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Aorounga Crater
Aorounga is an eroded meteorite impact crater in Chad, Africa. The exposed remnant of the crater is in diameter and its age is estimated to be less than 345 million years (Carboniferous or younger).VINCENT P.M., BEAUVILAIN A., 1996. Découverte d'un nouveau cratère d'impact météoritique en Afrique : l'astroblème de Gweni-Fada (Ennedi, Sahara du Tchad). C. R. Acad. Sci. Paris, t. 323, série II a, pp. 987-997 Description An outer and an inner ring (11 and 7 km, respectively) rise about 100 m above the mean level of the surrounding plain (see topographic map). Both aforementioned rings are separated by a relatively flat depression of uniform width. A possible central hill, maybe an uplift structure, of 1.5 km is almost centrally located in the depression. The crater is accompanied by two nearby circular features revealed by Space Shuttle SIR-C radar. These may be related impact craters, and if correct, Aorounga may be part of a crater chain. On the assumption that this hypot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synthetic Aperture Radar
Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide finer spatial resolution than conventional stationary beam-scanning radars. SAR is typically mounted on a moving platform, such as an aircraft or spacecraft, and has its origins in an advanced form of side looking airborne radar (SLAR). The distance the SAR device travels over a target during the period when the target scene is illuminated creates the large ''synthetic'' antenna aperture (the ''size'' of the antenna). Typically, the larger the aperture, the higher the image resolution will be, regardless of whether the aperture is physical (a large antenna) or synthetic (a moving antenna) – this allows SAR to create high-resolution images with comparatively small physical antennas. For a fixed antenna size and orientation, objects which are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crater Chain
A crater chain is a line of craters along the surface of an astronomical body. The descriptor term for crater chains is catena , plural catenae (Latin for "chain"), as specified by the International Astronomical Union's rules on planetary nomenclature. Many examples of such chains are thought to have been formed by the impact of a body that was broken up by tidal forces into a string of smaller objects following roughly the same orbit. An example of such a tidally disrupted body that was observed prior to its impact on Jupiter is Comet Shoemaker-Levy 9. During the Voyager observations of the Jupiter system, planetary scientists identified 13 crater chains on Callisto and three on Ganymede (except those formed by secondary craters). Later some of these chains turned out to be secondary or tectonic features, but some other chains were discovered. As of 1996, 8 primary chains on Callisto and 3 on Ganymede were confirmed. Other cases, such as many of those on Mars, represent c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carboniferous Impact Craters
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago (Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous'' means "coal-bearing", from the Latin '' carbō'' ("coal") and '' ferō'' ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern 'system' names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession. The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial animal life was well established by the Carboniferous Period. Tetrapods (four limbed vertebrates), which had originated from lobe-finned fish during the preceding Devonian, became pentadactylous in and diversified during the Carboniferous, including early amphibian lineages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impact Craters Of Chad
Impact may refer to: * Impact (mechanics), a high force or shock (mechanics) over a short time period * Impact, Texas, a town in Taylor County, Texas, US Science and technology * Impact crater, a meteor crater caused by an impact event * Impact event, the collision of a meteoroid, asteroid or comet with Earth * Impact factor, a measure of the citations to a science or social science journal Books and magazines * ''Impact'' (novel), a 2010 novel by Douglas Preston *'' Impact Press'', a former Orlando, Florida-based magazine * Impact Magazines, a former UK magazine publisher * ''Impact'' (conservative magazine), a British political magazine * ''Impact'' (British magazine), a British action film magazine * ''Impact'', a French action film magazine spun off from '' Mad Movies'' * ''Impact'' (UNESCO magazine), a former UNESCO quarterly titled ''IMPACT of science on society'' * ''Impact'' (student magazine), a student magazine for the University of Nottingham, England * ''Bath ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gweni-Fada Crater
Gweni-Fada is a meteorite impact crater, crater in the Ennedi Plateau, Chad.VINCENT P.M., BEAUVILAIN A.The circular structure of Gweni-Fada, Ennedi : a new meteoritic impact crater in northern Chad C.R. Acad. Sci. Paris, t. 323, série II a, pp. 987-997, 1996. The Gweni Fada structure was first noted on the map NE 34 X Fada of the Institut national de l'information géographique et forestière, IGN (National Geographic Institute France) and aerial photographs in the 1950s of IGN by Alain Beauvilain (Paris X- Nanterre University). In April 1995, at the initiative of CNAR (National Center to Help Research of Chad) a team of French geologists (Pierre Vincent, University of Clermont-Ferrand, Alain and Najia Beauvilain, CNAR Chad) visited the site and reported evidence of shock metamorphism within rock samples they had collected inside the structure. Centered at 17°25′N and 21°45′E, being slightly wider in the NW-SE direction (cf. topographic map), the asymmetric structure i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Impact Craters In Africa
