Stock Photo - Extinction of the dinosaurs. Artwork of flying reptiles near the point of impact of a large asteroid. This asteroid is impacting the Earth's atmosphere at a speed of several kilometres per second ... . It is is some ten kilometres across. An event like this is thought to have caused the extinction of the dinosaurs 65 million years ago. The asteroid hit the ocean, sending tsunamis massive waves around the globe, destroying coastal areas. Water vapour thrown into the atmosphere lowered global temperatures. Plant and then animal life began to die off. The dinosaurs never recovered, and mammals rose to become the dominant form of life.