Miocene Impact Craters - Nordlinger Ries, Gatun Structure, Steinheim Crater, Bigach Crater (Paperback)

Chapters: Nordlinger Ries, Gatun Structure, Steinheim Crater, Bigach Crater. Source: Wikipedia. Pages: 18. Not illustrated. Free updates online. Purchase includes a free trial membership in the publisher's book club where you can select from more than a million books without charge. Excerpt: The Nordlinger Ries is a large circular depression in western Bavaria, Germany, located north of the Danube in the district of Donau-Ries. The city of Nordlingen is located about 6 kilometers (3.7 mi) 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 "Nordlinger" is actually redundant, as there is no other place called Ries. The depression is interpreted as a meteorite impact crater formed about 14.3 million14.5 million years ago in the Miocene. The crater is most commonly referred to simply as the Ries or Ries crater. The original crater rim had an estimated diameter of 24 kilometers (15 mi). The present floor of the depression is about 100150 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 Nordlingen town church, constructed from locally derived stone. Two petrographical papers of Johannes Baier have shown that suevite was formed from mesozoic sediments. 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 simultane...More: http: //booksllc.net/?id=25328