The extinction of the dinosaurs 65 million years ago was caused by a meteorite plummeting through Earth’s atmosphere and crashing into the Yucatán Peninsula in Mexico. At least, that has long been the accepted theory.
But a new study – published in Science Advances, co-authored by Don Baker, a professor in McGill University's Department of Earth and Planetary Sciences – suggests that there may have been another deadly force at play: volcanoes.
Scientists involved in the study believe that massive volcanic eruptions on the Deccan Traps – a vast plateau in Western India formed by molten lava – may have played a key role in cooling the global climate around 65 million years ago, setting the stage for the mass extinction.
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"Our research demonstrates that climatic conditions were almost certainly unstable, with repeated volcanic winters that could have lasted decades, prior to the extinction of the dinosaurs,” said Professor Don Baker.
“This instability would have made life difficult for all plants and animals and set the stage for the dinosaur extinction event. Thus, our work helps explain this significant extinction event that led to the rise of mammals and the evolution of our species."
Researchers on the project took samples from the Deccan Traps and analysed them in labs in England and Sweden, looking specifically at how much sulfur and fluorine was pushed into the atmosphere by the volcanic activity around the time of the extinction.
Findings showed that the sulfur release could have caused a global temperature drop – a phenomenon known as a volcanic winter.
According to Professor Baker, estimating sulfur and fluorine releases is a complex process: "Imagine making pasta at home,” he said. “You boil the water, add salt, and then the pasta. Some of the salt from the water goes into the pasta, but not much of it." Much like the pasta, Professor Baker explained, some elements become trapped in minerals as they cool following a volcanic eruption. Just as you could work out salt concentrations in the water that cooked the pasta from analysing salt in the pasta itself, scientists were able to measure sulfur and fluorine in rock samples. They could then calculate the amount of sulfur and fluorine released during the eruptions.
The research summarises that "two events share the stage as main drivers of the Cretaceous-Paleogene mass extinction—Deccan Traps volcanism, and an asteroid impact recorded by the Chicxulub crater" in Mexico.
Find out more about the research: Recurring volcanic winters during the latest Cretaceous: Sulfur and fluorine budgets of Deccan Traps lavas.