Did volcanoes kill the dinosaurs? Nope, it was all about the asteroid, new study finds

The debate has raged: Was it massive volcanic eruptions or an asteroid that played the biggest role in the demise of the dinosaurs?

A new study by Yale researchers puts the blame squarely on the asteroid impact.

About 66 million years ago at the end of the Cretaceous period, 75% of life on earth went extinct. Recent studies, including one released from Princeton researchers last year have suggested that massive volcanic eruptions at a site called the Deccan Traps in India may have contributed to the mass extinction event known as K-Pg.

Volcanoes can drive mass extinctions because they release deadly gasses like sulfur and carbon dioxide, but recent research has focused more on the lava eruptions than the gas, according to Pincelli Hull, assistant professor of geology & geophysics at Yale and lead author of the study.

Some studies have suggested the gas emission happened right before the asteroid hit, but Hull said there are no geological or temperature records that support that theory.

Hull and her team examined global temperature records, the carbon isotopes from marine fossils, and models to test different scenarios to determine when the gas emission occurred.

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Her research, published Thursday in the peer-review journal Science, suggests that the toxic gasses started spewing sometime between 350,000 and 200,000 years before the asteroid impact.

The gasses are believed to have caused a relatively large global warming event, raising temperatures by about 2 degree Celsius and forcing species to move to a higher latitudes. But the rising temperatures didn't cause a mass extinction event and the ecosystem returned to its baseline before the asteroid hit, the study concludes.

"They changed in response to warming, but they changed back again prior to the impact," Hull said. "It really leads us to say 'well hey its the impact that drives the extinction and the volcanic warming and cooling is happening, but it’s not contributing to what we’re seeing right at the boundaries.'"

The study can't exactly pinpoint when the lava eruptions occurred, but Hull said their best predictive model is similar to a timeline suggested by researchers at University of California–Berkeley that indicated about half the "outgassing" occurred after the impact.

Researchers have wondered for years why there was no global warming event after this second outgassing, and Hull's research led her to the answer: The mass extinction caused by the asteroid altered the carbon cycle so much that it absorbed the volcanic emissions.

Hull said more research needs to be done to determine exactly how effects of the impact changed the evolution of ecosystems.

"I think is a question that has relevance to how we understand the changes in our modern world today," she said.

Consider this: 950 earthquakes have hit Puerto Rico so far this year. Why? Blame it on an 'earthquake swarm'

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This article originally appeared on USA TODAY: Dinosaur extinction caused by asteroid, not volcanoes, study finds