Back when I read this in 1983, this was groundbreaking research-- proof (iridium layers in the earth) that a comet/asteroid had collided with earth at a point in history just before the dinosaurs mysteriously died out. I feel sorry for the dinosaurs!
Not well-regarded at the time, the Chicxulub crater in the Yucatan Penisula has since become accepted as the primary source of the extinction of the dinosaurs. This was the first greatbook to bring this theory to the light of day.