1.
Terrestrial planet
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A terrestrial planet, telluric planet, or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the planets are the inner planets closest to the Sun, i. e. Mercury, Venus, Earth. The terms terrestrial planet and telluric planet are derived from Latin words for Earth, as these planets are, in terms of composition, Earth-like. All terrestrial planets may have the basic type of structure, such as a central metallic core, mostly iron. The Moon is similar, but has a smaller iron core. Io and Europa are also satellites that have internal structures similar to that of terrestrial planets, terrestrial planets can have canyons, craters, mountains, volcanoes, and other surface structures, depending on the presence of water and tectonic activity. The Solar System has four planets, Mercury, Venus, Earth. Only one terrestrial planet, Earth, is known to have an active hydrosphere, during the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. The Earths Moon has a density of 3.4 g·cm−3 and Jupiters satellites, Io,3.528 and Europa,3.013 g·cm−3, the uncompressed density of a terrestrial planet is the average density its materials would have at zero pressure. A greater uncompressed density indicates greater metal content, uncompressed density differs from the true average density because compression within planet cores increases their density, the average density depends on planet size as well as composition. The uncompressed density of terrestrial planets trends towards lower values as the distance from the Sun increases, the rocky minor planet Vesta orbiting outside of Mars is less dense than Mars still, at 3.4 g·cm−3. It is unknown whether extrasolar terrestrial planets in general will also follow this trend, most of the planets discovered outside the Solar System are giant planets, because they are more easily detectable. But since 2005, hundreds of terrestrial extrasolar planets have been found. Most of these are super-Earths, i. e. planets with masses between Earths and Neptunes, super-Earths may be gas planets or terrestrial, depending on their mass and other parameters. During the early 1990s, the first extrasolar planets were discovered orbiting the pulsar PSR B1257+12, with masses of 0.02,4.3 and it was later found to be a gas giant. In 2005, the first planets around stars that may be terrestrial were found, Gliese 876 d, has a mass 7 to 9 times that of Earth. It orbits the red dwarf Gliese 876,15 light years from Earth, oGLE-2005-BLG-390Lb, about 5.5 times the mass of Earth, orbits a star about 21,000 light years away in the constellation Scorpius. From 2007 to 2010, three potential terrestrial planets were orbiting the red dwarf Gliese 581
2.
Rock (geology)
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Rock or stone is a natural substance, a solid aggregate of one or more minerals or mineraloids. For example, granite, a rock, is a combination of the minerals quartz, feldspar. The Earths outer solid layer, the lithosphere, is made of rock, rock has been used by mankind throughout history. The minerals and metals found in rocks have been essential to human civilization, three major groups of rocks are defined, igneous, sedimentary, and metamorphic. The scientific study of rocks is called petrology, which is a component of geology. At a granular level, rocks are composed of grains of minerals, the aggregate minerals forming the rock are held together by chemical bonds. The types and abundance of minerals in a rock are determined by the manner in which the rock was formed, many rocks contain silica, a compound of silicon and oxygen that forms 74. 3% of the Earths crust. This material forms crystals with other compounds in the rock, the proportion of silica in rocks and minerals is a major factor in determining their name and properties. Rocks are geologically classified according to such as mineral and chemical composition, permeability, the texture of the constituent particles. These physical properties are the end result of the processes that formed the rocks, over the course of time, rocks can transform from one type into another, as described by the geological model called the rock cycle. These events produce three general classes of rock, igneous, sedimentary, and metamorphic, the three classes of rocks are subdivided into many groups. However, there are no hard and fast boundaries between allied rocks, hence the definitions adopted in establishing rock nomenclature merely correspond to more or less arbitrary selected points in a continuously graduated series. Igneous rock forms through the cooling and solidification of magma or lava and this magma can be derived from partial melts of pre-existing rocks in either a planets mantle or crust. Typically, the melting of rocks is caused by one or more of three processes, an increase in temperature, a decrease in pressure, or a change in composition, igneous rocks are divided into two main categories, plutonic rock and volcanic. Plutonic or intrusive rocks result when magma cools and crystallizes slowly within the Earths crust, a common example of this type is granite. Volcanic or extrusive rocks result from magma reaching the surface either as lava or fragmental ejecta, the chemical abundance and the rate of cooling of magma typically forms a sequence known as Bowens reaction series. Most major igneous rocks are found along this scale, about 64. 7% of the Earths crust by volume consists of igneous rocks, making it the most plentiful category. Of these, 66% are basalts and gabbros, 16% are granite, only 0. 6% are syenites and 0. 3% peridotites and dunites
3.
Planetary differentiation
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Such a process tends to create a core and mantle. Sometimes a chemically distinct crust forms on top of the mantle, the process of planetary differentiation has occurred on planets, dwarf planets, the asteroid 4 Vesta, and natural satellites. When the Sun ignited in the nebula, hydrogen, helium. The solar wind and radiation pressure forced these low-density materials away from the Sun, rocks, and the elements comprising them, were stripped of their early atmospheres, but themselves remained, to accumulate into protoplanets. Protoplanets had higher concentrations of radioactive elements early in their history, heating due to radioactivity, impacts, and gravitational pressure melted parts of protoplanets as they grew toward being planets. In melted zones, it was possible for denser materials to sink towards the center, the compositions of some meteorites show that differentiation also took place in some asteroids, that are parental bodies for meteoroids. The short-lived radioactive isotope 26Al was probably the source of heat. When protoplanets accrete more material, the energy of impact causes local heating, in addition to this temporary heating, the gravitational force in a sufficiently large body creates pressures and temperatures which are sufficient to melt some of the materials. This allows chemical reactions and density differences to mix and separate materials, on Earth, a large piece of molten iron is sufficiently denser than continental crust material to force its way down through the crust to the mantle. In the outer Solar System a similar process may take place but with lighter materials, they may be such as methane, water as liquid or ice. High-density materials tend to sink through lighter materials and this tendency is affected by the relative structural strengths, but such strength is reduced at temperatures where both materials are plastic or molten. Iron, the most common element that is likely to form a dense molten metal phase. With it, many siderophile elements also travel downward, however, not all heavy elements make this transition as some chalcophilic heavy elements bind into low-density silicate and oxide compounds, which differentiate in the opposite direction. Even lighter still are the watery liquid hydrosphere and the gaseous, lighter materials tend to rise through material with a higher density. They may take on dome-shaped forms called diapirs when doing so, on Earth, salt domes are salt diapirs in the crust which rise through surrounding rock. Diapirs of molten low-density silicate rocks such as granite are abundant in the Earths upper crust, the hydrated, low-density serpentinite formed by alteration of mantle material at subduction zones can also rise to the surface as diapirs. Other materials do likewise, a low-temperature, near-surface example is provided by mud volcanos and it is also high in uranium and thorium. Magma in the Earth is produced by melting of a source rock
4.
Density
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The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
5.
Planetary core
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The planetary core consists of the innermost layer of a planet, which may be composed of solid and liquid layers. Cores of specific planets may be solid or entirely liquid. In the Solar System, core size can range from about 20% to 85% of a planets radius. Gas giants also have cores, though the composition of these are still a matter of debate and range in composition from traditional stony/iron. In 1798, Henry Cavendish calculated the density of the earth to be 5.48 times the density of water. The first detection of Earths core occurred in 1906 by Richard Dixon Oldham upon discovery of the P-wave shadow zone, by 1936 seismologists had determined the size of the overall core as well as the boundary between the fluid outer core and the solid inner core. Planetary systems form from a disk of dust and gas that accrete rapidly into planetesimals around 10 km in diameter. From here gravity takes over to produce Moon to Mars sized planetary embryos, Jupiter and Saturn most likely formed around previously existing rocky and/or icy bodies, rendering these previous primordial planets into gas-giant cores. This is the core accretion model of planet formation. Planetary differentiation is broadly defined as the development from one thing to many things, the hafnium-182/tungsten-182 isotopic system has a half-life of 9 million years, and is approximated as an extinct system after 45 million years. Hafnium is an element and tungsten is siderophile element. The observed Hf/W ratios in iron meteorites constrain metal segregation to under 5 million years, several factors control segregation of a metal core including the crystallization of perovskite. Crystallization of perovskite in a magma ocean is an oxidation process. Impacts between planet-sized bodies in the early Solar System are important aspects in the formation and growth of planets, the giant impact hypothesis states that an impact between a theoretical Mars-sized planet Theia and the early Earth formed the modern Earth and moon. During this impact the majority of the iron from Theia and the Earth became incorporated into the Earths core, core merging between the proto-mars and another differentiated planetoid could have been as fast as 1000 years or as slow as 300,000 years. Earths core contains half the Earths vanadium and chromium, and may contain considerable niobium and tantalum, Earths core is depleted in germanium and gallium. Sulfur is strongly siderophile and only moderately volatile and depleted in the silicate earth, by similar argument, phosphorus may be present up to 0.2 weight %. Hydrogen and carbon, however, are volatile and thus would have been lost during early accretion
6.
Crust (geology)
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In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle. The crust of the Earth is composed of a variety of igneous, metamorphic. The crust is underlain by the mantle, the upper part of the mantle is composed mostly of peridotite, a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovičić discontinuity, a boundary defined by a contrast in seismic velocity, the crust occupies less than 1% of Earths volume. The crust of the Earth is of two types, oceanic and continental. The oceanic crust is 5 km to 10 km thick and is composed primarily of basalt, diabase, the continental crust is typically from 30 km to 50 km thick and is mostly composed of slightly less dense rocks than those of the oceanic crust. Some of these less dense rocks, such as granite, are common in the continental crust, both the continental and oceanic crust float on the mantle. Because the continental crust is thicker, it both to greater elevations and greater depth than the oceanic crust. The slightly lower density of continental rock compared to basaltic oceanic rock contributes to the higher relative elevation of the top of the continental crust. As the top of the continental crust reaches elevations higher than that of the oceanic, the temperature of the crust increases with depth, reaching values typically in the range from about 200 °C to 400 °C at the boundary with the underlying mantle. The crust and underlying relatively rigid uppermost mantle make up the lithosphere, because of convection in the underlying plastic upper mantle and asthenosphere, the lithosphere is broken into tectonic plates that move. The temperature increases by as much as 30 °C for every kilometer locally in the part of the crust. Earth has probably always had some form of basaltic crust, in contrast, the bulk of the continental crust is much older. The oldest continental crustal rocks on Earth have ages in the range from about 3.7 to 4, some zircon with age as great as 4.3 billion years has been found in the Narryer Gneiss Terrane. The average age of the current Earths continental crust has been estimated to be about 2.0 billion years, most crustal rocks formed before 2.5 billion years ago are located in cratons. Such old continental crust and the underlying mantle asthenosphere are less dense than elsewhere in Earth, formation of new continental crust is linked to periods of intense orogeny, these periods coincide with the formation of the supercontinents such as Rodinia, Pangaea and Gondwana. The continental crust has a composition similar to that of andesite. The most abundant minerals in Earths continental crust are feldspars, which make up about 41% of the crust by weight, followed by quartz at 12%, Continental crust is enriched in incompatible elements compared to the basaltic ocean crust and much enriched compared to the underlying mantle
7.
