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Core–mantle Boundary
The core–mantle boundary (CMB) of Earth lies between the planet's silicate mantle and its liquid iron-nickel outer core. This boundary is located at approximately 2,891 km (1,796 miles) depth beneath Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth due to the differences between the acoustic impedances of the solid mantle and the molten outer core. P-wave velocities are much slower in the outer core than in the deep mantle while S-waves do not exist at all in the liquid portion of the core. Recent evidence suggests a distinct boundary layer directly above the CMB possibly made of a novel phase of the basic perovskite mineralogy of the deep mantle named post-perovskite. Seismic tomography studies have shown significant irregularities within the boundary zone and appear to be dominated by the African and Pacific Large Low-Shear-Velocity Provinces (LLSVP). The uppermost section of the outer core is thought to be about 500 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slice Earth
Slice may refer to: *Cutting Food and beverage *A portion of bread, pizza, cake, or meat that is cut flat and thin: :*Sliced bread :* Pizza by the slice, a fast food dish *Slice (drink), a line of fruit-flavored soft drinks In Australia and New Zealand *A category of sweet or savory dishes: :*Vanilla slice, a dessert cake similar to a brownie :*Zucchini slice, a savory dish similar to a quiche In arts and entertainment Music * ''Slice'', a Five for Fighting album, 2009 ** "Slice" (song), a 2009 song by Five for Fighting *''Slice'', a 1998 album by Arthur Loves Plastic * Slices (band) Other uses in arts and entertainment *Slice (TV channel), a Canadian TV channel formerly known as Life Network * ''Slice'' (film), 2018 film * Slice (G.I. Joe), a fictional character in the G.I. Joe universe *Slice, a region in Terry Pratchett's ''Discworld'' stories, see Discworld (world)#The Ramtops *Slice, in lieu of "chapter", in Norman Lindsay's children's book The Magic Pudding In math ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American Geophysical Union
The American Geophysical Union (AGU) is a 501(c)(3) nonprofit organization of Earth, atmospheric, ocean, hydrologic, space, and planetary scientists and enthusiasts that according to their website includes 130,000 people (not members). AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and international fields within the Earth and space sciences. The geophysical sciences involve four fundamental areas: atmospheric and ocean sciences; solid-Earth sciences; hydrologic sciences; and space sciences. The organization's headquarters is located on Florida Avenue in Washington, D.C. History The AGU was established in December 1919 by the National Research Council (NRC) to represent the United States in the International Union of Geodesy and Geophysics (IUGG), and its first chairman was William Bowie of the United States Coast and Geodetic Survey (USCGS). For more than 50 years, it operated as an unincorporated af ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The American Geological Institute
The American Geosciences Institute (AGI) is a nonprofit federation of about 50 geoscientific and professional organizations that represents geologists, geophysicists, and other earth scientists. The organization was founded in 1948. The name of the organization was changed from the American Geological Institute on October 1, 2011. The organization's offices are in Alexandria, Virginia. About AGI's monthly magazine ''Geotimes'' became ''EARTH Magazine'' on September 1, 2008, with an increased focus on public communication of geoscience research. As of April 1, 2019, ''EARTH Magazine'' suspended publication and has been folded into ''Nautilus'' magazine. Since 1966, AGI has produced GeoRef, a literature database for those studying the earth sciences. AGI operates the Center for Geosciences and Society. Mission The stated mission of AGI is to “represent and serve the geoscience community by providing collaborative leadership and information to connect Earth, science, and people ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Core–mantle Differentiation
Core–mantle differentiation is the set of processes that took place during the accretion stage of Earth's evolution (or more generally, of rocky planets) that results in the separation of iron-rich materials that eventually would conform a metal core, surrounded by a rocky mantle. According to the Safronov's model, protoplanets formed as the result of collisions of smaller bodies (planetesimals), which previously condensed from solid debris present in the original nebula. Planetesimals contained iron and silicates either already differentiated or mixed together. Either way, after impacting the Proto-Earth their materials very likely became homogenized. At this stage, the Proto-Earth was probably the size of Mars. Next followed the separation and stratification of the Proto-Earth's constituents, chiefly driven by their density contrasts. Factors such as pressure, temperature, and impact bodies in the primordial magma ocean were involved in the differentiation process. The dif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithosphere–asthenosphere Boundary
The lithosphere–asthenosphere boundary (referred to as the LAB by geophysicists) represents a mechanical difference between layers in Earth's inner structure. Earth's inner structure can be described both chemically ( crust, mantle, and core) and mechanically. The lithosphere–asthenosphere boundary lies between Earth's cooler, rigid lithosphere and the warmer, ductile asthenosphere. The actual depth of the boundary is still a topic of debate and study, although it is known to vary according to the environment. Definition The LAB is determined from the differences in the lithosphere and asthenosphere including, but not limited to, differences in grain size, chemical composition, thermal properties, and extent of partial melt; these are factors that affect the rheological differences in the lithosphere and asthenosphere. Mechanical boundary layer (MBL) The LAB separates the mechanically strong lithosphere from the weak asthenosphere. The depth to the LAB can be estimated fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gutenberg Discontinuity
