The impact of an asteroid, about 10–11 km in diameter, that struck the Earth about 65 Ma ago near Chicxulub, on the coast of northern Yucatán, Mexico. Initial evidence for the impact was an iridium-enriched layer of clays, found in many parts of the world. The Chicxulub crater, now filled with sediments, is about 180 km in diameter. Many scientists have concluded that the impact caused the mass extinction at the end of the Cretaceous.