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MIT Guyot
MIT Guyot is a guyot in the Pacific Ocean that rises to a depth of . It has a summit platform and formed during the Cretaceous in the region of present-day French Polynesia through volcanic eruptions. The volcano was eventually covered by a carbonate platform resembling that of a present-day atoll which was colonized by a number of animals. A major volcanic episode disrupted this platform, which subsequently redeveloped until it drowned in the late Albian. Name and research history MIT means Massachusetts Institute of Technology. Drilling in MIT Guyot recovered about of basaltic rocks as part of the Ocean Drilling Program which targeted MIT along with four other guyots of the Pacific Ocean. Geography and geology Local setting The seamount lies in the Western Pacific Ocean northwest of Marcus Island and about halfway between Japan and the Marshall Islands. The Marcus-Wake Seamounts lie nearby, but MIT Guyot is a more isolated volcanic edifice that is sometimes consi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guyot
In marine geology, a guyot (pronounced ), also known as a tablemount, is an isolated underwater volcanic mountain (seamount) with a flat top more than below the surface of the sea. The diameters of these flat summits can exceed .Guyot ''Encyclopædia Britannica Online'', 2010. Retrieved January 14, 2010. Guyots are most commonly found in the , but they have been identified in all the oceans except the . History Guyots were first recognized in 1945 by |
Kashima Fracture Zone
Kashima (鹿島) may refer to: Places in Japan *Kashima District, Ibaraki, a district in Ibaraki Prefecture **Kashima, Ibaraki, a city in Ibaraki Prefecture ***Kashima Soccer Stadium ****Kashima Soccer Stadium Station, railway station ***Kashima Power Station ***Kashimajingū Station, railway station ***Kashima-Ōno Station, railway station ***Kashima Shrine, a Shinto shrine *Kashima, Saga, a city in Saga Prefecture ** Hizen-Kashima Station, railway station **Kashima Gatalympics, an annual sporting event *Kashima, Kumamoto, a town in Kumamoto Prefecture *Kashima, Shimane, a town in Shimane Prefecture *Kashima, Fukushima, a former town in Fukushima Prefecture (now part of Minamisōma, Fukushima) **Kashima Station (Fukushima), railway station *Kashima District, Ishikawa, a district in Ishikawa Prefecture **Kashima, Ishikawa, a former town in Ishikawa Prefecture (now part of Nakanoto, Ishikawa) *Kashima, Kagoshima, a former village in Kagoshima Prefecture (now part of Satsumasendai, K ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basanite
Basanite () is an igneous, volcanic ( extrusive) rock with aphanitic to porphyritic texture. It is composed mostly of feldspathoids, pyroxenes, olivine, and plagioclase and forms from magma low in silica and enriched in alkali metal oxides that solidifies rapidly close to the Earth's surface. Description Basanite is an aphanitic (fine-grained) igneous rock that is low in silica and enriched in alkali metals. Of its total content of quartz, feldspar, and feldspathoid ( QAPF), between 10% and 60% by volume is feldspathoid and over 90% of the feldspar is plagioclase. Quartz is never present. This places basanite in the basanite/ tephrite field of the QAPF diagram. Basanite is further distinguished from tephrite by having a normative olivine content greater than 10%. While the IUGS recommends classification by mineral content whenever possible, volcanic rock can be glassy or so fine-grained that this is impractical, and then the rock is classified chemically using the TAS class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkali Basalt
Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt is characterized by relatively high alkali (Na2O and K2O) content relative to other basalts and by the presence of olivine and titanium-rich augite in its groundmass and phenocrysts, and nepheline in its CIPW norm. Geochemical characterization Alkali basalt is chemically classified as a rock in region B (basalt) of the total alkali versus silica (TAS) diagram that contains nepheline in its CIPW norm. Basalts that do not contain normative nepheline are characterized as sub-alkali basalts, which include tholeiitic basalts and calc-alkaline basalts. Petrography The groundmass of alkali basalt is mainly composed of olivine, titanium-rich augite and plagioclase feldspar and may have alkali feldspar or feldspathoid interstitially, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tahiti Hotspot
The Society hotspot is a volcanic hotspot in the south Pacific Ocean which is responsible for the formation of the Society Islands, an archipelago of fourteen volcanic islands and atolls spanning around 720 km of the ocean which formed between 4.5 and <1 Ma. There are currently two main hypotheses concerning the cause of volcanic activity. The conventional view is that the hotspot is underlain by a mantle plume which has transported hot material from the lower to the surface, creating the chain as the h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Darwin Rise
