Over 360 million years ago, an asteroid or comet struck this area at more than 10 miles per second, forming a crater 2.5 miles across and, in seconds, ejecting 0.3 cubic mile of rock. Deformed limestone beds seen in adjacent cliffs were violently uplifted to form a shattered central peak. This crater, now buried beneath younger rocks, was used by NASA/USGS in training Apollo astronauts and represents an important class of craters found on other planets and satellites in our solar system.