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Topic: Rochechouart crater

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Impact crater

List of craters on Europa

	Impact crater - Wikipedia, the free encyclopedia
		An impact crater (impact basin, astrobleme or sometimes crater) is a circular or oval depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteor) with the surface.
		Few underwater craters have been discovered because of the difficulty of surveying the sea floor; the rapid rate of change of the ocean bottom; and the subduction of the ocean floor into the Earth's interior by processes of plate tectonics.
		The distinctive mark of an impact crater is the presence of rock that has undergone shock-metamorphic effects, such as shatter cones, melted rocks, and crystal deformations.
	en.wikipedia.org /wiki/Impact_crater (1969 words)

	Impact crater - WikiGadugi (Site not responding. Last check: 2007-10-15)
		ᎤᎶᏍᏅ a ᎠᎴᏫᏍᏙᏗ ᎥᎿᎢ ᎠᎴᏰᏍ, ᏱᏂᎬᏛᎾ, an equilibrium ᎨᏍᎢ ᏭᎷᏨᎩ ᎭᏫᎾᏗᏢ ᎦᏙ ᎤᏍᏗ ᎠᎦᏴᎵ craters are ᎠᏲᏍᏔᏅ as ᏄᎵᏍᏛ as ᎢᏤ craters ᎤᏙᏢᏍ.
		ᎠᎵᏱᎵᏍ ᎧᏃᎮᏗ ᎠᎦᏍᏍᏗ ᎥᎿᎢ ᎯᎠ ᏓᎬᏩᎶᏛ ᎥᎿᎢ cratering ᎾᎿ ᎯᎠ ᎡᎶᎯ ᎧᏁᎢᏍᏙᏗ Ꮎ ᏂᏛᎴᏅᏓ ᏌᏊ to ᏦᎢ craters ᎬᏙᏗ a width ᎡᏆ ᎢᎨᏍᏙᏗ ᎬᎾᏬᏍᎬ 20 kilometers are ᎪᏢᏅᎯ ᏂᎦᎥᎢ ᎢᏳᏆᏗᏅᏓ ᏧᏕᏘᏴᏓ.
		ᎯᎠ Barringer crater ᎭᏫᎾᏗᏢ Arizona ᎨᏍᎢ a ᎧᎵᏬᎯ ᏱᏓᏟᎶᏍᏔᏅ ᎥᎿᎢ a ᏄᏦᏍᏛᎾ crater, a straightforward ᎠᏟᏍᏙᏗ ᎭᏫᎾᏗᏢ ᎯᎠ ᎦᏙᎯ.
	wikigadugi.org /wiki/Impact_crater (2112 words)

	Crater chain on two continents points to impact from fragmented comet (Site not responding. Last check: 2007-10-15)
		Three of the five craters, Rochechouart in France, and Manicouagan and Saint Martin in Canada, were at the same latitude–22.8 degrees–forming a nearly 5000-kilometer chain.
		One possible explanation for the alignments of the five craters is a fragmented comet that crashed to Earth in three major groups over a period of time as short as four hours, in two groups of two and one solitary chunk.
		Manicouagan, the largest of the five craters, is more than 100 kilometers in diameter, comparable to the 170-kilometer Chixulub crater in the Yucatan–the impact that is believed to have caused the mass extinction at the end of the Cretaceous period 65 million years ago, killing the dinosaurs.
	www-news.uchicago.edu /releases/98/980313.crater.chain.shtml (688 words)

	Rochechouart (Site not responding. Last check: 2007-10-15)
		Rochechouart Castle is build on a hill, which consists of polymict breccia.
		Reimold, W.U. Oskierski, W. 1987 The Rb-Sr-age of the Rochechouart impact structure, France, and geochemical constraints on impact melt-target rock-meteorite compositions.
		Reimold, W.U. Bischoff, L., Oskierski, W., Rehfeldt, A. and Schmidt, A. 1984 Genesis of pseudotachylite veins in the basement of the Rochechouart impact crater, France.
	www.unb.ca /passc/ImpactDatabase/images/rochechouart.htm (496 words)

