|
Manihiki Plateau
The Manihiki Plateau is an oceanic plateau in the south-west Pacific Ocean. The Manihiki Plateau was formed by volcanic activity 125 to 120 million years ago during the mid-Cretaceous period at a triple junction plate boundary called the Tongareva triple junction. 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: Danger, Nassau, Suvorov, 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 the shallowest and fla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Map Showing The Location Of Oceanic Plateaus (in Green) In The Australia-New Zealand Region Of The South Pacific
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes. Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although most commonly used to depict geography, maps may represent any space, real or fictional, without regard to context or scale, such as in brain mapping, DNA mapping, or computer network topology mapping. The space being mapped may be two dimensional, such as the surface of the earth, three dimensional, such as the interior of the earth, or even more abstract spaces of any dimension, such as arise in modeling phenomena having many independent variables. Although the earliest maps known are of the heavens, geographic maps of territory have a very long tradition and exist from ancient times. The word "map" comes from the , wherein ''mappa'' meant 'napkin' or 'cloth' and ''mundi'' 'the world'. Thus, "map" became a shortened term referring to ... [...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 sedimentation, sedimentary platform (geology), platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic rock, metamorphic or Igneous rock, 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". Crustal rocks are modified several times before they become basement, and these transitions alter their composition. Continental crust Basement rock is the thick foundation of ancient, and oldest, metamorphic and igneous rock that forms the Crust (geology), 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 145 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin wikt:creta#Latin, ''creta'', "chalk", which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation ''Kreide''. The Cretaceous was a period with a relatively warm climate, resulting in high Sea level#Local and eustatic, eustatic sea levels that created numerous shallow Inland sea (geology), 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 ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeare ... [...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. Definition In 1992 researchers first used the term ''large igneous province'' to describe very large accumulations—areas greater than 100,000 square kilometers (approximately the area of Iceland)—of mafic igneous rocks that were erupted or emplaced at depth within an extremely short geological time interval: a few million years or less. Maf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plateaus Of The Pacific Ocean
In geology and physical geography, a plateau (; ; ), 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 wide 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. The Columbia Plateau in the north-western United States is an example. They may be formed by upwelling of volcanic magma or extrusion of lava. The un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tonga-Kermadec Ridge
The Tonga-Kermadec Ridge is an oceanic ridge in the south-west Pacific Ocean underlying the Tonga-Kermadec island arc. It is the most linear, fastest converging, and most seismically active subduction boundary on Earth, and consequently has the highest density of submarine volcanoes. The Tonga-Kermadec Ridge stretches more than north-northeast from New Zealand's North Island. The Pacific Plate subducts westward beneath the Australian Plate along the ridge. It is divided into two segments, the northern Tonga Ridge and southern Kermadec Ridge, by the Louisville Seamount Chain. On its western side, the ridge is flanked by two back-arc basins, the Lau Basin and Havre Trough, that began opening at 6 and 2 Ma respectively. Together with these younger basins the ridge forms the eastward-migrating, 100 Ma-old Lau-Tonga-Havre-Kermadec arc/back-arc system or complex. The extension in the Lau-Havre basin results in a higher rate of subduction than convergence along the Au ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upwelling
Upwelling is an 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 currents or diverging open oc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extension (geology)
Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's 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 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 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. Large displacements may juxtapose syntectonic sediments against metamorphic roc ... [...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. Definition In 1992 researchers first used the term ''large igneous province'' to describe very large accumulations—areas greater than 100,000 square kilometers (approximately the area of Iceland)—of mafic igneous rocks that were erupted or emplaced at depth within an extremely short geological time interval: a few million years or less. Maf ... [...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 tecton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-ocean Ridge
A mid-ocean ridge (MOR) is a 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 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 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 ocean basis but regardless, are traditionally called mid-ocean rid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deep Sea Drilling Project
The Deep Sea Drilling Project (DSDP) was an ocean drilling project operated from 1968 to 1983. The program was a success, as evidenced by the data and publications that have resulted from it. The data are now hosted by Texas A&M University, although the program was coordinated by the Scripps Institution of Oceanography at the University of California, San Diego. DSDP provided crucial data to support the seafloor spreading hypothesis and helped to prove the theory of plate tectonics. DSDP was the first of three international scientific ocean drilling programs that have operated over more than 40 years. It was followed by the Ocean Drilling Program (ODP) in 1985, the Integrated Ocean Drilling Program in 2004 and the present International Ocean Discovery Program in 2013. History The initial contract between the National Science Foundation (NSF) and the Regents of the University of California was signed on June 24, 1966. This contract initiated the first phase of the DSDP, which wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
