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Vredefort Dome
The Vredefort impact structure is one of the largest impact structures on Earth. The crater, which has since been eroded away, has been estimated at across when it was formed, the latter estimate suggesting the initial crater was larger than Chicxulub crater, the largest mostly intact impact crater on Earth. The remaining structure, comprising the deformed underlying bedrock, is located in present-day Free State province of South Africa. It is named after the town of Vredefort, which is near its centre. The structure's central uplift is known as the Vredefort Dome, which is around in diameter. The impact structure was formed during the Paleoproterozoic Era, 2.023 billion (± 4 million) years ago. It is among the oldest known impact structures on Earth, after Yarrabubba (2.23 billion years old) and Antarctic Creek (3.47 billion years old). In 2005, the Vredefort Dome was added to the list of UNESCO World Heritage Sites for its geologic interest. Formation and struc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vaal River
The Vaal River ( ; Khoemana: ) is the largest tributary of the Orange River in South Africa. The river has its source near Breyten in Mpumalanga province, east of Johannesburg and about north of Ermelo and only about from the Indian Ocean. It then flows westwards to its confluence with the Orange River southwest of Kimberley in the Northern Cape. It is long, and forms the border between Mpumalanga, Gauteng and North West Province on its north bank, and the Free State on its south. It is the third largest river in South Africa after the Orange River (2200 km long) and the Limpopo River (1750 km long) and was established as the main source of water for the great Witswatersrand area after the 19th century gold rush. The Vaal Dam lies on the Vaal River in Deneysville just south of the border between Gauteng and the Free State. The Vaal River is the longest river wholly within the borders of South Africa. ''Vaal'' is a Dutch name (later Afrikaans), transla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antarctic Creek Impact Structure
The Antarctic Creek impact structure is an impact structure in the Pilbara Craton of Western Australia. With an age of around 3.47 billion years dating to the Paleoarchean, it is the oldest known impact structure on Earth by over a billion years and the only one known from the Archean. The structure is found in the East Pilbara Terrane, one of the oldest parts of the Pilbara Craton. A geological dome called the North Pole Dome likely represents the central uplift of the structure. Evidence of the impact is shatter cones and impact spherules (formed from condensed impact vapour) found in the Antarctic Creek Member, a thick layer of sedimentary rock including "felsic to mafic volcaniclastic rocks, chert, argillite, arenite and jaspilite intruded by dolerite", located within the otherwise entirely volcanic Mount Ada Basalt, which is thick, with the Antarctic Creek Member being overlain by pillow basalts of the Mount Ada Basalt. Uranium–lead dating of detrital zircons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dome (geology)
A dome is a feature in structural geology where a circular part of the Earth's surface has been pushed upward, tilting the pre-existing layers of earth away from the center. In technical terms, it consists of symmetrical anticlines that intersect each other at their respective wikt:apex, apices. Intact, domes are distinct, rounded, sphere, spherical-to-ellipsoidal-shaped protrusions on the Earth's surface. A slice parallel to Earth's surface of a dome features concentric rings of stratum, strata. If the top of a dome has been eroded flat, the resulting structure in Multiview_orthographic_projection#Plan, plan view appears as a Bullseye_(target), bullseye, with the youngest rock layers at the outside, and each ring growing progressively older moving inwards. These strata would have been horizontal at the time of Deposition_(geology), deposition, then later deformed by the Tectonic uplift, uplift associated with dome formation. Formation mechanisms There are many possible mechani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suavjärvi
Suavjärvi (in Karelian, Russian: ) is a lake in the Republic of Karelia, Russia about 50 km north of the town of Medvezhyegorsk. The lake is approximately wide. Mashchak and NaumovMashchak, M.S. and Naumov, M.V., 1996, ''The Suavjarvi Structure: An early proterozoic Impact site on the fennoscandian shield.'' ''Lunar and Planetary Science Conference'', 27(3), pp. 825–826.Mashchak, M.S. and Naumov, M.V., 2012. ''The Suavjärvi impact structure, NW Russia.'' ''Meteoritics & Planetary Science'', 47(10), pp.1644-1658. argue that Suavjärvi lies at the center of a deeply eroded and highly metamorphosed impact structure, the Suavjärvi structure, which has a diameter of . According to Mashchak and Naumov, this impact structure is characterized by gravity and magnetic lows and in its northeastern and southwestern parts, impact-generated polymict megabreccias. The megabreccias are composed of blocks of both basement granitoid A granitoid is a broad term referring to a diverse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maniitsoq Structure
The Maniitsoq structure is a geologic structure resembling a meteorite impact structure located in the Akia terrane of the North Atlantic Craton, centred about south-east of the town of Maniitsoq, Greenland, at . In spite of this resemblance, the structure is caused by regional geologic processes (magmatism, tectonism and metamorphism) that reworked and stabilized the North Atlantic Craton during the Mesoarchean to Neoarchean eras. Originally notable for being proposed as the oldest known impact crater on Earth (3 billion years old), the proposal was criticised for not meeting established criteria for impact craters. Subsequent studies demonstrated no evidence for an impact structure, and observations directly contradict the impact structure proposals. The Maniitsoq structure is not recognised as an impact structure by the Earth Impact Database. Impact structure proposal Garde ''et al''. suggested the presence of a ~ scale impact structure, formed by the impact of a large co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dhala Crater
