Immense Volcanic Eruptions AND An Asteroid Impact Were Both Responsible For Killing Off The Dinosaurs

Although the end-Cretaceous mass extinction was famous for killing off the non-avian dinosaurs, many other forms of life died out at the same time. Rod Beverley/Shutterstock

What killed off the non-avian dinosaurs? Although the spectacular asteroid impact 66 million years ago almost certainly delivered the coup de grâce, it turns out that there were many factors that weakened their grip on the planet beforehand, including the rise of opportunistic mammals.

Prolonged volcanism has also been blamed for accelerating the mass extinction of the dinosaurs. However, several recent studies have suggested that the hellish firestorm emerging from the Deccan Traps in India failed to significantly alter the climate for a long enough period of time. A new study in Nature Communications disagrees, and conclusively states that Cretaceous period volcanic activity shouldn’t be let off the hook just yet.

content-1467736761-bivalves.jpg“For such a long time, people have argued for either the volcanism or the impact,” lead author Sierra Petersen, a National Science Foundation ocean sciences postdoctoral researcher at the University of Michigan, told IFLScience. “This is a losing argument because a lot of evidence indicates that one of these alone is not enough.”

The research team decided to analyze various oxygen and carbon isotopes contained within fossilized ancient bivalve shells in the sediments of Seymour Island, a frigid high-rise Antarctic Peninsula island rich in Cretaceous period fossils. These isotopes give remarkably accurate indications as to what the atmospheric and oceanic temperatures were like at the time of their burial, and it just so happens that the late Cretaceous climatological record is stored in remarkably high resolution on this particular strip of land.

These isotopes indicate that when the Deccan Traps formed and began erupting 66.28 million years ago, the sheer amount of carbon dioxide that was unleashed caused a global warming effect of roughly 7.8°C (14°F). This lengthy temperature spike is matched to a widespread species die-off, which is also preserved in the fossil record of Seymour Island.

Image in text: Some of the Cretaceous bivalves analyzed for the study. Sierra V. Petersen

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