Dinosaur extinction. Illustration depicting the mass extinction that included the end of the dinosaurs some 65 million years ago, forming the divide between the Cretaceous and Tertiary periods. At left is a Triceratops. A Tyrannosaurus rex is at right. Clouds of smoke and ash fill the sky, and meteoric debris rains down, caused by the meteorite impact that is thought to have triggered the mass extinction. The impact threw trillions of tons of dust into the atmosphere and sent tsunamis (massive waves) around the globe, destroying coastal areas. Dust and water vapour in 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.