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Tectonic Subsidence
Tectonic subsidence is the Subsidence, sinking of the Earth's Crust (geology), crust on a large scale, relative to crustal-scale features or the geoid. The movement of Plate tectonics, crustal plates and accommodation spaces produced by Fault (geology), faulting brought about subsidence on a large scale in a variety of environments, including passive margins, aulacogens, fore-arc basins, foreland basins, intercontinental basins and pull-apart basins. Three mechanisms are common in the tectonic environments in which subsidence occurs: extension, cooling and loading. Mechanisms Extension Where the lithosphere undergoes horizontal extension at a normal fault or rift, rifting center, the crust will stretch until faulting occurs, either by a system of Fault (geology)#Dip-slip faults, normal faults (which creates horst (geology), horsts and grabens) or by a system of Fault (geology)#Listric fault, listric faults. These fault systems allow the region to stretch, while also decreasin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope movement. Processes that lead to subsidence include dissolution of underlying carbonate rock by groundwater; gradual compaction of sediments; withdrawal of fluid lava from beneath a solidified crust of rock; mining; pumping of subsurface fluids, such as groundwater or petroleum; or warping of the Earth's crust by tectonic forces. Subsidence resulting from tectonic deformation of the crust is known as tectonic subsidence and can create accommodation for sediments to accumulate and eventually lithify into sedimentary rock. Ground subsidence is of global concern to geologists, geotechnical engineers, surveyors, engineers, urban planners, landowners, and the public in general.National Research Council, 1991. ''Mitigating losses from land ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orogeny
Orogeny () is a mountain-mountain formation, building process that takes place at a convergent boundary, convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is tectonic uplift, uplifted to form one or more mountain ranges. This involves a series of geological processes collectively called orogenesis. These include both structural deformation (physics), deformation of existing continental crust and the creation of new continental crust through volcanism. Magma rising in the orogen carries less dense material upwards while leaving more dense material behind, resulting in compositional differentiation of Earth's lithosphere (crust (geology), crust and uppermost mantle (geology), mantle). A synorogenic (or synkinematic) process or event is one that occurs during an orogeny. The word ''orogeny'' comes . Although it was used before him, the American geologist Grove Karl Gilbert, G. K. Gilbert used the term in 1890 to me ... [...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. 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. Geophysical 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 of mantle material can carry inf ... [...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 serpentines. 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 tecton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretionary Wedge
An accretionary wedge or accretionary prism forms from sediments accreted onto the non- subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust, but in some cases the wedge includes the erosional products of volcanic island arcs formed on the overriding plate. An accretionary complex is a current (in modern use) or former accretionary wedge. Accretionary complexes are typically made up of a mix of turbidites of terrestrial material, basalts from the ocean floor, and pelagic and hemipelagic sediments. For example, most of the geological basement of Japan is made up of accretionary complexes. Materials within an accretionary wedge Accretionary wedges and accreted terranes are not equivalent to tectonic plates, but rather are associated with tectonic plates and accrete as a result of tectonic collision. Materials incorporated in accretionary wedge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subduction
Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second plate, the heavier plate dives beneath the other and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with rates of convergence as high as 11 cm/year. Subduction is possible because the cold and rigid oceanic lithosphere is slightly denser than the underlying asthenosphere, the hot, ductile layer in the upper mantle. Once initiated, stable subduction is driven mostly by the negative buoyancy of the dense subducting lithosphere. The down-going slab sinks into the mantle largely under its own ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forearc
A forearc is a region in a subduction zone between an oceanic trench and the associated volcanic arc. Forearc regions are present along convergent margins and eponymously form 'in front of' the volcanic arcs that are characteristic of convergent plate margins. A back-arc region is the companion region behind the volcanic arc. Many forearcs have an accretionary wedge which may form a topographic ridge known as an outer arc ridge that parallels the volcanic arc. A forearc basin between the accretionary wedge and the volcanic arc can accumulate thick deposits of sediment, sometimes referred to as an outer arc trough. Due to collisional stresses as one tectonic plate subducts under another, forearc regions are sources for powerful earthquakes. Formation During subduction, an oceanic plate is thrust below another tectonic plate, which can be oceanic or continental. Water and other volatiles in the subducting plate cause flux melting in the upper mantle, creating magma that ri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Arc System SVG En
A volcano is commonly defined as a vent or fissure in the Crust (geology), crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where list of tectonic plates, tectonic plates are divergent boundary, diverging or convergent boundary, converging, and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example, a mid-ocean ridge, such as the Mid-Atlantic Ridge, has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes resulting from divergent tectonic activity are usually non-explosive whereas those resulting from convergent tectonic activity cause violent eruptions."Mid-ocean ridge tectonics, volcanism and geomorphology." Geology 26, no. 455 (2001): 458. https://macdonald.faculty.geol.ucsb.edu/papers/Macd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pull-apart Basin
In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping (en echelon) strike-slip faults or a fault bend create an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length of overlap.Frisch, Wolfgang, Martin Meschede, and Ronald C. Blakey. ''Plate tectonics: Continental drift and mountain building''. Springer, 2010. Mechanics and fault configuration The inhomogeneity and structural complexity of continental crust causes faults to deviate from a straight course and frequently causes bends or step-overs in fault paths. Bends and step-overs of adjacent faults become favorable locations for extensional and compressional stress or transtension and transpression stress, if the shear motion is ob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aulacogen
An aulacogen is a failed arm of a triple junction. Aulacogens are a part of plate tectonics where oceanic and continental crust is continuously being created, destroyed, and rearranged on the Earth’s surface. Rift zones are places where new crust is formed. An aulacogen is a rift zone that is no longer active. Origin of term The term ''aulacogen'' is derived from Greek ''aulax'' ' furrow' and was suggested by the Soviet geologist Nikolay Shatsky in 1946. Formation A triple junction is the point where three tectonic plates meet; the boundaries of these plates are characterized by divergence, causing a rift zone or spreading center; a transform fault; or convergence causing subduction or uplift of crust and forming mountains. The failed arm of a triple junction can be either a transform fault that has been flooded with magma, or more commonly, an inactive rift zone. Aulacogen formation starts with the termination of an active rift zone, which leaves behind a graben-like ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pangea
Pangaea or Pangea ( ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia (continent), Siberia during the Carboniferous period approximately 335 million years ago, and began to break apart about 200 million years ago, at the end of the Triassic–Jurassic extinction event, Triassic and beginning of the Jurassic. Pangaea was C-shaped, with the bulk of its mass stretching between Earth's northern and southern polar regions and surrounded by the superocean Panthalassa and the Paleo-Tethys Ocean, Paleo-Tethys and subsequent Tethys Oceans. Pangaea is the most recent supercontinent to have existed and was the first to be reconstructed by geologists. Origin of the concept The name "Pangaea" is derived from Ancient Greek ''pan'' (, "all, entire, whole") and ''Gaia (mythology), Gaia'' or Gaea (, "Mother goddess, Mother Earth, land"). The first to suggest that the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross Section
Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture and engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Absorption cross section **Nuclear cross section **Neutron cross section **Photoionisation cross section **Gamma ray cross section * ''Cross Section'' (album), 1956 musical album by Billy Taylor See also * Cross section (fiber), microscopic view of textile fibers. *Section (fiber bundle), in differential and algebraic geometry and topology, a section of a fiber bundle or sheaf *Cross-sectional data, in statistics, econometrics, and medical research, a data set drawn from a single point in time **Cross-sectional study, a scientific investigation utilizing cross-sectional data ***Cross-sectional regression In statistics and econometrics, a cross-sectional regression is a type of Regression analysis, regression in which the Dependent and i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
