RadioLab has an excellent podcast featuring Jay Melosh, a geophysicist who specializes in impact craters, and who advocates the hypothesis that the entire extinction event that killed off the dinosaurs at the boundary between the Cretaceous and Tertiary (the K-T boundary) took place over a period of two hours. The asteroid impact vaporized the crust of the Earth where it hit (near the Yucatan peninsula) and blasted this rock gas into space. There it cooled down to create little glass particles that reentered the atmosphere. On reentry the glass burned up, but there was so much of it that it raised the temperature of the atmosphere by several hundred degrees Celsius. Anything near the surface (mostly the dinosaurs) was cooked, but anything living just beneath the surface could have survived.