Scientists zero in on the role of volcanoes in the demise of dinosaurs

Recent research has identified a global warming event that occurred several hundred thousand years before the end-Cretaceous extinction. Some scientists have linked the eruption of the Deccan Traps to this warming event, but there is debate over whether the lavas that erupted could have released enough CO₂ into the atmosphere to cause it. Adding to this mystery, the lava volumes that erupted during this time are relatively small compared to the volumes erupted during subsequent stages of Deccan Traps activity. A major challenge in this debate has been the lack of CO₂ data on Deccan magmas from this time.

"Our team analyzed Deccan Traps CO₂ budgets that coincided with the warming event, and we found that carbon outgassing from lava volumes alone couldn't have caused that level of global warming," said Andres Hernandez Nava, a Ph.D. student in The Graduate Center, CUNY's Earth and Environmental Science program and first author of a newly published paper in the Proceedings of the National Academy of Sciences journal detailing new findings about this event. "But, when we factored in outgassing from magmas that froze beneath the surface rather than erupting, we found that the Deccan Traps could have released enough CO₂ to explain this warming event."

For their study, the team -- which included Hernadez Nava and Professor Benjamin Black from The Graduate Center and The City College of New York (CUNY); geochemist Sally Gibson from University of Cambridge; geoscientist Robert Bodnar from Virginia Tech; geologist Paul Renne of University of California, Berkeley; and geochemist Loÿc Vanderkluysen of Drexel University -- used lasers and beams of ions to measure the amount of CO₂ inside of tiny droplets of frozen magma trapped inside Deccan Traps crystals from the end-Cretaceous time period. They also measured the amounts of other elements, such as barium and niobium, which can serve proxies for how much CO₂ the magmas started out with. Finally, they performed modeling of the latest Cretaceous climate to test the impacts of Deccan Traps carbon release on surface temperatures.

The team's findings help fill a significant knowledge gap about how magmas interacted with climate during this crucial period in Earth's history. Their data show that CO₂ outgassing from Deccan Traps magmas can explain a warming of Earth's global temperatures by roughly 3 degrees Celsius during the early phases of Deccan volcanism, but that there was not nearly that much warming by the time we reached the mass extinction event, supporting the idea that later Deccan magmas were not releasing as much CO₂. These new insights disfavor the theory that volcanic CO₂ was a major driver of the most recent mass extinction.

"Our lack of insight into the carbon released by magmas during some of Earth's largest volcanic eruptions has been a critical gap for pinning down the role of volcanic activity in shaping Earth's past climate and extinction events," said Black, the study's principal investigator and a professor in the Earth and Environmental Science program at The Graduate Center CUNY and City College of New York. "This work brings us closer to understanding the role of magmas in fundamentally shaping our planet's climate, and specifically helps us test the contributions of volcanism and the asteroid impact in the end-Cretaceous mass extinction."

This research was funded by the National Science Foundation through grant EAR 1615147.