The impact of asteroids, not volcanoes, made Earth uninhabitable for dinosaurs

Modeling the impact of the asteroid Chicxulub 66 million years ago shows that it created a world largely unsuitable for dinosaurs to live.

The asteroid, which struck the Earth off the coast of Mexico at the end of the Cretaceous era 66 million years ago, is believed to have caused the disappearance of all dinosaur species except those that became birds.

However, some researchers have suggested that tens of thousands of years of large volcanic eruptions may have been the actual cause of the extinction event, which also killed nearly 75% of life on Earth.

Now, a research team from Imperial College London, the University of Bristol, and University College London have shown that only the impact of asteroids could have created unfavorable conditions for dinosaurs worldwide.

They also show that massive volcanism could also have helped life recover from long-term asteroid attack. Their results are published today in procedures of the National Academy of Sciences.

The principal investigator, Dr. Alessandro Chiarenza, who carried out this work while studying for his Ph.D. at the Department of Earth Sciences and Engineering at Imperial, he said: “We showed that the asteroid had an impact in the winter for decades, and that these environmental effects decimated suitable environments for dinosaurs. By contrast, the effects of intense volcanic eruptions were not strong enough to substantially alter global ecosystems.

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

The asteroid attack would have released particles and gases into the atmosphere, blocking the Sun for years and causing permanent winters. Volcanic eruptions also produce particles and gases with sun block effects, and around the time of the mass extinction there were tens of thousands of years of eruptions in the Deccan traps in present-day India.

To determine which factor, the asteroid or volcanism, had the most power for climate change, researchers have traditionally used geological climate markers and powerful mathematical models. In the new document, the team combined these methods with information on what kinds of environmental factors, such as rain and temperature, each dinosaur species needed to thrive.

They were then able to map where these conditions would continue to exist in a world after an asteroid attack or massive volcanism. They discovered that only the asteroid destroyed all potential dinosaur habitats, while volcanism left some viable regions around the equator.

Study co-author Dr. Alex Farnsworth of the University of Bristol said: “Instead of just using the geological record to model the effect on climate that the asteroid or volcanism could have caused worldwide, We took this approach one step further, adding an ecological dimension to the study to reveal how these climatic fluctuations severely affected ecosystems. “

Co-author Dr. Philip Mannion of University College London added: “In this study we added a modeling approach to key geological and climatic data showing the devastating effect of asteroid impact on global habitats. Essentially, it produces a blue screen of death for dinosaurs. “

Although volcanoes release gases and particles that block the sun, they also release carbon dioxide, a greenhouse gas. In the short term after an eruption, sunscreens have a greater effect, causing a “volcanic winter.” However, in the long term, these particles and gases leave the atmosphere, while carbon dioxide remains and accumulates, heating the planet.

After the initial drastic global winter caused by the asteroid, the team’s model suggests that in the long term, volcanic warming could have helped restore many habitats, helping the new life that evolved after the disaster to thrive.

Dr. Chiarenza said: “We provide new evidence to suggest that volcanic eruptions occurring around the same time may have reduced the effects on the environment caused by the impact, particularly by accelerating the rise in temperatures after the winter impact. The warming helped boost the survival and recovery of the animals and plants that achieved extinction, and many groups expanded immediately afterward, including birds and mammals. ”