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Maud Rise
Maud Rise () is an oceanic plateau, which rises, at its shallowest, to depths of about a 1,000 meters. It is located in the Weddell Sea in the Southern Ocean. Its name was approved by the Advisory Committee for Undersea Features in June 1987. Geology Maud Rise formed part of the south-eastern African large igneous province (LIP) which developed south of Africa (Ma). This LIP first formed 140-122 Ma east of South Africa where the Mozambique Ridge is now located. There it reached a maximum extent around 120 Ma when the African-Antarctic spreading zone was located below its eastern flank. Astrid Ridge was possibly part of this LIP as well. The LIP formation then continued intermittently until it finally reached its maximum extent south of South Africa 100 Ma. This volcanism ended 94 Ma after which sea-floor spreading divided the LIP into the Agulhas Plateau (south of South Africa), Northeast Georgia Rise (near South Georgia Island off South America), and Maud Rise. See also *W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Plateau
An oceanic or submarine plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. There are 184 oceanic plateaus in the world, covering an area of or about 5.11% of the oceans. The South Pacific region around Australia and New Zealand contains the greatest number of oceanic plateaus (see map). Oceanic plateaus produced by large igneous provinces are often associated with hotspots, mantle plumes, and volcanic islands — such as Iceland, Hawaii, Cape Verde, and Kerguelen. The three largest plateaus, the Caribbean, Ontong Java, and Mid-Pacific Mountains, are located on thermal swells. Other oceanic plateaus, however, are made of rifted continental crust, for example the Falkland Plateau, Lord Howe Rise, and parts of Kerguelen, Seychelles, and Arctic ridges. Plateaus formed by large igneous provinces were formed by the equivalent of continental flood basalts such as the Deccan Traps in India and the Snak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weddell Sea
The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha Coast, Queen Maud Land. To the east of Cape Norvegia is the King Haakon VII Sea. Much of the southern part of the sea is covered by a permanent, massive ice shelf field, the Filchner-Ronne Ice Shelf. The sea is contained within the two overlapping Antarctic territorial claims of Argentine Antarctica, the British Antarctic Territory, and also resides partially within the Antarctic Chilean Territory. At its widest the sea is around across, and its area is around . Various ice shelves, including the Filchner-Ronne Ice Shelf, fringe the Weddell sea. Some of the ice shelves on the east side of the Antarctic Peninsula, which formerly covered roughly of the Weddell Sea, had completely disappeared by 2002. The Weddell Sea has been deemed by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-smallest of the five principal oceanic divisions: smaller than the Pacific, Atlantic, and Indian oceans but larger than the Arctic Ocean. Over the past 30 years, the Southern Ocean has been subject to rapid climate change, which has led to changes in the marine ecosystem. By way of his voyages in the 1770s, James Cook proved that waters encompassed the southern latitudes of the globe. Since then, geographers have disagreed on the Southern Ocean's northern boundary or even existence, considering the waters as various parts of the Pacific, Atlantic, and Indian oceans, instead. However, according to Commodore John Leech of the International Hydrographic Organization (IHO), recent oceanographic research has discovered the importance of Southern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advisory Committee For Undersea Features
The United States Board on Geographic Names (BGN) is a federal body operating under the United States Secretary of the Interior. The purpose of the board is to establish and maintain uniform usage of geographic names throughout the federal government of the United States. History On January 8, 1890, Thomas Corwin Mendenhall, superintendent of the US Coast and Geodetic Survey Office, wrote to 10 noted geographers "to suggest the organization of a Board made up of representatives from the different Government services interested, to which may be referred any disputed question of geographical orthography." President Benjamin Harrison signed executive order 28 on September 4, 1890, establishing the ''Board on Geographical Names''. "To this Board shall be referred all unsettled questions concerning geographic names. The decisions of the Board are to be accepted y federal departmentsas the standard authority for such matters." The board was given authority to resolve all unsettled quest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Large Igneous Province
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation of LIPs is variously attributed to mantle plumes or to processes associated with divergent plate tectonics. The formation of some of the LIPs in the past 500 million years coincide in time with mass extinctions and rapid climatic changes, which has led to numerous hypotheses about causal relationships. LIPs are fundamentally different from any other currently active volcanoes or volcanic systems. Definition In 1992 researchers first used the term ''large igneous province'' to describe very large accumulations—areas greater than 100,000 square kilometers (approximately the area of Iceland)—of mafic igneous rocks that were erupted or emplaced at depth within an extremely short geological time interval: a few million years or less. Maf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mozambique Ridge
Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Africa to the southwest. The sovereign state is separated from the Comoros, Mayotte and Madagascar by the Mozambique Channel to the east. The capital and largest city is Maputo. Notably Northern Mozambique lies within the monsoon trade winds of the Indian Ocean and is frequentely affected by disruptive weather. Between the 7th and 11th centuries, a series of Swahili port towns developed on that area, which contributed to the development of a distinct Swahili culture and language. In the late medieval period, these towns were frequented by traders from Somalia, Ethiopia, Egypt, Arabia, Persia, and India. The voyage of Vasco da Gama in 1498 marked the arrival of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southwest Indian Ridge