Earth
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Earth, otherwise known as the World, or the Globe, is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets, according to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earths gravity interacts with objects in space, especially the Sun. During one orbit around the Sun, Earth rotates about its axis over 365 times, thus, Earths axis of rotation is tilted, producing seasonal variations on the planets surface. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earths orientation on its axis, Earths lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earths surface is covered with water, mostly by its oceans, the remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earths polar regions are covered in ice, including the Antarctic ice sheet, Earths interior remains active with a solid iron inner core, a liquid outer core that generates the Earths magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earths history, life appeared in the oceans and began to affect the Earths atmosphere and surface, some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earths distance from the Sun, physical properties, in the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely, over 7.4 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humans have developed diverse societies and cultures, politically, the world has about 200 sovereign states, the modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most often spelled eorðe. It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþō, originally, earth was written in lowercase, and from early Middle English, its definite sense as the globe was expressed as the earth. By early Modern English, many nouns were capitalized, and the became the Earth. More recently, the name is simply given as Earth. House styles now vary, Oxford spelling recognizes the lowercase form as the most common, another convention capitalizes Earth when appearing as a name but writes it in lowercase when preceded by the. It almost always appears in lowercase in colloquial expressions such as what on earth are you doing, the oldest material found in the Solar System is dated to 4. 5672±0.0006 billion years ago. By 4. 54±0.04 Gya the primordial Earth had formed, the formation and evolution of Solar System bodies occurred along with the Sun
8.
Mercury (planet)
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Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 88 days is the shortest of all the planets in the Solar System and it is named after the Roman deity Mercury, the messenger to the gods. Like Venus, Mercury orbits the Sun within Earths orbit as a planet, so it can only be seen visually in the morning or the evening sky. Also, like Venus and the Moon, the displays the complete range of phases as it moves around its orbit relative to Earth. Seen from Earth, this cycle of phases reoccurs approximately every 116 days, although Mercury can appear as a bright star-like object when viewed from Earth, its proximity to the Sun often makes it more difficult to see than Venus. Mercury is tidally or gravitationally locked with the Sun in a 3,2 resonance, as seen relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the Sun. As seen from the Sun, in a frame of reference that rotates with the orbital motion, an observer on Mercury would therefore see only one day every two years. Mercurys axis has the smallest tilt of any of the Solar Systems planets, at aphelion, Mercury is about 1.5 times as far from the Sun as it is at perihelion. Mercurys surface appears heavily cratered and is similar in appearance to the Moons, the polar regions are constantly below 180 K. The planet has no natural satellites. Mercury is one of four planets in the Solar System. It is the smallest planet in the Solar System, with a radius of 2,439.7 kilometres. Mercury is also smaller—albeit more massive—than the largest natural satellites in the Solar System, Ganymede, Mercury consists of approximately 70% metallic and 30% silicate material. Mercurys density is the second highest in the Solar System at 5.427 g/cm3, Mercurys density can be used to infer details of its inner structure. Although Earths high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller, therefore, for it to have such a high density, its core must be large and rich in iron. Geologists estimate that Mercurys core occupies about 55% of its volume, Research published in 2007 suggests that Mercury has a molten core. Surrounding the core is a 500–700 km mantle consisting of silicates, based on data from the Mariner 10 mission and Earth-based observation, Mercurys crust is estimated to be 35 km thick. One distinctive feature of Mercurys surface is the presence of narrow ridges
9.
Moon
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The Moon is an astronomical body that orbits planet Earth, being Earths only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, following Jupiters satellite Io, the Moon is second-densest satellite among those whose densities are known. The average distance of the Moon from the Earth is 384,400 km, the Moon is thought to have formed about 4.51 billion years ago, not long after Earth. It is the second-brightest regularly visible celestial object in Earths sky, after the Sun and its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its cycle of phases have made the Moon an important cultural influence since ancient times on language, calendars, art. The Moons gravitational influence produces the ocean tides, body tides, and this matching of apparent visual size will not continue in the far future. The Moons linear distance from Earth is currently increasing at a rate of 3.82 ±0.07 centimetres per year, since the Apollo 17 mission in 1972, the Moon has been visited only by uncrewed spacecraft. The usual English proper name for Earths natural satellite is the Moon, the noun moon is derived from moone, which developed from mone, which is derived from Old English mōna, which ultimately stems from Proto-Germanic *mǣnōn, like all Germanic language cognates. Occasionally, the name Luna is used, in literature, especially science fiction, Luna is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon. The principal modern English adjective pertaining to the Moon is lunar, a less common adjective is selenic, derived from the Ancient Greek Selene, from which is derived the prefix seleno-. Both the Greek Selene and the Roman goddess Diana were alternatively called Cynthia, the names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric. The name Diana is connected to dies meaning day, several mechanisms have been proposed for the Moons formation 4.51 billion years ago, and some 60 million years after the origin of the Solar System. These hypotheses also cannot account for the angular momentum of the Earth–Moon system. This hypothesis, although not perfect, perhaps best explains the evidence, eighteen months prior to an October 1984 conference on lunar origins, Bill Hartmann, Roger Phillips, and Jeff Taylor challenged fellow lunar scientists, You have eighteen months. Go back to your Apollo data, go back to computer, do whatever you have to. Dont come to our conference unless you have something to say about the Moons birth, at the 1984 conference at Kona, Hawaii, the giant impact hypothesis emerged as the most popular. Afterward there were only two groups, the giant impact camp and the agnostics. Giant impacts are thought to have been common in the early Solar System, computer simulations of a giant impact have produced results that are consistent with the mass of the lunar core and the present angular momentum of the Earth–Moon system
10.
Jupiter
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Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, Jupiter and Saturn are gas giants, the other two giant planets, Uranus and Neptune are ice giants. Jupiter has been known to astronomers since antiquity, the Romans named it after their god Jupiter. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium and it may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rotation, the planets shape is that of an oblate spheroid. The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence, a prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere, Jupiter has at least 67 moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a greater than that of the planet Mercury. Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. In late February 2007, Jupiter was visited by the New Horizons probe, the latest probe to visit the planet is Juno, which entered into orbit around Jupiter on July 4,2016. Future targets for exploration in the Jupiter system include the probable ice-covered liquid ocean of its moon Europa, Earth and its neighbor planets may have formed from fragments of planets after collisions with Jupiter destroyed those super-Earths near the Sun. Astronomers have discovered nearly 500 planetary systems with multiple planets, Jupiter moving out of the inner Solar System would have allowed the formation of inner planets, including Earth. Jupiter is composed primarily of gaseous and liquid matter and it is the largest of the four giant planets in the Solar System and hence its largest planet. It has a diameter of 142,984 km at its equator, the average density of Jupiter,1.326 g/cm3, is the second highest of the giant planets, but lower than those of the four terrestrial planets. Jupiters upper atmosphere is about 88–92% hydrogen and 8–12% helium by percent volume of gas molecules, a helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms. Thus, Jupiters atmosphere is approximately 75% hydrogen and 24% helium by mass, the atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon-based compounds. There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, the outermost layer of the atmosphere contains crystals of frozen ammonia. The interior contains denser materials - by mass it is roughly 71% hydrogen, 24% helium, through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found
11.
Natural satellite
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A natural satellite or moon is, in the most common usage, an astronomical body that orbits a planet or minor planet. In the Solar System there are six planetary satellite systems containing 178 known natural satellites, four IAU-listed dwarf planets are also known to have natural satellites, Pluto, Haumea, Makemake, and Eris. As of January 2012, over 200 minor-planet moons have been discovered, the Earth–Moon system is unique in that the ratio of the mass of the Moon to the mass of Earth is much greater than that of any other natural-satellite–planet ratio in the Solar System. At 3,474 km across, Earths Moon is 0.27 times the diameter of Earth, the first known natural satellite was the Moon, but it was considered a planet until Copernicus introduction of heliocentrism in 1543. Until the discovery of the Galilean satellites in 1610, however, galileo chose to refer to his discoveries as Planetæ, but later discoverers chose other terms to distinguish them from the objects they orbited. The first to use of the satellite to describe orbiting bodies was the German astronomer Johannes Kepler in his pamphlet Narratio de Observatis a se quatuor Iouis satellitibus erronibus in 1610. He derived the term from the Latin word satelles, meaning guard, attendant, or companion, the term satellite thus became the normal one for referring to an object orbiting a planet, as it avoided the ambiguity of moon. In 1957, however, the launching of the artificial object Sputnik created a need for new terminology, to further avoid ambiguity, the convention is to capitalize the word Moon when referring to Earths natural satellite, but not when referring to other natural satellites. A few recent authors define moon as a satellite of a planet or minor planet, there is no established lower limit on what is considered a moon. Small asteroid moons, such as Dactyl, have also been called moonlets, the upper limit is also vague. Two orbiting bodies are described as a double body rather than primary. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition of what constitutes a moon, some authors consider the Pluto–Charon system to be a double planet. In contrast, irregular satellites are thought to be captured asteroids possibly further fragmented by collisions, most of the major natural satellites of the Solar System have regular orbits, while most of the small natural satellites have irregular orbits. The Moon and possibly Charon are exceptions among large bodies in that they are thought to have originated by the collision of two large proto-planetary objects. The material that would have placed in orbit around the central body is predicted to have reaccreted to form one or more orbiting natural satellites. As opposed to planetary-sized bodies, asteroid moons are thought to form by this process. Triton is another exception, although large and in a close, circular orbit, its motion is retrograde, most regular moons in the Solar System are tidally locked to their respective primaries, meaning that the same side of the natural satellite always faces its planet. The only known exception is Saturns natural satellite Hyperion, which rotates chaotically because of the influence of Titan
12.
