commonwealth of Australia. Australia has since maintained a liberal democratic political system that functions as a federal parliamentary constitutional monarchy comprising six states. The population of 24 million is highly urbanised and heavily concentrated on the eastern seaboard, Australia has the worlds 13th-largest economy and ninth-highest per capita income. With the second-highest human development index globally, the country highly in quality of life, health, education, economic freedom. The name Australia is derived from the Latin Terra Australis a name used for putative lands in the southern hemisphere since ancient times, the Dutch adjectival form Australische was used in a Dutch book in Batavia in 1638, to refer to the newly discovered lands to the south. On 12 December 1817, Macquarie recommended to the Colonial Office that it be formally adopted, in 1824, the Admiralty agreed that the continent should be known officially as Australia. The first official published use of the term Australia came with the 1830 publication of The Australia Directory and these first inhabitants may have been ancestors of modern Indigenous Australians. The Torres Strait Islanders, ethnically Melanesian, were originally horticulturists, the northern coasts and waters of Australia were visited sporadically by fishermen from Maritime Southeast Asia. The first recorded European sighting of the Australian mainland, and the first recorded European landfall on the Australian continent, are attributed to the Dutch. The first ship and crew to chart the Australian coast and meet with Aboriginal people was the Duyfken captained by Dutch navigator, Willem Janszoon. He sighted the coast of Cape York Peninsula in early 1606, the Dutch charted the whole of the western and northern coastlines and named the island continent New Holland during the 17th century, but made no attempt at settlement. William Dampier, an English explorer and privateer, landed on the north-west coast of New Holland in 1688, in 1770, James Cook sailed along and mapped the east coast, which he named New South Wales and claimed for Great Britain. The first settlement led to the foundation of Sydney, and the exploration, a British settlement was established in Van Diemens Land, now known as Tasmania, in 1803, and it became a separate colony in 1825. The United Kingdom formally claimed the part of Western Australia in 1828. Separate colonies were carved from parts of New South Wales, South Australia in 1836, Victoria in 1851, the Northern Territory was founded in 1911 when it was excised from South Australia
30.
Indochinite
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An Indochinite is a type of tektite. Tektites were ejected into the Earths upper atmosphere by a meteorite impact, indochinites are distinctly dark black in contrast to the green of European moldavite tektites. It is estimated that these bodies of solidified magma are 700,000 years old, the largest indochinite is a Muong-Nong type tektite, which had a mass of 29.0 kg. Origin of Indochinite Tektites, by Virgil E. Barnes and Kaset Pitakpaivan
31.
Southeast Asia
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Southeast Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies near the intersection of geological plates, with seismic and volcanic activity. Southeast Asia consists of two regions, Mainland Southeast Asia, also known historically as Indochina, comprising Vietnam, Laos, Cambodia, Thailand, Myanmar. Maritime Southeast Asia, comprising Indonesia, East Malaysia, Singapore, Philippines, East Timor, Brunei, Cocos Islands, definitions of Southeast Asia vary, but most definitions include the area represented by the countries listed below. All of the states are members of the Association of Southeast Asian Nations, the area, together with part of South Asia, was widely known as the East Indies or simply the Indies until the 20th century. Sovereignty issues exist over some territories in the South China Sea, Papua New Guinea has stated that it might join ASEAN, and is currently an observer. Southeast Asia is geographically divided into two subregions, namely Mainland Southeast Asia and Maritime Southeast Asia, Mainland Southeast Asia includes, Maritime Southeast Asia includes, The Andaman and Nicobar Islands of India are geographically considered part of Southeast Asia. Eastern Bangladesh and the Seven Sister States of India are culturally part of Southeast Asia, the eastern half of Indonesia and East Timor are considered to be biogeographically part of Oceania. Homo sapiens reached the region by around 45,000 years ago, homo floresiensis also lived in the area up until 12,000 years ago, when they became extinct. Austronesian people, who form the majority of the population in Indonesia, Malaysia, Brunei, East Timor. Solheim and others have shown evidence for a Nusantao maritime trading network ranging from Vietnam to the rest of the archipelago as early as 5000 BC to 1 AD. The peoples of Southeast Asia, especially those of Austronesian descent, have been seafarers for thousands of years and their vessels, such as the vinta, were ocean-worthy. Magellans voyage records how much more manoeuvrable their vessels were, as compared to the European ships, Passage through the Indian Ocean aided the colonisation of Madagascar by the Austronesian people, as well as commerce between West Asia and Southeast Asia. Gold from Sumatra is thought to have reached as far west as Rome and this was later replaced by Hinduism. Theravada Buddhism soon followed in 525, in the 15th century, Islamic influences began to enter. This forced the last Hindu court in Indonesia to retreat to Bali, in Mainland Southeast Asia, Burma, Cambodia and Thailand retained the Theravada form of Buddhism, brought to them from Sri Lanka. This type of Buddhism was fused with the Hindu-influenced Khmer culture, very little is known about Southeast Asian religious beliefs and practices before the advent of Indian merchants and religious influences from the 2nd century BCE onwards. Prior to the 13th century CE, Hinduism and Buddhism were the religions in Southeast Asia
32.
