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, as evidenced by the following three items:
A long, very thorough and scientific review of geological and biological changes caused by meteor strikes throughout the earth's history. (McLaren, Digby J.; "Bolides and Biostratigraphy," Geological Society of America, Bulletin, 94:313, 1983.)
A shorter, popular version of the above. (McLaren, Digby; "Impacts That Changed the Course of Evolution," New Scientist, 100:588, 1983.)
Evidence is growing that the collision of planetary material with the Earth can profoundly affect local geology, and that impacts of very large meteorites may have influenced the evolution of the Earth and the life that exists upon it.
This quotation is from the lead-in to the article references below, which also has a nice world map of major impact sites over 1 km in diameter.