The Dhala impact structure (N25°17'59.7" and E78°8'3.1") is an impact structure formed by an asteroid impact. It is situated near Bhonti village in Pichhore block of Shivpuri district of Madhya Pradesh state in India. It is the largest impact structure in India, and between the Mediterranean and Southeast Asia. The diameter of the structure is estimated at , while other sources estimate its diameter to be 11 km diameter. It is the second such structure found in India, after Lonar lake. It is 200 km east of the Ramgarh crater. Impact date It is estimated that the impact occurred between 2.44 and 2.24 Ga. Basement rocks are predominantly composed of granitoids. Largest in India This impact structure on the Bundelkhand craton is the largest in India. See also ; Impact craters in India * Lonar crater at Lonar in Buldhana district of Maharashtra * Luna crater at Kutch district of Gujarat * Shiva crater, a proposed undersea crater west of India ; Other related topic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sudbury Basin
The Sudbury Basin (), also known as Sudbury Structure or the Sudbury Nickel Irruptive, is a major geology, geological structure in Ontario, Canada. It is among the oldest- and largest-known List of impact structures on Earth, impact structures on Earth. The structure, the eroded remnant of an Impact structure, impact crater, was formed by the impact of an asteroid 1.849 billion years ago in the Paleoproterozoic era. The ores of the Sudbury Basin are known to contain nickel, copper, gold, silver, platinum, palladium, rhodium, iridium, and ruthenium. The basin is located on the Canadian Shield in the city of Greater Sudbury, Ontario. The former municipalities of Rayside-Balfour, Valley East and Capreol lie within the Sudbury Basin, which is referred to locally as "The Valley". The urban core of the former city of Sudbury lies on the southern outskirts of the basin. An Ontario Historical Plaque was erected by the province to commemorate the discovery of the Sudbury Basin. Format ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isostatic Rebound
Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound and isostatic depression are phases of glacial isostasy (glacial isostatic adjustment, glacioisostasy), the deformation of the Earth's crust in response to changes in ice mass distribution. The direct raising effects of post-glacial rebound are readily apparent in parts of Northern Eurasia, Northern America, Patagonia, and Antarctica. However, through the processes of ''ocean siphoning'' and ''continental levering'', the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets.Milne, G.A., and J.X. Mitrovica (2008) ''Searching for eustasy in deglacial sea-level histories.'' Quaternary Science Reviews. 27:2292–2302. Overview During the last glacial period, much of northern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bolide
A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large Impact crater, crater-forming body, or to one that explodes in the atmosphere. It can be a synonym for a Meteoroid#Fireball, fireball, sometimes specific to those with an apparent magnitude of −4 or brighter. Definitions The word ''bolide'' (; from Italian language, Italian via Latin, ) may refer to somewhat different phenomena depending on the context in which the word appears, and readers may need to make inferences to determine which meaning is intended in a particular publication. An early usage occurs in ''Natural History (Pliny), Natural History'', where Pliny the Elder describes two types of prodigium, prodigies, "those which are called lampades and those which are called bolides". At least one of the prodigies described by Pliny (a "spark" that fell, grew to the "size of the moon", and "returned into the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hadean
The Hadean ( ) is the first and oldest of the four geologic eons of Earth's history, starting with the planet's formation about 4.6 billion years ago (estimated 4567.30 ± 0.16 million years ago set by the age of the oldest solid material in the Solar System—protoplanetary disk dust particles—found as chondrules and calcium–aluminium-rich inclusions in some meteorites about 4.567 billion years old), and ended 4.031 billion years ago, the age of the oldest known intact rock formations on Earth as recognized by the International Commission on Stratigraphy. The interplanetary collision that created the Moon occurred early in this eon. The Hadean eon was succeeded by the Archean eon, with the Late Heavy Bombardment hypothesized to have occurred at the Hadean-Archean boundary. Hadean rocks are very rare, largely consisting of granular zircons from one locality ( Jack Hills) in Western Australia. Hadean geophysical models remain controversial among geologis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). Asteroids are rocky, metallic, or icy bodies with no atmosphere, and are broadly classified into C-type asteroid, C-type (carbonaceous), M-type asteroid, M-type (metallic), or S-type asteroid, S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres (dwarf planet), Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies. Of the roughly one million known asteroids, the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 astronomical unit, AU ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