Philippines
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The Philippines, officially the Republic of the Philippines, is a sovereign island country in Southeast Asia situated in the western Pacific Ocean. It consists of about 7,641 islands that are categorized broadly under three main geographical divisions from north to south, Luzon, Visayas, and Mindanao, the capital city of the Philippines is Manila and the most populous city is Quezon City, both part of Metro Manila. The Philippines has an area of 300,000 square kilometers, and it is the eighth-most populated country in Asia and the 12th most populated country in the world. As of 2013, approximately 10 million additional Filipinos lived overseas, multiple ethnicities and cultures are found throughout the islands. In prehistoric times, Negritos were some of the archipelagos earliest inhabitants and they were followed by successive waves of Austronesian peoples. Exchanges with Chinese, Malay, Indian, and Islamic nations occurred, then, various competing maritime states were established under the rule of Datus, Rajahs, Sultans or Lakans. The arrival of Ferdinand Magellan in Homonhon, Eastern Samar in 1521 marked the beginning of Hispanic colonization, in 1543, Spanish explorer Ruy López de Villalobos named the archipelago Las Islas Filipinas in honor of Philip II of Spain. With the arrival of Miguel López de Legazpi from Mexico City, in 1565, the Philippines became part of the Spanish Empire for more than 300 years. This resulted in Roman Catholicism becoming the dominant religion, during this time, Manila became the western hub of the trans-Pacific trade connecting Asia with Acapulco in the Americas using Manila galleons. Aside from the period of Japanese occupation, the United States retained sovereignty over the islands until after World War II, since then, the Philippines has often had a tumultuous experience with democracy, which included the overthrow of a dictatorship by a non-violent revolution. It is a member of the United Nations, World Trade Organization, Association of Southeast Asian Nations, the Asia-Pacific Economic Cooperation forum. It also hosts the headquarters of the Asian Development Bank, the Philippines was named in honor of King Philip II of Spain. Spanish explorer Ruy López de Villalobos, during his expedition in 1542, named the islands of Leyte, eventually the name Las Islas Filipinas would be used to cover all the islands of the archipelago. Before that became commonplace, other such as Islas del Poniente. The official name of the Philippines has changed several times in the course of its history, during the Philippine Revolution, the Malolos Congress proclaimed the establishment of the República Filipina or the Philippine Republic. From the 1898 Treaty of Paris, the name Philippines began to appear, since the end of World War II, the official name of the country has been the Republic of the Philippines. The metatarsal of the Callao Man, reliably dated by uranium-series dating to 67,000 years ago is the oldest human remnant found in the archipelago to date and this distinction previously belonged to the Tabon Man of Palawan, carbon-dated to around 26,500 years ago. Negritos were also among the archipelagos earliest inhabitants, but their first settlement in the Philippines has not been reliably dated, there are several opposing theories regarding the origins of ancient Filipinos
33.
