Massive eruptions did not trigger dinosaur extinction

Massive volcanic eruptions in India, once theorized as a potential cause of dinosaur extinction, likely played a minimal role in their demise, according to new research by climate scientists at Utrecht University and the University of Manchester. Their findings suggest that while these eruptions caused a temporary cooling period, their climatic effects had dissipated thousands of years before the Chicxulub meteorite struck Earth 66 million years ago, marking the end of the dinosaur era.

For decades, scientists have debated whether the dramatic lava flows on the Indian continent - occurring before and after the meteorite impact - contributed to the extinction of dinosaurs. These volcanic events released vast amounts of CO2, dust, and sulfur, altering the climate on different timescales compared to the meteorite's immediate and catastrophic impact.

Peat analysis and climate insights

The study, published in Science Advances, used fossil molecules from ancient peats in the United States to reconstruct air temperatures during the period of the volcanic eruptions and meteorite impact. The data revealed a major volcanic eruption approximately 30,000 years before the meteorite strike, resulting in a 5C global cooling due to sulfur emissions blocking sunlight. However, the scientists observed that by 20,000 years before the impact, temperatures had already rebounded, likely aided by volcanic CO2 emissions.

"These volcanic eruptions and associated CO2 and sulfur releases would have had drastic consequences for life on Earth," said Lauren O'Connor of Utrecht University. "But these events occurred millennia before the meteorite impact and probably played only a small part in the extinction of dinosaurs."

The Chicxulub meteorite's fatal blow

This research underscores the Chicxulub meteorite as the primary cause of the dinosaur mass extinction. "The asteroid impact unleashed a cascade of disasters, including wildfires, earthquakes, tsunamis, and an 'impact winter' that blocked sunlight and devastated ecosystems," explained Rhodri Jerrett of the University of Manchester. "We believe the asteroid ultimately delivered the fatal blow."

The analysis of ancient bacterial membrane molecules preserved in fossil peats allowed researchers to establish a detailed temperature timeline leading up to the extinction event. "This timeline helps us compare climatic changes with the fossil record to better understand the sequence of events," O'Connor noted.

Research Report:Terrestrial evidence for volcanogenic sulfate-driven cooling event ~30 ka before the Cretaceous - Paleogene mass extinction