Noerdlingen and the Ries Crater

8-9 November

The Reis crater was created as a result of an asteroid impact about 14.5 million years ago. The crater is approximately 25km in diameter and 600m in depth. Noerdlingen is a walled medieval town lying South West of the centre of impact on the central crater rim.

Our first experience of the Ries crater occurred as we travelled towards Noerdlingen from Solnhofen. There was a sudden change in topography as we drove over the rim and into the crater. The weather was perfect and some of the party were trying desperately to photograph the sun going down over the rim. Mine were unsatisfactory as are most sunsets taken from moving coaches.

Last time we visited this area the coach was too high to go through any of the 4 gates into Noerdlingen and we did a circular tour looking for a break in the fortifications. This time Manfred (our driver) had no problems. There was not much opportunity for sightseeing as darkness descended. Not to be missed, though, is Daniels tower situated in the centre of the town. Fashioned from locally quarried suevite, there had been some fears for its safety following reports that suevite contains diamonds. However, as the tower, allegedly contains only 600-900g of diamonds, the biggest being 0.5mm, I suspect it is safe from the jewellery business.

Next morning there was some time to wander round the town before meeting at the Rieskrater Museum. Here, we were privileged to be given a guided tour by Dr. Michael Schieber, Director of the museum.

The exhibits were excellent. There was a topographic map of the area enabling us to orientate ourselves. Michael pointed out that the crater rim was lower in the Northwest. A suggested explanation being that this was the direction of impact. Other geologists have evidence for other directions though, so the debate continues.

A short film demonstrated how planets were formed and the impact of meteorites. There was also a display of meteorites found locally. Bavaria seems to have more than its fair share but this may just reflect the enthusiasm of the local collectors and geologists.

Michael explained how moist air flows into the crater and is forced to rise forming clouds at the crater rim. We were able to see this phenomenon later when out in the field.

The star of the show was a small piece of Moon rock, cosseted in a glass dome, thus protected from the Bavarian environment. A series of cartoons demonstrated the probable sequence of events during the formation of the crater. This can be summarised as follows:

1. An asteroid roughly the same size as the walled city of Noerdlingen travelling at a velocity of more than 20km per second collides with the earth surface.
2. The asteroid penetrates into the basement ejecting affected material and vaporising both rock and meteorite. A temporary crater approx. 12km in diameter and 4km deep is formed.
3. After 2 to 4 seconds, the compressed rock from the bottom of the crater springs back. Material is thrown up and a cloud rises up to a height of about 30km.
4. Upward movement ceases and material falls forming suevite. The rim collapses creating a shallower crater with a greater diameter. After about 8 minutes, leaving a "smoking gun" effect. The maximum range of ejected materials is that of Moldovites which have been found up to 400km away.

We were then shown into the back rooms, often the most interesting places for geologists at any museum. Here was the rock store of a 600m core taken in 1973. These were stored in one metre lengths- an amazing facility for research students. The diagram on the wall indicated where the core had been extracted and showed the megablock zone at the crater rim which was to be our destination after lunch.

When we emerged from the museum, the weather had deteriorated so our hopes for a simple sandwich consumed in the open air evaporated as we headed for a cosy café for lunch.

On returning to the coach, we were informed of a drama at the Gasthof. Someone, who shall be nameless, had not returned their room key as requested. For this crime, our driver and coach were held to ransom. The key had to be found before the coach could continue.

Our afternoon visit was to a megablock at the crater rim. We were fortunate to be able to see into the interior of one of these mega blocks as it has been partly quarried (Holhelm). I feel we were all impressed with the size of the megablock. This was roughly 2km long by 1km wide and 100m high. This was still the right way up but during the impact had been pushed up to the crater rim and then slipped back. We were informed that the bedding planes of the megablock bore no relationship to the regional dip. Note the prophetic sign. Situated at the top of the megablock were the Ofnet caves formed in the karst limestone. Here, skulls of Stone Age people have been found. These were mostly women and some were drilled suggesting a mystic ritual. The skulls are now located in the city museum along with "eye witness" accounts of witch-hunts in the area. It was here that another drama occurred. One of our party slipped and broke her arm. The efficiency of the Bavarian emergency services was experienced as the ambulance, the emergency Dr. and the fire brigade arrived to transport Brigitte to the hospital in Noerdlingen. Within a few hours her arm had been fixed and she was back on the coach heading for Munich and home in style the next day.

Those members of the party who took the short way down were able to view the Roman farm (Villa Rustica) at closer quarters.

Meanwhile, the rest of the party continued with the geology. Our next stop was the Altenberg quarry, colloquially known as Goat quarry, so named because the vegetation had been cleared by South African mountain goats. It was suggested that RIGs groups should purchase a herd of these animals for clearing sites in Britain. In the quarry, we were able to examine closely the structure of the suevite. It is a mixture of sediment and crystals combined with glassy particles of the melt. There was some debate as to whether it was sedimentary, igneous, or metamorphic. In fact all these processes went into the formation of this rock. The vesicles, we had been informed at the museum, contain Argon so the age of the impact crater can be determined.

On our return to Noerdlingen, we said Good-bye and Thank You to Michael for a most interesting day and also to Dave Williams and Dee Edwards. They were leaving us to pick up previously acquired Solnhofen limestone and to gain ideas for future field trips (We hope). Many thanks to all participants who contributed to such a successful trip.

Heather Rogers
Stephen Darlington