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Suevite
Suevite is a rock consisting partly of melted material, typically forming a breccia containing glass and crystal or lithic fragments, formed during an impact event. It forms part of a group of rock types and structures that are known as impactites. Name The word "suevite" is derived from "Suevia", Latin name of Swabia. It was suggested by Adolf Sauer in 1901. Formation Suevite is thought to form in and around impact craters by the sintering of molten fragments together with unmelted clasts of the country rock. Rocks formed from more completely melted material found in the crater floor are known as '' tagamites''. Suevite is distinct from the pseudotachylite in an impact structure as the latter is thought to have formed by frictional effects within the crater floor and below the crater during the initial compression phase of the impact and the subsequent formation of the central uplift. Occurrence Suevite is one of the diagnostic rock-types for large impact structures. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Suevite Aumühle
Suevite is a rock consisting partly of melted material, typically forming a breccia containing glass and crystal or lithic fragments, formed during an impact event. It forms part of a group of rock types and structures that are known as impactites. Name The word "suevite" is derived from "Suevia", Latin name of Swabia. It was suggested by Adolf Sauer in 1901. Formation Suevite is thought to form in and around impact craters by the sintering of molten fragments together with unmelted clasts of the country rock. Rocks formed from more completely melted material found in the crater floor are known as '' tagamites''. Suevite is distinct from the pseudotachylite in an impact structure as the latter is thought to have formed by frictional effects within the crater floor and below the crater during the initial compression phase of the impact and the subsequent formation of the central uplift. Occurrence Suevite is one of the diagnostic rock-types for large impact structures. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chicxulub Crater
The Chicxulub crater () is an impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is offshore near the community of Chicxulub, after which it is named. It was formed slightly over 66 million years ago when a large asteroid, about in diameter, struck Earth. The crater is estimated to be in diameter and in depth. It is the second largest confirmed impact structure on Earth, and the only one whose peak ring is intact and directly accessible for scientific research. The crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatán Peninsula during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact with Alan R. Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature. Evidence for the crater's impact origin includes shocked quartz, a gravity anomaly, and tektites ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nördlinger Ries
The Nördlinger Ries is an impact crater and large circular depression in western Bavaria and eastern Baden-Württemberg. It is located north of the Danube in the district of Donau-Ries. The city of Nördlingen is located within the depression, about south-west of its centre. Etymology "Ries" is derived from Raetia, since the tribe of Raetians lived in the area in pre- Roman times. Description The depression is a meteorite impact crater formed 14.808 ± 0.038 million years ago in the Miocene. The crater is most commonly referred to simply as ''Ries crater'' or ''the Ries''. The original crater rim had an estimated diameter of . The present floor of the depression is about below the eroded remains of the rim. It was originally assumed that the Ries was of volcanic origin. In 1960 Eugene Shoemaker and Edward C. T. Chao showed that the depression was caused by meteorite impact. The key evidence was the presence of coesite, which, in unmetamorphosed rocks, can only ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shock Metamorphism
Shock metamorphism or impact metamorphism describes the effects of shock-wave related deformation and heating during impact events. The formation of similar features during explosive volcanism is generally discounted due to the lack of metamorphic effects unequivocally associated with explosions and the difficulty in reaching sufficient pressures during such an event. Effects Mineral microstructures Planar fractures Planar fractures are parallel sets of multiple planar cracks or cleavages in quartz grains; they develop at the lowest pressures characteristic of shock waves (~5–8 GPa) and a common feature of quartz grains found associated with impact structures. Although the occurrence of planar fractures is relatively common in other deformed rocks, the development of intense, widespread, and closely spaced planar fractures is considered diagnostic of shock metamorphism. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azuara Impact Structure
The Azuara impact structure is a structural feature of about diameter,Mikheeva, 2017 located in northeastern Spain, roughly south of Zaragoza. The name is attributed to the small town of Azuara located near the center of the structure. The first hint to a possible impact origin was given by Wolfgang Hammann as early as 1980, and the first field evidence was provided by Johannes Fiebag in the early eighties. In 1985, Ernstson et al. published the occurrence of shock metamorphism, and Azuara was established (Grieve & Shoemaker 1994, Hodge 1994, Norton 2002Grieve R. A. F. and Shoemaker E. M. (1994) The record of past impacts on Earth. In Hazards Due to Comets and Asteroids, edited by T. Gehrels. Space Science Series Tucson, Arizona, USA: Univ. Arizona Press. pp. 417-462Hodge P. (1994) Meteorite craters and impact structures of the Earth. Cambridge, UK: Cambridge University Press. 124 p."Norton, O.R. (2002) The Cambridge Encyclopedia of Meteorites" as an authentic impact structure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kara Crater
