http://www.science-frontiers.com/sf031/sf031p11.htm
After being ridiculed for well over a century, astronomical catastrophism is now coming into its own. First, there was the admission that a few small craters, like Meteor Crater in Arizona, just might be of meteoric origin; then, more and bigger craters (astroblemes) were recognized; and, recently, the discovery of the iridium-rich layer at the Cretaceious-Tertiary boundary has made the subject very popular.