Io (moon)
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Io /ˈaɪ. oʊ/ is the innermost of the four Galilean moons of the planet Jupiter. It is the fourth-largest moon, has the highest density of all the moons and it was discovered in 1610 and was named after the mythological character Io, a priestess of Hera who became one of Zeuss lovers. With over 400 active volcanoes, Io is the most geologically active object in the Solar System, several volcanoes produce plumes of sulfur and sulfur dioxide that climb as high as 500 km above the surface. Ios surface is dotted with more than 100 mountains that have been uplifted by extensive compression at the base of Ios silicate crust. Some of these peaks are taller than Mount Everest, unlike most satellites in the outer Solar System, which are mostly composed of water ice, Io is primarily composed of silicate rock surrounding a molten iron or iron-sulfide core. Most of Ios surface is composed of extensive plains coated with sulfur, Ios volcanism is responsible for many of its unique features. Numerous extensive lava flows, several more than 500 km in length, the materials produced by this volcanism make up Ios thin, patchy atmosphere and Jupiters extensive magnetosphere. Ios volcanic ejecta also produce a large torus around Jupiter. Io played a significant role in the development of astronomy in the 17th and 18th centuries and it was discovered in January 1610 by Galileo Galilei, along with the other Galilean satellites. This discovery furthered the adoption of the Copernican model of the Solar System, the development of Keplers laws of motion, and the first measurement of the speed of light. In 1979, the two Voyager spacecraft revealed Io to be a geologically active world, with numerous volcanic features, large mountains, the Galileo spacecraft performed several close flybys in the 1990s and early 2000s, obtaining data about Ios interior structure and surface composition. These spacecraft also revealed the relationship between Io and Jupiters magnetosphere and the existence of a belt of high-energy radiation centered on Ios orbit, Io receives about 3,600 rem of ionizing radiation per day. Further observations have made by Cassini–Huygens in 2000 and New Horizons in 2007, as well as from Earth-based telescopes. From the surface of Io, Jupiter would subtend an arc of 19. 5°, although Simon Marius is not credited with the sole discovery of the Galilean satellites, his names for the moons were adopted. Based on a suggestion from Johannes Kepler in October 1613, he devised a naming scheme whereby each moon was named for a lover of the Greek mythological Zeus or his Roman equivalent. He named the innermost large moon of Jupiter after the Greek mythological figure Io, since the surface was first seen up close by Voyager 1, the International Astronomical Union has approved 225 names for Ios volcanoes, mountains, plateaus, and large albedo features. The approved feature categories used for Io for different types of volcanic features include patera, fluctus, vallis, named mountains, plateaus, layered terrain, and shield volcanoes include the terms mons, mensa, planum, and tholus, respectively. Named, bright albedo regions use the term regio, examples of named features are Prometheus, Pan Mensa, Tvashtar Paterae, and Tsũi Goab Fluctus
13.
Europa (moon)
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Europa /jʊˈroʊpə/, is the smallest of the four Galilean moons orbiting Jupiter, and the sixth-closest to the planet. It is also the sixth-largest moon in the Solar System, Europa was discovered in 1610 by Galileo Galilei and was named after Europa, the legendary mother of King Minos of Crete and lover of Zeus. Slightly smaller than Earths Moon, Europa is primarily made of rock and has a water-ice crust. It has an atmosphere composed primarily of oxygen. Its surface is striated by cracks and streaks, whereas craters are relatively rare, in addition to Earth-bound telescope observations, Europa has been examined by a succession of space probe flybys, the first occurring in the early 1970s. Europa has the smoothest surface of any solid object in the Solar System. The apparent youth and smoothness of the surface have led to the hypothesis that a water ocean exists beneath it, sea salt from a subsurface ocean may be coating some geological features on Europa, suggesting that the ocean is interacting with the seafloor. This may be important in determining if Europa could be habitable, in addition, the Hubble Space Telescope detected water vapor plumes similar to those observed on Saturns moon Enceladus, which are thought to be caused by erupting cryogeysers. The Galileo mission, launched in 1989, provides the bulk of current data on Europa, no spacecraft has yet landed on Europa, although there have been several proposed exploration missions. The European Space Agencys Jupiter Icy Moon Explorer is a mission to Ganymede that is due to launch in 2022, NASAs planned Europa Multiple-Flyby Mission will be launched in the mid-2020s. Europa, along with Jupiters three other large moons, Io, Ganymede, and Callisto, was discovered by Galileo Galilei on 8 January 1610, and possibly independently by Simon Marius. The first reported observation of Io and Europa was made by Galileo Galilei on 7 January 1610 using a 20×-magnification refracting telescope at the University of Padua. However, in observation, Galileo could not separate Io and Europa due to the low magnification of his telescope. The following day,8 January 1610, Io and Europa were seen for the first time as separate bodies during Galileos observations of the Jupiter system, Europa is named after Europa, daughter of the king of Tyre, a Phoenician noblewoman in Greek mythology. Like all the Galilean satellites, Europa is named after a lover of Zeus, Europa was courted by Zeus and became the queen of Crete. The naming scheme was suggested by Simon Marius, who discovered the four satellites independently, Marius attributed the proposal to Johannes Kepler. The names fell out of favor for a time and were not revived in general use until the mid-20th century. In much of the astronomical literature, Europa is simply referred to by its Roman numeral designation as Jupiter II or as the second satellite of Jupiter
14.
Asteroid
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Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids and these terms have historically been applied to any astronomical object orbiting the Sun that did not show the disc of a planet and was not observed to have the characteristics of an active comet. As minor planets in the outer Solar System were discovered and found to have volatile-based surfaces that resemble those of comets, in this article, the term asteroid refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There are millions of asteroids, many thought to be the remnants of planetesimals. The large majority of known asteroids orbit in the belt between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects, individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups, C-type, M-type, and S-type. These were named after and are identified with carbon-rich, metallic. The size of asteroids varies greatly, some reaching as much as 1000 km across, asteroids are differentiated from comets and meteoroids. In the case of comets, the difference is one of composition, while asteroids are composed of mineral and rock, comets are composed of dust. In addition, asteroids formed closer to the sun, preventing the development of the aforementioned cometary ice, the difference between asteroids and meteoroids is mainly one of size, meteoroids have a diameter of less than one meter, whereas asteroids have a diameter of greater than one meter. Finally, meteoroids can be composed of either cometary or asteroidal materials, only one asteroid,4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye, and this only in very dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be visible to the eye for a short time. As of March 2016, the Minor Planet Center had data on more than 1.3 million objects in the inner and outer Solar System, the United Nations declared June 30 as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, the first asteroid to be discovered, Ceres, was found in 1801 by Giuseppe Piazzi, and was originally considered to be a new planet. In the early half of the nineteenth century, the terms asteroid. Asteroid discovery methods have improved over the past two centuries. This task required that hand-drawn sky charts be prepared for all stars in the band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would, hopefully, the expected motion of the missing planet was about 30 seconds of arc per hour, readily discernible by observers
15.
4 Vesta
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Vesta, minor-planet designation 4 Vesta, is one of the largest objects in the asteroid belt, with a mean diameter of 525 kilometres. It was discovered by the German astronomer Heinrich Wilhelm Olbers on 29 March 1807 and is named after Vesta, Vesta is the second-most-massive and second-largest body in the asteroid belt after the dwarf planet Ceres, and it contributes an estimated 9% of the mass of the asteroid belt. It is slightly larger than Pallas, though more massive. Vesta is the last remaining rocky protoplanet of the kind that formed the terrestrial planets, numerous fragments of Vesta were ejected by collisions one and two billion years ago that left two enormous craters occupying much of Vestas southern hemisphere. Debris from these events has fallen to Earth as howardite–eucrite–diogenite meteorites, Vesta is the brightest asteroid visible from Earth. Its maximum distance from the Sun is slightly greater than the distance of Ceres from the Sun. NASAs Dawn spacecraft entered orbit around Vesta on 16 July 2011 for an exploration and left orbit on 5 September 2012 en route to its final destination. Researchers continue to examine data collected by Dawn for additional insights into the formation, Heinrich Olbers discovered Pallas in 1802, the year after the discovery of Ceres. He proposed that the two objects were the remnants of a destroyed planet and these orbital intersections were located in the constellations of Cetus and Virgo. Olbers commenced his search in 1802, and on 29 March 1807 he discovered Vesta in the constellation Virgo—a coincidence, because Ceres, Pallas, and Vesta are not fragments of a larger body. Because the asteroid Juno had been discovered in 1804, this made Vesta the fourth object to be identified in the region that is now known as the asteroid belt, the discovery was announced in a letter addressed to German astronomer Johann H. Schröter dated 31 March. Gauss decided on the Roman virgin goddess of home and hearth, Vesta was the fourth asteroid to be discovered, hence the number 4 in its formal designation. The name Vesta, or national variants thereof, is in use with two exceptions, Greece and China. In Greek, the name adopted was the Hellenic equivalent of Vesta, Hestia, in English, in Chinese, Vesta is called the hearth-god star, 灶神星 zàoshénxīng, in contrast to the goddess Vesta, who goes by her Latin name. Upon its discovery, Vesta was, like Ceres, Pallas, the symbol representing the altar of Vesta with its sacred fire and was designed by Gauss. In Gausss conception, this was drawn, in its modern form, after the discovery of Vesta, no further objects were discovered for 38 years, and the Solar System was thought to have eleven planets. However, in 1845, new asteroids started being discovered at a rapid pace and it soon became clear that it would be impractical to continue inventing new planetary symbols indefinitely, and some of the existing ones proved difficult to draw quickly. That year, the problem was addressed by Benjamin Apthorp Gould, who suggested numbering asteroids in their order of discovery, thus, the fourth asteroid, Vesta, acquired the generic symbol ④
16.
Silicate
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A silicate is a compound containing an anionic silicon compound. The great majority of the silicates are oxides, but hexafluorosilicate, orthosilicate is the anion SiO4−4 or its compounds. Related to orthosilicate are families of anions with the formula 2n−, important members are the cyclic and single chain silicates n and the sheet-forming silicates n. Silicates constitute the majority of Earths crust, as well as the terrestrial planets, rocky moons. Sand, Portland cement, and thousands of minerals are examples of silicates, silicate compounds, including the minerals, consist of silicate anions whose charge is balanced by various cations. Myriad silicate anions can exist, and each can form compounds with many different cations, hence this class of compounds is very large. Both minerals and synthetic materials fit in this class, in the vast majority of silicates, including silicate minerals, the Si occupies a tetrahedral environment, being surrounded by 4 oxygen centres. In these structures, the bonds to silicon conform to the octet rule. These tetrahedra sometimes occur as isolated SiO4−4 centres, but most commonly, commonly the silicate anions are chains, double chains, sheets, and three-dimensional frameworks. All these such species have negligible solubility in water at normal conditions, silicates are well characterized as solids, but are less commonly observed in solution. The anion SiO4−4 is the base of silicic acid, Si4. Instead, solutions of silicates are usually observed as mixtures of condensed, the nature of soluble silicates is relevant to understanding biomineralization and the synthesis of aluminosilicates, such as the industrially important catalysts called zeolites. Although the tetrahedron is the coordination geometry for silicon compounds. A well-known example of such a high number is hexafluorosilicate. Octahedral coordination by 6 oxygen centres is observed, at very high pressure, even SiO2 adopts this geometry in the mineral stishovite, a dense polymorph of silica found in the lower mantle of the Earth. This structure is formed by shock during meteorite impacts. In geology and astronomy, the silicate is used to denote types of rock that consist predominantly of silicate minerals. On Earth, a variety of silicate minerals occur in an even wider range of combinations as a result of the processes that form
17.
