|
Orca Seamount
Orca Seamount is a seamount (underwater volcano) near King George Island in Antarctica, in the Bransfield Strait. While it is inactive, last volcanic activity at Orca Seamount is judged to have occurred in the recent past as there are temperature anomalies in the seawater around the seamount. Thermophilic and hyperthermophilic microorganisms have been found at the seamount. The crater rim is about 3 km wide and about 500 m above the ocean floor. The seamount was first named by Professor O. González-Ferrán of Chile in 1987, after the orca (killer whale) often sighted in these waters. It was mapped and studied by the ship RV ''Polarstern'' during an Antarctic cruise (number ANT-XI/3) in 2005. The variant name of Viehoff Seamount (approved in 6/95 ACUF 263) was named for Dr. Thomas Viehoff, a remote sensing specialist in marine sciences. Name proposed by Dr. G.B. Udintsev, Vernadsky Institute of Geochemistry (VIG). Geology The submarine volcano is a Pleistocene- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
King George Island (Antarctica)
King George Island (Argentinian Spanish: Isla 25 de Mayo, Chilean Spanish: Isla Rey Jorge, Russian: Ватерло́о Vaterloo) is the largest of the South Shetland Islands, lying off the coast of Antarctica in the Southern Ocean. The island was named after King George III. Geography King George island has three major bays, Maxwell Bay, Admiralty Bay, and King George Bay. Admiralty Bay contains three fjords, and is protected as an Antarctic Specially Managed Area under the Protocol on Environmental Protection to the Antarctic Treaty. History The island was first claimed for Britain on 16 October 1819, formally annexed by Britain as part of the Falkland Islands Dependencies in 1908, and now as part of the separate British Antarctic Territory. The Island was claimed by Chile in 1940, as part of the Chilean Antarctic Territory. It was also claimed by Argentina in 1943, now as part of Argentine Antarctica, called by the Argentines ''Isla Veinticinco de Mayo'' (25 May) in ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bransfield Basin
The Bransfield Basin is a back-arc rift basin located off the northern tip of the Antarctic Peninsula. The basin lies within a Northeast and Southwest trending strait that separates the peninsula from the nearby South Shetland Islands to the Northwest. The basin extends for more than from Smith Island (South Shetland Islands) to a portion of the Hero Fracture Zone. The basin can be subdivided into three basins: Western, Central, and Eastern. The Western basin is long by wide with a depth of , the Central basin is long by wide with a depth of , and the Eastern basin is long by wide with a depth of over . The three basins are separated by the Deception Island and Bridgeman Island. The moho depth in the region has been seismically interpreted to be roughly deep. Tectonic development The Bransfield Basin is considered to be a back-arc basin that is located behind the South Shetland Islands. The Islands are believed to have formed from a period of subduction that occ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Igneous Intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and compositions, illustrated by examples like the Palisades Sill of New York and New Jersey; the Henry Mountains of Utah; the Bushveld Igneous Complex of South Africa; Shiprock in New Mexico; the Ardnamurchan intrusion in Scotland; and the Sierra Nevada Batholith of California. Because the solid country rock into which magma intrudes is an excellent insulator, cooling of the magma is extremely slow, and intrusive igneous rock is coarse-grained (phaneritic). Intrusive igneous rocks are classified separately from extrusive igneous rocks, generally on the basis of their mineral content. The relative amounts of quartz, alkali feldspar, plagioclase, and feldspathoid is particularly important in classifying intrusive igneous rocks. Intrusions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
King George Island (South Shetland Islands)
King George Island (Argentinian Spanish: Isla 25 de Mayo, Chilean Spanish: Isla Rey Jorge, Russian: Ватерло́о Vaterloo) is the largest of the South Shetland Islands, lying off the coast of Antarctica in the Southern Ocean. The island was named after King George III. Geography King George island has three major bays, Maxwell Bay, Admiralty Bay, and King George Bay. Admiralty Bay contains three fjords, and is protected as an Antarctic Specially Managed Area under the Protocol on Environmental Protection to the Antarctic Treaty. History The island was first claimed for Britain on 16 October 1819, formally annexed by Britain as part of the Falkland Islands Dependencies in 1908, and now as part of the separate British Antarctic Territory. The Island was claimed by Chile in 1940, as part of the Chilean Antarctic Territory. It was also claimed by Argentina in 1943, now as part of Argentine Antarctica, called by the Argentines ''Isla Veinticinco de Mayo'' (25 May) in ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquakes
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time period. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word ''tremor'' is also used for non-earthquake seismic rumbling. At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake Swarm
