Catastrophic failure of Earth`s global systems led to the extinction of the dinosaurs - we may yet go the same way
(PHYSorg.com Archaeology & Fossils)

`Why did the dinosaurs die out?` The consensus, among palaeontologists and dinosaur crazy seven-year-olds alike, seems to be that about 66m years ago a 10km diameter asteroid crashed into what is now Central America. It raised up a cloud of dust and ash that spread across the upper atmosphere, blocking out the sun, cooling the Earth and destroying the ozone layer that protects life from harmful cosmic radiation.