Chicxulub crater
Further research identified the giant Chicxulub crater, buried under Chicxulub on the coast of Yucatán, as the source of the K–Pg boundary clay. Identified in 1990 based on work by geophysicist Glen Penfield in 1978, the crater is oval, with an average diameter of roughly , about the size calculated by the Alvarez team. The discovery of the crater—a prediction of the impact hypothesis—provided conclusive evidence for a K–Pg impact, and strengthened the hypothesis that it caused the extinction.