Dinosaur extinction was not caused by global volcanic eruptions 

A new study provides compelling evidence that the Chicxulub meteorite impact, rather than massive volcanic activity, was the principal driver behind the extinction of the dinosaurs 66 million years ago. 

Climate scientists from Utrecht University and the University of Manchester have found that the climatic disturbances caused by colossal volcanic eruptions in India had largely subsided thousands of years before the meteorite struck, leaving the asteroid impact as the ultimate reason for the dinosaurs’ demise. 

The findings, published in Science Advances, help resolve a decades-long scientific debate.

“These volcanic eruptions and associated CO₂ and sulphur release would have had drastic consequences for life on Earth,” said Lauren O’Connor, a researcher at Utrecht University. “But these events happened millennia before the meteorite impact and probably played only a small part in the extinction of dinosaurs.”

Controversy over dinosaur extinction 

For many years, researchers have debated whether the catastrophic asteroid impact near the present-day Gulf of Mexico or the extensive volcanic eruptions of the Deccan Traps in India led to the mass extinction that ended the Cretaceous Period. 

Both events significantly impacted Earth’s climate and ecosystems. The asteroid impact unleashed a chain of disasters including massive wildfires, tsunamis, earthquakes, and a lingering “impact winter” that darkened the skies and devastated the global food chain.

Meanwhile, the Deccan Traps eruptions, occurring both before and after the asteroid strike, released huge volumes of CO₂, dust, and sulphur into the atmosphere. 

These emissions could have induced substantial warming or cooling, depending on their composition and duration. Determining which event bore the greatest responsibility for the dinosaurs’ extinction has long proved challenging due to their overlapping timelines and complex climatic effects.

Clues in ancient peats

To break this impasse, the research team turned to an innovative method: examining ancient peats in the United States for molecular fossils that record past temperatures. 

Certain bacteria produce characteristic membrane-spanning molecules that vary in structure with ambient temperature. 

By analyzing these molecular traces in sediments from the time leading up to the dinosaur extinction, the researchers reconstructed detailed timelines of Earth’s climate.

Temperature timeline leading to dinosaur extinction 

The analysis uncovered a distinct sequence of events. Approximately 30,000 years before the asteroid impact, a major phase of Deccan Traps volcanism triggered significant climate change, cooling the Earth’s surface by at least 5° Celsius. 

This cooling was most likely caused by volcanic sulphur emissions, which blocked incoming sunlight. 

However, the record shows that some 20,000 years before the asteroid struck, global temperatures had already rebounded, returning to levels similar to those before the volcanic eruptions.

“We were able to create a detailed ‘temperature timeline’ for the years leading up to the dinosaur extinction,” O’Connor explained. “By aligning these climate changes with the fossil record, we can better understand the relative timing of these events.”

Volcanic effects had faded before the impact

The revelation that Earth’s climate had stabilized well in advance of the Chicxulub meteorite impact is crucial. Although the Deccan Traps eruptions undoubtedly stressed ecosystems and altered climates, their effects had dissipated long before the asteroid arrived. 

With the volcanic disruptions out of the picture during the critical window, the data strongly point to the meteorite collision as the primary catalyst for the extinction event.

This finding helps distinguish between the gradual, prolonged influence of volcanism and the abrupt, globally catastrophic consequences of the asteroid strike. 

The volcanoes may have prepared a stage of ecological vulnerability, but they did not deliver the final, fatal blow. By the time the asteroid hit, Earth’s systems had largely recovered from the volcanic perturbations.

The asteroid’s fatal blow

With volcanic influences waning thousands of years before the end of the Cretaceous, the Chicxulub meteorite impact emerges more clearly than ever as the decisive factor behind the dinosaurs’ extinction. 

Unlike volcanic activity, which occurs over extended periods, the asteroid collision was sudden and brutally efficient, throwing a shroud of debris into the atmosphere, blocking sunlight, and triggering a cascade of environmental calamities.

“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,” said Rhodri Jerrett of the University of Manchester. “We believe the asteroid ultimately delivered the fatal blow.”

This swift and worldwide onslaught overwhelmed ecosystems, knocking out plant life dependent on sunlight and collapsing food webs that supported large terrestrial animals like dinosaurs. 

While some species survived – leading to the rise of mammals and, eventually, humans – the mighty dinosaurs could not endure this sudden catastrophe.

An accurate picture of Earth’s past

The methods employed in this study highlight the power of molecular paleoclimatology. By examining microscopic bacterial remains embedded in ancient sediments, scientists can now resolve the timing and intensity of climate changes from millions of years ago with remarkable precision. 

These advances allow researchers to clarify the interplay between volcanic eruptions, asteroid impacts, and mass extinctions, painting a more accurate picture of Earth’s deep past.

The study’s conclusions provide a clearer understanding of why the dinosaurs disappeared. While volcanic activity did shape the Earth’s environment, it was not the immediate executioner.

Instead, the researchers confirm that the Chicxulub impact, with its sudden and universal repercussions, was the ultimate cause of the dinosaurs’ end.

“These findings help us understand the relative timing of events and confirm that the asteroid was the ultimate driver of the extinction event,” O’Connor said.

Armed with these insights, scientists can continue to refine their understanding of ancient Earth crises, shedding light on how life responds to abrupt environmental shifts – lessons that may prove valuable as our planet faces its own ecological challenges today.

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