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Juan Fernández Plate
The Juan Fernandez Plate is a small tectonic plate (microplate) in the Pacific Ocean. With a surface area of approximately 105 km2, the microplate is located between 32° and 35°S and 109° and 112°W. The plate is located at a triple junction between the Antarctic Plate, the Nazca Plate, and the Pacific Plate. Approximately 2,000 km to the west of South America, it is, on average, 3,000 meters deep with its shallowest point coming to approximately 1,600 meters, and its deepest point reaching 4,400 meters.Anderson-Fontana, S., J. F. Engeln, P. Lundgren, R. L. Larson, and S. SteinTectonics and evolution of the Juan Fernandez microplate at the Pacific-Nazca-Antarctic triple junction J. Geophys. Res., 91, 2005–2018, 1986. Discovery The Juan Fernandez Microplate was first discovered in 1972 via seismicity charts, which showed semi-circular patterns at the Pacific-Nazca-Antarctica triple junction. This implied that shear zone was present that were inconsistent with existing p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Tectonic Plates
This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around thick and consist of two principal types of material: oceanic crust (also called ''sima'' from silicon and magnesium) and continental crust (''sial'' from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks. Current plates Geologists generally agree that the following tectonic plates currently exist on Earth's surface with roughly definable boundaries. Tectonic plates are sometimes subdivided into three fairly arbitrary categories: ''major'' (or ''primary'') ''plates'', ''minor'' (or ''secondary'') ''plates'', and ''microplates'' (or ''tertiary plates''). Major plates These plates comprise the bulk of the continents and the P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seafloor Mapping
Seafloor mapping (or seabed mapping), also called seafloor imaging (or seabed imaging), is the measurement, mapping, and imaging of water depth of the ocean (''seabed topography'') or another given body of water. Bathymetric measurements are conducted with various methods, from depth sounding, sonar and Lidar techniques, to buoys and satellite altimetry. Various methods have advantages and disadvantages and the specific method used depends upon the scale of the area under study, financial means, desired measurement accuracy, and additional variables. Despite modern computer-based research, the ocean seabed in many locations is less measured than the topography of Mars. History The earliest methods of depth measurement on record are the use of sounding poles and weighted lines, recorded from Egypt more than 3000 years ago, and in use without significant improvement until the voyage of HMS ''Challenger'' in the 1870s, when similar systems using wires and a winch were used fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals and gas bubbles. Magma is produced by melting of the mantle or the crust in various tectonic settings, which on Earth include subduction zones, continental rift zones, mid-ocean ridges and hotspots. Mantle and crustal melts migrate upwards through the crust where they are thought to be stored in magma chambers or trans-crustal crystal-rich mush zones. During magma's storage in the crust, its composition may be modified by fractional crystallization, contamination with crustal melts, magma mixing, and degassing. Following its ascent through the crust, magma may feed a volcano and be extruded as lava, or it may solidify underground to form an intrusion, such as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fracture Zone
A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on either side of an active transform fault move in opposite directions; here, strike-slip activity occurs. Fracture zones extend past the transform faults, away from the ridge axis; seismically inactive (because both plate segments are moving in the same direction), they display evidence of past transform fault activity, primarily in the different ages of the crust on opposite sides of the zone. In actual usage, many transform faults aligned with fracture zones are often loosely referred to as "fracture zones" although technically, they are not. Structure and formation Mid-ocean ridges are divergent plate boundaries. As the plates on either side of an offset mid-ocean ridge move, a transform fault forms at the offset between the two ridges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chile Rise
The Chile Ridge, also known as the Chile Rise, is a submarine oceanic ridge formed by the divergent plate boundary between the Nazca Plate and the Antarctic Plate. It extends from the triple junction of the Nazca, Pacific, and Antarctic plates to the Southern coast of Chile. The Chile Ridge is easy to recognize on the map, as the ridge is divided into several segmented fracture zones which are perpendicular to the ridge segments, showing an orthogonal shape toward the spreading direction. The total length of the ridge segments is about 550–600 km. The continuously spreading Chile Ridge collides with the southern South America Plate to the east, and the ridge has been subducting underneath the Taitao Peninsula since 14 million years ago (Ma). The ridge-collision has generated a slab window beneath the overlying South America Plate, with smaller volume of upper mantle magma melt, proven by an abrupt low velocity of magma flow rate below the separating Chile ridge. The subductio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
East Pacific Rise