Callisto (moon)
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Callisto /kəˈlɪstoʊ/ is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System and the largest object in the Solar System not to be properly differentiated, Callisto was discovered in 1610 by Galileo Galilei. At 4821 km in diameter, Callisto has about 99% the diameter of the planet Mercury and it is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1883000 km. It is not in an orbital resonance like the three other Galilean satellites—Io, Europa, and Ganymede—and is thus not appreciably tidally heated. Callistos rotation is locked to its orbit around Jupiter, so that the same hemisphere always faces inward. It is less affected by Jupiters magnetosphere than the inner satellites because of its more remote orbit. Callisto is composed of equal amounts of rock and ices, with a density of about 1.83 g/cm3. Compounds detected spectroscopically on the surface water ice, carbon dioxide, silicates. Investigation by the Galileo spacecraft revealed that Callisto may have a small silicate core, the surface of Callisto is the oldest and most heavily cratered in the Solar System. Its surface is covered with impact craters. Prominent surface features include multi-ring structures, variously shaped impact craters, at a small scale, the surface is varied and made up of small, sparkly frost deposits at the tips of high spots, surrounded by a low-lying, smooth blanket of dark material. The absolute ages of the landforms are not known, Callisto is surrounded by an extremely thin atmosphere composed of carbon dioxide and probably molecular oxygen, as well as by a rather intense ionosphere. Callisto is thought to have formed by accretion from the disk of the gas. Callistos gradual accretion and the lack of tidal heating meant that not enough heat was available for rapid differentiation, the likely presence of an ocean within Callisto leaves open the possibility that it could harbor life. However, conditions are thought to be less favorable than on nearby Europa, various space probes from Pioneers 10 and 11 to Galileo and Cassini have studied Callisto. Because of its low levels, Callisto has long been considered the most suitable place for a human base for future exploration of the Jovian system. Callisto was discovered by Galileo in January 1610, along three other large Jovian moons—Ganymede, Io, and Europa. Callisto is named one of Zeuss many lovers in Greek mythology
18.
Titan (moon)
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Titan is the largest moon of Saturn. It is the only known to have a dense atmosphere. Titan is the sixth ellipsoidal moon from Saturn, frequently described as a planet-like moon, Titan is 50% larger than Earths Moon, and it is 80% more massive. It is the second-largest moon in the Solar System, after Jupiters moon Ganymede, and is larger than the smallest planet, Mercury, discovered in 1655 by the Dutch astronomer Christiaan Huygens, Titan was the first known moon of Saturn, and the sixth known planetary satellite. Titan orbits Saturn at 20 Saturn radii, from Titans surface, Saturn subtends an arc of 5.09 degrees and would appear 11.4 times larger in the sky than the Moon from Earth. Titan is primarily composed of ice and rocky material. The geologically young surface is smooth, with few impact craters, although mountains. The atmosphere of Titan is largely nitrogen, minor components lead to the formation of methane and ethane clouds and nitrogen-rich organic smog. The climate—including wind and rain—creates surface features similar to those of Earth, such as dunes, rivers, lakes, seas, and deltas, Huygens was inspired by Galileos discovery of Jupiters four largest moons in 1610 and his improvements in telescope technology. Christiaan, with the help of his brother Constantijn Huygens, Jr. began building telescopes around 1650 and it was the sixth moon to be discovered. He named it Saturni Luna, publishing in the 1655 tract De Saturni Luna Observatio Nova, after Giovanni Domenico Cassini published his discoveries of four more moons of Saturn between 1673 and 1686, astronomers fell into the habit of referring to these and Titan as Saturn I through V. Other early epithets for Titan include Saturns ordinary satellite, Titan is officially numbered Saturn VI because after the 1789 discoveries the numbering scheme was frozen to avoid causing any more confusion. Numerous small moons have been discovered closer to Saturn since then and he suggested the names of the mythological Titans, brothers and sisters of Cronus, the Greek Saturn. In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, Titan orbits Saturn once every 15 days and 22 hours. Because of this, there is a point on its surface. Longitudes on Titan are measured westward, starting from the passing through this point. Its orbital eccentricity is 0.0288, and the plane is inclined 0.348 degrees relative to the Saturnian equator. Viewed from Earth, Titan reaches a distance of about 20 Saturn radii from Saturn
19.
Triton (moon)
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Triton is the largest natural satellite of the planet Neptune. It was discovered on October 10,1846, by English astronomer William Lassell and it is the only large moon in the Solar System with a retrograde orbit, an orbit in the opposite direction to its planets rotation. At 2,700 kilometres in diameter, it is the seventh-largest moon in the Solar System, because of its retrograde orbit and composition similar to Plutos, Triton is thought to have been a dwarf planet captured from the Kuiper belt. Triton has a surface of frozen nitrogen, a mostly water-ice crust, an icy mantle. The core makes up two-thirds of its total mass, Triton has a mean density of 2.061 g/cm3 and is composed of approximately 15–35% water ice. Triton is one of the few moons in the Solar System known to be geologically active, as a consequence, its surface is relatively young with sparse impact craters, and a complex geological history revealed in intricate cryovolcanic and tectonic terrains. Part of its surface has geysers erupting sublimated nitrogen gas, contributing to a nitrogen atmosphere less than 1/70,000 the pressure of Earths atmosphere at sea level. Triton was discovered by British astronomer William Lassell on October 10,1846, a brewer by trade, Lassell began making mirrors for his amateur telescope in 1820. When John Herschel received news of Neptunes discovery, he wrote to Lassell suggesting he search for possible moons, Lassell did so and discovered Triton eight days later. Lassell also claimed to have discovered rings, although Neptune was later confirmed to have rings, they are so faint and dark that it is doubtful that he actually saw them. Triton is named after the Greek sea god Triton, the son of Poseidon, the name was first proposed by Camille Flammarion in his 1880 book Astronomie Populaire, and was officially adopted many decades later. Until the discovery of the second moon Nereid in 1949, Triton was commonly referred to as the satellite of Neptune. Lassell did not name his own discovery, he successfully suggested the name Hyperion, previously chosen by John Herschel. Triton is unique among all large moons in the Solar System for its orbit around its planet. Most of the irregular moons of Jupiter and Saturn also have retrograde orbits. However, these moons are all much more distant from their primaries, and are small in comparison, Tritons orbit is associated with two tilts, the inclination of Neptunes spin to Neptunes orbit, 30°, and the inclination of Tritons orbit to Neptunes spin, 157°. Tritons orbit precesses forward relative to Neptunes spin with a period of about 678 Earth years and that inclination is currently 130°, Tritons orbit is now near its maximum departure from coplanarity with Neptunes. Tritons rotation is locked to be synchronous with its orbit around Neptune
20.
Ice
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Ice is water frozen into a solid state. Depending on the presence of such as particles of soil or bubbles of air. In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far away as the Oort cloud objects, beyond the Solar System, it occurs as interstellar ice. It falls as snowflakes and hail or occurs as frost, icicles or ice spikes, Ice molecules can exhibit up to sixteen different phases that depend on temperature and pressure. When water is cooled rapidly, up to three different types of ice can form depending on the history of its pressure and temperature. When cooled slowly correlated proton tunneling occurs below 20 K giving rise to macroscopic quantum phenomena, virtually all the ice on Earths surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice Ih with minute traces of cubic ice denoted as ice Ic. The most common phase transition to ice Ih occurs when water is cooled below 0°C at standard atmospheric pressure. It may also be deposited directly by water vapor, as happens in the formation of frost, the transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety of ways, including cooling, winter sports, as a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered a mineral. It possesses a regular crystalline structure based on the molecule of water, an unusual property of ice frozen at atmospheric pressure is that the solid is approximately 8. 3% less dense than liquid water. The density of ice is 0.9167 g/cm3 at 0 °C, liquid water is densest, essentially 1.00 g/cm³, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid, density of ice increases slightly with decreasing temperature and has a value of 0.9340 g/cm³ at −180 °C. When water freezes, it increases in volume and it is also a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes. The result of this process is that ice floats on liquid water, sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates an environment for bacterial and algal colonies. When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C, during the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the bonds between ice molecules. Energy becomes available to increase the thermal energy only after enough hydrogen bonds are broken that the ice can be considered liquid water, the amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion
21.
Geologic time scale
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The table of geologic time spans, presented here, agrees with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy. Evidence from radiometric dating indicates that Earth is about 4.54 billion years old, the geology or deep time of Earth’s past has been organized into various units according to events which took place in each period. Older time spans, which predate the reliable record, are defined by their absolute age. Some other planets and moons within the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus, Mars, dominantly fluid planets, such as the gas giants, do not preserve their history in a comparable manner. Apart from the Late Heavy Bombardment, events on other planets probably had little influence on the Earth. Construction of a scale that links the planets is, therefore, of only limited relevance to the Earths time scale. The existence, timing, and terrestrial effects of the Late Heavy Bombardment is still debated, the largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs, the terms eonothem, erathem, system, series, and stage are used to refer to the layers of rock that correspond to these periods of geologic time in Earths history. Geologists qualify these units as early, mid, and late when referring to time, and lower, middle, for example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology. The adjectives are capitalized when the subdivision is formally recognized, and lower case when not, thus early Miocene but Early Jurassic. Geologic units from the time but different parts of the world often look different and contain different fossils. For example, in North America the Lower Cambrian is called the Waucoban series that is subdivided into zones based on succession of trilobites. In East Asia and Siberia, the unit is split into Alexian, Atdabanian. A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology, the term Anthropocene is used informally by popular culture and a growing number of scientists to describe the current epoch in which we are living. The term was coined by Paul Crutzen and Eugene Stoermer in 2000 to describe the current time, others say that humans have not even started to leave their biggest impact on Earth, and therefore the Anthropocene hasnt even started yet. Whatever the case, the ICS has not officially approved the term, leonardo da Vinci concurred with Aristotles interpretation that fossils represented the remains of ancient life. The 11th-century Persian geologist Avicenna and the 13th-century Dominican bishop Albertus Magnus extended Aristotles explanation into a theory of a petrifying fluid. Avicenna also first proposed one of the principles underlying geologic time scales, the Chinese naturalist Shen Kuo also recognized the concept of deep time
22.
