Onyx is a banded variety of the oxide mineral chalcedony. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands, agate has curved bands, the colors of its bands range from white to almost every color. Commonly, specimens of onyx contain bands of black and/or white, onyx comes through Latin, from the Greek ὄνυξ, meaning claw or fingernail. With its fleshtone color, onyx can be said to resemble a fingernail, the English word nail is cognate with the Greek word. Onyx is formed of bands of chalcedony in alternating colors and it is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel to one another, as opposed to the more chaotic banding that often occurs in agates, sardonyx is a variant in which the colored bands are sard rather than black. Black onyx is perhaps the most famous variety, but is not as common as onyx with colored bands, artificial treatments have been used since ancient times to produce both the black color in black onyx and the reds and yellows in sardonyx.
Most black onyx on the market is artificially colored, the name has sometimes been used, incorrectly, to label other banded lapidary materials, such as banded calcite found in Mexico and other places, and often carved and sold. This material is softer than true onyx, and much more readily available. The majority of carved items sold as onyx today are this carbonate material, artificial onyx types have been produced from common chalcedony and plain agates. The first-century naturalist Pliny the Elder described these techniques being used in Roman times and these techniques are still used, as well as other dyeing treatments, and most so-called black onyx sold is artificially treated. In addition to dye treatments and treatment with nitric acid have been used to lighten or eliminate undesirable colors and it has a long history of use for hardstone carving and jewelry, where it is usually cut as a cabochon or into beads. It has used for intaglio and hardstone cameo engraved gems. Some onyx is natural but much of the material in commerce is produced by the staining of agate, onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.
Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos, Brazilian green onyx was often used as plinths for art deco sculptures created in the 1920s and 1930s. The German sculptor Ferdinand Preiss used Brazilian green onyx for the base on the majority of his chryselephantine sculptures, green onyx was used for trays and pin dishes – produced mainly in Austria – often with small bronze animals or figures attached. Onyx is mentioned in the Bible many times, sardonyx is mentioned in the Bible as well. Onyx was known to the Ancient Greeks and Romans, the first-century naturalist Pliny the Elder described both type of onyx and various artificial treatment techniques in his Naturalis Historia
The Atacama Desert is a plateau in South America, covering a 1, 000-kilometre strip of land on the Pacific coast, west of the Andes mountains. It is the driest non-polar desert in the world, according to estimates, the Atacama Desert proper occupies 105,000 square kilometres, or 128,000 square kilometres if the barren lower slopes of the Andes are included. Most of the desert is composed of terrain, salt lakes, sand. The National Geographic Society considers the area of southern Peru to be part of the Atacama Desert. Peru borders it on the north and the Chilean Matorral ecoregion borders it on the south, to the east lies the less arid Central Andean dry puna ecoregion. The drier portion of this ecoregion is located south of the Loa River between the parallel Sierra Vicuña Mackenna and Cordillera Domeyko, to the north of the Loa lies the Pampa del Tamarugal. The Coastal Cliff of northern Chile west of the Chilean Coast Range is the topographic feature of the coast. The geomorphology of the Atacama Desert has been characterized as a low-relief bench similar to a giant uplifted terrace by Armijo and co-workers.
The intermediate depression forms a series of basins in much of Atacama Desert south of latitude 19°30’ S. North of this latitude the intermediate depression drains into the Pacific Ocean. Although the almost total lack of precipitation is the most prominent characteristic of the Atacama Desert, in 2012, the altiplano winter brought floods to San Pedro de Atacama. On 25 March 2015, heavy rainfall affected the part of the Atacama desert. Resulting floods triggered mudflows that affected the cities of Copiapo, Tierra Amarilla, Chanaral, the Atacama Desert is commonly known as the driest non-polar place in the world, especially the surroundings of the abandoned Yungay town. The average rainfall is about 15 mm per year, although some locations, such as Arica and Iquique, some weather stations in the Atacama have never received rain. Periods of up to four years have been registered with no rainfall in the sector, delimited by the cities of Antofagasta and Copiapó. Evidence suggests that the Atacama may not have had any significant rainfall from 1570 to 1971, the Atacama Desert may be the oldest desert on earth, and has experienced extreme hyperaridity for at least 3 million years, making it the oldest continuously arid region on earth.
