Asteroid Impact Created Conditions That Killed Most Dinosaurs, Not Volcanoes

An Ankylosaurus magniventris, a large armored dinosaur species that was present during the impact of the Chicxulub asteroid. Fabio Manucci

Sixty-six million years ago, 75 percent of all life on Earth, including most dinosaurs, went extinct. The cause is believed to be a large asteroid that slammed into a region off the coast of modern-day Mexico.

However, there has been much debate about how much of an effect intense volcanism had on life on Earth at the time. Now new research suggests the asteroid didn’t need any help from volcanism in making the planet inhospitable for dinosaurs and many others.

The work, published in the Proceedings of the National Academy of Sciences, looked at the effects of the Chicxulub asteroid impact in the Yucatán Peninsula and the eruption of the Deccan Traps in present-day India. Both phenomena released gases and material into the atmosphere – one instantaneously and the other over the course of many tens of millennia. These releases affected the climate but scientists were unsure of their relative contribution. 

To investigate deeper, the team used both mathematical models and geological markers of climate and combined them with environmental factors such as precipitation and temperature. The work suggests that the asteroid alone was responsible for releasing particles that blocked the Sun, plunging the planet into a winter that lasted for decades.

“We show that the asteroid caused an impact winter for decades, and that these environmental effects decimated suitable environments for dinosaurs. In contrast, the effects of the intense volcanic eruptions were not strong enough to substantially disrupt global ecosystems,” lead author Dr Alessandro Chiarenza, who conducted this work whilst studying for his PhD in the Department of Earth Science and Engineering at Imperial, said in a statement.

“Our study confirms, for the first time quantitatively, that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide.”

The research flips the script on the Deccan Traps completely. The work instead suggests the intense volcanism helped some species to overcome the devastation of the impact winter.

“We provide new evidence to suggest that the volcanic eruptions happening around the same time might have reduced the effects on the environment caused by the impact, particularly in quickening the rise of temperatures after the impact winter,” Dr Chiarenza added. “This volcanic-induced warming helped boost the survival and recovery of the animals and plants that made through the extinction, with many groups expanding in its immediate aftermath, including birds and mammals.”

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