Extinction of the dinosaurs. Artwork of a pair of dinosaurs watching the explosion from an asteroid impact. This is the asteroid that is thought to have caused the extinction of the dinosaurs around 65 million years ago. The impact took place at sea and sent 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.