The long history of aridity raises the possibility that supergene mineralisation, under the conditions, can form in arid environments. This desert is so arid, many mountains higher than 6,000 m are free of glaciers. Only the highest peaks have some permanent snow coverage, the southern part of the desert, between 25 and 27°S, may have been glacier-free throughout the Quaternary, though permafrost extends down to an altitude of 4,400 m and is continuous above 5,600 m
President Dwight D. Eisenhower established NASA in 1958 with a distinctly civilian orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29,1958, disestablishing NASAs predecessor, the new agency became operational on October 1,1958. Since that time, most US space exploration efforts have led by NASA, including the Apollo Moon landing missions, the Skylab space station. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle, the agency is responsible for the Launch Services Program which provides oversight of launch operations and countdown management for unmanned NASA launches. NASA shares data with various national and international such as from the Greenhouse Gases Observing Satellite. Since 2011, NASA has been criticized for low cost efficiency, from 1946, the National Advisory Committee for Aeronautics had been experimenting with rocket planes such as the supersonic Bell X-1.
In the early 1950s, there was challenge to launch a satellite for the International Geophysical Year. An effort for this was the American Project Vanguard, after the Soviet launch of the worlds first artificial satellite on October 4,1957, the attention of the United States turned toward its own fledgling space efforts. This led to an agreement that a new federal agency based on NACA was needed to conduct all non-military activity in space. The Advanced Research Projects Agency was created in February 1958 to develop technology for military application. On July 29,1958, Eisenhower signed the National Aeronautics and Space Act, a NASA seal was approved by President Eisenhower in 1959. Elements of the Army Ballistic Missile Agency and the United States Naval Research Laboratory were incorporated into NASA, earlier research efforts within the US Air Force and many of ARPAs early space programs were transferred to NASA. In December 1958, NASA gained control of the Jet Propulsion Laboratory, NASA has conducted many manned and unmanned spaceflight programs throughout its history.
Some missions include both manned and unmanned aspects, such as the Galileo probe, which was deployed by astronauts in Earth orbit before being sent unmanned to Jupiter, the experimental rocket-powered aircraft programs started by NACA were extended by NASA as support for manned spaceflight. This was followed by a space capsule program, and in turn by a two-man capsule program. This goal was met in 1969 by the Apollo program, reduction of the perceived threat and changing political priorities almost immediately caused the termination of most of these plans. NASA turned its attention to an Apollo-derived temporary space laboratory, to date, NASA has launched a total of 166 manned space missions on rockets, and thirteen X-15 rocket flights above the USAF definition of spaceflight altitude,260,000 feet. The X-15 was an NACA experimental rocket-powered hypersonic research aircraft, developed in conjunction with the US Air Force, the design featured a slender fuselage with fairings along the side containing fuel and early computerized control systems
A crow is a bird of the genus Corvus. The term crow is used both as part of the name of many species, and collectively for all of Corvus
South America is a continent located in the western hemisphere, mostly in the southern hemisphere, with a relatively small portion in the northern hemisphere. It may be considered a subcontinent of the Americas, which is the used in nations that speak Romance languages. The reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean, North America and it includes twelve sovereign states, a part of France, and a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands and Tobago, South America has an area of 17,840,000 square kilometers. Its population as of 2005 has been estimated at more than 371,090,000, South America ranks fourth in area and fifth in population. Brazil is by far the most populous South American country, with more than half of the population, followed by Colombia, Venezuela. In recent decades Brazil has concentrated half of the regions GDP and has become a first regional power, most of the population lives near the continents western or eastern coasts while the interior and the far south are sparsely populated.
Most of the continent lies in the tropics, the continents cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the majority of South Americans speak Portuguese or Spanish. South America occupies the portion of the Americas. The continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border. Almost all of mainland South America sits on the South American Plate, South Americas major mineral resources are gold, copper, iron ore and petroleum. These resources found in South America have brought high income to its countries especially in times of war or of rapid growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity often has hindered the development of diversified economies and this is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export.
South America is one of the most biodiverse continents on earth, South America is home to many interesting and unique species of animals including the llama, piranha, vicuña, and tapir. The Amazon rainforests possess high biodiversity, containing a proportion of the Earths species. Brazil is the largest country in South America, encompassing around half of the land area
Salar de Atacama
Salar de Atacama is the largest salt flat in Chile. It is located 55 km south of San Pedro de Atacama, is surrounded by mountains, in the east it is enclosed by the main chain of the Andes, while to the west lies a secondary mountain range of the Andes called Cordillera de Domeyko. Large volcanoes dominate the landscape, including the Licancabur, Aguas Calientes, the last is one of the most active volcanoes in Chile. All of them are located along the side of the Salar de Atacama. The salt flat encompasses 3,000 km2, is about 100 km long and 80 km wide and its average elevation is about 2,300 m above sea level. Some areas of the flat form part of Los Flamencos National Reserve. The Laguna Cejar is a sink hole lake in the Salar de Atacama,18 km from San Pedro and it has a salt concentration that ranges from 5 to 28%, producing at the higher end of the range an effect of floating like the Dead Sea. At present the Salar de Atacama depression conforms a subsiding sedimentary basin, comparing with neighboring areas of the Andes the Salar de Atacama depression is a major topographical anomaly.