Viscosity
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The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the concept of thickness, for example. Viscosity is a property of the fluid which opposes the motion between the two surfaces of the fluid in a fluid that are moving at different velocities. For a given velocity pattern, the stress required is proportional to the fluids viscosity, a fluid that has no resistance to shear stress is known as an ideal or inviscid fluid. Zero viscosity is observed only at low temperatures in superfluids. Otherwise, all fluids have positive viscosity, and are said to be viscous or viscid. A fluid with a high viscosity, such as pitch. The word viscosity is derived from the Latin viscum, meaning mistletoe, the dynamic viscosity of a fluid expresses its resistance to shearing flows, where adjacent layers move parallel to each other with different speeds. It can be defined through the situation known as a Couette flow. This fluid has to be homogeneous in the layer and at different shear stresses, if the speed of the top plate is small enough, the fluid particles will move parallel to it, and their speed will vary linearly from zero at the bottom to u at the top. Each layer of fluid will move faster than the one just below it, in particular, the fluid will apply on the top plate a force in the direction opposite to its motion, and an equal but opposite one to the bottom plate. An external force is required in order to keep the top plate moving at constant speed. The magnitude F of this force is found to be proportional to the u and the area A of each plate. The proportionality factor μ in this formula is the viscosity of the fluid, the ratio u/y is called the rate of shear deformation or shear velocity, and is the derivative of the fluid speed in the direction perpendicular to the plates. Isaac Newton expressed the forces by the differential equation τ = μ ∂ u ∂ y, where τ = F/A. This formula assumes that the flow is moving along parallel lines and this equation can be used where the velocity does not vary linearly with y, such as in fluid flowing through a pipe. Use of the Greek letter mu for the dynamic viscosity is common among mechanical and chemical engineers. However, the Greek letter eta is used by chemists, physicists
23.
Fluid
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In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas, fluids are substances that have zero shear modulus, or, in simpler terms, a fluid is a substance which cannot resist any shear force applied to it. Although the term includes both the liquid and gas phases, in common usage, fluid is often used as a synonym for liquid. For example, brake fluid is hydraulic oil and will not perform its required incompressible function if there is gas in it and this colloquial usage of the term is also common in medicine and in nutrition. Liquids form a surface while gases do not. The distinction between solids and fluid is not entirely obvious, the distinction is made by evaluating the viscosity of the substance. Silly Putty can be considered to behave like a solid or a fluid and it is best described as a viscoelastic fluid. There are many examples of substances proving difficult to classify, a particularly interesting one is pitch, as demonstrated in the pitch drop experiment currently running at the University of Queensland. Fluids display properties such as, not resisting deformation, or resisting it only slightly, and these properties are typically a function of their inability to support a shear stress in static equilibrium. Solids can be subjected to stresses, and to normal stresses—both compressive. In contrast, ideal fluids can only be subjected to normal, real fluids display viscosity and so are capable of being subjected to low levels of shear stress. In a solid, shear stress is a function of strain, a consequence of this behavior is Pascals law which describes the role of pressure in characterizing a fluids state. The study of fluids is fluid mechanics, which is subdivided into fluid dynamics, matter Liquid Gas Bird, Byron, Stewart, Warren, Lightfoot, Edward
24.
Structure of the Earth
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The interior structure of the Earth is layered in spherical shells, like an onion. These layers can be defined by their chemical and their rheological properties, Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. The force exerted by Earths gravity can be used to calculate its mass, astronomers can also calculate Earths mass by observing the motion of orbiting satellites. Earth’s average density can be determined through gravitometric experiments, which have historically involved pendulums, the mass of Earth is about 6×1024 kg. The structure of Earth can be defined in two ways, by properties such as rheology, or chemically. Mechanically, it can be divided into lithosphere, asthenosphere, mesospheric mantle, outer core, chemically, Earth can be divided into the crust, upper mantle, lower mantle, outer core, and inner core. The core does not allow shear waves to pass through it, the changes in seismic velocity between different layers causes refraction owing to Snells law, like light bending as it passes through a prism. Likewise, reflections are caused by an increase in seismic velocity and are similar to light reflecting from a mirror. The crust ranges from 5–70 kilometres in depth and is the outermost layer, the thin parts are the oceanic crust, which underlie the ocean basins and are composed of dense iron magnesium silicate igneous rocks, like basalt. The thicker crust is continental crust, which is dense and composed of sodium potassium aluminium silicate rocks. The rocks of the crust fall into two major categories – sial and sima and it is estimated that sima starts about 11 km below the Conrad discontinuity. The uppermost mantle together with the crust constitutes the lithosphere, the crust-mantle boundary occurs as two physically different events. First, there is a discontinuity in the velocity, which is most commonly known as the Mohorovičić discontinuity or Moho. The cause of the Moho is thought to be a change in composition from rocks containing plagioclase feldspar to rocks that contain no feldspars. Earths mantle extends to a depth of 2,890 km, the mantle is divided into upper and lower mantle. The upper and lower mantle are separated by the transition zone, the lowest part of the mantle next to the core-mantle boundary is known as the D″ layer. The pressure at the bottom of the mantle is ≈140 GPa, the mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust. Although solid, the temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales
25.
Iron
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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, ruthenium 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 also 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, tissues, muscles, bone marrow, blood proteins, enzymes, ferritin, hemosiderin, 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 also been studied extensively
26.
Nickel
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Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a golden tinge. Nickel belongs to the metals and is hard and ductile. Meteoric nickel is found in combination with iron, a reflection of the origin of elements as major end products of supernova nucleosynthesis. An iron–nickel mixture is thought to compose Earths inner core, use of nickel has been traced as far back as 3500 BCE. Nickel was first isolated and classified as an element in 1751 by Axel Fredrik Cronstedt. The elements name comes from a mischievous sprite of German miner mythology, Nickel, an economically important source of nickel is the iron ore limonite, which often contains 1–2% nickel. Nickels other important ore minerals include garnierite, and pentlandite, major production sites include the Sudbury region in Canada, New Caledonia in the Pacific, and Norilsk in Russia. Nickel is slowly oxidized by air at room temperature and is considered corrosion-resistant, historically, it has been used for plating iron and brass, coating chemistry equipment, and manufacturing certain alloys that retain a high silvery polish, such as German silver. About 6% of world production is still used for corrosion-resistant pure-nickel plating. Nickel-plated objects sometimes provoke nickel allergy, Nickel has been widely used in coins, though its rising price has led to some replacement with cheaper metals in recent years. Nickel is one of four elements that are ferromagnetic around room temperature, alnico permanent magnets based partly on nickel are of intermediate strength between iron-based permanent magnets and rare-earth magnets. The metal is valuable in modern times chiefly in alloys, about 60% of world production is used in nickel-steels, other common alloys and some new superalloys comprise most of the remainder of world nickel use, with chemical uses for nickel compounds consuming less than 3% of production. As a compound, nickel has a number of chemical manufacturing uses. Nickel is a nutrient for some microorganisms and plants that have enzymes with nickel as an active site. Nickel is a metal with a slight golden tinge that takes a high polish. It is one of four elements that are magnetic at or near room temperature. Its Curie temperature is 355 °C, meaning that bulk nickel is non-magnetic above this temperature, the unit cell of nickel is a face-centered cube with the lattice parameter of 0.352 nm, giving an atomic radius of 0.124 nm
27.
Volcanism
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It includes all phenomena resulting from and causing magma within the crust or mantle of the body, to rise through the crust and form volcanic rocks on the surface. Magma from the mantle or lower crust rises through its crust towards the surface, if magma reaches the surface, its behavior depends on the viscosity of the molten constituent rock. Viscous magma produces volcanoes characterised by explosive eruptions, while non-viscous magma produce volcanoes characterised by effusive eruptions pouring large amounts of lava onto the surface, in some cases, rising magma can cool and solidify without reaching the surface. Instead, the cooled and solidified igneous mass crystallises within the crust to form an igneous intrusion, as magma cools the chemicals in the crystals formed are effectively removed from the main mix of the magma, so the chemical content of the remaining magma evolves as it solidifies slowly. Fresh unevolved magma injections can remobilise more evolved magmas, allowing eruptions from more viscous magmas, movement of molten rock in the mantle, caused by thermal convection currents, coupled with gravitational effects of changes on the earths surface drive plate tectonic motion and ultimately volcanism. Volcanoes are places where magma reaches the earths surface, the type of volcano depends on the location of the eruption and the consistency of the magma. These are formed where magma pushes between existing rock, intrusions can be in the form of batholiths, dikes, sills, earthquakes are generally associated with plate tectonic activity, but some earthquakes are generated as a result of volcanic activity. These are formed where water interacts with volcanism and these include geysers, fumaroles, hotsprings and mudpots, they are often used as a source of geothermal energy. The amount of gas and ash emitted by volcanic eruptions has a significant effect on the Earths climate, large eruptions correlate well with some significant climate change events. When the magma cools it solidifies and forms rocks, the type of rock formed depends on the composition of the magma. Magma that reaches the surface to become lava cools rapidly resulting in rocks with small crystals such as basalt, some of this magma may cool extremely rapidly and will form volcanic glass such as obsidian. Magma that remains trapped below ground in thin intrusions cools slower than magma exposed to the surface, magma that remains trapped in large quantities below ground cools most slowly resulting in rocks with larger crystals - such as granite and gabbro. Existing rocks that come into contact with magma may be melted and assimilated into the magma, other rocks adjacent to the magma may be altered by contact metamorphism or metasomatism as they are affected by the heat and escaping or externally circulating hydrothermal fluids. Volcanism is not confined only to Earth, but is thought to be found on any body having a solid crust, evidence of volcanism should still be found on any body that has had volcanism at some point in its history. It can be surmised that volcanism exists on planets and moons of this type in other systems as well. In 2014, scientists found 70 lava flows which formed on the Moon in the last 100 million years, bimodal volcanism Continental drift Hotspot Volcanic arc Glossary of Volcanic Terms. G. J. Hudak, University of Wisconsin Oshkosh,2001, crumpler, L. S. and Lucas, S. G. Volcanoes of New Mexico, An Abbreviated Guide For Non-Specialists. New Mexico Museum of Natural History and Science Bulletin, archived from the original on 2007-03-21
