Stock Photo - Cretaceous-Tertiary extinction event ... . Artwork of the K-T asteroid upper left seen in the sky just before the impact that caused the mass extinction event 65 million years ago at the end of the Cretaceous period. A Tyrannosaurus rex dinosaur is about to scavenge a dead hadrosaur dinosaur Parasaurolophus. The asteroid impact took place at sea. Water vapour thrown into the atmosphere lowered global temperatures, and plant and then animal life began to die off. The dinosaurs never recovered, and mammals rose to become the dominant form of life. The storm clouds and volcano symbolise the end of an era.