The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from (north to south) the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate. It runs south from the Gulf of California in the Salton Sea basin in Southern California to a point near 55° S, 130° W, where it joins the Pacific-Antarctic Ridge trending west-southwest towards Antarctica, near New Zealand (though in some uses the PAR is regarded as the southern section of the EPR). Much of the rise lies about 3200 km (2000 mi) off the South American coast and rises about 1,800–2,700 m (6,000–9,000 ft) above the surrounding seafloor. Overview The oceanic crust is moving away from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roger Clive Searle
Roger Clive Searle (born 24 October 1944 in St Ives, Cambridgeshire, Huntingdonshire) is an English geophysicist, known for using sonar imaging in research on the geology and geophysics of the ocean floor. In particular, he has made important contributions to understanding the oceanic spreading system and the mid-ocean spreading centres. Biography Searle graduated from the University of Cambridge with a B.A. (with a major in physics) in 1966 and an M.A. in 1970. He received a Ph.D. in geophysics from the University of Newcastle upon Tyne in 1969. He was from 1970 to 1973 an assistant professor at Haile Selassie University in Addis Ababa. At the Institute of Oceanographic Sciences in Wormsley Park, Searle was a senior science officer from 1973 to 1978; a principal science officer, civil service grade 7, from 1978 to 1988; and a senior principal science officer, civil service grade 6 (Individual Merit), from 1988 to 1989. At the University of Durham, he was a professor of geophys ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compression (geology)
In geology, the term compression refers to a set of stress directed toward the center of a rock mass. Compressive strength refers to the maximum compressive stress that can be applied to a material before failure occurs. When the maximum compressive stress is in a horizontal orientation, thrust faulting can occur, resulting in the shortening and thickening of that portion of the crust. When the maximum compressive stress is vertical, a section of rock will often fail in normal faults, horizontally extending and vertically thinning a given layer of rock. Compressive stresses can also result in folding of rocks. Because of the large magnitudes of lithostatic stress in tectonic plates, tectonic-scale deformation is always subjected to net compressive stress. See also *Gravitational compression Gravitational compression is a phenomenon in which gravity, acting on the mass of an object, compresses it, reducing its size and increasing the object's density. At the center of a plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretion (geology)
Accretion, in geology, is a process by which material is added to a tectonic plate at a subduction zone, frequently on the edge of existing continental landmasses. The added material may be sediment, volcanic arcs, seamounts, oceanic crust or other igneous features. Description Accretion involves the addition of material to a tectonic plate via subduction, the process by which one plate is forced under the other when two plates collide. The plate which is being forced down, the subducted plate, is pushed against the upper, over-riding plate. Sediment on the ocean floor of the subducting plate is often scraped off as the plate descends. This accumulated material is called an accretionary wedge (or accretionary prism), which is pushed against and attaches to the upper plate. In addition to accumulated ocean sediments, volcanic island arcs or seamounts present on the subducting plate may be amalgamated onto existing continental crust on the upper plate, increasing the continental ... [...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] |
RV Endeavor
RV ''Endeavor'' is a research vessel owned by the National Science Foundation and operated by the University of Rhode Island The University of Rhode Island (URI) is a public land-grant research university with its main campus in Kingston, Rhode Island, United States. It is the flagship public research as well as the land-grant university of the state of Rhode Island ... (URI) under a Charter Party Agreement as part of the University-National Oceanographic Laboratory System (UNOLS) fleet. The vessel is homeported at the Narragansett, Rhode Island at the URI Bay Campus. The 185 foot ''Endeavor'', built by Peterson Builders, Inc., Sturgeon Bay, Wisconsin, replaced RV ''Trident'' in 1976. It was likely named for Captain James Cook's ship , for which the Space Shuttle ''Endeavour'' is also named. References External links Research Vessel ''Endeavor''URI Graduate School of Oceanography: ''Endeavor'' SpecificationsURI Marine Technical Services Group University-National ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shear Zones
image:boudin_vein.jpg, Boudinaged quartz vein (with strain fringe) showing ''Fault (geology), sinistral shear sense'', Starlight Pit, Fortnum Gold Mine, Western Australia In geology, shear is the response of a rock to Deformation (engineering), deformation usually by compressive stress and forms particular textures. Shear can be homogeneous or non-homogeneous, and may be pure shear or simple shear. Study of geological shear is related to the study of structural geology, rock microstructure or List of rock textures, rock texture and Fault (geology), fault mechanics. The process of shearing occurs within brittle, brittle-ductile, and ductile rocks. Within purely brittle rocks, compressive stress results in Fracture (geology), fracturing and simple Fault (geology), faulting. Rocks Rocks typical of shear zones include mylonite, cataclasite, Tectonite, S-tectonite and Tectonite, L-tectonite, pseudotachylite, certain breccias and highly Foliation (geology), foliated versions of the w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
