Volcanic activity in India altered the climate but didn’t kill the dinosaurs; the Chicxulub meteorite did, by triggering an impact winter and massive environmental changes.
Massive volcanic eruptions on the Indian subcontinent have long been suggested as a possible cause of the dinosaurs’ extinction. These eruptions occurred shortly before Earth was struck by a meteorite 66 million years ago. For decades, scientists have debated the extent to which this volcanism affected Earth’s climate and contributed to the dinosaurs’ demise.
Now, researchers from Utrecht University and the University of Manchester have found that while the volcanic activity caused a temporary period of global cooling, its effects had faded thousands of years before the meteorite impact. Based on this evidence, the scientists conclude that the meteorite impact was the primary driver of the dinosaur extinction event.
Dinosaur Extinction Theories
What caused the extinction of the dinosaurs — was it the Chicxulub meteorite, or did massive volcanic eruptions also play a role? These two ideas have fueled debate for decades and even appear in modern children’s books about dinosaur history.
The meteorite impact in the Gulf of Mexico, occurring roughly 66 million years ago, is widely recognized as the event that marked the end of the dinosaur era. However, scientists have long debated whether colossal volcanic eruptions in India, which happened before and after the meteorite strike, also contributed to the dinosaurs’ demise. These eruptions released enormous amounts of CO₂, sulfur, and dust into the atmosphere, drastically altering Earth’s climate — but in ways and on timescales different from those caused by a meteorite impact.
Climate Impact of Volcanic Eruptions
A new publication in the prestigious scientific journal Science Advances by climate scientists from Utrecht University and the University of Manchester now provides compelling evidence that while the volcanic eruptions in India had a clear impact on global climate, they likely had little to no effect on the mass extinction of the dinosaurs.
By analyzing fossil molecules in ancient peats from the United States of America, the scientific team reconstructed air temperatures for the time period covering both the volcanic eruptions and the meteorite impact. Using this method, the researchers show that a major volcanic eruption occurred about 30,000 years before the meteor impact, coinciding with at least a 5° Celsius cooling of the climate. They also concluded that this cooling was likely the result of volcanic sulfur emissions blocking sunlight from reaching the Earth’s surface.
Climate Recovery and Volcanic Influence
Importantly, the scientists discovered that by around 20.000 years before the meteorite impact, temperatures on Earth had already stabilized and had climbed back to similar temperatures before the volcanic eruptions started. This period of global warming was likely aided by volcanic CO2 emissions, says Lauren O’Connor at Utrecht University: “These volcanic eruptions and associated CO2 and sulfur release would have had drastic consequences for life on earth. But these events happened millennia before the meteorite impact and probably played only a small part in the extinction of dinosaurs.”
Ruling Out Volcanic Effects
With the effects of volcanism practically ruled out, this would leave the Chicxulub meteorite impact as the primary cause of the dinosaur mass extinction. “By comparison, the impact from the asteroid unleashed a chain of disasters, including wildfires, earthquakes, tsunamis, and an ‘impact winter’ that blocked sunlight and devastated ecosystems. We believe the asteroid that ultimately delivered the fatal blow,” says Rhodri Jerrett at the University of Manchester.
The fossil peats that the researchers analyzed contain specific membrane-spanning molecules produced by bacteria. The structure of these molecules changes depending on the temperature of their environment. By analyzing the composition of these molecules preserved in ancient sediments, scientists are able to calculate past temperatures. O’Connor adds: “This way, we were able to create a detailed ‘temperature timeline’ for the years leading up to the dinosaur extinction, which we can compare to the fossil record to understand the relative timing of events.”
Reference: “Terrestrial evidence for volcanogenic sulfate-driven cooling event ~30 kyr before the Cretaceous–Paleogene mass extinction” by Lauren K. O’Connor, Rhodri M. Jerrett, Gregory D. Price, Tyler R. Lyson, Sabine K. Lengger, Francien Peterse and Bart E. van Dongen, 18 December 2024, Science Advances.
DOI: 10.1126/sciadv.ado5478
The researchers from Utrecht University, the University of Manchester, Plymouth University, and the Denver Museum of Nature & Science, are now applying the same approach to reconstruct past climate at other critical periods in Earth’s history.
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