The Salar de Atacama depression is thought to be caused by a block that due to its high density has remained at lower position than the rest of the Andes. The high density would derive from the times the Salar de Atacama depression was a rift arm of the Salta Rift Basin located further east in Argentine territory. Salar de Atacama basin is bordered on the north by the Salado River basin, to the east, the drainage divide approximately coincides with the international border with Bolivia until the Portezuelo del Cajón. The dividing range includes the volcanoes Cerros de Tocorpuri, Curiquinca, going southward, the water divide runs along a chain of volcanoes that lie entirely in Chilean territory. To the west, the Cordillera Domeyko separates the Salar de Atacama basin from arheic areas and its main tributaries are the San Pedro and Vilama rivers, which originate to the north of the salt flat. Salar de Atacamas evaporation rate is the highest in the industry, followed by Puna de Atacama, Argentina.
Gerardo Díaz del Río, Ramiro Bonilla Parra, Fernando Peralta Toro, geología de superficie, sub-superficie y geoquímica del Salar de Atacama. Bottled Lightning, Electric Cars, and the New Lithium Economy, geoquímica del Salar de Atacama, parte 1, origen de los componentes y balance salino. Ortiz, J. F. Muñoz, P. Adkins and land surface energy budget at the Salar de Atacama, Northern Chile
Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron.
Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, muscles, bone marrow, blood proteins, ferritin and transport in plasma.
The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have been studied extensively
The Internet Archive launched the Wayback Machine in October 2001. It was set up by Brewster Kahle and Bruce Gilliat, and is maintained with content from Alexa Internet, the service enables users to see archived versions of web pages across time, which the archive calls a three dimensional index. Since 1996, the Wayback Machine has been archiving cached pages of websites onto its large cluster of Linux nodes and it revisits sites every few weeks or months and archives a new version. Sites can be captured on the fly by visitors who enter the sites URL into a search box, the intent is to capture and archive content that otherwise would be lost whenever a site is changed or closed down. The overall vision of the machines creators is to archive the entire Internet, the name Wayback Machine was chosen as a reference to the WABAC machine, a time-traveling device used by the characters Mr. Peabody and Sherman in The Rocky and Bullwinkle Show, an animated cartoon. These crawlers respect the robots exclusion standard for websites whose owners opt for them not to appear in search results or be cached, to overcome inconsistencies in partially cached websites, Archive-It.
Information had been kept on digital tape for five years, with Kahle occasionally allowing researchers, when the archive reached its fifth anniversary, it was unveiled and opened to the public in a ceremony at the University of California, Berkeley. Snapshots usually become more than six months after they are archived or, in some cases, even later. The frequency of snapshots is variable, so not all tracked website updates are recorded, Sometimes there are intervals of several weeks or years between snapshots. After August 2008 sites had to be listed on the Open Directory in order to be included. As of 2009, the Wayback Machine contained approximately three petabytes of data and was growing at a rate of 100 terabytes each month, the growth rate reported in 2003 was 12 terabytes/month, the data is stored on PetaBox rack systems manufactured by Capricorn Technologies. In 2009, the Internet Archive migrated its customized storage architecture to Sun Open Storage, in 2011 a new, improved version of the Wayback Machine, with an updated interface and fresher index of archived content, was made available for public testing.