Germany
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Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in central-western Europe. It includes 16 constituent states, covers an area of 357,021 square kilometres, with about 82 million inhabitants, Germany is the most populous member state of the European Union. After the United States, it is the second most popular destination in the world. Germanys capital and largest metropolis is Berlin, while its largest conurbation is the Ruhr, other major cities include Hamburg, Munich, Cologne, Frankfurt, Stuttgart, Düsseldorf and Leipzig. Various Germanic tribes have inhabited the northern parts of modern Germany since classical antiquity, a region named Germania was documented before 100 AD. During the Migration Period the Germanic tribes expanded southward, beginning in the 10th century, German territories formed a central part of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation, in 1871, Germany became a nation state when most of the German states unified into the Prussian-dominated German Empire. After World War I and the German Revolution of 1918–1919, the Empire was replaced by the parliamentary Weimar Republic, the establishment of the national socialist dictatorship in 1933 led to World War II and the Holocaust. After a period of Allied occupation, two German states were founded, the Federal Republic of Germany and the German Democratic Republic, in 1990, the country was reunified. In the 21st century, Germany is a power and has the worlds fourth-largest economy by nominal GDP. As a global leader in industrial and technological sectors, it is both the worlds third-largest exporter and importer of goods. Germany is a country with a very high standard of living sustained by a skilled. It upholds a social security and universal health system, environmental protection. Germany was a member of the European Economic Community in 1957. It is part of the Schengen Area, and became a co-founder of the Eurozone in 1999, Germany is a member of the United Nations, NATO, the G8, the G20, and the OECD. The national military expenditure is the 9th highest in the world, the English word Germany derives from the Latin Germania, which came into use after Julius Caesar adopted it for the peoples east of the Rhine. This in turn descends from Proto-Germanic *þiudiskaz popular, derived from *þeudō, descended from Proto-Indo-European *tewtéh₂- people, the discovery of the Mauer 1 mandible shows that ancient humans were present in Germany at least 600,000 years ago. The oldest complete hunting weapons found anywhere in the world were discovered in a mine in Schöningen where three 380, 000-year-old wooden javelins were unearthed
34.
Moldavite
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Moldavite is an olive-green or dull greenish vitreous substance possibly formed by a meteorite impact in southern Germany, which would make it one kind of tektite. Zippe first used the term derived from the town of Moldauthein - now in Bohemia. In 1900, F. E. Boldly attributing the material to a cosmic origin, however, for a long time, it was generally believed to be a variety of obsidian. Splatters of material that was melted by the impact cooled while they were actually airborne, currently, moldavites have been found in an area that includes southern Bohemia, western Moravia, the Cheb Basin, Lusatia, and Waldviertel. Isotope analysis of samples of moldavites have shown a beryllium-10 isotope composition similar to the composition of Australasian tektites, 99% of all moldavite finds have come from the South Bohemian localities, 1% were found in South Moravian localities. Only tens of pieces were found in the Lusatian area, Cheb basin area, principal occurrences of moldavites in Bohemia are associated with Tertiary sediments of the České Budějovice and Třeboň Basins. The most prominent localities are concentrated in a NW-SE strip along the margin of the České Budějovice Basin. The majority of occurrences are bound to the Vrábče Member. Prominent localities in the Třeboň Basin are bound to gravels and sands of the Domanín Formation, in Moravia, moldavite occurrences are restricted to an area roughly bounded by the towns of Třebíč, Znojmo and Brno. The colour of Moravian moldavites usually differs from their Bohemian counterparts, taking into account the number of pieces found, Moravian localities are considerably less productive than the Bohemian ones, however, the average weight of the moldavites found is much higher. The oldest moldavite-bearing sediments lie between Slavice and Třebíč, the chemical formula of moldavite is SiO2. Its properties are similar to that of types of glass. Moldavite can be transparent or translucent with a green color, with swirls. The total amount of moldavite scattered around the world is estimated at 275 tons, there are typically two grades of moldavite, high quality, often referred to as museum grade, and regular grade. Museum and regular grade moldavites can be told apart by their appearance, the regular grade pieces are usually darker and more saturated in their green colour, and the surface is seen as closely spaced pitting or weathering. This type sometimes appears to have broken apart from a larger chunk. Moldavite is also found to be compatible with borosilicate glass and can be fused to it with ease, the museum grade has a distinct fern-like pattern and is much more translucent than the regular grade. There is usually a big difference in the price between the two
35.