{{unreferenced, date=November 2020 The Gutenberg discontinuity occurs within Earth's interior at a depth of about 2,900 km (1,800 mi) below the surface, where there is an abrupt change in the seismic waves (generated by earthquakes or explosions) that travel through Earth. At this depth, primary seismic waves (P waves) decrease in velocity while secondary seismic waves (S waves) disappear completely. S waves shear material, and cannot transmit through liquids, so it is believed that the unit above the discontinuity is solid, while the unit below is in a liquid, or molten, form. This distinct change marks the boundary between two sections of the earth's interior, known as the lower mantle (which is considered solid) and the underlying outer core (believed to be molten). This discontinuity is also called the Wrichert-Gutenberg discontinuity. The molten section of the outer core is thought to be about 700 °C (1,292 °F) hotter than the overlying mantle. It is also d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beno Gutenberg
Beno Gutenberg (; June 4, 1889 – January 25, 1960) was a German-American seismologist who made several important contributions to the science. He was a colleague and mentor of Charles Francis Richter at the California Institute of Technology and Richter's collaborator in developing the Richter magnitude scale for measuring an earthquake's magnitude. Early life, family and education Gutenberg was born in Darmstadt, Germany. His father owned a factory. He obtained his doctorate in physics from the University of Göttingen in 1911. His advisor was Emil Wiechert. Career During World War I, Gutenberg served in the German Army as a meteorologist in support of gas warfare operations. Gutenberg held positions at the University of Strasbourg, which he lost when Strasbourg became French in 1918. After some years during which he had to sustain himself with managing his father's soap factory, he obtained in 1926 a junior professorship at University of Frankfurt-am-Main, which was p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physics Of The Earth And Planetary Interiors
''Physics of the Earth and Planetary Interiors'', established in October 1967, is a biweekly peer-reviewed scientific journal published by Elsevier. The co-editors are A. Ferreira (University College London), K. Hirose (Tokyo Institute of Technology), D. Jault (Grenoble Alpes University), and C. Michaut ( Ecole normale superieure de Lyon). The journal covers the physical and chemical processes of planetary interiors. Topical coverage broadly encompasses planetary physics, geodesy, and geophysics. Publishing formats include original research papers, review articles, short communications and book reviews on a regular basis. Occasional special issues are set aside for proceedings of conferences. The journal has a 2020 impact factor of 2.261. Abstracting and indexing This journal is indexed in the following bibliographic databases: * Science Citation Index * Current Contents/Physical, Chemical & Earth Sciences * Chemical Abstracts Service – CASSI * AGI's Bibliography and I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra Low Velocity Zone
Ultra low velocity zones (ULVZs) are patches on the core-mantle boundary that have extremely low seismic velocities. The zones are mapped to be hundreds of kilometers in diameter and tens of kilometers thick. Their shear wave velocities can be up to 30% lower than surrounding material. The composition and origin of the zones remain uncertain. The zones appear to correlate with edges of the African and Pacific Large low-shear-velocity provinces (LLSVPs) as well as the location of hotspots. Discovery and constraints ULVZs are discovered by the delay and scattering of body waves that reflect and diffract on or are refracted by the core-mantle boundary. Different body waves types give different constraints on the dimensions or velocity contrasts of the ULVZ. Even though ULVZs are discovered in places, it remains difficult to map out their extent and constrain their density and velocity. Usually trade-offs between various parameters exist. In general though, ULVZs appear to be a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle Convection
Mantle convection is the very slow creeping motion of Earth's solid silicate mantle as convection currents carrying heat from the interior to the planet's surface. The Earth's surface lithosphere rides atop the asthenosphere and the two form the components of the upper mantle. The lithosphere is divided into a number of tectonic plates that are continuously being created or consumed at plate boundaries. Accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading. Upwelling beneath the spreading centers is the rising component of mantle convection. The hot material added at spreading centers cools down by conduction and convection of heat as it moves away from the spreading centers. At the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction usually at an ocean trench. Subduction is the descending component of mantle convection. This sub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hotspot (geology)
In geology, hotspots (or hot spots) are volcanic locales thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii, Iceland, and Yellowstone hotspots. A hotspot's position on the Earth's surface is independent of tectonic plate boundaries, and so hotspots may create a chain of volcanoes as the plates move above them. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The alternative plate theory is that the mantle source beneath a hotspot is not anomalously hot, rather the crust above is unusually weak or thin, so that lithospheric extension permits the passive rising of melt from shallow depths. Origin The origins of the concept of hotspots lie in the work of J. Tuzo Wilson, who postulated in 1963 that the formation of the Hawaiian Islands resulted from the slow movement of a te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary Core
A planetary core consists of the innermost layers of a planet. Cores may be entirely solid or entirely liquid, or a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core sizes range from about 20% (the Moon) to 85% of a planet's radius ( Mercury). Gas giants also have cores, though the composition of these are still a matter of debate and range in possible composition from traditional stony/iron, to ice or to fluid metallic hydrogen. Gas giant cores are proportionally much smaller than those of terrestrial planets, though they can be considerably larger than the Earth's nevertheless; Jupiter's is 10–30 times heavier than Earth, and exoplanet HD149026 b may have a core 100 times the mass of the Earth. Planetary cores are challenging to study because they are impossible to reach by drill and there are almost no samples that are definitively from the core. Thus, they are studied via indirect techniques such as seismology, mineral physics, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
