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Vanuatu Subduction Zone
The Vanuatu subduction zone (previously called New Hebrides subduction zone) is currently one of the most active subduction zones on earth, producing great earthquakes (magnitude 8.0 or greater), with potential for tsunami hazard to all coastlines of the Pacific ocean. There are active volcanoes associated with arc volcanism. Geography The zone includes most of the islands of Vanuatu , the Santa Cruz islands of the southern Solomon Islands, and the Loyalty Islands. A number of ocean floor features are related to the zone, in particular the New Hebrides Trench (South New Hebridies Trench) and the North New Hebrides Trench (Torres Trench) which is separated from the southern trench by the d'Entrecasteaux Ridge and the island of Espiritu Santo. The d'Entrecasteaux Ridge is at this point of intersection two parallel, east-west trending ridges that are above the surrounding abyssal plain. Geology Shore based observations had characterised the islands of the volcanic arc as having ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanuatu
Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; bi, Ripablik blong Vanuatu), is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of northern Australia, northeast of New Caledonia, east of New Guinea, southeast of the Solomon Islands, and west of Fiji. Vanuatu was first inhabited by Melanesian people. The first Europeans to visit the islands were a Spanish expedition led by Portuguese navigator Fernandes de Queirós, who arrived on the largest island, Espíritu Santo, in 1606. Queirós claimed the archipelago for Spain, as part of the colonial Spanish East Indies, and named it . In the 1880s, France and the United Kingdom claimed parts of the archipelago, and in 1906, they agreed on a framework for jointly managing the archipelago as the New Hebrides through an Anglo-French condominium. An independence movement arose in the 1970s, and the Republic of Vanuatu was fou ... [...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] |
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] |
Hunter Fracture Zone
The Hunter Fracture Zone is a sinistral (left-lateral) transform faulting fracture zone, that to its south is part of a triple junction with the New Hebrides Trench, and the North Fiji Basin Central Spreading Ridge. The Hunter Fracture Zone, with the Hunter Ridge, an area with recent volcanic activity to its north, is the southern boundary of the North Fiji Basin. This boundary area in the south-western part of the Hunter Fracture Zone is associated with hot subduction, and a unique range of volcanic geochemistry. Geography The Hunter Fracture Zone is located to the south and southwest of Fiji and starts where the southern part of the New Hebrides Trench ends due to the increasing obliqueness of convergence lending to more strike slip faulting than subducting. It terminates around the International Date Line, with the Kadavu Islands immediately to its north. However some earlier work has postulated that the fault structures around Suva on Fiji itself are related and different au ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rifting
In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-graben with normal faulting and rift-flank uplifts mainly on one side. Where rifts remain above sea level they form a rift valley, which may be filled by water forming a rift lake. The axis of the rift area may contain volcanic rocks, and active volcanism is a part of many, but not all, active rift systems. Major rifts occur along the central axis of most mid-ocean ridges, where new oceanic crust and lithosphere is created along a divergent boundary between two tectonic plates. ''Failed rifts'' are the result of continental rifting that failed to continue to the point of break-up. Typically the transition from rifting to spreading develops at a triple junction where three converging rifts meet over a hotspot. Two of these evolve to the poin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conway Reef Plate
The Conway Reef Plate is a small tectonic plate (microplate) located in the south Pacific west of Fiji. The western boundary is with the New Hebrides Plate while the eastern is with the Australian Plate. A short transform boundary also exists with the Balmoral Reef Plate. Much of the plate underlies the south central portion of the North Fiji Basin. Within the North Fiji Basin it lies between the spreading centers of the Central Spreading Ridge on the west and the West Fiji Ridge on the east. The plate is rotating counterclockwise with respect to all of its neighbours. The plate's existence was first modelled in 2003 by Bird. Its boundaries and angular momentum were further defined in 2011 and 2018 with refinement of tectonic plate deformation and strain rate. The region is complex and may well have several other microplates or blocks.. See also *North Fiji Basin The North Fiji Basin (NFB) is an oceanic basin west of Fiji in the south-west Pacific Ocean. It is an activ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Fiji Basin
