Chicxulub impact event. Illustration of the asteroid impact that is thought to have caused the extinction of the dinosaurs around 65 million years ago. The impact took place at sea near the coast of the Yucatan Peninsula in Mexico, forming the Chicxulub crater (around 200 kilometres across). The impact threw trillions of tons of dust into the atmosphere and sent tsunamis 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.