Lake Bosumtwi
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Lake Bosumtwi is the only natural lake in Ashanti and Ghana. It is situated within an ancient impact crater that is about 10.5 kilometres in diameter and it is about 30 km south-east of Kumasi the capital of Ashanti and is a popular recreational area. There are about 30 villages near crater lake Lake Bosumtwi, with a population of about 70,000 Ashanti people. The Ashanti consider Bosumtwi a sacred lake, according to traditional belief, the souls of the dead come here to bid farewell to the god Asase Ya. Because of this, it is considered permissible to fish in the only from wooden planks. Among the fish species in the lake is the endemic cichlid Hemichromis frempongi, and the near-endemic cichlids Tilapia busumana and T. discolor. The Lake Bosumtwi impact crater is 10.5 km in diameter, slightly larger than the present lake which is approximately 8 kilometres across, there is a highly speculative theory that connects this event to the short-term Jaramillo geomagnetic reversal. Depth of crater is approximately 380 m, but, if counted together with the depth of lake sediments -750 m, the crater has been partly eroded, and is situated in dense rainforest, making it difficult to study and confirm its origin by meteorite impact. Shock features such as shatter cones are largely overgrown by vegetation or covered by the lake, however, drilling of the craters central uplift beneath the lake floor has recently provided an abundance of shocked materials for scientific study. Tektites, believed to be from this impact, are found in the country of Ivory Coast. Before the asteroid hit, there was a lush rainforest filled with animals, the crater from the asteroids impact filled with rainwater, so now there is a lake. Periods of heavy rainfall filled the crater with water, causing the level to rise above the lowest points of the rim. Such periods are evidenced from fossils of fish found on hilltops, water even flowed from the basin through an overflow channel. However, there were times when the water level was so low that the rainforest entered the basin rendering the lake only a small pond. Such a period, according to legend and now proved by paleoclimate records, the legends say that in 1648 an Ashanti hunter named Akora Bompe from the city of Asaman was chasing an injured antelope through the rainforest. Suddenly, the disappeared in a small pond. It was as if this body of water wanted to save the animals life, the hunter never got the antelope, though he settled close to the water and started catching fish. This place he named “Bosomtwe”, meaning “antelope god” and this story suggests that at that time the lake level was very low
36.
Chesapeake Bay impact crater
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The Chesapeake Bay impact crater was formed by a bolide that impacted the eastern shore of North America about 35.5 ±0.3 million years ago, in the late Eocene epoch. It is one of the best-preserved wet-target or marine impact craters, continued slumping of sediments over the rubble of the crater has helped shape the Chesapeake Bay. During the warm late Eocene, sea levels were high, the bolide made impact at a speed of many kilometers per second, punching a deep hole through the sediments and into the granite continental basement rock. The bolide itself was completely vaporized, with the basement rock being fractured to depths of 8 km, the deep crater,38 km across, is surrounded by a flat-floored terrace-like ring trough with an outer edge of collapsed blocks forming ring faults. The entire circular crater is about 85 km in diameter and 1.3 km deep, an area twice the size of Rhode Island, and nearly as deep as the Grand Canyon. However, numerical modeling techniques by Collins et al. indicate that the diameter was likely to have been around 40 km. The surrounding region suffered massive devastation, an enormous tsunami engulfed the land and possibly even reached the Blue Ridge Mountains. The sedimentary walls of the crater progressively slumped in, widened the crater, the slump blocks were then covered with the rubble or breccia. The entire bolide event, from impact to the termination of breccia deposition. In the perspective of time, the 1.2 km breccia is an instantaneous deposit. The crater was buried by additional sedimentary beds that have accumulated during the 35 million years following the impact. The impact has been identified as the source of the North American tektite field, until 1983, no one suspected the existence of a large impact crater buried beneath the lower part of the Chesapeake Bay and its surrounding peninsulas. The first hint was a 20 cm -thick layer of ejecta that turned up in a drilling core taken off Atlantic City, New Jersey, the layer contained the fused glass beads called tektites and shocked quartz grains that are unmistakable signs of a bolide impact. In 1993, data from oil exploration revealed the extent of the crater, the continual slumping of the rubble within the crater has affected the flow of the rivers and shaped the Chesapeake Bay. The impact crater created a long-lasting topographic depression which helped predetermine the course of local rivers, most important for present-day inhabitants of the area, the impact disrupted aquifers. The crater is one of three factors contributing to the sinking of land near the Chesapeake Bay. For example, Hampton Roads is gradually sinking at a rate between 15 and 23 centimeters per century, toms Canyon structure probable impact crater 322 km to the northeast. Popigai crater of similar age Grande Coupure Poag, C, Chesapeake Invader, Discovering Americas Giant Meteorite Crater
37.
Megaannum
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A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days
38.
