Massive volcanic eruptions were not the cause of dinosaur extinction, climate scientists say

A massive volcanic eruption on the Indian peninsula has long been proposed as an alternative cause of the dinosaur extinction. This phase of active volcanism occurred 66 million years ago, just before a meteorite hit the Earth. The impact of these volcanic eruptions on Earth’s climate has been the subject of intense scientific debate for decades.

Now, climate scientists from Utrecht University and the University of Manchester have shown that volcanic activity caused a temporary cooling period, but that its effects had already dissipated thousands of years before the meteorite impact. Scientists therefore concluded that a meteorite impact was the ultimate cause of the dinosaur extinction event.

The study was published in the journal Science Advances.

The meteorite impact in the Gulf of Mexico approximately 66 million years ago is well-studied and widely credited with marking the end of the dinosaur era. However, geoscientists have been fiercely debating for decades whether the massive eruptions of lava into India that occurred before and after the meteorite impact also contributed to the extinction of Earth-roaming dinosaur populations. I’ve done it.

These volcanic eruptions released enormous amounts of CO2, dust, and sulfur, thereby significantly changing the Earth’s climate, but in ways and timescales that varied depending on the meteorite impact.

ancient peat

This new publication convincingly shows that while volcanic eruptions in India had a clear impact on Earth’s climate, they may have had little or no effect on the dinosaur mass extinction. provides evidence.

By analyzing fossil molecules in ancient peat in the United States, a scientific team reconstructed temperatures during a period covering both volcanic eruptions and meteorite strikes. Using this method, the researchers showed that a major volcanic eruption occurred about 30,000 years before the meteorite impact, and that it coincided with a cooling of the climate by at least 5 degrees Celsius. They also conclude that this cooling is likely the result of volcanic sulfur emissions blocking sunlight from reaching the surface.

Importantly, scientists found that by about 20,000 years before the meteorite impact, temperatures on Earth were already stable and rising to similar temperatures before volcanic eruptions began. Lauren O’Connor from Utrecht University said global warming during this period was likely driven by volcanic carbon dioxide emissions.

“These volcanic eruptions and the associated release of carbon dioxide and sulfur would have had a dramatic impact on life on Earth. However, these events occurred thousands of years before the meteorite impact, and probably caused the dinosaurs to “It would have played only a small role in the extinction of the species,” she explains.

Shocking winter

Once the effects of volcanic activity are effectively eliminated, the Chicxulub meteorite impact remains the main cause of the dinosaur mass extinction.

“By comparison, impacts from asteroids caused a series of disasters, including wildfires, earthquakes, tsunamis, and an ‘impact winter’ that blocked sunlight and destroyed ecosystems. “I believe this was a fatal blow to the country,” said Rodri Gerrett. at the University of Manchester.

The fossil peat that the researchers analyzed contains specific transmembrane molecules produced by bacteria. The structure of these molecules changes depending on the temperature of the environment. By analyzing the composition of these molecules preserved in ancient sediments, scientists can calculate past temperatures.

Professor O’Connor said: “In this way, we were able to create a detailed ‘temperature timeline’ of the years leading up to the extinction of the dinosaurs. We compared this with the fossil record to get a relative picture of the events. You can understand the timing,” he added.

Researchers from Utrecht University, the University of Manchester, the University of Plymouth, and the Denver Museum of Nature and Science are now applying the same approach to reconstruct past climates during other key periods in Earth’s history.