The index driving the classic Wayback Machine only has a bit of material past 2008. In January 2013, the company announced a ground-breaking milestone of 240 billion URLs, in October 2013, the company announced the Save a Page feature which allows any Internet user to archive the contents of a URL. This became a threat of abuse by the service for hosting malicious binaries, as of December 2014, the Wayback Machine contained almost nine petabytes of data and was growing at a rate of about 20 terabytes each week. Between October 2013 and March 2015 the websites global Alexa rank changed from 162 to 208, in a 2009 case, Netbula, LLC v. Chordiant Software Inc. defendant Chordiant filed a motion to compel Netbula to disable the robots. Netbula objected to the motion on the ground that defendants were asking to alter Netbulas website, in an October 2004 case, Telewizja Polska USA, Inc. v. Echostar Satellite, No.02 C3293,65 Fed. 673, a litigant attempted to use the Wayback Machine archives as a source of admissible evidence, Telewizja Polska is the provider of TVP Polonia and EchoStar operates the Dish Network
Weathering is the breaking down of rocks and minerals as well as wood and artificial materials through contact with the Earths atmosphere and biological organisms. Two important classifications of weathering processes exist – physical and chemical weathering, mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions, such as heat, water and pressure. While physical weathering is accentuated in very cold or very dry environments, chemical reactions are most intense where the climate is wet, both types of weathering occur together, and each tends to accelerate the other. For example, physical abrasion decreases the size of particles and therefore increases their surface area, the various agents act in concert to convert primary minerals to secondary minerals and release plant nutrient elements in soluble forms. The materials left over after the rock breaks down combined with organic material creates soil, in addition, many of Earths landforms and landscapes are the result of weathering processes combined with erosion and re-deposition.
Physical weathering, recognized as mechanical weathering, is the class of processes that causes the disintegration of rocks without chemical change, the primary process in physical weathering is abrasion. However and physical weathering often go hand in hand, physical weathering can occur due to temperature, frost etc. For example, cracks exploited by physical weathering will increase the area exposed to chemical action. Abrasion by water and wind loaded with sediment can have tremendous cutting power, as is amply demonstrated by the gorges, ravines. In glacial areas, huge moving ice masses embedded with soil and rock fragments grind down rocks in their path, plant roots sometimes enter cracks in rocks and pry them apart, resulting in some disintegration, Burrowing animals may help disintegrate rock through their physical action. However, such influences are usually of importance in producing parent material when compared to the drastic physical effects of water, wind. Physical weathering is called mechanical weathering or disaggregation.
Thermal stress weathering results from the expansion and contraction of rock, for example, heating of rocks by sunlight or fires can cause expansion of their constituent minerals. As some minerals expand more than others, temperature changes set up differential stresses that cause the rock to crack apart. Because the outer surface of a rock is often warmer or colder than the more protected inner portions and this process may be sharply accelerated if ice forms in the surface cracks. When water freezes, it expands with a force of about 1465 Mg/m^2, disintegrating huge rock masses, thermal stress weathering comprises two main types, thermal shock and thermal fatigue. Thermal stress weathering is an important mechanism in deserts, where there is a diurnal temperature range, hot in the day. The repeated heating and cooling exerts stress on the layers of rocks
Catamarca is a province of Argentina, located in the northwest of the country. The province has a population of 334,568 as per the 2001 census, neighbouring provinces are, Tucumán, Santiago del Estero, Córdoba, and La Rioja. To the west it borders Chile, the capital is San Fernando del Valle de Catamarca, usually shortened to Catamarca. Other important cities include Andalgalá, and Belén, located in an arid and semi-arid climate zone, the scarce water resources determine the human settlement pattern. Agricultural activities are concentrated in the pockets and valleys between the mountains, in the east the population is concentrated around a number of water courses, water being distributed by canals and irrigation ditches. The province is located with the region of Argentina. Mean annual precipitation of the province is around 400 to 500 millimetres which decreases significantly to the west, the province is characterized by the presence of different microclimates based on variations in altitude.
In general, there are three different climatic zones found within the province, the northeastern parts of the province has a subtropical highland climate that is characterized by abundant rainfall and high temperatures. Summers are hot while winters are mild with abundant humidity, at the highest peaks of Sierra del Aconquija, snow cover is permanment. Most of the province and its valleys have an arid climate. Within these valleys includes the provincial capital, the climate is characterized by its extreme aridity, large thermal amplitudes. The region is characterized by abundant sunshine with winds predominantly coming from the northeast and southeast, there is large variation between different locations owing to differences in altitude and differences in the relief and altitudes of the surrounding mountains that enclose the valleys. Mean annual precipitation ranges from 500 to 700 millimetres in the parts of the region to less than 150 millimetres in the west. In the arid valleys, mean precipitation is around 160 millimetres.
Most of the precipitation occurs during summer, falling as short, mean annual temperatures range between 16 to 18 °C with eastern and central parts having mean annual temperatures of 20 °C. In summer, the temperature is 25 °C although they can reach up to 45 °C. Winters, with a temperature of 10 °C are characterized by frequent frosts. Locations in the west experience colder winters due to their higher altitudes with temperatures that can decrease to −30 °C, during winter, the Zonda Wind occasionally occurs, leading to very dry conditions that can lead to dust storms