The Darwin Rise is broad triangular region in the north central Pacific Ocean where there is a concentration of atolls. During his voyage across the globe Charles Darwin realised that vertical crustal motion must be responsible for the formation of continents and ocean basins, as well as isolated atolls in the Pacific. He deduced that the central basin of the Pacific had subsided while surrounding areas had risen. In 1964 U.S. geologist Henry Menard subsequently named the uplifted area in the Pacific after the English naturalist. Geological context Covering an area of , the Darwin Rise is limited to the east by the Izu–Bonin and Mariana trenches, to the west by the Line Islands. Two major plateaux, the Shatsky Rise to the north and the Ontong Java Plateau to the south, border the Darwin Rise. How these plateaux relate to the rise remains disputed. There are six major chains of seamounts on the rise — the Japanese, Magellan, Wake, Marshall Islands, Line Islands sea ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Crust
Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. The crust overlies the rigid uppermost layer of the mantle. The crust and the rigid upper mantle layer together constitute oceanic lithosphere. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or sial, generally less than 10 kilometers thick; however, it is denser, having a mean density of about 3.0 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter. The crust uppermost is the result of the cooling of magma derived from mantle material below the plate. The magma is injected into the spreading center, which consists mainly of a partly solidified crystal mush derived f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Subsidence
In geology and geophysics, thermal subsidence is a mechanism of subsidence in which conductive cooling of the mantle thickens the lithosphere and causes it to decrease in elevation. This is because of thermal contraction: as mantle material cools and becomes part of the mechanically rigid lithosphere, it becomes denser than the surrounding material. Additional material added to the lithosphere thickens it and further causes a buoyant decrease in the elevation of the lithosphere. This creates accommodation space into which sediments can deposit, forming a sedimentary basin. Causes Thermal subsidence can occur anywhere in which a temperature differential exists between a section of the lithosphere and its surroundings. There are a variety of contributing factors that can initiate thermal subsidence or affect the process as it is ongoing. Delamination As endogenous and exogenous processes cause denudation of the earth's surface, lower, warmer sections of the lithosphere are exposed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plate Tectonics
Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago. The model builds on the concept of '' continental drift'', an idea developed during the first decades of the 20th century. Plate tectonics came to be generally accepted by geoscientists after seafloor spreading was validated in the mid to late 1960s. Earth's lithosphere, which is the rigid outermost shell of the planet (the crust and upper mantle), is broken into seven or eight major plates (depending on how they are defined) and many minor plates or "platelets". Where the plates meet, their relative motion determines the type of plate boundary: '' convergent'', '' divergent'', or '' transform''. Earthquakes, volcanic activity, mountain-building, and ocea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seamount
A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abruptly and are usually found rising from the seafloor to in height. They are defined by oceanographers as independent features that rise to at least above the seafloor, characteristically of conical form.IHO, 2008. Standardization of Undersea Feature Names: Guidelines Proposal form Terminology, 4th ed. International Hydrographic Organization and Intergovernmental Oceanographic Commission, Monaco. The peaks are often found hundreds to thousands of meters below the surface, and are therefore considered to be within the deep sea. During their evolution over geologic time, the largest seamounts may reach the sea surface where wave action erodes the summit to form a flat surface. After they have subsided and sunk below the sea surface such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sinkhole
A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openings where surface water enters into underground passages known as '' ponor'', swallow hole or swallet. A '' cenote'' is a type of sinkhole that exposes groundwater underneath. A ''sink'' or ''stream sink'' are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock. Most sinkholes are caused by karst processes – the chemical dissolution of carbonate rocks, collapse or suffosion processes. Sinkholes are usually circular and vary in size from tens to hundreds of meters both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide. Formation Natural processes Sinkholes may capture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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