The asteroid collision theory is well-known model that attributes the demise of the dinosaurs at the end of the Cretaceous period to a bolide impact, believed to have occurred roughly 66 million years ago. Evidence suggests that the 5-15 kilometer (3.1 to 9.3 mile) rock hit the vicinity of what is the Yucatán Peninsula today, and triggered a mass extinction event, either directly due to its impact, or indirectly due to the resulting changes in Earth’s atmosphere. The theory, although widely supported, is now being revisited due to new research that points to the occurrence of a double catastrophe. The findings are now published in the journal Science.
SO WHAT REALLY HAPPENED TO THE DINOSAURS?
The study, conducted by Berkeley geologists, doesn’t rule out the asteroid collision theory, but it does put a slight twist to it. For years, scientists have been aware of the volcanism that was occurring in India during the same time period, which spread lava across a region known as the Deccan Traps. However, debate has been focused around the role of the eruptions in the mass extinction: were they irrelevant or did they cause a chain of reactions that ultimately lead to the long-term die-off of the dinosaurs?
Initial dating of the Deccan Traps formations indicated the former, as the flood of lava seemed to have occurred long before the impact. New evidence, however, has revealed the most accurate dates yet, giving rise to the theory that the asteroid impact could have changed the volcano’s plumbing system, accelerating the eruptions for hundreds of thousands of years to come.The culmination of these events is thought to have covered the planet with dust and fumes, ultimately causing a huge change in the climate. Long-term eruptions would also result in the delayed recovery of life for 500,000 years after end of the Cretaceous and the beginning of the Tertiary period (K-T boundary), during which many organisms seemed to have disappeared from the fossil record.
But while this does give a clearer picture of what really happened, it doesn’t necessarily ascribe the extinction of the dinosaurs to one initial cause. Scientists are fairly certain that the impact and volcanism occurred roughly 50,000 years of the extinction, but “both phenomena were clearly at work at the same time.”
“…it becomes somewhat artificial to distinguish between them as killing mechanisms: said lead researcher Paul Renne, the director of the Berkeley Geochronology Center. “It is going to be basically impossible to ascribe actual atmospheric effects to one or the other.