Kara is a meteorite crater in the Yugorsky Peninsula, Nenetsia, Russia. Heavily eroded, it is presently in diameter, though it is thought to be originally before erosion. Its age is estimated to be 70.3 ± 2.2 million years old (Late Cretaceous). Impactite outcrops located on the Baydarata Gulf (Baydaratskaya) shore north-east of the crater imply that the original size of the crater could have been the 4th largest on Earth. The crater is not exposed at the surface. The Kara crater lies in the southeastern end of the Yugorsky Peninsula, while the Ust-Kara site lies offshore, east of the small Kara or Karskaya Guba inlet. It was formerly believed that these two sites were two separate craters and that they formed a twin impact structure from the Late Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is ... [...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 geological structure in Ontario, Canada. It is the third-largest known impact crater or astrobleme on Earth, as well as one of the oldest. The crater formed 1.849 billion years ago in the Paleoproterozoic era. 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. Formation The Sudbury basin formed as a result of an impact into the Nuna supercontinent from a bolide approximately in diameter that occurred 1.849 billion years ago in the Paleoproterozoic era. Debris from the impact was scattered over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain. Lunar impact craters range from microscopic craters on lunar rocks returned by the Apollo Program and small, simple, bowl-shaped depressions in the lunar regolith to large, complex, multi-ringed impact basins. Meteor Crater is a well-known example of a small impact crater on Earth. Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids. On other planets and moons that experience more active surface geological processes, such as Earth, Venus, Europa, Io and Titan, visible impact craters are less common because they become ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impactite
Impactite is rock created or modified by one or more impacts of a meteorite. Impactites are considered metamorphic rock, because their source materials were modified by the heat and pressure of the impact. On Earth, impactites consist primarily of modified terrestrial material, sometimes with pieces of the original meteorite. Creation When a large meteorite hits a planet, it can radically deform the rocks and regolith that it hits. The heat, pressure, and shock of the impact changes these materials into impactite. Only very massive impacts generate the heat and pressure needed to transform a rock, so impactites are created rarely. Characteristics Impactite includes shock-metamorphosed target rocks, melts ( suevites) and mixtures of the two, as well as sedimentary rocks with significant impact-derived components (shocked mineral grains, tektites, anomalous geochemical signatures, etc.). In June 2015, NASA reported that impact glass has been detected on the planet Mars. Such ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sintering
Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing process used with metals, ceramics, plastics, and other materials. The atoms in the materials diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece. Because the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting points such as tungsten and molybdenum. The study of sintering in metallurgical powder-related processes is known as powder metallurgy. An example of sintering can be observed when ice cubes in a glass of water adhere to each other, which is driven by the temperature difference between the water and the ice. Examples of pressure-driven sintering are the compact ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meteorite Shock Stage
Meteorite shock stage is a measure of the degree of fracturing of the matrix of a common chondrite meteorite. Impacts on the parent body of a meteoroid can produce very large pressures. These pressures heat, melt and deform the rocks. This is called shock metamorphism. Meteorites are often given a rating from 1 to 6 showing the level of shock metamorphism. However, the degree of shock can vary within a meteorite on the scale of centimeters. Smaller bodies colliding with one another would not have sufficiently great impact velocity to produce the pressures and temperatures required to produce shock effects, due to their lesser gravitational attraction for one another. High instantaneous pressures, in excess of 5 GPa (1 GPa = 10,000 atmospheres), are necessary to produce shock metamorphism. Shock grade The fracturing of crystals and other features must be observed under a microscope with shock effects observed under polarized light. Larger structures, such as shock veins, are vis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Popigai Impact Structure
The Popigai impact structure is the eroded remnant of an impact crater in northern Siberia, Russia. It is tied with the Manicouagan structure as the fourth largest verified impact structure on Earth. A large bolide impact created the diameter crater approximately 35 million years ago during the late Eocene epoch ( Priabonian stage). It might be linked to the Eocene–Oligocene extinction event. The structure is east from the outpost of Khatanga and northeast of the city of Norilsk, NNE of the Anabar Plateau. It is designated by UNESCO as a Geopark, a site of special geological heritage. There is a small possibility that the Popigai impact crater may have formed simultaneously with the approximately 35-million-year-old Chesapeake Bay and Toms Canyon impact craters. For decades, the Popigai impact structure has fascinated paleontologists and geologists, but the entire area was completely off limits because of the diamonds found there. However, a major investigatory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