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Xenolith
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A xenolith is a rock fragment which becomes enveloped in a larger rock during the latters development and solidification. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement, a xenocryst is an individual foreign crystal included within an igneous body. Examples of xenocrysts are quartz crystals in a silica-deficient lava and diamonds within kimberlite diatremes, although the term xenolith is most commonly associated with igneous inclusions, a broad definition could include rock fragments which have become encased in sedimentary rock. Xenoliths are sometimes found in recovered meteorites, xenoliths and xenocrysts provide important information about the composition of the otherwise inaccessible mantle. Basalts, kimberlites, lamproites and lamprophyres, which have their source in the mantle, often contain fragments. Xenoliths of dunite, peridotite and spinel lherzolite in basaltic lava flows are one example, kimberlites contain, in addition to diamond xenocrysts, fragments of lherzolites of varying composition. The aluminium-bearing minerals of these fragments provide clues to the depth of origin, calcic plagioclase is stable to a depth of 25 km. Between 25 km and about 60 km, spinel is the stable aluminium phase, at depths greater than about 60 km, dense garnet becomes the aluminium-bearing mineral. Some kimberlites contain xenoliths of eclogite, which is considered to be the high-pressure metamorphic product of basaltic oceanic crust, the large-scale inclusion of foreign rock strata at the margins of an igneous intrusion is called a roof pendant. Blatt, Harvey, and Robert J. Tracy
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Asthenosphere
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The asthenosphere is the highly viscous, mechanically weak and ductilely deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between approximately 80 and 200 km below the surface, the Lithosphere-Asthenosphere boundary is usually referred to as LAB. The asthenosphere is generally solid, although some of its regions could be melted, the lower boundary of the asthenosphere is not well defined. The thickness of the asthenosphere depends mainly on the temperature, in some regions the asthenosphere could extend as deep as 700 km. It is considered the region of mid-ocean ridge basalt. The asthenosphere is a part of the mantle just below the lithosphere that is involved in plate tectonic movement. The lithosphere-asthenosphere boundary is taken at the 1300 °C isotherm, above which the mantle behaves in a rigid fashion. Seismic waves pass relatively slowly through the asthenosphere compared to the lithospheric mantle, thus it has been called the low-velocity zone. This decreasing in seismic waves velocity from lithosphere to asthenosphere could be caused by the presence of a small percentage of melt in the asthenosphere. The lower boundary of the LVZ lies at a depth of 180–220 km, in the old oceanic mantle the transition from the lithosphere to the asthenosphere, the so-called lithosphere-asthenosphere boundary is shallow with a sharp and large velocity drop. At the mid-ocean ridges the LAB rises to within a few kilometers of the ocean floor, the upper part of the asthenosphere is believed to be the zone upon which the great rigid and brittle lithospheric plates of the Earths crust move about. In this way, it flows like a current, radiating heat outward from the Earths interior. Above the asthenosphere, at the rate of deformation, rock behaves elastically and, being brittle, can break. The rigid lithosphere is thought to float or move about on the slowly flowing asthenosphere, an Introduction to the Solar System. San Diego State University, The Earths internal heat energy and interior structure
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Plasticity (physics)
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In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from elastic behavior to plastic behavior is called yield, plastic deformation is observed in most materials, particularly metals, soils, rocks, concrete, foams, bone and skin. However, the mechanisms that cause plastic deformation can vary widely. At a crystalline scale, plasticity in metals is usually a consequence of dislocations, such defects are relatively rare in most crystalline materials, but are numerous in some and part of their crystal structure, in such cases, plastic crystallinity can result. In brittle materials such as rock, concrete and bone, plasticity is caused predominantly by slip at microcracks, for many ductile metals, tensile loading applied to a sample will cause it to behave in an elastic manner. Each increment of load is accompanied by an increment in extension. When the load is removed, the returns to its original size. However, once the load exceeds a threshold – the yield strength – the extension increases more rapidly than in the region, now when the load is removed. Elastic deformation, however, is an approximation and its quality depends on the time frame considered, if, as indicated in the graph opposite, the deformation includes elastic deformation, it is also often referred to as elasto-plastic deformation or elastic-plastic deformation. Perfect plasticity is a property of materials to undergo irreversible deformation without any increase in stresses or loads, plastic materials with hardening necessitate increasingly higher stresses to result in further plastic deformation. Generally, plastic deformation is dependent on the deformation speed. Such materials are said to deform visco-plastically, the plasticity of a material is directly proportional to the ductility and malleability of the material. Plasticity in a crystal of pure metal is primarily caused by two modes of deformation in the lattice, slip and twinning. Slip is a deformation which moves the atoms through many interatomic distances relative to their initial positions. Twinning is the plastic deformation takes place along two planes due to a set of forces applied to a given metal piece. Most metals show more plasticity when hot than when cold, lead shows sufficient plasticity at room temperature, while cast iron does not possess sufficient plasticity for any forging operation even when hot. This property is of importance in forming, shaping and extruding operations on metals, most metals are rendered plastic by heating and hence shaped hot
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Lithosphere
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A lithosphere is the rigid, outermost shell of a terrestrial-type planet or natural satellite that is defined by its rigid mechanical properties. On Earth, it is composed of the crust and the portion of the mantle that behaves elastically on time scales of thousands of years or greater. The outermost shell of a planet, the crust, is defined on the basis of its chemistry. Earths lithosphere includes the crust and the uppermost mantle, which constitute the hard, the lithosphere is subdivided into tectonic plates. The uppermost part of the lithosphere that chemically reacts to the atmosphere, hydrosphere and biosphere through the forming process is called the pedosphere. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, the study of past and current formations of landscapes is called geomorphology. The concept of the lithosphere as Earth’s strong outer layer was described by A. E. H, love in his 1911 monograph Some problems of Geodynamics and further developed by Joseph Barrell, who wrote a series of papers about the concept and introduced the term lithosphere. The concept was based on the presence of significant gravity anomalies over continental crust and these ideas were expanded by Reginald Aldworth Daly in 1940 with his seminal work Strength and Structure of the Earth and have been broadly accepted by geologists and geophysicists. The temperature at which olivine begins to deform viscously is often used to set this isotherm because olivine is generally the weakest mineral in the upper mantle, the mantle part of the lithosphere consists largely of peridotite. The crust is distinguished from the mantle by the change in chemical composition that takes place at the Moho discontinuity. Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle and is denser than continental lithosphere, oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle and causes the oceanic lithosphere to become increasingly thick, the thickness of the mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time. H ∼2 κ t Here, h is the thickness of the mantle lithosphere, κ is the thermal diffusivity for silicate rocks. The age is equal to L/V, where L is the distance from the spreading centre of mid-oceanic ridge. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years and this is because the chemically differentiated oceanic crust is lighter than asthenosphere, but thermal contraction of the mantle lithosphere makes it more dense than the asthenosphere. New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones, geoscientists can directly study the nature of the subcontinental mantle by examining mantle xenoliths brought up in kimberlite, lamproite, and other volcanic pipes. The histories of these xenoliths have been investigated by many methods, such studies have confirmed that mantle lithospheres below some cratons have persisted for periods in excess of 3 billion years, despite the mantle flow that accompanies plate tectonics. Cryosphere Geosphere Kola Superdeep Borehole Plate tectonics Solid Earth Chernicoff, Stanley, Whitney, earths Crust, Lithosphere and Asthenosphere Crust and Lithosphere
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Ringwoodite
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Ringwoodite is a high-pressure phase of Mg2SiO4 formed at high temperatures and pressures of the Earths mantle between 525 and 660 km depth. It is polymorphous with the olivine phase forsterite, ringwoodite is notable for being able to contain hydroxide ions within its structure. This mineral was first identified in the Tenham meteorite in 1969, olivine, wadsleyite, and ringwoodite are polymorphs found in the upper mantle of the earth. At depths greater than about 660 km, other minerals, including some with the structure, are stable. The properties of these minerals determine many of the properties of the mantle, ringwoodite is polymorphous with forsterite, 2SiO4, and has a spinel structure. Spinel group minerals crystallize in the system with an octahedral habit. Ringwoodite is thought to be the most abundant mineral phase in the part of Earth’s transition zone. The physical and chemical property of this mineral partly determine properties of the mantle at those depths, the pressure range for stability of ringwoodite lies in the approximate range from 18 to 23 GPa. Apart from the mantle, natural ringwoodite has been found in many shocked chondritic meteorites, natural ringwoodite generally contains much more Mg than Fe but can form a gapless solid solution series from the pure Mg endmember to the pure Fe endmember. The latter has been discovered in a sample only recently and was named ahrensite. In meteorites, ringwoodite occurs in the veinlets of quenched shock-melt cutting the matrix, in Earths interior, olivine occurs in the upper mantle at depths less than about 410 km, and ringwoodite is inferred to be present within the transition zone from about 520 to 660 km depth. Seismic activity discontinuities at about 410 km,520 km, and at 660 km depth have been attributed to phase changes involving olivine, the solubility of hydroxide in ringwoodite is important because of the effect of hydrogen upon rheology. Ringwoodite synthesized at conditions appropriate for the zone has been found to contain up to 2.6 weight percent water. In regions of subduction zones, the stability field hosts high levels of seismicity. The gemstone, about 5mm long, was blasted up from the depths by a diatreme eruption, the ringwoodite inclusion is too small to see with the eye. The mantle reservoir is found to contain about three times more water, in the form of hydroxide contained within the wadsleyite and ringwoodite crystal structure, ringwoodite crystallizes in the isometric crystal system with space group Fd3m. On an atomic scale, magnesium and silicon are in octahedral and tetrahedral coordination with oxygen, the Si-O and Mg-O bonds are both ionic and covalent. The cubic unit cell parameter is 8.063 Å for pure Mg2SiO4 and 8.234 Å for pure Fe2SiO4, ringwoodite compositions range from pure Mg2SiO4 to Fe2SiO4 in synthesis experiments
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World ocean