Lake Elgygytgyn
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Lake Elgygytgyn is an impact crater lake located in the Chukotka Autonomous Okrug in northeast Siberia, about 150 km southeast of Chaunskaya Bay. The word Elgygytgyn means white lake in the Chukchi language, the lake is of particular interest to scientists because it has never been covered by glaciers. This has allowed the uninterrupted build-up of 400 m of sediment at the bottom of the lake, Lake Elgygytgyn is drained to the southeast by the Enmybaam branch of the Belaya River. It is approximately 12 km in diameter and has a depth of 174 m +/- 2m. The lake is centered within a crater with a rim diameter of 18 km that formed 3.6 million years ago during the Pliocene. Before it was dated, preliminary papers in the late 1970s suggested either Elgygytgyn or Zhamanshin as the source of the Australasian strewnfield. In Late 2008 and Early 2009, a team from Germany, Russia. The resulting cores are designated ICPD Site 5011-1 and 5011-3 and this co-sponsored by the International Continental Scientific Drilling Program, with funding also provided by the U. S. The conditions in the Elgygytgyn lake are extremely severe for fish life, even so, there are three species permanently inhabiting the lakes harsh aquatic environment. These are three types of char, Salvelinus boganidae, S. elgyticus and Salvethymus svetovidovi, the two latter species are endemic to the Elgygytgyn lake. The golets has been introduced recently, fish species in the lake are adapted to its very cold waters, which are generally just above the freezing point, and spend most of the year in total darkness. The surface is frozen for about 10 months of the year and it may start to melt in the summer, but some years it never fully thaws. List of lakes of Russia Dr. Matt Nolan at the University of Alaska Fairbanks Polar Expedition to Siberian Lake will Yield Details of Past Climate PhysOrg. com
39.
Karakul (Tajikistan)
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Karakul, Qarokul is a 25 km diameter lake within a 52 km impact crater. It is located in the Tajik National Park in the Pamir Mountains in Tajikistan, Karakul lies within a circular depression interpreted as an impact crater with a rim diameter of 52 km. The crater is relatively recent, its age is estimated variously as 25 Ma, less than 23 Ma, the Earth Impact Database lists it as less than 5 Ma, or during the Pliocene. It is larger than the Eltanin impact, which has already suggested as a contributor to the cooling. The Karakul impact structure was first identified through studies of imagery taken from space, the lake was formerly known as Lake Victoria, named after Queen Victoria by the British cartographers/military geographers. It was marked as such by most maps of the area until the 1920s when a Kyrgyz name, Karakul, or the Black Lake, the lake/crater lies at an elevation of 3,960 m above mean sea level. It is endorheic and the water is brackish, there is a small village with the same name on the eastern shore of the lake. Although the lake lies within a park, much of the surroundings are used as pasture. The lakes islands are the places where waterbirds rest and nest. The only fish in the lake is a species of stone loach, higher than Lake Titicaca, Karakul hosted the Roof of the World Regatta for the first time in September 2014. This replaced the Alpine Bank Dillon Open, held on the Dillon Reservoir in Summit County, Colorado, as the highest sailing regatta in the world
40.
Popigai crater
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The Popigai crater in Siberia, Russia is tied with the Manicouagan Crater as the fourth largest verified impact crater on Earth. A large bolide impact created the 100-kilometre diameter crater approximately 35 million years ago during the late Eocene epoch and it is conjectured that it may have influenced the Eocene–Oligocene extinction event. The crater is 300 km east from the outpost of Khatanga and 880 km NE of the city of Norilsk and it is designated by UNESCO as a Geopark, a site of special geological heritage. There is a possibility that Popigai impact crater formed simultaneous with the approximately 35-million-year-old Chesapeake Bay. However, a major expedition was undertaken in 1997, which greatly advanced understanding of the enigmatic structure. The impactor in this event has been identified as either an 8 km diameter chondrite asteroid, the shock pressures from the impact instantaneously transformed graphite in the ground into diamonds within a 13.6 km radius of the impact point. These diamonds are usually 0.5 to 2 mm in diameter, the diamonds not only inherited the tabular shape of the original graphite grains but they additionally preserved the original crystals delicate striations. Most modern industrial diamonds are produced synthetically, so the deposits at Popigai may not be profitable because of the remote location, many of the diamonds at Popigai contain crystalline lonsdaleite, an allotrope of carbon that has a hexagonal lattice. Pure, laboratory-created lonsdaleite is 58% harder than diamonds, though it is unknown whether the natural. The diamonds also contain unusual abrasive features and large size which could make them extremely useful for industrial. These types of diamonds are known as impact diamonds because they are thought to be produced when a meteorite strikes a graphite deposit at high velocity and they may have industrial uses but are considered unsuitable as gems. Additionally, carbon polymorphs even harder than lonsdaleite have been discovered in the crater
41.