	Gravity surveys
		A low-density breccia lens at the crater floor, post-impact young crater sediments, and fracturing of the rocks beneath and around the crater may contribute to the mass deficit.
		The Bouguer negative anomaly of the Ries crater is embedded in a regional field with considerable "relief", which implies several possibilities to construct a reliable residual field.
		The Steinheim Basin with a prominent central uplift is thought to be a smaller companion to the Ries crater.
	www.impact-structures.com /geophysic/geophysikgravimtrie.html (759 words)

	virtual-geology.info (Site not responding. Last check: 2007-10-15)
		The Rochechouart impact crater, west of Limoges in central France (maps), was created around 214 million years ago, during the late Triassic Period, by a large extraterrestrial body striking the Earth.
		Churches in nearby villages are built of glassy melt rocks produced by the impact (map of the breccias).
		It is now thought that the Rochechouart structure is just one of a chain of at least five impact craters formed when a fragmented comet hit the Earth.
	www.virtual-geology.info /eurogeol/rochech.html (422 words)

	Rochechouart crater - Museum fuer Naturkunde Berlin (Site not responding. Last check: 2007-10-15)
		On the basis of field observations in the Rochechouart crater, France, and numerical computations, we suggest the existence of low-angle faults dipping gently towards the crater centre.
		In craters with final diameters of 20-30 km, low-angle normal faults might have a lateral extent of approximately 5 km and predominantly occur at a distance of approximately 3-8 km away from the crater centre.
		Faulting along gently dipping shear zones may be the result of an impact-induced rheological stratification of the crater floor and a passive rotation of the shear zones due to the uplift of the central peak.
	www.museum.hu-berlin.de /min/forsch/forschprojects/impact/rochechouart.asp?lang=1 (368 words)

	Naturics - The timescale of the evolution of life is written down in the impact craters of the Earth' crust (Site not responding. Last check: 2007-10-15)
		The ages of the craters are evidently grouped around those "tick-events" of the cosmic clock (to be alternatively understood also as the cosmic quantum jumps) which had resulted in the extraordinarily strong mass extinctions of the living organisms.
		It is one further example of a crater the age of which has been estimated exactly enough for to choose the proper group of the cosmic events but not precisely enough for to decide which one of them was the real event forming the crater.
		It demonstrates that for the smaller craters even some relatively precise observational estimation of the crater age (with an error of only 3 per cent in that case) is sometimes not precise enough for to separate one of the four possible levels of the events of the Cosmic Hierarchy.
	www.naturics.de /e_books/impact_craters/discussion.html (5717 words)

	KILLER COMET STORM HIT EARTH (Site not responding. Last check: 2007-10-15)
		No matter how accurate the dating techniques used to establish the ages of the craters, it would be impossible to prove that the craters were created within just a few hours as a disrupted comet or asteroid splattered fragments across the face of the Earth.
		The evidence that clinches the case for a multi-impact comet strike is the fact that if the Laurasian land are placed in their original alignment, the largest three craters, Rochechouart, Manicouagan and St Martin, lie at the same paleolatitude, 22.8 degrees north.
		Only the largest craters survived, but we can be sure that during the few hours that Earth was in the firing line, it would have been hit by a constant rain of billions of fragments, ranging in size from microparticles up to several kilometres in diameter.
	www.irysec.vic.edu.au /sci/goneill/triassicimpact.htm (1919 words)

	Science News Online (5/16/98): Target Earth -- Geologists link a chain of craters By RICHARD MONASTERSKY
		Called the Rochechouart impact structure, the feature measures about 25 kilometers in diameter and is so worn by erosion that it no longer looks like a crater.
		Because the Manicouagan crater is so much larger than Rochechouart, the molten rocks would have cooled much more slowly at the Canadian site, taking thousands or hundreds of thousands of years longer to lock in a record of Earth's magnetic field.
		The Manicouagan crater is a little over half the size of the Chicxulub crater, but according to impact theories, it is large enough to cause many of the same effects.
	www.sciencenews.org /pages/sn_arc98/5_16_98/bob1.htm (2438 words)