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The unity and continuity of the World Ocean, with relatively free interchange among its parts, is of fundamental importance to oceanography. In turn, oceanic waters are interspersed by many smaller seas, gulfs, a global ocean has existed in one form or another on Earth for eons, and the notion dates back to classical antiquity in the form of Oceanus. The contemporary concept of the World Ocean was coined in the early 20th century by the Russian oceanographer Yuly Shokalsky to refer to the ocean that covers. If viewed from the pole of Earth, the Atlantic, Indian. Farther north, the Atlantic opens into the Arctic Ocean, which is connected to the Pacific by the Bering Strait, the Pacific Ocean, the largest of the oceans, also reaches northward from the Southern Ocean to the Arctic Ocean. It spans the gap between Australia and Asia, and the Americas, the Pacific Ocean meets the Atlantic Ocean south of South America at Cape Horn. The Atlantic Ocean, the second largest, extends from the Southern Ocean between the Americas, and Africa and Europe, to the Arctic Ocean, the Atlantic Ocean meets the Indian Ocean south of Africa at Cape Agulhas. The Indian Ocean, the third largest, extends northward from the Southern Ocean to India, the Indian Ocean joins the Pacific Ocean to the east, near Australia. The Arctic Ocean is the smallest of the five and it joins the Atlantic Ocean near Greenland and Iceland and joins the Pacific Ocean at the Bering Strait. It overlies the North Pole, touching North America in the Western Hemisphere, the Arctic Ocean is partially covered in sea ice, the extent of which varies according to the season. The Southern Ocean is an ocean surrounding Antarctica, dominated by the Antarctic Circumpolar Current. The Southern Ocean is partially covered in sea ice, the extent of which according to the season. The Southern Ocean is the second smallest of the five named oceans, plate tectonics, post-glacial rebound and sea level rise continually change the coastline and structure of the world ocean. Superocean World Ocean Atlas Chekin, L.2002, the world ocean in medieval cartography. Vavilov Institute of the History of Science and Technology of the Russian Academy of Sciences, the Columbia Encyclopedia, 6th ed.2003. New York, Columbia University Press, also, Danabasoglu, Gokhan, McWilliams, the role of mesoscale tracer transports in the global ocean circulation. Boyer, Timothy P. and Stephens, Cathy, warming of the world ocean, abstract, article. Maps of the world ocean
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Gros Morne National Park
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Gros Morne National Park is a world heritage site located on the west coast of Newfoundland. At 1,805 km2, it is the second largest national park in Atlantic Canada, it is surpassed by Torngat Mountains National Park, the park takes its name from Newfoundlands second-highest mountain peak located within the park. Its French meaning is large mountain standing alone, or more literally great sombre, Gros Morne is a member of the Long Range Mountains, an outlying range of the Appalachian Mountains, stretching the length of the islands west coast. It is the remnants of a mountain range formed 1.2 billion years ago. The park provides an example of the process of continental drift, where deep ocean crust. The Gros Morne National Park Reserve was established in 1973, and was made a park on October 1,2005. The park was the subject of a film in 2011s National Parks Project, directed by Sturla Gunnarsson and scored by Melissa Auf der Maur, Sam Shalabi. The park is located in the Great Northern Peninsula of Western Newfoundland and this peninsula is referred to as the Humber Zone, a Miogeocline, the Highlands of which contain the largest external basement massif of the Grenville Orogeny in the Appalachian Orogen. This Precambrian basement is known as the Long Range Inlier, Long Range Complex or Basement Gneiss Complex, big Level lie within this Inlier. Finally, a Pleistocene ice cap flowed radially across the island, the Tablelands, found between the towns of Trout River and Woody Point in south west of Gros Morne National Park, look more like a barren desert than traditional Newfoundland. This is due to the ultramafic rock – peridotite – which makes up the Tablelands and it is thought to originate in the Earths mantle and was forced up from the depths during a plate collision several hundred million years ago. Peridotite lacks the usual nutrients required to sustain most plant life, the rock is very low in calcium, very high in magnesium, and has toxic amounts of heavy metals. Peridotite is also high in iron, which accounts for its brownish colour, underneath this weathered zone, the rock is really a dark green colour. The many soil associations mapped in the park reflect the variety of bedrock. The Silver Mountain soil association, dominant in the area, is a very stony sandy loam developed on glacial till overlying granite, granitic gneiss. Similar rocks underlie the St. Pauls Inlet association farther west, sedimentary rocks in the southeastern sector support the North Lake association of stony sandy loam. An association of mostly-shallow loam, the Coxs Cove, occupies a band over shale, slate. The coastal strip north of Bonne Bay is mostly underlain by the peaty Gulls Marsh association, the stony infertile soils of the ultramafic tablelands south of Bonne Bay belong to the Serpentine Range association
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Provinces and territories of Canada
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Canadas geography is divided into administrative divisions known as provinces and territories that are responsible for delivery of sub-national governance. Over its history, Canadas international borders have changed several times, the ten provinces are Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, Quebec, and Saskatchewan. Several of the provinces were former British colonies, Quebec was originally a French colony, the three territories are Northwest Territories, Nunavut, and Yukon, which govern the rest of the area of the former British North America. Together, the provinces and territories make up the worlds second-largest country by area, the powers flowing from the Constitution Act are divided between the federal government and the provincial governments to exercise exclusively. In modern Canadian constitutional theory, the provinces are considered to be co-sovereign divisions, the territories are not sovereign, but simply part of the federal realm, and have a commissioner who represents the federal government. Notes, There are three territories in Canada, unlike the provinces, the territories of Canada have no inherent sovereignty and have only those powers delegated to them by the federal government. They include all of mainland Canada north of latitude 60° north and west of Hudson Bay, the following table lists the territories in order of precedence. Prior to Confederation, Ontario and Quebec were united as the Province of Canada, over the following years, Manitoba, British Columbia, and Prince Edward Island were added as provinces. The Hudsons Bay Company controlled large swathes of western Canada referred to as Ruperts Land and the North-Western Territory until 1870, subsequently, the area was re-organized into the province of Manitoba and the Northwest Territories. The remaining Arctic islands were transferred by Britain to Canada in 1880,1898 saw the Yukon Territory, later renamed simply as Yukon, carved from the parts of the Northwest Territories surrounding the Klondike gold fields. On September 1,1905, a portion of the Northwest Territories south of the 60th parallel north became the provinces of Alberta and Saskatchewan. In 1912, the boundaries of Quebec, Ontario and Manitoba were expanded northward, Manitobas to the 60° parallel, Ontarios to Hudson Bay, in 1907, Newfoundland acquired dominion status. In the middle of the Great Depression in Canada with Newfoundland facing a period of economic crisis. In 2001, it was officially renamed Newfoundland and Labrador, in 1903, the Alaska Panhandle Dispute fixed British Columbias northwestern boundary. This was one of two provinces in Canadian history to have its size reduced. In 1999, Nunavut was created from the portion of the Northwest Territories. Yukon lies in the portion of The North, while Nunavut is in the east. All three territories combined are the most sparsely populated region in Canada, covering 3,921,739 km2 in land area and they are often referred to as a single region, The North, for organisational and economic purposes
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Newfoundland and Labrador
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Newfoundland and Labrador is the most easterly province of Canada. Situated in the countrys Atlantic region, it comprises the island of Newfoundland and mainland Labrador to the northwest, in 2013, the provinces population was estimated at 526,702. About 92% of the population lives on the island of Newfoundland. The province is Canadas most linguistically homogeneous, with 97. 6% of residents reporting English as their mother tongue in the 2006 census, historically, Newfoundland was also home to unique varieties of French and Irish, as well as the extinct Beothuk language. In Labrador, local dialects of Innu-aimun and Inuktitut are also spoken, Newfoundland and Labradors capital and largest city, St. Johns, is Canadas 20th-largest census metropolitan area and is home to almost 40 percent of the provinces population. St. Johns is the seat of government, home to the House of Assembly of Newfoundland and Labrador and to the highest court in the jurisdiction and it became the tenth province to enter the Canadian Confederation on March 31,1949, as Newfoundland. On December 6,2001, an amendment was made to the Constitution of Canada to change the official name to Newfoundland. The name Newfoundland is a translation of the Portuguese Terra Nova, the influence of early Portuguese exploration is also reflected in the name of Labrador, which derives from the surname of the Portuguese navigator João Fernandes Lavrador. Newfoundland and Labrador is the most easterly province in Canada, and is located at the corner of North America. The Strait of Belle Isle separates the province into two divisions, Labrador, which is a large area of mainland Canada, and Newfoundland. The province also includes over 7,000 tiny islands, each side is about 400 km long, and its area is 108,860 km2. Newfoundland and its small islands have a total area of 111,390 km2. Newfoundland extends between latitudes 46°36′N and 51°38′N, Labrador is an irregular shape, the western part of its border with Quebec is the drainage divide of the Labrador Peninsula. Lands drained by rivers that flow into the Atlantic Ocean are part of Labrador, most of Labradors southern boundary with Quebec follows the 52nd parallel of latitude. Labradors extreme northern tip, at 60°22′N, shares a border with Nunavut. Together, Newfoundland and Labrador make up 4. 06% of Canadas area, Labrador is the easternmost part of the Canadian Shield, a vast area of ancient metamorphic rock comprising much of northeastern North America. Colliding tectonic plates have shaped much of the geology of Newfoundland, gros Morne National Park has a reputation as an outstanding example of tectonics at work, and as such has been designated a World Heritage Site. The Long Range Mountains on Newfoundlands west coast are the northeasternmost extension of the Appalachian Mountains, the north-south extent of the province, prevalent westerly winds, cold ocean currents and local factors such as mountains and coastline combine to create the various climates of the province
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Macquarie Island
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Macquarie Island, a UNESCO World Heritage Site, lies in the southwest Pacific Ocean, about halfway between New Zealand and Antarctica, at 54°30 S, 158°57 E. Politically a part of Tasmania, Australia, since 1900, it became a Tasmanian State Reserve in 1978 and was inscribed on the World Heritage List in 1997 and it was a part of Esperance Municipality until 1993 when the municipality was merged with other municipalities to Huon Valley. The island is home to the royal penguin population during their annual nesting season. Ecologically, the island is part of the Antipodes Subantarctic Islands tundra ecoregion, since 1948 the Australian Antarctic Division has maintained a permanent base, the Macquarie Island Station, on the isthmus at the northern end of the island at the foot of Wireless Hill. The population of the base, the only human inhabitants. A heliport is located near the base, in September 2016, the Australian Antarctic Division confirmed it will close its research station on the island in 2017. The Australian/Briton Frederick Hasselborough discovered the uninhabited island accidentally on 11 July 1810 when looking for new sealing grounds and he claimed Macquarie Island for Britain and annexed it to the colony of New South Wales in 1810. The island took its name after Colonel Lachlan Macquarie, Governor of New South Wales from 1810 to 1821, Hasselborough reported a wreck of ancient design, which has given rise to speculation that the island may have been visited before by Polynesians or others. Fabian Gottlieb von Bellingshausen, who explored the area for Alexander I of Russia, Bellingshausen landed on the island on 28 November 1820, defined its geographical position and traded his rum and food for Macquarie Islands fauna with the sealers. Between 1810 and 1919, seals and then penguins were hunted almost to the point of extinction, the conditions on the island and the surrounding seas were considered so harsh that a plan to use it as a penal settlement was rejected. In 1877, the crew of the schooner Bencleugh was shipwrecked on the islands for four months, the ships owner, John Sen Inches Thomson, wrote a book on his sea travels, including his time on the island. The book, written in 1912, was entitled Voyages and Wanderings In Far-off Seas, in 1890, New South Wales transferred the island to Tasmania, which leased it to Joseph Hatch between 1902 and 1920 for his oil industry based on harvesting penguins. Between 1911 and 1914, the became a base for the Australasian Antarctic Expedition under Sir Douglas Mawson. George Ainsworth operated a station between 1911 and 1913, followed by Harold Power and by Arthur Tulloch from 1914 until it was shut down in 1915. The Australian National Antarctic Research Expeditions established its headquarters on 25 May 1948 on Macquarie Island. The island had status as a reserve under the Man. On 23 December 2004, an earthquake measuring 8.1 on the moment magnitude scale rocked the island, geoscience Australia issued a Tsunami Inundation Advice for Macquarie Island Station. Such a tsunami would likely affect other parts of the coastline, such a significant earthquake at Macquarie Island capable of causing such a tsunami is a high risk according to several papers