The Southwest Indian Ridge (SWIR) is a mid-ocean ridge located along the floors of the south-west Indian Ocean and south-east Atlantic Ocean. A divergent tectonic plate boundary separating the Somali Plate to the north from the Antarctic Plate to the south, the SWIR is characterised by ultra-slow spreading rates (only exceeding those of the Gakkel Ridge in the Arctic) combined with a fast lengthening of its axis between the two flanking triple junctions, Rodrigues () in the Indian Ocean and Bouvet () in the Atlantic Ocean. Geological setting Spreading rates The spreading rate along the SWIR varies: the transition between slow (30 mm/yr) and ultra-slow (15 mm/yr) spreading occur at magnetic anomaly C6C (ca. 24 Ma). This occurs between 54°–67°E, the deepest, and perhaps coldest and most melt-poor, part of Earth's mid-ocean ridge system. Crustal thickness decreases quickly as spreading rates drop below c. 20 mm/yr and in the SWIR there is an absence of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrid Ridge
Astrid Ridge is an undersea ridge on the continental margin of Dronning Maud Land, East Antarctica. It is present on the GEBCO 5th edition charts. The name was approved by the Advisory Committee for Undersea Features in June 1987. The ocean along the continental margin of Dronning Maud Land, the Riiser-Larsen and Lazarev seas, are dominated by three topographic features: Astrid Ridge, Maud Rise, a large volcanic plateau in the Lazarev Sea (3°E, 65°S), and Gunnerus Ridge (33.5°E), probably underlain by continental crust. Astrid Ridge, extending from 65°S to the Antarctic margin and located between 9°E and 17°E, forms the eastern border of the Lazarev Sea and the western border of the Riiser-Larsen Sea. It is divided into two parts by the Astrid Fracture Zone: south of 67°S Astrid Ridge stretches N-S while the northern part follows the SW—NE direction of the fracture zone. The geological evolution of the Astrid Ridge remains enigmatic. The Riiser-Larsen Sea is a conju ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agulhas Plateau
The Agulhas Plateau is an oceanic plateau located in the south-western Indian Ocean about south of South Africa. It is a remainder of a large igneous province (LIP), the Southeast African LIP, that formed (Ma) at or near the triple junction where Gondwana broke-up into Antarctica, South America, and Africa. The plateau formed together with Northeast Georgia Rise and Maud Rise (now located near the Falkland Island and Antarctica respectively) when the region passed over the Bouvet hotspot. Geology History of research The Agulhas Plateau is one of the key structures in the reconstruction of the Gondwana break-up. It was first mapped in 1964 (i.e. part of what would become the Heezen- Tharp map of the world's ocean floor finally published in 1977), but its crustal composition, paleoposition, and geological origin remained enigmatic for decades. The boundary between the Earth's crust and the mantle (the Moho) rises from between the Agulhas Bank (south of South Africa) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northeast Georgia Rise
The Northeast Georgia Rise is an oceanic plateau located in the South Atlantic Ocean northeast of South Georgia Island and west of the Falkland Plateau. Bathymetry The rise is separated from South Georgia Island by the Northeast Georgia Passage. The Georgia Basin surrounds the northern end of the rise. The Agulhas-Falkland Fracture Zone (AFFZ) stretches across the Atlantic north of the Northeast Georgia Rise. A group of small seamounts north of the rise are aligned with a gap in the AFFZ. East of this gap the AFFZ is a single ridge with an average height of but west of the gap the AFFZ is a double ridge with an average height of . On the eastern flank of the rise is a prominent ridge, the Soledad Ridge, about tall. It has the same orientation as the southeastern part of the rise. It is a Basement (geology), basement-feature in which bottom-water have scoured a channel. Both the Northeast Georgia Rise and the Islas Orcadas Rise east of it, are seemingly dissected by transver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Georgia Island
South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east–west direction, South Georgia is around long and has a maximum width of . The terrain is mountainous, with the central ridge rising to at Mount Paget. The northern coast is indented with numerous bays and fjords, serving as good harbours. Discovered by Europeans in 1675, South Georgia had no indigenous population due to its harsh climate and remoteness. Captain James Cook in made the first landing, survey and mapping of the island, and on 17 January 1775 he claimed it a British possession, naming it "Isle of Georgia" after King George III. Through its history, it served as a whaling and seal hunting base, with intermittent population scattered in several whaling bases, the most important historically being Grytviken. The main settleme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weddell Polynya
The Weddell Polynya, or Weddell Sea Polynya, is a polynya or irregular area of open water surrounded by sea ice in the Weddell Sea of the Southern Ocean off Antarctica and near the Maud Rise. The formation of the polynya exposes relatively warmer ocean waters (at surface freezing temperatures of -1.9°C) to a cold atmosphere, leading to a large exchange of heat which drives deep convection in the ocean, often reaching depths of a 1,000 to 2,000 meters! Occurrences The size of New Zealand, it re-occurred each winter between 1974 and 1976. These were the first three austral winters observed by the Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR). From 1976 to 2015 this polynya was rarely observed. The polynya reoccurred in 2016, and has since appeared in 2017. The 2010s occurrence has been smaller than the 1970s occurrence, being about the size of Maine in 2017, or roughly . Since the 1970s, the polar Southern Ocean south of the Antarctic Circumpolar Current has freshened a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
