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Christmas Island Seamount Province
The Christmas Island Seamount Province (also known as the Christmas Island Seamounts) is an unusual seamount ( submarine volcano) formation named for Christmas Island, an Australian territory and wildlife reserve that is also part of the chain. The province consists of more than 50 seamounts, up to in height, within a area. Unlike most seamount groups, the Christmas Island seamount formation does not form a long hotspot-based chain of increasingly older volcanoes, instead being a scattered grouping of volcanoes within a large radius. The origins of the formation have long been enigmatic for scientists; the Christmas Island area does not exhibit the hotspot chain formation that most seamount groups have, nor does it run perpendicular to a local rift zone, instead lying roughly parallel to the edge of the Australian Plate. Many of the seamounts are flat-topped guyots, showing that at one point the province was likely a group of active volcanic islands, before it was slowly e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LiveScience
Live Science is a science news website run by Future via Purch, which it purchased from Imaginova in 2009. Stories and editorial commentary are typically syndicated to major news outlets, such as Yahoo!, MSNBC, AOL, and Fox News.{{fact, date=March 2020 Live Science was originally launched in 2004, but was subsequently shut down and re-launched in 2007. Live Science covers scientific breakthroughs, research ventures and odd facts from around the world in an online newsmagazine format. Purch consumer brands (including Live Science) were acquired by Future in 2018.{{Cite web , url=https://www.futureplc.com/brand/live-science/ , title=Live Science , work=Future plc Future plc is an international multimedia company established in the United Kingdom in 1985. The company has over 220 brands that span magazines, newsletters, websites, and events in fields such as video games, technology, films, music, photogr ... , access-date=18 December 2018 References {{reflist External links ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water Erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as ''physical'' or ''mechanical'' erosion; this contrasts with ''chemical'' erosion, where soil or rock material is removed from an area by dissolution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres. Agents of erosion include rainfall; bedrock wear in rivers; coastal erosion by the sea and waves; glacial plucking, abrasion, and scour; areal flooding; wind abrasion; groundwater processes; and mass movement processes in steep landscapes like landslides and debris flows. The rates at which such processes act control how fast a surface is eroded. Typically, physical erosi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delamination (geology)
In geodynamics, delamination refers to the loss and sinking (foundering) of the portion of the lowermost lithosphere from the tectonic plate to which it was attached. Mechanism The outer portion of the Earth is divided into an upper, lithosphere layer and a lower, asthenosphere layer. The lithosphere layer is composed of two parts, an upper, the crustal lithosphere and lower, the mantle lithosphere. The crustal lithosphere is in unstable mechanical equilibrium because the underlying mantle lithosphere has a greater density than the asthenosphere below.Bird, P. (1979). Continental delamination and the Colorado Plateau. Journal of Geophysical Research: Solid Earth (1978–2012), 84(B13), 7561-7571. The difference in densities can be explained by thermal expansion/contraction, composition, and phase changes.Kay, R. W., & Mahlburg Kay, S. (1993). Delamination and delamination Negative buoyancy of the lower continental crust and mantle lithosphere drive delamination.Meissner, R., & ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crustal Recycling
Crustal recycling is a tectonic process by which surface material from the lithosphere is recycled into the mantle by subduction erosion or delamination. The subducting slabs carry volatile compounds and water into the mantle, as well as crustal material with an isotopic signature different from that of primitive mantle. Identification of this crustal signature in mantle-derived rocks (such as mid-ocean ridge basalts or kimberlites) is proof of crustal recycling. Historical and theoretical context Between 1906 and 1936 seismological data were used by R.D. Oldham, A. Mohorovičić, B. Gutenberg and I. Lehmann to show that the earth consisted of a solid crust and mantle, a fluid outer core and a solid innermost core. The development of seismology as a modern tool for imaging the Earth's deep interior occurred during the 1980s, and with it developed two camps of geologists: whole-mantle convection proponents and layered-mantle convection proponents. Layered-mantle convection ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages of break-up, involving the separation of Antarctica from South America (forming the Drake Passage) and Australia, occurred during the Paleogene. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separated from it. To differentiate it from the Indian region of the same name (see ), it is also commonly called Gondwanaland. Gondwana was formed by the accretion of several cratons. Eventually, Gondwana became the largest piece of continental crust of the Palaeozoic Era, covering an area of about , about one-fifth of the Earth's surface. During the Carboniferous Period, it merged with Laurasia to form a larger supercontinent called Pangaea. Gondwana ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plate Reconstruction