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Saint Peter and Saint Paul Archipelago
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The Saint Peter and Saint Paul Archipelago is a group of 15 small islets and rocks in the central equatorial Atlantic Ocean. It lies in the Intertropical Convergence Zone, a region of the Atlantic characterized by low average winds punctuated with local thunderstorms, the islets expose serpentinized abyssal mantle peridotite and kaersutite-bearing ultramafic mylonite atop the worlds highest and yet only second largest megamullion. This grouping is the location in the Atlantic Ocean where the abyssal mantle is exposed above sea level. In 1986, the archipelago was designated a protected area. This is now part of the Fernando de Noronha Environmental Protection Area, since 1998, the Brazilian Navy has maintained a permanently manned research facility on the islands. The main economic activity around the islets is tuna fishing, on April 20,1511, a Portuguese Navy fleet composed of six caravels under the command of Captain Garcia de Noronha discovered the islets by accident while on their journey to India. While navigating in open sea at night, the Saint Peter caravel, under the command of Captain Manuel de Castro Alcoforado. The crew was rescued by the Saint Paul caravel, forming the name given to the islets, on the morning of February 16,1832, the rocks were visited by Charles Darwin on the first leg of his voyage on HMS Beagle around the world. Darwin listed all the fauna he could find, noting that not a plant or even a lichen could be found on the island. Darwin found two birds, a booby and a noddy, a crab that stole the fish intended for baby birds, a fly that lived on the booby. He found a moth that lived on feathers, a beetle, a woodlouse that lived on dung, Darwin felt that these rocks represented how life first took hold on a newly formed outcrop. Darwin was correct in noting that, unusually, these islands were not volcanic. Darwins account formed the basis of an episode in Patrick OBrians historical novel HMS. Surprise, when the naturalist Stephen Maturin is briefly marooned and survives by drinking fouled rainwater, the then called “St. Pauls Rocks” were visited by James Clark Ross on 29 November 1839. He was in charge of an expedition to the Antarctic regions with two vessels, the HMS Erebus and the HMS Terror, robert McCormick gave some geological and biological remarks on St. Pauls Rocks in the report on the expedition. Another famous person to visit the rocks was Ernest Shackleton, on his last expedition to Antarctica, in 1942, during World War II, the islets were declared to be part of the Federal Territory of Fernando de Noronha. In early 1960, the served as the starting-point and terminus for the first submerged circumnavigation of the world by the American nuclear-powered submarine USS Triton. On June 25,1998, the Brazilian Navy inaugurated the Saint Peter, the station is manned with four researchers, who are rotated in and out every 15 days
39.
Lizard Complex
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The Lizard Complex, Cornwall is generally accepted to represent a preserved example of an exposed ophiolite complex in the United Kingdom. The rocks found in The Lizard area are analogous to those found in such areas as the Troodos Mountains, Cyprus. The Lizard comprises three units, the serpentinites, the oceanic complex and the metamorphic basement. The serpentinites are actually the metamorphosed and deformed remains of the layers of the mantle. The metamorphosis has in most cases taken the form of deformation and serpentinisation. In many cases the rocks have also been subject to varying degrees of later brittle deformation, pre-deformation they would have been a combination of undepleted mantle in the form of lherzolite peridotite and depleted harzburgite mantle from which basaltic phases had been removed. In the area of Ogo dour at the Northern reaches of Predannack, dunite and they believed that the foliations were the result of mass flux within the cooling magma body, and that the different types of serpentinite were the result of an igneous cooling alteration rim. The oceanic complex consists of the Crousa Gabbro, locally intruded by a suite of dolerite dykes, the hornblende schist, found in contact with the serpentine mass directly to the North and to the South is the metamorphic remnant of basaltic intrusives into the upper crust. It is typified by a texture and visible crystals of black or dark green hornblende. Structural studies of the hornblende schist indicate that it has been subject to at least three stages of deformation, folding of the schist at Housel Bay indicates that the formation was also subject to more than one subsequent stage of shear stress. On the South-east tip of the Lizard the hornblende schist is inter-bedded with pale yellow/green veins and these bands can extend laterally for many metres and lie in line with the schistose foliations of the surrounding rock. Chemical analysis of the schist draws parallels between it and mantle-derived material found at mid-ocean-ridge and back-arc settings, the basement comprises a group of schists and gneisses of the Old Lizard Head Series and the Man of War gneisses. The Man of War Gneiss is interpreted as a sequence of metamorphosed igneous rocks, locally thrust contacts can be seen showing evidence of northwestward movement between parts of the ophiolite and between the ophiolitic rocks and the metamorphic basement. It has been suggested that the Kennack Gneiss was formed by partial melting during the obduction of the ophiolite onto the continental crust. Although an earlier stage of hot emplacement is not ruled out, it is now accepted that in the final stage of emplacement, during the Variscan orogeny. The formation of the oceanic crust found at the Lizard, its obduction and this is based on U-Pb dating of zircons from various parts of the complex. The Lizard Guidebook Friendly Guides ISBN 978-1-904645-06-1 Geology of Cornwall A virtual field trip to the Lizard, from the Camborne School of Mines Virtual Museum
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Semail Ophiolite
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It is located on the eastern corner of the Arabian Peninsula and covers an area of approximately 100,000 km2. Based on uranium-lead dating techniques, the Semail Ophiolite formed in the Late Cretaceous and it is primarily made of silicate rocks with content ranging from 45–77 wt%. The Semail Ophiolite is important because it is rich in copper and chromite ore bodies also provides information about the ocean floor. Geologists have studied the area attempting to find the best model explaining the formation of the Semail Ophiolite, the Arabian continental margin formed in early Paleozoic and possibly late Proterozoic. After that the thrust sheets are from low to high structurally, The autochthonous units, the allochthonous unite from low to high structurally, The Sumeini group, the Hawasina complex, the Haybi complex, the Ophiolite, and the Batinah complex. From the Sumeini group to the Haybi Complex make up the slope with an age range from Middle Triassic to Late Cretaceous. The ophiolite formed in the Late Cretaceous and consists of a basal metamorphic sole, peridotite tectonic, igneous peridotite and gabbro, sheeted dikes, lavas. The Batinah complex containing continental margin sediments came from beneath the ophiolite during late-stage extensional faulting and this requires an elevated source region, which presents difficulties. The suprasubduction model, The obduction of an arc-trench gap ophiolite due to the collision of a volcanic arc, also, that is where the proto Semail Ophiolite and volcanism starts to form a volcanic arc. Figure 2-B, from 95 to 87 Ma the mid-ocean ridge is spreading, figure 2-C, from 87 to 76 Ma the mid-ocean ridge is spreading and the ocean lithosphere being pushed and over thrusted the continental lithosphere by the help of the volcanic arc. The obducting model, The oceanic lithosphere over thrust continental lithosphere, figure 3-A, older than 101 to 95 Ma the mid-ocean ridge is spreading and the oceanic lithosphere subducted under both continental lithosphere. The Semail Ophiolite initial place is marked on the oceanic lithosphere. Figure 3-B, from 95 to 87 Ma the mid-ocean ridge stopped spreading, where the left oceanic lithosphere subducted under the right oceanic lithosphere with the Semail Ophiolite, which are accreted at amphibolite facies conditions at the base of the Semail Ophiolite. This model is supported by geologists. Samail Ophiolite Detachment and Emplacement, Mechanisms and Timing
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Ophiolite
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An ophiolite is a section of the Earths oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. Ophio is Greek for snake, and lite means stone from the Greek lithos, the term was little-used in other areas until the late 1950s to early 1960s, with the recognition that this assemblage provided an analog for oceanic crust and the process of seafloor spreading. Moores and Vine concluded that the dike complex at Troodos could form only by a process similar to the seafloor spreading proposed by Vine. Thus, it widely accepted that ophiolites represent oceanic crust that had been emplaced on land. This insight was one of the pillars of plate tectonics, and ophiolites have always played a central role in plate tectonic theory. The stratigraphic sequence observed in ophiolites corresponds to the processes at mid-oceanic ridges, Sediments, muds. Extrusive sequence, basaltic pillow lavas show magma/seawater contact, sheeted dike complex, vertical, parallel dikes that fed lavas above. High level intrusives, isotropic gabbro, indicative of fractionated magma chamber, layered gabbro, resulting from settling out of minerals from a magma chamber. Cumulate peridotite, dunite-rich layers of minerals that settled out from a magma chamber, the Penrose field conference on ophiolites in 1972 redefined the term ophiolite to include only the igneous rocks listed above, excluding the sediments formed independently of the crust they sit on. Oceanic crust has a layered velocity structure that implies a layered rock series similar to that listed above, in detail there are problems, with many ophiolites exhibiting thinner accumulations of igneous rock than are inferred for oceanic crust. Another problem relating oceanic crust and ophiolites is that the thick layer of ophiolites calls for large magma chambers beneath mid-ocean ridges. Seismic sounding of mid-ocean ridges has revealed only a few magma chambers beneath ridges, a few deep drill holes into oceanic crust have intercepted gabbro, but it is not layered like ophiolite gabbro. For example, plagioclase, pyroxenes, and olivine in the dikes and lavas will alter to albite, chlorite. Thus there is reason to believe that ophiolites are indeed oceanic mantle and crust, however and these chemical differences extend to a range of trace elements as well. The crystallization order of feldspar and pyroxene in the gabbros is reversed, indeed, there is increasing evidence that most ophiolites are generated when subduction begins and thus represent fragments of fore-arc lithosphere. This led to introduction of the term supra-subduction zone ophiolite in the 1980s to acknowledge that some ophiolites are more related to island arcs than ocean ridges. A fore-arc setting for most ophiolites also solves the problem of how oceanic lithosphere can be emplaced on top of continental crust. Most ophiolites can be divided one of two groups, Tethyan and Cordilleran
