How did the dinosaurs perish about 66 million years ago? Scientists now largely accept the explanation of a massive asteroid impact that spelled the dinosaurs’ doom. But the possible role of volcanoes has also been debated. Could it have been both? On December 18, 2024, researchers at Utrecht University in the Netherlands and the University of Manchester in the U.K. said that while intense volcanic activity caused a cold period before the asteroid impact, it was the asteroid that ultimately caused the demise of dinosaurs.
The researchers also published their peer-reviewed findings in Science Advances on December 18.
The huge Chicxulub asteroid impact, off Mexico’s Yucatán Peninsula, is generally accepted as the primary cause of the extinction of the dinosaurs about 66 million years ago. But there was also intense volcanic activity in what is now India just before and after that event. This resulted in huge amounts of lava being deposited on the Indian continent and dust being blown into the atmosphere.
The volcanism before the impact did cause a cooling of the atmosphere, but its effects had worn off by the time the impact occurred. Could it still have contributed to the dinosaurs’ extinction?
#Volcanic eruptions in India caused temporary cooling but did not lead to dinosaur extinction. The #MeteoriteImpact 66 million years ago remains the primary cause, according to climate analysis. @UniUtrecht @ScienceAdvances https://t.co/f3RfGDswvW https://t.co/zowuJsA9EP
— Phys.org (@physorg_com) December 18, 2024
There was a major volcanic eruption about 30,000 years before the impact. This initially cooled the global climate by around 5 degrees Celsius (9 degrees F), due to sulfur emissions. However, temperatures had stabilized again about 20,000 years before the impact occurred. In fact, the climate was starting to warm up again. Volcanic eruptions played a part in that as well, by pumping carbon dioxide into the atmosphere. Lead author Lauren O’Connor at Utrecht University said:
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.
Volcanism, therefore, played only a very small role, if any, in the demise of the dinosaurs.
The researchers analyzed fossil molecules in ancient peat bogs. Peat is the surface organic layer of a soil that consists of partially decomposed organic matter. These molecules were produced by bacteria. Notably, temperatures can alter their structure. So by examining the structure of the molecules, the researchers could determine what the temperatures were at the time of their existence before fossilization. O’Connor said:
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.
The molecules preserved a record of when the climate cooled, then warmed again, due to the volcanic eruptions, but well before the asteroid impact. This showed that the global cooling didn’t play a part in the extinction of the dinosaurs.
So if volcanoes didn’t end the dinosaurs’ rule on Earth, that leaves the asteroid. The Chicxulub asteroid impact was massive, hitting in what is now the Gulf of Mexico, off Mexico’s Yucatán Peninsula. It single-handedly pretty much sealed the dinosaurs’ fate. As Rhodri Jerrett at the University of Manchester explained:
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 it was the asteroid that ultimately delivered the fatal blow.
The impact kicked up so much dust that it caused a years-long global winter. Scientists estimate that about 75% of life on Earth, not just dinosaurs, was wiped out.
Bottom line: Did an asteroid cause the demise of dinosaurs? Or was it volcanoes, or both? A new study said the huge Chicxulub asteroid impact is still to blame.
Read more: After the asteroid, dust killed the dinosaurs, study says
Read more: Did a 2nd asteroid help kill the dinosaurs?
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