About 66 million years ago, a giant asteroid collided with our planet, unleashing a terrible firestorm that smashed the sun and killed the dinosaurs.
Or did you do that? A new study has cast doubt on the theory that dinosaurs were only wiped out by a mountain-sized asteroid – and instead pointed fingers at volcanoes.
Researchers believe that it was the massive volcanic eruptions that spanned the length of the continent that caused the mass extinctions — and others in Earth’s history.
They said that the presence of an asteroid made matters worse.
Their study was published in Proceedings of the National Academy of Sciences (PNAS), claims that volcanic activity was the main driver of the mass extinction.
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Indeed, a certain type of volcanic activity may also explain other mass extinctions in history, the researchers said.
“All the other theories that tried to explain why the dinosaurs, including volcanoes, were killed, were accelerated when the Chickxulub impact crater was discovered,” said co-author Briannen Keeler, associate professor of Earth sciences at Dartmouth College in New Hampshire.
But he added that there is very little evidence for similar impact events that have coincided with other mass extinctions despite decades of exploration.
“While it is difficult to determine whether a particular volcanic eruption caused a particular mass extinction, our results make it difficult to ignore the role of volcanoes in the extinction,” Keeler said.
The researchers found that four out of five mass extinctions occurred at the same time as a type of volcanic outflow called a basalt flood.
These eruptions inundated vast regions – even an entire continent – with lava in a mere million years, in the blink of a geological eye.
They left behind giant fingerprints as evidence – vast areas of step-like igneous rock (solidified by exploding lava) that geologists call “big igneous provinces.”
To be counted as “large,” a igneous province must contain at least 100,000 cubic kilometers of magma.
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For context, the 1980 eruption of St. Helens involved less than one cubic kilometer of magma.
A series of volcanic eruptions in present-day Siberia triggered the most devastating mass extinction event about 252 million years ago, releasing a giant pulse of carbon dioxide into the atmosphere and stifling nearly all life.
Witness this is the Siberian Traps, a large area of volcanic rock roughly the size of Australia.
Volcanic eruptions also rocked the Indian subcontinent around the time of the great dinosaur death, creating what is known today as the Deccan Plateau. This, just like the asteroid impact, would have had far-reaching global effects, blanketing the atmosphere with dust and toxic fumes, suffocating dinosaurs and other life as well as changing the climate on long time scales.
The researchers compared the best available estimates of basalt flood volcanic eruptions with violent species killing periods in the geologic time scale, including but not limited to the five mass extinctions.
“Our results indicate that there was likely to be a mass extinction in the Cretaceous boundary to a significant degree, regardless of whether or not there was an impact, which can now be shown from the Quantitative aspect.
“The fact that there was an effect made things worse, no doubt.”
The rate of eruptions of the Deccan Traps in India suggests the theater is set for widespread extinction even without the asteroid, said lead author Theodore Green.
Greene, who conducted this research as part of the first fellowship program at Dartmouth and is now a graduate student at Princeton University, added that the effect was a double whammy that sounded the death knell of the dinosaurs loudly.
Greene said flood basalt eruptions are not uncommon in the geological record. The last one of the comparable but significantly smaller scale occurred about 16 million years ago in the Pacific Northwest of the United States.
“While the total amount of carbon dioxide released into the atmosphere under modern climate change is still much less than the amount released from a large pyrotechnic province, fortunately we are emitting it very quickly, which is cause for concern,” Keeler said.
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