	Earth
		Although smaller than the Chicxulub impact structure that may have contributed to the demise of the Dinosaurs, Manicouagan, a 214-million-year-old crater in eastern Canada (Quebec) that has been eroded nearly flat by glaciers, is easily seen from space because of its huge 62-mile (100-km) diameter.
		It is comprised primarily of the heavily cratered and very old uplands ("highlands") and the relatively smooth and younger maria.
		The maria (which comprise about 16 percent of the Moon's surface) are huge impact craters that were later flooded by molten lava.
	www.solstation.com /stars/earth.htm (2193 words)

	Rochechouart crater - Wikipedia, the free encyclopedia
		It is 23 km in diameter and the age is estimated to be 214 ± 8 million years placing it in the Upper Triassic.
		It is located 4 km west of Rochechouart, in the Haute-Vienne département, and covers part of the communes and villages of Rochechouart, Chaillac, Étagnac, Pressignac, Saint-Quentin-sur-Charente, Chéronnac, Chassenon and Chabanais.
		The theoretically possible age-values of the impact crater
	en.wikipedia.org /wiki/Rochechouart_crater (130 words)

	History
		Since then, a million and a half centuries have eroded the crater formed by the meteorite's impact.
		The crater (ASTROBLEME) with a diameter of 20 km, is almost completely eroded and can no longer be distinguished.
		The meteorite, with a diameter of 1 km 5 weighinh 6000 million tons impacted at 20 km/second, giving off energy equivalent to (300 000 megatons of TNT (14 000 000 times more powerful than Hiroshima).
	www.ville-rochechouart.fr /english/history.htm (159 words)

	Impact_crater (Site not responding. Last check: 2007-10-15)
		An '''impact crater''' ('''impact basin''' or sometimes '''crater''') is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteorite) with the surface.
		In the center of craters on Earth a crater lake often accumulates, and a central island or peak (caused by rebounding crustal rock after the impact) is usually a prominent feature in the lake.
		Charles A. Wood and Leif Andersson, ''[http://adsabs.harvard.edu//full/seri/LPSC./0009//0003669.000.html New Morphometric Data for Fresh Lunar Craters]'', 1978, Procedings 9th Lunar and Planet.
	q-basic.xodox.de /Impact_crater (1987 words)

	Athena Review 2,1: Impact craters on Venus
		The study of craters in our Solar System is growing in scope and significance, as images of the planets increase along with our knowledge of the correlation of impact events with changing planetary climates.
		Such small, simple bowl-shaped craters, quite common on the Moon and Mars and even known on Earth (ie, Barringer Crater, 1.2 km diameter), are actually scarce on Venus, where no craters smaller than 3 kilometers (1.9 miles) in diameter have been observed (Phillips et al., 1991).
		The Rochechouart impact in France, along with the Manicouagan crater in Quebec and the Saint Martin impact structure in Manitoba would have had a combined impact strength of the object which struck Chicxulub.
	www.athenapub.com /venus1.htm (1444 words)

	Stardust \| JPL \| NASA
		They asked Rowley to help figure out how the craters were aligned when the impacts occurred -- because of plate tectonics, the continents have moved extensively in the last 214 million years.
		Three of the five craters, Rochechouart in France, and Manicouagan and Saint Martin in Canada, were at the same latitude -- 22.8 degrees -- forming a nearly 5000-kilometer chain.
		Manicouagan, the largest of the five craters, is more than 100 kilometers in diameter, comparable to the 170-kilometer Chixulub crater in the Yucatan -- the impact that is believed to have caused the mass extinction at the end of the Cretaceous period 65 million years ago, killing the dinosaurs.
	stardust.jpl.nasa.gov /news/news12.html (740 words)

	Rochechouart Impactite Gallery
		This is a slice of Impact rock from the Rochechouart Impact structure is Europe. About 214 million years ago, during the Jurassic age the fall of a cosmic body west of Rochechouart, created a large meteorite crater.
		Since then, a million and a half centuries have eroded the crater into its currant condition today.
		Different types of breccias and melts are found around the crater and named from the town that they are collected at. Below you will find a list of some of the Rochechouart impactite specimens in my collection.
	www.meteoritearticles.com /colrochechouart.html (104 words)

