Death of the Dinosaurs

Everything within 300 miles of the impact was instantly incinerated. But this asteroid had a global impact. Masses of dust produced by the collision blasted into the atmosphere where it blotted out the heat and light of the sun. Consequently, the Earth was plunged into a bitter darkness that lasted for months. The food chain collapsed, and the 165-million-year reign of the dinosaur came to a dramatic end. All larger creatures perished. Only a lucky 15% of land animal species survived.

This hardy minority exploded into the huge diversity of species we see today. The iridium-rich stratum divided the age of the dinosaurs and the age of the mammal. Without the 'terrible dragons' dominating the scene, mammalian life managed to get a foothold. In other words, without the K-T extinction, we might not be here now.

BBC - Age of the Dinosaurs
http://www.bbc.co.uk/sn/prehistoric_life/dinosaurs/

DinoBuzz - What Killed the Dinosaurs?
http://www.ucmp.berkeley.edu/diapsids/extinction.html

Video: Armageddon [ Firstscience presents]
What are the chances of being hit by a killer asteriod? This film analyses all of the evidence, all of the odds, and predicts the day that the world will end.