Nördlinger Ries
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The Nördlinger Ries is a large circular depression in western Bavaria, Germany, located north of the Danube in the district of Donau-Ries. The city of Nördlingen is located about 6 kilometers southwest of the centre of the depression.
The word "Ries" is not a German word; it is believed that the term is derived from Raetia, since the tribe of Raetians lived in the area in pre-Roman times. The addition "Nördlinger" is actually redundant, as there is no other place called Ries.
For human settlement within the Nördlinger Ries region, see Donau-Ries.
[edit] Ries impact crater
The depression is interpreted as a meteorite impact crater formed about 14.3 - 14.5 million years ago in the Miocene.[1] The crater is most commonly referred to simply as the Ries or Ries crater. The original crater rim had an estimated diameter of 24 km. The present floor of the depression is about 100–150 meters below the eroded remains of the rim.
It was originally assumed that the Ries was of volcanic origin. In 1960 two American scientists, Eugene Shoemaker and Edward Chao, proved that the depression was caused by meteorite impact. The key evidence was the presence of coesite (shocked quartz), which, in natural unmetamorphosed rocks can only be formed by the shock pressures associated with meteorite impact. The coesite was found in the building stone (suevite) of the Nördlingen town church, constructed from locally derived stone.[2]
Another impact crater, the much smaller (3.8 km diameter) Steinheim crater, is located about 42 kilometers west-southwest from the centre of Ries. The two craters are believed to have formed nearly simultaneously by the impact of a binary asteroid.
Recent computer modeling of the impact event indicates that the impactors probably had diameters of about 1.5 km (Ries) and 150 meters (Steinheim), had a pre-impact separation of some tens of kilometers, and impacted the target area at an angle around 30 to 50 degrees from the surface in a west-southwest to east-northeast direction. The impact velocity is thought to have been about 20 km/s. The resulting explosion had the power of 1.8 million Hiroshima bombs.
The Ries crater impact event is believed to be the source of moldavite tektites found in Bohemia and Moravia (Czech Republic). [3] The tektite melt originated from a sand-rich surface layer and was ejected to distances up to 450 km downrange of the crater.
Stone buildings in Nordlingen contain millions of tiny diamonds, all less than 0.2 millimeters across. The impact that caused the Nördlinger Ries crater created an estimating 72000 tons of them when it impacted a local graphite deposit. Stone from this area was quarried and used to build the stone buildings.
[edit] References
- ^ J. Baier: Die Auswurfprodukte des Ries-Impakts, Deutschland, in Documenta Naturae, Vol. 162, München, 2007. ISBN 978-3-86544-162-1
- ^ Exploring Space: The Quest for Life, 2005, Nova.
- ^ G. Graup, P. Horn, H. Köhler & D. Müller-Sohnius: Source material for moldavites and bentonites. In Naturwissenschaften. Vol. 67, Berlin, 1981.
Emsley, John (2001). NATURE'S BUILDING BLOCKS. Oxford University Press, pp. 99. ISBN 0-19-850341-5.
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