Radiometric dating
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Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geological time scale. Among the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating, by allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change. Radiometric dating is used to date archaeological materials, including ancient artifacts. Different methods of radiometric dating vary in the timescale over which they are accurate, all ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus. Additionally, elements may exist in different isotopes, with each isotope of an element differing in the number of neutrons in the nucleus, a particular isotope of a particular element is called a nuclide. That is, at point in time, an atom of such a nuclide will undergo radioactive decay. This transformation may be accomplished in a number of different ways, including alpha decay, another possibility is spontaneous fission into two or more nuclides. After one half-life has elapsed, one half of the atoms of the nuclide in question will have decayed into a daughter nuclide or decay product, Isotopic systems that have been exploited for radiometric dating have half-lives ranging from only about 10 years to over 100 billion years. For most radioactive nuclides, the half-life depends solely on nuclear properties and is essentially a constant and it is not affected by external factors such as temperature, pressure, chemical environment, or presence of a magnetic or electric field. The only exceptions are nuclides that decay by the process of capture, such as beryllium-7, strontium-85. For all other nuclides, the proportion of the nuclide to its decay products changes in a predictable way as the original nuclide decays over time. This predictability allows the relative abundances of related nuclides to be used as a clock to measure the time from the incorporation of the original nuclides into a material to the present. The basic equation of radiometric dating requires that neither the parent nuclide nor the product can enter or leave the material after its formation. The possible confounding effects of contamination of parent and daughter isotopes have to be considered and it is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration. Precision is enhanced if measurements are taken on multiple samples from different locations of the rock body and this can reduce the problem of contamination. In uranium-lead dating, the diagram is used which also decreases the problem of nuclide loss. Finally, correlation between different isotopic dating methods may be required to confirm the age of a sample, the procedures used to isolate and analyze the parent and daughter nuclides must be precise and accurate
42.
Czech Republic
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The Czech Republic, also known as Czechia, is a nation state in Central Europe bordered by Germany to the west, Austria to the south, Slovakia to the east and Poland to the northeast. The Czech Republic covers an area of 78,866 square kilometres with mostly temperate continental climate and it is a unitary parliamentary republic, has 10.5 million inhabitants and the capital and largest city is Prague, with over 1.2 million residents. The Czech Republic includes the territories of Bohemia, Moravia. The Czech state was formed in the late 9th century as the Duchy of Bohemia under the Great Moravian Empire, after the fall of the Empire in 907, the centre of power transferred from Moravia to Bohemia under the Přemyslid dynasty. In 1002, the duchy was formally recognized as part of the Holy Roman Empire, becoming the Kingdom of Bohemia in 1198 and reaching its greatest territorial extent in the 14th century. Following the Battle of Mohács in 1526, the whole Crown of Bohemia was gradually integrated into the Habsburg Monarchy alongside the Archduchy of Austria, the Protestant Bohemian Revolt against the Catholic Habsburgs led to the Thirty Years War. After the Battle of the White Mountain, the Habsburgs consolidated their rule, reimposed Roman Catholicism, the Czech part of Czechoslovakia was occupied by Germany in World War II, and was liberated in 1945 by the armies of the Soviet Union and the United States. The Czech country lost the majority of its German-speaking inhabitants after they were expelled following the war, the Communist Party of Czechoslovakia won the 1946 elections. Following the 1948 coup détat, Czechoslovakia became a one-party communist state under Soviet influence, in 1968, increasing dissatisfaction with the regime culminated in a reform movement known as the Prague Spring, which ended in a Soviet-led invasion. Czechoslovakia remained occupied until the 1989 Velvet Revolution, when the communist regime collapsed, on 6 March 1990, the Czech Socialistic Republic was renamed to the Czech Republic. On 1 January 1993, Czechoslovakia peacefully dissolved, with its constituent states becoming the independent states of the Czech Republic and the Slovak Republic. The Czech Republic joined NATO in 1999 and the European Union in 2004, it is a member of the United Nations, the OECD, the OSCE, and it is a developed country with an advanced, high income economy and high living standards. The UNDP ranks the country 14th in inequality-adjusted human development, the Czech Republic also ranks as the 6th most peaceful country, while achieving strong performance in democratic governance. It has the lowest unemployment rate in the European Union, the traditional English name Bohemia derives from Latin Boiohaemum, which means home of the Boii. The current name comes from the endonym Čech, spelled Cžech until the reform in 1842. The name comes from the Slavic tribe and, according to legend, their leader Čech, the etymology of the word Čech can be traced back to the Proto-Slavic root *čel-, meaning member of the people, kinsman, thus making it cognate to the Czech word člověk. The country has traditionally divided into three lands, namely Bohemia in the west, Moravia in the southeast, and Czech Silesia in the northeast. Following the dissolution of Czechoslovakia at the end of 1992, the Czech part of the former nation found itself without a common single-word geographical name in English, the name Czechia /ˈtʃɛkiə/ was recommended by the Czech Ministry of Foreign Affairs
