What with my fixation on apocalypse, you can imagine that I'm crazy for the geological evidence for impact craters. Lots of us probably have seen the Meteor Crater near Winslow, Arizona. I was reading about diamonds this morning when I learned that there is a Bavarian medieval town called Nördlingen that not only sits within a 14-million-year-old crater (called the Nördlinger Ries), but also has buildings made of impact stone containing millions of very tiny diamonds formed when the meteor struck a local graphite deposit.
Nördlingen is an impossibly quaint town that boasts one of the few intact city walls in Germany. It was the setting for the 1970 version of "Willy Wonka and the Chocolate Factory." Here, from the Earth Impact Database site, is a geological map showing the small town's placement toward the southwestern edge of the 15-mile-wide crater, which shows up clearly as a flattened disk set in an otherwise hilly area. The map also shows the interesting splattered mineral deposits.
Here is a delightful site covering all kinds of impact craters, with some of the best and most varied pictures I've ever seen. Take a look at this Siberian rock mess resulting from an impact at Popigai about 35 million years ago:
The website has a long and interesting explanation of the evidence for and against the meteor at Chicxulub, Yucatan, as the Dinosaur Killer that ended the Mesozoic (Cretaceous) and started the Cenozoic (Tertiary) 65 million years ago. It looks like the Yucatan meteor may have hit about 300,000 years too early to be a perfect explanation for the fate of the dinosaurs, but there may have been another huge strike that coincides more closely with the big die-off at the K-T Boundary. If so, you've got to call that some spectacular bad luck, since strikes of that size normally are separated by more like 60 million than 300,000 years. The website shows a map of the hot-rock splash and tsunami debris line from the Yucatan hit that extends well into Central Texas. Not that it would have mattered much; either strike probably would have set off worldwide firestorms.
Other strikes may account for earlier, even more catastrophic die-offs, such as the Permian Extinction between the Paleozoic and the Mesozoic 248 million years ago, but of course the older the craters get, the harder it is to identify them.
One last picture: some beautiful glass spherules splashed up by the Yucatan impact:
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