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Arc-continent
A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin. The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops. The magmatism and petrogenesis of continental crust are complicated: in essence, continental arcs reflect a mixture of oceanic crust materials, mantle wedge and continental crust materials. Origin When two tectonic plates collide, relatively denser oceanic crust will be subducted under relatively lighter continental crust. Because of the subduction process, the relatively cooler oceanic crust, along with water, is subducted to the asthenosphere, where pressures and temperatures are much higher than the surface of Earth. Under such conditions, the downgoing plate releases volatiles such as H2O and CO2, which cause partial melti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc located further from the subducting plate than the trench. The oceanic plate is saturated with water, mostly in the form of hydrous minerals such as micas, amphiboles, and serpentine minerals. As the oceanic plate is subducted, it is subjected to increasing pressure and temperature with increasing depth. The heat and pressure break down the hydrous minerals in the plate, releasing water into the overlying mantle. Volatiles such as water drastically lower the melting point of the mantle, causing some of the mantle to melt and form magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone. Volcanic arcs are distinct from volcanic chains formed over hotspots in the middle of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust. Geological significance Igneous and metamorphic rocks make up 90–95% of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fractional Crystallization (geology)
Fractional crystallization, or crystal fractionation, is one of the most important geochemical and physical processes operating within crust and mantle of a rocky planetary body, such as the Earth. It is important in the formation of igneous rocks because it is one of the main processes of magmatic differentiation. Fractional crystallization is also important in the formation of sedimentary evaporite rocks. Igneous rocks Fractional crystallization is the removal and segregation from a melt of mineral precipitates; except in special cases, removal of the crystals changes the composition of the magma. In essence, fractional crystallization is the removal of early formed crystals from an originally homogeneous magma (for example, by gravity settling) so that these crystals are prevented from further reaction with the residual melt. The composition of the remaining melt becomes relatively depleted in some components and enriched in others, resulting in the precipitation of a sequen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underplating
Magmatic underplating occurs when basaltic magmas are trapped during their rise to the surface at the Mohorovičić discontinuity or within the Crust (geology), crust. Entrapment (or 'stalling out') of magmas within the crust occurs due to the difference in relative densities between the rising magma and the surrounding rock. Magmatic underplating can be responsible for thickening of the crust when the magma cools. geophysics, Geophysical seismology, seismic studies (as well as igneous petrology and geochemistry) utilize the differences in densities to identify underplating that occurs at depth. Evidence Magmatic underplating has been identified using multiple techniques that are non-specific to the area in which they are used. Geochemistry allows geologists to determine levels of association between igneous units: in the Karoo Province of southern Africa, large volumes of rhyolite along the continental margin were produced from melts with initially basaltic compositions. Xenoliths ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithophile
Lithophiles are micro-organisms that can live within the pore interstices of sedimentary rock, sedimentary and even fractured igneous rock, igneous rocks to depths of several kilometers. Some are known to live on surface rocks, and make use of photosynthesis for energy. Those that live in deeper rocks cannot use photosynthesis to gather energy, but instead extract energy from minerals around them. They live in cracks in the rock where water seeps down. The water contains dissolved carbon dioxide (CO2) which the organisms use for their carbon needs. They have been detected in rocks down to depths of nearly three km, where the temperature is approximately 75 °C. Terrestrial lithophiles can be found in canyons primarily composed of granite, an igneous rock, and soils saturated with fractured rock. Organisms from the genus ''Elliptochloris'', a subaerial photosynthetic green algae, demonstrate lithophilic preferences through colonization in granite cracks and in proximity to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tholeiitic Basalt