	Impact crater - QuickSeek Encyclopedia (Site not responding. Last check: 2007-10-15)
		An impact crater (impact basin or sometimes crater) is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteor) with the surface.
		Curiously, the largest and youngest (700,000 years ago) tektite strewnfield, known as the Australasian field, has no known crater associated with it; this fact strongly suggests that, at least in this case, the tektites are not linked to an impact.
		Charles A. Wood and Leif Andersson, New Morphometric Data for Fresh Lunar Craters, 1978, Procedings 9th Lunar and Planet.
	impactcrater.quickseek.com (1998 words)

	The Rochechouart meteorite (Site not responding. Last check: 2007-10-15)
		A crater 12 miles wide was formed within 42 seconds, vaporising some 8 cubic miles of the earth's crust and vitrifying a further 42 cubic miles.
		In the intervening 200 million years the crater shape has been gradually worn down leaving scientists and geologists with one of the few accessible crater beds in the world.
		The Roman Baths at Chassenon are made of it; the church and castle at Rochechouart are; the church in Pressignac; and many of the local old buildings - including parts of our gite.
	www.dumar.co.uk /france/meteorit.htm (244 words)

	Rochechouart crater: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-10-15)
		A meteor is the visible path of a meteoroid that enters the earths (or another bodys) atmosphere, commonly called a shooting star or falling star....
		A crater (basin or impact crater) is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body....
		It is located 4 km west of Rochechouart Rochechouart quick summary:
	www.absoluteastronomy.com /encyclopedia/r/ro/rochechouart_crater.htm (511 words)

	Articles - Impact crater (Site not responding. Last check: 2007-10-15)
		* A layer of shattered or "brecciated" rock under the floor of the crater.
		The inner walls are not * ´´TRI´´ — these complex craters are large enough so that their inner walls have slumped to the floor.
		See the a website concerned with over 160 identified impact craters on the Earth.
	www.zdiamond.net /articles/Impact_crater (1919 words)

	Meteorite Impact References by Location
		Lambert, P., 1977, Rouchechouart impact crater: Statistical geochemical investigations and meteoritic contamination: in- Impact and explosion cratering*, D.J. Rodfdy, R.O. pepin, and R.B. Merrils, eds., Pergamon, Elmsford, p.
		Lambert, P., 1977, The meteoritic contamination in the Rochechouart* crater: statistical geochemical investigations: in- Planetary cratering mechanics-Proceedings os a Symposium, Flagstaff, Arizona, Sept 13-17, 1976.
		Chao, E.C.T., 1973, Geologic implications of the Apollo 14 Fra Mauro breccias and comparison with ejecta from the Ries crater*, Germany: USGS Jour.
	skywalker.cochise.edu /wellerr/meteorite-impact-ref/metref-loc-C-G.htm (1094 words)

	Comet and Asteriod Risks to Earth
		Geologists attributed 91 the craters of the Moon to volcanoes, and craters on Earth likewise.
		Meteor Crater, a kilometre-wide hole in the desert near Winslow, Arizona, was only belatedly, after about 1929, recognized to be the work of a meteorite one that hit some fifty thousand years ago.
		The shape of the crater together with evidence of an ejecta-spray pattern suggests that the killer sailed in at an oblique angle of impact that spewed white-hot debris across North America.
	www.dhushara.com /book/future/comet.htm (7560 words)

	[No title]
		The long axes of the craters point roughly in the same direction; and the craters tend to be arranged in lines like those of the Carolina Bays.
		Scientists believe the impact crater was caused by a 3-mile (5-kilometer) wide asteroid slamming into the area, causing a wave of extinction 200 million to 360 million years ago.
		The Arizona Crater (also known as the Iturralde Structure) is a suspected crater from an impactor which struck northern Bolivia approximately 20,000 years ago.
	saturniancosmology.org /files/space/impacts.txt (13473 words)

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