The fifth and most recent mass extinction was the [[K-T extinction]]. In 66 Ma, a [[asteroid]] struck Earth just off the [[Yucatán Peninsula]]—somewhere in the southwestern tip of then Laurasia—where the [[Chicxulub crater]] is today. This ejected vast quantities of particulate matter and vapor into the air that occluded sunlight, inhibiting photosynthesis. 75% of all life, including the non-avian dinosaurs, became extinct, marking the end of the Cretaceous period and Mesozoic era.