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Oceanic Trenches
Oceanic trenches are prominent, long, narrow topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding oceanic floor, but can be thousands of kilometers in length. There are about of oceanic trenches worldwide, mostly around the Pacific Ocean, but also in the eastern Indian Ocean and a few other locations. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of below sea level. Oceanic trenches are a feature of the Earth's distinctive plate tectonics. They mark the locations of convergent plate boundaries, along which lithospheric plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. Oceanic lithosphere moves into trenches at a global rate of about per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to and about from a vol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cold Seep
A cold seep (sometimes called a cold vent) is an area of the ocean floor where seepage of fluids rich in hydrogen sulfide, methane, and other hydrocarbons occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the seepage is lower than that of the surrounding sea water; on the contrary, its temperature is often slightly higher. The "cold" is relative to the very warm (at least ) conditions of a hydrothermal vent. Cold seeps constitute a biome supporting several endemic species. Cold seeps develop unique topography over time, where reactions between methane and seawater create carbonate rock formations and reefs. These reactions may also be dependent on bacterial activity. Ikaite, a hydrous calcium carbonate, can be associated with oxidizing methane at cold seeps. Types Types of cold seeps can be distinguished according to the depth, as shallow cold seeps and deep cold seeps. Cold seeps can also be distinguished in detail, as follow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New Caledonia
New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a Overseas France#Sui generis collectivity, ''sui generis'' collectivity of the French Republic, a legal status unique in overseas France, and is enshrined in a dedicated chapter of the French Constitution. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre (New Caledonia), Grande Terre, the Loyalty Islands, the Chesterfield Islands, the Belep archipelago, the Isle of Pines (New Caledonia), Isle of Pines, and a few remote islets. The Chesterfield Islands are in the Coral Sea. French people, especially locals, call Grande Terre , a nickname also used more generally for the entire New Caledonia. Kanak people#Agitation for independence, Pro-independence Kanak parties use the name (''pron.'' ) to refer to New Caledonia, a term coined in the 1980s from the ethnic name of the indi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lesser Antilles Subduction Zone
The Lesser Antilles subduction zone is a convergent plate boundary on the seafloor along the eastern margin of the Lesser Antilles Volcanic Arc. In this subduction zone, oceanic crust of the South American plate The South American plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African plate, with which it forms the southern part of the Mid ... is being subducted under the Caribbean plate. References ''Deep structure of an island arc backstop, Lesser Antilles subduction zone'', Christeson et al, (2003) Journal of Geophysical Research, V.108, p.2327 Plate tectonics Subduction zones Lesser Antilles Seismic faults of North America {{Marine-geo-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lesser Antilles
The Lesser Antilles is a group of islands in the Caribbean Sea, forming part of the West Indies in Caribbean, Caribbean region of the Americas. They are distinguished from the larger islands of the Greater Antilles to the west. They form an arc which begins east of Geography of Puerto Rico, Puerto Rico at the Virgin Islands, archipelago of the Virgin Islands, swings southeast through the Leeward Islands, Leeward and Windward Islands towards South America, and turns westward through the Leeward Antilles along the Geography of Venezuela, Venezuelan coast. Most of them are part of a long, partially volcanic arc, volcanic island arc between the Greater Antilles to the north-west and the continent of South America."West Indies." ''Merriam-Webster's Geographical Dictionary'', 3rd ed. 2001. () Springfield, MA: Merriam-Webster Inc., p. 1298. The islands of the Lesser Antilles form the eastern boundary of the Caribbean Sea where it meets the Atlantic Ocean. Together, the Lesser Antilles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cascadia Subduction Zone
The Cascadia subduction zone is a convergent plate boundary, about off the Pacific coast of North America, that stretches from northern Vancouver Island in Canada to Northern California in the United States. It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30 m (100 ft) high. The Oregon Department of Emergency Management estimates shaking would last 5–7 minutes along the coast, with strength and intensity decreasing further from the epicenter. It is a very long, sloping subduction zone where the Explorer, Juan de Fuca, and Gorda plates move to the east and slide below the much larger mostly continental North American plate. The zone varies in width and lies offshore beginning near Cape Mendocino, Northern California, passing through Oregon and Washington, and terminating in Canada at about Vancouver Island in British Columbia. The Explorer, Juan de Fuca, and Gorda plates are some of the remnants of the vast ancient Farallon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Makran
