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Manihiki Plateau
The Manihiki Plateau is an oceanic plateau in the south-west Pacific Ocean. The Manihiki Plateau was formed by volcanic activity 126 to 116 million years ago during the mid-Cretaceous period at a triple junction plate boundary called the Tongareva triple junction. Initially at 125 million years ago the Manihiki Plateau formed part of the giant Ontong Java-Manihiki- Hikurangi plateau. Geological setting The Manihiki Plateau extends from 3°S to 6°S and 159°W to 169°W covering and has an estimated volume of with a crustal thickness of . Several of the Cook Islands are located on the southern part: Pukapuka, Nassau, Suwarrow, Rakahanga, and Manihiki. The Tokelau Basin borders it to the west, the Samoan Basin to the south, the Penrhyn Basin to the east, and the Central Pacific Basin to the north. It reaches up to below sea level, several kilometres shallower than the surrounding basins. The plateau can be divided into three regions. The south-eastern High Plateau is t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial planet, rocky planet or natural satellite, moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of volcanism on Venus, Venus, which cover ~80% of the surface, are basaltic; the lunar mare, lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basement (geology)
In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The basement rocks lie below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. In the same way, the sediments or sedimentary rocks on top of the basement can be called a "cover" or "sedimentary cover". Basement rock consists of continental crustal rock which has been modified several times through tectonic events including deformation, metamorphism, deposition, partial melting and magmatism. Continental crust Basement rock is the thick foundation of ancient, and oldest, metamorphic and igneous rock that forms the crust of continents, often in the form of granite. Basement rock is contrasted to overlying sedimentary rocks which are laid down ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cretaceous Volcanism
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 77.1 million years, it is the ninth and longest geological period of the entire Phanerozoic. The name is derived from the Latin , 'chalk', which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation . The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites, and rudists, while dinosaurs continued to dominate on land. The world was largely ice-free, although there is some evidence of brief periods of glaciation during the cooler first half, and forests extended to the poles. Many of the dominant taxonomic groups present in modern times can be ultimately traced back to origins in the C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Large Igneous Provinces
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive ( sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems. Overview Definition In 1992, Coffin and Eldholm initially defined the term "large igneous province" as representing a variety of mafic igneous provinces with areal extent greater than 100,000 km2 that represented "massive crustal emplacements of predominantly mafic (magnesium- and iron-rich) extrusive and intrusive rock, and origina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plateaus Of The Pacific Ocean
In geology and physical geography, a plateau (; ; : plateaus or plateaux), also called a high plain or a tableland, is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Often one or more sides have deep hills or escarpments. Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, and erosion by water and glaciers. Plateaus are classified according to their surrounding environment as intermontane, piedmont, or continental. A few plateaus may have a small flat top while others have wider ones. Formation Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, plate tectonics movements, and erosion by water and glaciers. Volcanic Volcanic plateaus are produced by volcanic activity. They may be formed by upwelling of volcanic magma or extrusion of lava. The underlining mechanism in forming plateaus from up ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osbourn Trough
The Osbourn Trough, is a -long extinct mid-ocean ridge, that may have stopped spreading as recently as 79 million years ago. It is a west-to-east oriented sea floor feature, located to the east of the present Tonga-Kermadec Ridge where the present Pacific Plate is under going subduction under a micro-plate of the Australian Plate. The Osbourn Trough is key to understanding the postulated breakup mechanism of the historic massive Ontong Java-Manihiki-Hikurangi large igneous province (LIP), as it has been shown to be the spreading centre that lead to the separation of the Manihiki Plateau to its north and the Hikurangi Plateau to its south close to New Zealand. Geology Its basement is known to be oceanic basaltic crust with compositional affinity with a Pacific mid-ocean ridge basalt ( MORB ) mantle source. There is only relatively thin sediment overlay to this, often less than thick. The ocean depth ranges between to over the trough which has been characterised as having at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upwelling
Upwelling is an physical oceanography, oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. The biomass of phytoplankton and the presence of cool water in those regions allow upwelling zones to be identified by cool sea surface temperatures (SST) and high concentrations of chlorophyll a. The increased availability of nutrients in upwelling regions results in high levels of primary production and thus fishery production. Approximately 25% of the total global marine fish catches come from five upwellings, which occupy only 5% of the total ocean area.Jennings, S., Kaiser, M.J., Reynolds, J.D. (2001) "Marine Fisheries Ecology." Oxford: Blackwell Science Ltd. Upwellings that are driven by coastal ocean curr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extension (geology)
Extensional tectonics is concerned with the structures formed by, and the Tectonics, tectonic processes associated with, the stretching of a planetary body's Crust (geology), crust or lithosphere. Deformation styles The types of structure and the geometries formed depend on the amount of stretching involved. Stretching is generally measured using the parameter ''β'', known as the ''beta factor'', where : \beta = \frac \,, ''t''0 is the initial crustal thickness and ''t''1 is the final crustal thickness. It is also the equivalent of the Strain (materials science), strain parameter ''stretch''. Low beta factor In areas of relatively low crustal stretching, the dominant structures are high to moderate angle normal faults, with associated half grabens and tilted block faulting, tilted fault blocks. High beta factor In areas of high crustal stretching, individual extensional faults may become rotated to too low a dip to remain active and a new set of faults may be generated. Lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Large Igneous Province
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive ( sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems. Overview Definition In 1992, Coffin and Eldholm initially defined the term "large igneous province" as representing a variety of mafic igneous provinces with areal extent greater than 100,000 km2 that represented "massive crustal emplacements of predominantly mafic (magnesium- and iron-rich) extrusive and intrusive rock, and origin ... [...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 (geology), mantle that is anomalously hot compared with the surrounding mantle. Examples include the Hawaii hotspot, Hawaii, Iceland hotspot, Iceland, and Yellowstone hotspots. A hotspot's position on the Earth's surface is independent of plate boundary, 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 (volcanism), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-ocean Ridge
A mid-ocean ridge (MOR) is a undersea mountain range, seafloor mountain system formed by plate tectonics. It typically has a depth of about and rises about above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a Divergent boundary, divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin. The production of new seafloor and oceanic lithosphere results from Mantle (geology), mantle upwelling in response to plate separation. The melt rises as magma at the linear weakness between the separating plates, and emerges as lava, creating new oceanic crust and lithosphere upon cooling. The first discovered mid-ocean ridge was the Mid-Atlantic Ridge, which is a spreading center that bisects the North and South Atlantic basins; hence the origin of the name 'mid-ocean ridge'. Most oceanic spreading centers are not in the middle of their hosting oce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