The South Fiji Basin ( also Fiji Basin ) is a large deep oceanic basin in the south-west Pacific Ocean, south of Fiji. It was formed from the then Indo-Australian Plate and is delimited to the north west by the New Hebrides Trench, and the Hunter Fracture Zone, to the west by the Three Kings Ridge, to the east by the Lau-Colville Ridge, and to the south by the continental shelf of Zealandia. Geology Over the basement volcanics is deposited up to of sediment. The thicker sediments of the Kupe Abyssal Plain nearer New Zealand and land commenced to accumulate from the end of the Oligocene onwards and terminated in the Pliocene with likely minor contributions from southern Lau-Colville Ridge volcanoes. The oldest basalt dredged from the Minerva Abyssal Plain is 26.0 ± 1.0 but it is unknown if this is of basement or later volcanic origin. However drill site 285 in the Minerva Abyssal Plain also has basement volcanics that are dated to 26 Ma. The oldest other drill basem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Izanagi Plates. The Pacific Plate subsequently grew to where it underlies most of the Pacific Ocean basin. This reduced the Farallon Plate to a few remnants along the west coast of North America and the Phoenix Plate to a small remnant near the Drake Passage, and destroyed the Izanagi Plate by subduction under Asia. The Pacific Plate contains an interior hot spot forming the Hawaiian Islands. Boundaries The north-eastern side is a divergent boundary with the Explorer Plate, the Juan de Fuca Plate and the Gorda Plate forming respectively the Explorer Ridge, the Juan de Fuca Ridge and the Gorda Ridge. In the middle of the eastern side is a transform boundary with the North American Plate along the San Andreas Fault, and a boundary with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Convergent Boundary
A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more Plate tectonics, lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, Orogeny, orogenesis, destruction of lithosphere, and Deformation (geology), deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types. Plate tectonics is driven by convection cells in the mantle. Convection cells are the result of heat generated by the radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surfac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiji
Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about 110 are permanently inhabited—and more than 500 islets, amounting to a total land area of about . The most outlying island group is Ono-i-Lau. About 87% of the total population of live on the two major islands, Viti Levu and Vanua Levu. About three-quarters of Fijians live on Viti Levu's coasts: either in the capital city of Suva; or in smaller urban centres such as Nadi—where tourism is the major local industry; or in Lautoka, where the Sugarcane, sugar-cane industry is dominant. The interior of Viti Levu is sparsely inhabited because of its terrain. The majority of Fiji's islands were formed by Volcano, volcanic activity starting around 150 million years ago. Some geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vanuata
Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; bi, Ripablik blong Vanuatu), is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of northern Australia, northeast of New Caledonia, east of New Guinea, southeast of the Solomon Islands, and west of Fiji. Vanuatu was first inhabited by Melanesian people. The first Europeans to visit the islands were a Spanish expedition led by Portuguese navigator Fernandes de Queirós, who arrived on the largest island, Espíritu Santo, in 1606. Queirós claimed the archipelago for Spain, as part of the colonial Spanish East Indies, and named it . In the 1880s, France and the United Kingdom claimed parts of the archipelago, and in 1906, they agreed on a framework for jointly managing the archipelago as the New Hebrides through an Anglo-French condominium. An independence movement arose in the 1970s, and the Republic of Vanuatu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adakite
Adakites are volcanic rocks of intermediate to felsic composition that have geochemical characteristics of magma originally thought to have formed by partial melting of altered basalt that is subducted below volcanic arcs. Most magmas derived in subduction zones come from the mantle above the subducting plate when hydrous fluids are released from minerals that break down in the metamorphosed basalt, rise into the mantle, and initiate partial melting. However, Defant and Drummond recognized that when young oceanic crust (less than 25 million years old) is subducted, adakites are typically produced in the arc. They postulated that when young oceanic crust is subducted it is "warmer" (closer to the mid-ocean ridge where it formed) than crust that is typically subducted. The warmer crust enables melting of the metamorphosed subducted basalt rather than the mantle above. Experimental work by several researchers has verified the geochemical characteristics of "slab melts" and the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
