What really killed the dinosaurs?

The disappearance of the dinosaurs, along with 70% of all species in the fossil record, about 66 million years ago is widely attributed to the Chicxulub impact in Yucatán, Mexico �" a discovery credited to a Berkeley team led by Walter and Luis Alvarez. However, at the same time, one of the largest volcanic eruptions in Earth history, the Deccan Traps, was occurring in India �" a coincidence that has confounded geologists for three decades, and is made all the more remarkable since the four most recent mass extinctions in Earth history all correspond very closely in time to huge volcanic eruptions. Several new lines of evidence, including high-precision radioisotopic dating work at Berkeley, now suggest that the Chicxulub impact accelerated the Deccan Traps eruptions right at the time of the dinosaurs’ extinction. It is therefore difficult to know whether T. rex and friends were exterminated mainly by the impact itself or by the impact-triggered Deccan eruptions, since both events would have affected the environment in similar ways. So the great murder mystery once considered “solved” by the impact theory will require further research to sort out the true kill mechanisms for what appears to have been a double-edged catastrophe 66 million years ago.

Speaker: Dr. Mark Richards, UC Berkeley