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Lau Basin
The Lau Basin is a back-arc basin (also addressed as "interarc basin") at the Australian-Pacific plate boundary. It is formed by the Pacific plate subducting under the Australian plate. The Tonga-Kermadec Ridge, a frontal arc, and the Lau-Colville Ridge, a Back-arc region, remnant arc, sit to the eastern and western sides of the basin, respectively.Gill, J. B. 1976. "Composition and Age of Lau Basin and Ridge Volcanic Rocks: Implications for Evolution of an Interarc Basin and Remnant Arc." Bulletin of the Geological Society of America 87 (10): 1384–1395. The basin has a raised transition area to the south where it joins the Havre Trough. History Lau Basin is a young basin (much is less than 5 million years old) that separates a previously continuous island arc by Extensional tectonics, extensional rifting and spreading. During the Pliocene, the Pacific plate was subducting beneath the Australian plate. The slab of the Pacific plate melted as it was thrust down, and then rose to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kermadec Arc
Kermadec or de Kermadec may refer to: Geography * Kermadec Islands, a subtropical island arc in the South Pacific Ocean northeast of New Zealand * Kermadec Plate, a long narrow tectonic plate located west of the Kermadec Trench * Kermadec Trench, one of Earth's deepest oceanic trenches, reaching a depth of 10047 m * Kermadec-Tonga subduction zone, a convergent plate boundary * Tonga-Kermadec Ridge, an oceanic ridge in the south-west Pacific Ocean People * Eugène de Kermadec (1899–1976), French painter * François Pierre Huon de Kermadec (1726–1787), French Navy officer * Gil de Kermadec (1922–2011), French tennis player * Jean-Marie Huon de Kermadec (1747–1796), French Navy officer * Jean-Michel Huon de Kermadec (1748–1792), French navigator * Liliane de Kermadec (1928–2020), French film director and screenwriter See also * ''Kermadecia'' * {{disambiguation, geo, surname ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magma Supply Rate
The magma supply rate measures the production rate of magma at a volcano. Global magma production rates on Earth are about . Definitions Magma supply rate is also known as the Armstrong unit, where 1 Armstrong Unit = . Armstrong unit can also refer to volcanic flux rate per length of arc in discussions of volcanic arcs, in that case km2/year. Sometimes in discussion of large volcanic systems such as volcanic arcs the volcanic flux rate is normalized to a surface area, similar to Darcy's law in hydrodynamics. It is often easier to measure magma supply rates when they are normalized for an exposed surface area as it is often difficult to delimit an intrusion. Measurement difficulties Estimating the volcanic flux rate or magma supply of a volcanic system is inherently difficult for a number of reasons, and different measurements can come to different conclusions about the volcanic flux rate of a given volcanic system. Not all volcanic bodies are equally well exposed, and it is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dacite
Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz. Dacite is relatively common, occurring in many tectonic settings. It is associated with andesite and rhyolite as part of the subalkaline tholeiitic and calc-alkaline magma series. Etymology The word ''dacite'' comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains (now modern Romania and Moldova) where the rock was first described. The term ''dacite'' was used for the first time in the scientific literature in the book ''Geologie Siebenbürgens'' (''The Geology of Transylvania'') by Austrian geologists Franz Ritter von Hauer and Guido Stache. Dacite was originally defined as a new rock type to separate calc-alkaline ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MORB
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louisville Seamount Chain
The Louisville Ridge, often now referred to as the Louisville Seamount Chain, is an underwater chain of over 70 seamounts located in the Southwest portion of the Pacific Ocean. One of the longest seamount chains on Earth, it stretches some Vanderkluysen, L.; Mahoney, J. J.; Koppers, A. A.; and Lonsdale, P. F. (2007)Geochemical Evolution of the Louisville Seamount Chain American Geophysical Union, Fall Meeting 2007, abstract #V42B-06. from the Pacific-Antarctic Ridge northwest to the Tonga- Kermadec Trench, where it subducts under the Indo-Australian Plate as part of the Pacific Plate. The chain's formation is best explained by movement of the Pacific Plate over the Louisville hotspot, although others have suggested that it formed by leakage of magma from the shallow mantle up through the Eltanin fracture zone, which it follows closely for some of its course. Depth-sounding data first revealed existence consistent with a seamount chain in 1972, although some of the seamount ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ʻAta
Ata is a depopulated island in the far southern end of the Tonga archipelago, situated approximately south-southwest of Tongatapu. It is distinct from Atā, an uninhabited, low coral island in the string of small atolls along the Piha passage along the north side of Tongatapu. An unrelated traditional chiefly title from Kolovai is "Ata". Although superficially spelled in similar ways, Ata means ''reflection'' in Tongan; Ata means ''dawn'' and is the title of a chief; and Atā means more room or expanding. Geography Most of Ata's land is a high plateau above sea level, with steep cliffs and rocky beaches ringing the shoreline of the entire island. There are three minor peaks: two on the west side and one on the east side of the island, ranging in elevation from (eastern) to (western). It has a total land area of approximately . Although it was apparently formed by volcanic action, no record of volcanic activity exists. The anchorage for Ata is on the west side of the isla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Niuatahi
Niuatahi or also called Volcano O is a submarine volcano located in the far northern territory of Tonga. Since the cone in the middle is named Motutahi, the volcano is sometimes referred to as Niuatahi-Motutahi. Despite not having any record of any eruption, Niuatahi does have a record of recent hydrothermal vents, hydrothermal activity. Etymology Niuatahi was named by the Tonga Ministry of Lands, Environment, Climate Change and Natural Resources. In the Tongan language, Niuatahi means ''sea''. The name Motutahi means ''island in the sea'' in the Tongan language. Geography The volcano can be found approximately northwest of Niuatoputapu and southwest of the Samoan Islands. It is also located southwest of the far more known and more active West Mata submarine volcano, located in the same volcanic group as Niuatahi. An active ridge can also be found just west of the caldera walls. Structure Niuatahi is a submarine volcano mostly known for its circular shape and enormous width. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mantle (geology)
A mantle is a layer inside a planetary body bounded below by a Planetary core, core and above by a Crust (geology), crust. Mantles are made of Rock (geology), rock or Volatile (astrogeology), ices, and are generally the largest and most massive layer of the planetary body. Mantles are characteristic of planetary bodies that have undergone planetary differentiation, differentiation by density. All Terrestrial planet, terrestrial planets (including Earth), half of the giant planets, specifically ice giants, a number of Asteroid, asteroids, and some planetary Natural satellite, moons have mantles. Examples Earth The Earth's mantle is a layer of Silicate minerals, silicate rock between the Crust (geology), crust and the Earth's outer core, outer core. Its mass of 4.01 × 1024 kg is 67% the mass of the Earth. It has a thickness of making up about 84% of Earth's volume. It is predominantly solid, but in Geologic time scale, geological time it behaves as a Viscosity, visc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Graben
In geology, a graben () is a depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 'trench'. The first known usage of the word in the geologic context was by Eduard Suess in 1883. The plural form is either ''graben'' or ''grabens''. Formation A graben is a valley with a distinct escarpment on each side caused by the displacement of a block of land downward. Graben often occur side by side with Horst (geology), horsts. Horst and graben structures indicate tensional forces and crustal stretching. Graben are produced by sets of normal faults that have parallel fault traces, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between graben; the bounding faults of a horst t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Geology of Mars, Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