Makran (), also mentioned in some sources as ''Mecran'' and ''Mokrān'', is the southern coastal region of Balochistan. It is a semi-desert coastal strip in the Balochistan province in Pakistan and in Iran, along the coast of the Gulf of Oman. It extends westwards, from the Sonmiani Bay to the northwest of Karachi in the east, to the fringes of the region of Bashkardia/Bāšgerd in the southern part of the Sistan and Baluchestan province of modern Iran. Makrān is thus bisected by the modern political boundary between Pakistan and Iran. In January 2025, a government spokesperson informed that Iran is investigating the possibility of moving its capital to the Makran region. Etymology The southern part of Balochistan is called ''Kech Makran'' on the Pakistani side and Makran on the Iranian side which is also the name of a former Iranian province. The location corresponds to that of the Maka satrapy in Achaemenid times. The Sumerian trading partners of Magan are identified wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trough (geology)
In geology, a trough is a linear structural depression that extends laterally over a distance. Although it is less steep than a ''trench'', a trough can be a narrow basin or a geologic rift. These features often form at the rim of tectonic plates. There are various oceanic troughs on the ocean floors. Examples of oceanic troughs * Benue Trough * Cayman Trough * Hesperides Trough * Kings Trough * Mariana Trough * Nankai Trough * Northumberland Trough * Okinawa Trough in the East China Sea * Rockall Trough and others along the rift of the mid-oceanic ridge * Salton Trough * South Shetland Trough * Suakin TroughDinwiddie, Robert et al. (2008) ''Ocean: The World's Last Wilderness Revealed'', London, Dorling Kindersley, page 452. in the Red Sea * Timor Trough See also * Oceanic basin * Thalweg * Walker Lane The Walker Lane is a geologic trough roughly aligned with the California/Nevada border southward to where Death Valley intersects the Garlock Fault, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orogen
An orogenic belt, orogen, or mobile belt, is a zone of Earth's crust affected by orogeny. An orogenic belt develops when a continental plate crumples and is uplifted to form one or more mountain ranges; this involves a series of geological processes collectively called ''orogenesis''. Overview Orogeny typically produces ''orogenic belts'', which are elongated regions of deformation bordering continental cratons. Young orogenic belts, in which subduction is still taking place, are characterized by frequent volcanic activity and earthquakes. Older orogenic belts are typically deeply eroded to expose displaced and deformed strata. These are often highly metamorphosed and include vast bodies of intrusive igneous rock called batholiths. File:Active Margin.svg, Subduction of an oceanic plate beneath a continental plate to form an accretionary orogen. (example: the Andes) File:Continental-continental convergence Fig21contcont.gif, Continental collision of two continental pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Island Arcs
Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone. They are the principal way by which continental growth is achieved. Island arcs can either be active or inactive based on their seismicity and presence of volcanoes. Active arcs are ridges of recent volcanoes with an associated deep seismic zone. They also possess a distinct curved form, a chain of active or recently extinct volcanoes, a deep-sea trench, and a large negative Bouguer anomaly on the convex side of the volcanic arc. The small positive gravity anomaly associated with volcanic arcs has been interpreted by many authors as due to the presence of dense volcanic rocks beneath the arc. Inactive arcs are a chain of islands which contains older volcanic and volcaniclastic rocks. The curved shape of many ... [...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 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, orogenesis, destruction of lithosphere, and 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 surface to the mantle. These convection cells bri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacific Elevation2
The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the continents of Asia and Australia in the west and the Americas in the east. At in area (as defined with a southern Antarctic border), the Pacific Ocean is the largest division of the World Ocean and the hydrosphere and covers approximately 46% of Earth's water surface and about 32% of the planet's total surface area, larger than its entire land area ().Pacific Ocean . ''Encyclopædia Britannica, Britannica Concise.'' 2008: Encyclopædia Britannica, Inc. The centers of both the Land and water hemispheres, water hemisphere and the Western Hemisphere, as well as the Pole of inaccessi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