:''This article describes techniques; for a history of the movement of tectonic plates, see Geological history of Earth.'' Plate reconstruction is the process of reconstructing the positions of tectonic plates relative to each other (relative motion) or to other reference frames, such as the earth's magnetic field or groups of hotspots, in the geological past. This helps determine the shape and make-up of ancient supercontinents and provides a basis for paleogeographic reconstructions. Defining plate boundaries An important part of reconstructing past plate configurations is to define the edges of areas of the lithosphere that have acted independently at some time in the past. Present plate boundaries Most present plate boundaries are easily identifiable from the pattern of recent seismicity. This is now backed up by the use of geodetic data, such as GPS/ GNSS, to confirm the presence of significant relative movement between plates. Past plate boundaries Identifying past (but ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle). The crusts of Earth, Mercury, Venus, Mars, Io, the Moon and other planetary bodies formed via igneous processes and were later modified by erosion, impact cratering, volcanism, and sedimentation. Most terrestrial planets have fairly uniform crusts. Earth, however, has two distinct types: continental crust and oceanic crust. These two types have different chemical compositions and physical properties and were formed by different geological processes. Types of crust Planetary geologists divide crust into three categories based on how and when it formed. Primary crust / primordial crust This is a planet's "original" crust. It forms from solidification of a magma ocean. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Crust
Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. The crust overlies the rigid uppermost layer of the mantle. The crust and the rigid upper mantle layer together constitute oceanic lithosphere. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or sial, generally less than 10 kilometers thick; however, it is denser, having a mean density of about 3.0 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter. The crust uppermost is the result of the cooling of magma derived from mantle material below the plate. The magma is injected into the spreading center, which consists mainly of a partly solidified crystal mush derived from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Crust
Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' because its bulk composition is richer in aluminium silicates (Al-Si) and has a lower density compared to the oceanic crust, called ''sima'' which is richer in magnesium silicate (Mg-Si) minerals. Changes in seismic wave velocities have shown that at a certain depth (the Conrad discontinuity), there is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character. The continental crust consists of various layers, with a bulk composition that is intermediate (SiO2 wt% = 60.6). The average density of continental crust is about , less dense than the ultramafic material that makes up the mantle, which has a density of around . Continental crust is also less dense ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, lead is a shiny gray with a hint of blue. It tarnishes to a dull gray color when exposed to air. Lead has the highest atomic number of any stable element and three of its isotopes are endpoints of major nuclear decay chains of heavier elements. Lead is toxic, even in small amounts, especially to children. Lead is a relatively unreactive post-transition metal. Its weak metallic character is illustrated by its amphoteric nature; lead and lead oxides react with acids and bases, and it tends to form covalent bonds. Compounds of lead are usually found in the +2 oxidation state rather than the +4 state common with lighter members of the carbon group. Exceptions are mostly limited to organolead compounds. Like the lighter members of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hafnium
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Dirk Coster and George de Hevesy, making it the penultimate stable element to be discovered (the last being rhenium in 1925). Hafnium is named after , the Latin name for Copenhagen, where it was discovered. Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nanometers and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination with niobium, titanium, or tungsten. Hafnium's large neutron capture cross section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neodymium
Neodymium is a chemical element with the symbol Nd and atomic number 60. It is the fourth member of the lanthanide series and is considered to be one of the rare-earth metals. It is a hard, slightly malleable, silvery metal that quickly tarnishes in air and moisture. When oxidized, neodymium reacts quickly producing pink, purple/blue and yellow compounds in the +2, +3 and +4 oxidation states. It is generally regarded as having one of the most complex spectra of the elements. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach, who also discovered praseodymium. It is present in significant quantities in the minerals monazite and bastnäsite. Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Neodymium is fairly common—about as common as cobalt, nickel, or copper—and is widely distributed in the Earth's crust. Most of the world's commercial neodymium is mined in China, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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