__TOC__ Confirmed impact craters This list of impact craters in Africa includes all 20 confirmed impact craters as listed in the Earth Impact Database. These features were caused by the collision of large meteorites or comets with the Earth. For eroded or buried craters, the stated diameter typically refers to an estimate of original rim diameter, and may not correspond to present surface features. Unconfirmed impact craters The following craters are officially considered "unconfirmed" because they are not listed in the Earth Impact Database. Due to stringent requirements regarding evidence and peer-reviewed publication, newly discovered craters or those with difficulty collecting evidence generally are known for some time before becoming listed. However, entries on the unconfirmed list could still have an impact origin disproven. Notes Mahas was anonymously added Jan 2015, but the coordinates do show a convincing impact-like structure. It appears to me the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aorounga Crater
Aorounga is an eroded meteorite impact crater in Chad, Africa. The exposed remnant of the crater is in diameter and its age is estimated to be less than 345 million years (Carboniferous or younger).VINCENT P.M., BEAUVILAIN A., 1996. Découverte d'un nouveau cratère d'impact météoritique en Afrique : l'astroblème de Gweni-Fada (Ennedi, Sahara du Tchad). C. R. Acad. Sci. Paris, t. 323, série II a, pp. 987-997 Description An outer and an inner ring (11 and 7 km, respectively) rise about 100 m above the mean level of the surrounding plain (see topographic map). Both aforementioned rings are separated by a relatively flat depression of uniform width. A possible central hill, maybe an uplift structure, of 1.5 km is almost centrally located in the depression. The crater is accompanied by two nearby circular features revealed by Space Shuttle SIR-C radar. These may be related impact craters, and if correct, Aorounga may be part of a crater chain. On the assumption that this hypot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geomorphology
Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand why landscapes look the way they do, to understand landform and terrain history and dynamics and to predict changes through a combination of field observations, physical experiments and numerical modeling. Geomorphologists work within disciplines such as physical geography, geology, geodesy, engineering geology, archaeology, climatology, and geotechnical engineering. This broad base of interests contributes to many research styles and interests within the field. Overview Earth's surface is modified by a combination of surface processes that shape landscapes, and geologic processes that cause tectonic uplift and subsidence, and shape the coastal geography. Surface processes co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yardang
A yardang is a streamlined protuberance carved from bedrock or any consolidated or semiconsolidated material by the dual action of wind abrasion by dust and sand and deflation (the removal of loose material by wind turbulence.) Yardangs become elongated features typically three or more times longer than wide, and when viewed from above, resemble the hull of a boat. Facing the wind is a steep, blunt face that gradually gets lower and narrower toward the lee end. Yardangs are formed by wind erosion, typically of an originally flat surface formed from areas of harder and softer material. The soft material is eroded and removed by the wind, and the harder material remains. The resulting pattern of yardangs is therefore a combination of the original rock distribution, and the fluid mechanics of the air flow and resulting pattern of erosion. Names The word itself is of Turkic origin, meaning ‘steep bank’, as this type of spectacular landscapes rising are best developed in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Shuttle
The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program name was Space Transportation System (STS), taken from a 1969 plan for a system of reusable spacecraft where it was the only item funded for development. The first ( STS-1) of four orbital test flights occurred in 1981, leading to operational flights (STS-5) beginning in 1982. Five complete Space Shuttle orbiter vehicles were built and flown on a total of 135 missions from 1981 to 2011. They launched from the Kennedy Space Center (KSC) in Florida. Operational missions launched numerous satellites, interplanetary probes, and the Hubble Space Telescope (HST), conducted science experiments in orbit, participated in the Shuttle-''Mir'' program with Russia, and participated in construction and servicing of the International Space Station (ISS). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sahara
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Carboniferous
The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferous'' means "coal-bearing", from the Latin '' carbō'' ("coal") and '' ferō'' ("bear, carry"), and refers to the many coal beds formed globally during that time. The first of the modern 'system' names, it was coined by geologists William Conybeare and William Phillips in 1822, based on a study of the British rock succession. The Carboniferous is often treated in North America as two geological periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial animal life was well established by the Carboniferous Period. Tetrapods (four limbed vertebrates), which had originated from lobe-finned fish during the preceding Devonian, became pentadactylous in and diversified during the Carboniferous, including early amphibian line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