The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt, ferro-basalt, tholeiitic basaltic andesite, tholeiitic andesite, dacite and rhyolite. The variety of basalt in the series was originally called ''tholeiite'' but the International Union of Geological Sciences recommends that ''tholeiitic basalt'' be used in preference to that term.Le Maitre ''et al.'' 2002 Tholeiitic rock types tend to be more enriched in iron and less enriched in aluminium than calc-alkaline rock types. They are thought to form in a less oxidized environment than calc-alkaline rocks. Tholeiitic basalt is formed at mid-ocean ridges and makes up much of the oceanic crust. Almost all the basalt found on the Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickly on the surface. For this reason, olivine has been proposed as a good candidate for accelerated weathering to sequester carbon dioxide from the Earth's oceans and atmosphere, as part of climate change mitigation. Olivine also has many other historical uses, such as the gemstone peridot (or chrysolite), as well as industrial applications like metalworking processes. The ratio of magnesium to iron varies between the two endmembers of the solid solution series: forsterite (Mg-endmember: ) and fayalite (Fe-endmember: ). Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and fayalite (Fa) (''e.g.'', Fo70Fa30). Forsterite's melting temperature is unusually high at atmospheric pressure, almost , while ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehydration
In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers. Most people can tolerate a 3-4% decrease in total body water without difficulty or adverse health effects. A 5-8% decrease can cause fatigue and dizziness. Loss of over ten percent of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs at a loss of between fifteen and twenty-five percent of the body water.Ashcroft F, Life Without Water in Life at the Extremes. Berkeley and Los Angeles, 2000, 134-138. Mild dehydration is characterized by thirst and general discomfort and is usually resolved with oral rehydration. Dehydration can cause hypernatremia (high levels of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Arc Sketch
Continental may refer to: Places * Continent, the major landmasses of Earth * Continental, Arizona, a small community in Pima County, Arizona, US * Continental, Ohio, a small town in Putnam County, US Arts and entertainment * ''Continental'' (album), an album by Saint Etienne * Continental (card game), a rummy-style card game * ''Continental'' (film), a 2013 film * Continental Singers, a Christian music organization Companies * Continental AG, a German automotive parts and technologies manufacturer * Continental Airlines, a former American airline * Continental Electronics, an American radio transmitter manufacturer * Continental Films, a German-controlled French film company during the Nazi occupation of France * Continental Illinois, a defunct large bank * Continental Mortgage and Loan Company (later known as Continental, Inc.), the former name of HomeStreet Bank * Continental Motors, Inc., a Chinese manufacturer of aircraft engines * Continental Records, a former Ameri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underplating
Magmatic underplating occurs when basaltic magmas are trapped during their rise to the surface at the Mohorovičić discontinuity or within the Crust (geology), crust. Entrapment (or 'stalling out') of magmas within the crust occurs due to the difference in relative densities between the rising magma and the surrounding rock. Magmatic underplating can be responsible for thickening of the crust when the magma cools. geophysics, Geophysical seismology, seismic studies (as well as igneous petrology and geochemistry) utilize the differences in densities to identify underplating that occurs at depth. Evidence Magmatic underplating has been identified using multiple techniques that are non-specific to the area in which they are used. Geochemistry allows geologists to determine levels of association between igneous units: in the Karoo Province of southern Africa, large volumes of rhyolite along the continental margin were produced from melts with initially basaltic compositions. Xenoliths ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subcontinental Lithospheric Mantle
The subcontinental lithospheric mantle (SCLM) is the uppermost solid part of Earth's mantle associated with the continental lithosphere. The modern understanding of the Earth's upper mantle is that there are two distinct components - the lithospheric part and the asthenosphere. The lithosphere, which includes the continental plates, acts as a brittle solid whereas the asthenosphere is hotter and weaker due to mantle convection. The boundary between these two layers is rheologically based and is not necessarily a strict function of depth. Specifically, oceanic lithosphere (lithosphere underneath the oceanic plates) and subcontinental lithosphere, is defined as a mechanical boundary layer that heats via conduction and the asthenosphere is a convecting adiabatic layer. In contrast to oceanic lithosphere, which experiences quicker rates of recycling, subcontinental lithosphere is chemically distinct, cold, and older. This translated into the differences between the SCLM and the o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy. Earth's lithosphere Earth's lithosphere, which constitutes the hard and rigid outer vertical layer of the Earth, includes the crust and the uppermost mantle. The lithosphere is underlain by the asthenosphere which is the weaker, hotter, and deeper part of the upper mantle. The lithosphere–asthenosphere boundary is defined by a difference in response to stress. The lithosphere remains rigid for very long periods of geologic time in which it deforms elastically and through brittle failure, while the asthenosphere deforms viscously and accommodates strain through plastic deformation. The thickness of the lithosphere is thus considered to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
