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The Ries Crater
The Ries impact crater (diameter of original crater: ~ 27 km) is the larger crater of a „doublet crater“ (Ries and Steinheim Basin) formed by an asteroid with a diameter of about 1.2 km which was orbited by a small moon, some 200 m in size. The crater was formed some 15 million years ago in a 500 to 700 m thick layer of Mesozoic sediments underlain by crystalline basement. It has 5 major structural elements (Figure): (1) a central, ~ 700 m deep cavity (radius r = 6 km), (2) an uplifted inner ring and (3) a megablock zone from r = 6 to 13 km, (4) a “tectonic” rim at r = 13 - 15 km, and (5) an outer ejecta blanket from r = 13 to ca. 45 km. In addition there are discontinuous distal ejecta: (1) The so-called Reuter blocks (Upper Malmian limestone fragments, up to some decimeter in size) found in the Bavarian Tertiary Molasse Basin up to 70 km from the point of impact, and (2) the moldavite tektites forming a large strewn field in the Czech Republic, East Germany and North West Austria up to a distance of 450 km from the point of impact. The geography of the strewn field allows the reconstruction of the direction of the impactor which obviously came from WSW on an inclined trajectory causing the ejection of the moldavites downrange in a ENE direction. The main impact formation is the “Bunte Breccia”, a polymict breccia forming the continuous ejecta blanket that is overlain by suevite (outer suevite) for which the Ries is the type locality (Figure). Inside the central crater which is filled with post-impact sediments a layer of suevite (crater suevite), up to some 250 m in thickness, is covering the crater floor above the brecciated and uplifted crystalline basement.
Cross section of the Ries crater (from Jean Pohl, Munich, 1977, 2000) with location of research drilling FBN73 (Nördlingen 19173)
Formation of the Ries crater (simplified); picture series drafted by D. Stöffler
© Geopark Ries
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The locations of the Ries and Steinheim craters and of the moldavite (tektite) strewn field (from Stöffler et al., 2002)
Modified after Hüttner and Schmidt-Kahler (2003)
