In western Bavaria there is a broad, circular, low-relief basin some 24 km in diameter that is home to a story-book perfect village dating to medieval times. Appropriately, the village of Nordlingen, with wall and moat, is also circular.
At the center of town stands an ancient cathedral with a magnificent 90m steeple, all built of stone blocks quarried nearby. The stone was understood to be a welded volcanic ash, and the great Ries depression itself was also interpreted to be of volcanic origin.
Until 1960 that is, when Eugene Shoemaker and Edward Chou visited the church and experienced an epiphany: these stone blocks were not welded volcanic ash. They were once incandescent fallout from a meteorite impact fireball that left a crater some 24 km (15 mi) in diameter! Ries was finally recognized as a meteorite crater. It has subsequently been dated to about 14 million years.
It encountered earth as a binary (or more?) bolide. About 42 kms (26 miles) WSW of the 24 km Ries crater is a much smaller coeval 3.8 km diameter crater, called Steinheim. There were two asteroidal fragments traveling in close formation. Lithographic limestones in that area once offered shatter cone specimens of highest quality.
Scars of mechanical shock spraying into the earth, shatter cones are one of the most visual lines of evidence for impact found at deeper levels in the target bedrock.
Stratigraphically, the first impact ejecta deposited in or around the crater was a colorful polymictic breccia consisting of shattered fragments of mostly Triassic and Jurassic marine lithologies that constituted the local country rock at the time of the event. This is termed the Bunte Breccia.
The Bunte Breccias give the impression of a largely mechanical cratering event at the beginning, without any obvious glassy components or signs of thermal welding.
But then, things changed. The sintered ash of the impact inferno that dug deep into the earth began to rain down. Vesiculated cinders, rock flour, and blobs of semi-molten glass—the stars of this episode—largely filled the crater and mantled the landscape for many tens of kms outwards. The welded impact ash breccias have come to be known as “suevite” (SWAYvite). A characteristic component of the suevite are the embedded glass “bombs” (with reference to volcanic analogs).
The glass bombs are of two main sorts, termed the grey- and black- Ries impact melts. The grays are much more abundant and larger, but the name gives the wrong impression. The glass appears (and is outwardly,) gray due in large part to a creamy-colored film or thin crust that coats every old surface including the interior walls of gas vesicles. I suppose this to be a hydration rind like that used to date obsidian artifacts times fourteen million years. The bombs weather out cleanly, quite free off any welded adhesions. The upper surface is deeply featured, with high-relief folds and complex collapsed bubble flaps. There are common examples of splits in a once rigid skin with taffy-like stretch marks, similar to Nininger’s famous “stretch tektites”.
In this tour of proximal Ries impact products, something is conspicuous by its absence. Green glass. Ries is the poster-child prime example of an impact coeval with a tektite fall 300 to 600 km away. Moldavites.
As you may know from my previous articles, when I see Muong Nong-type tektites (and there are some good ones found in the Czech Republic), I hear airburst alarms sounding loud. BUT, as for moldavites, the most popular party line is that they consist of instantly fused clays and sands entrained in plasma jets squirting like torches from the final closing gap between earth and meteor. All the other Ries impactites are derived from deeper rocks in the cratering process.
Maybe we could meet half-way. We already know that the bolide was at least , binary, given Ries and Steinheim craters. Why not consider a threesome, with an aerial burst over the Moldau River country? This would relieve the angst amongst geoscientists struggling to find a way to squirt tektites 300 to 600 kms from a hypothetical surficial source material obliterated completely (and conveniently) by impact. Wouldn’t it be ironic to find a connection between Shoemaker (of Shoemaker-Levy vs. Jupiter fame, where a lengthy string of cometary fragments were observed impacting Jupiter sequentially) and a multiple impact feature in Europe, first understood to be meteoritic by Shoemaker himself?
There is an attractive symmetry to the story.
Be sure and check out Bob Verish’s article describing search for flaedle at Ries: https://www.meteorite-times.com/bobs-findings/hunting-for-fladle-at-ries-crater/