In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period. The time span used to define a swarm varies, but may be days, months, or years. Such an energy release is different from the situation when a major earthquake (main shock) is followed by a series of aftershocks: in earthquake swarms, no single earthquake in the sequence is obviously the main shock. In particular, a cluster of aftershocks occurring after a mainshock ''is not'' a swarm. History and generalities In the Ore Mountains (Erzgebirge), which form the border between the Czech Republic and Germany, western Bohemia and the Vogtland region, have been known since the 16th century as prone to frequent earthquake swarms, which typically last a few weeks to a few months. Austrian geologist Josef Knett, while studying in 1899 a swarm of about a hundred events felt in western Bohemia/Vogtland in January-February 1824, coined the noun ''Schwarmbeben'', ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phoenix Plate
The Phoenix Plate (also known as the Aluk Plate or Drake Plate) was a tectonic plate that existed during the early Paleozoic through late Cenozoic time. It formed a triple junction with the Izanagi and Farallon plates in the Panthalassa Ocean as early as 410 million years ago, during which time the Phoenix Plate was subducting under eastern Gondwana. By the Late Jurassic–Early Cretaceous 150–130 million years ago, the Pacific Plate arose from the Izanagi-Farallon-Phoenix triple junction, resulting in the creation of the Izanagi-Pacific-Phoenix and Farallon-Pacific-Phoenix triple junctions. Subduction ceased east of Australia about 120 million years ago, during which time a transform/transpressional boundary formed. This transform/transpressional boundary with the Phoenix Plate lasted until about 80 million years ago as the plate continued to descend southwards as a result of Late Cretaceous subduction under the Antarctic Peninsula. During the Late Cretaceous o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Plate
The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau, and some remote islands in the Southern Ocean and other surrounding oceans. After breakup from Gondwana (the southern part of the supercontinent Pangea), the Antarctic plate began moving the continent of Antarctica south to its present isolated location, causing the continent to develop a much colder climate. The Antarctic Plate is bounded almost entirely by extensional mid-ocean ridge systems. The adjoining plates are the Nazca Plate, the South American Plate, the African Plate, the Somali Plate, the Indo-Australian Plate, the Pacific Plate, and, across a transform boundary, the Scotia Plate. The Antarctic Plate has an area of about . It is Earth's fifth-largest tectonic plate. The Antarctic Plate's movement is estimated to be at least per year towards the Atlantic Ocean. Subduction beneath South America The Antarctic Plate started to subduct beneath South America 14 mil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scotia Plate
The Scotia Plate () is a tectonic plate on the edge of the South Atlantic and Southern oceans. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates South America from Antarctica, it is a minor plate whose movement is largely controlled by the two major plates that surround it: the South American Plate and the Antarctic Plate. The Scotia Plate takes its name from the steam yacht ''Scotia'' of the Scottish National Antarctic Expedition (1902–04), the expedition that made the first bathymetric study of the region. Roughly rhomboid, extending between and , the plate is wide and long. It is moving WSW at /year and the South Sandwich Plate is moving east at /year in an absolute reference frame. The Scotia Plate is made of oceanic crust and continental fragments now distributed around the Scotia Sea. Before the formation of the plate began (40Ma), these fragments formed a continuous landmass from Patagonia to the Antarctic Penin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhyolite
Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent to granite. Rhyolitic magma is extremely viscous, due to its high silica content. This favors explosive eruptions over effusive eruptions, so this type of magma is more often erupted as pyroclastic rock than as lava flows. Rhyolitic ash-flow tuffs are among the most voluminous of continental igneous rock formations. Rhyolitic tuff has been extensively used for construction. Obsidian, which is rhyolitic volcanic glass, has been used for tools from prehistoric times to the present day because it can be shaped to an extremely sharp edge. Rhyolitic pumice finds use as an abrasive, in concrete, and as a soil amendment. Description Rhyolite i ... [...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 volcanic rock, subalkaline tholeiite, tholeiitic and calc-alkaline magma series. Composition Dacite consists mostly of plagioclase feldspar and quartz with biotite, hornblende, and pyroxene (augite or enstatite). The quartz appears as rounded, corroded phenocrysts, or as an element of the ground-mass. The plagioclase in dacite ranges from oligoclase to andesine and labradorite. Sanidine occurs, although in small proportions, in some dacites, and when abundant gives rise to rocks that form rhyodacite, transitions to the rhyolites. The rel ... [...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 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) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
