The dinosaurs weren’t wiped out by an asteroid 66 million years ago

Illustration of Pteranodon sp.  flying reptiles observing a massive asteroid approaching the earth's surface.  A similar impact is believed to have killed the dinosaurs some 65 million years ago.  The impact would have thrown trillions of tons of dust into the atmosphere and significantly cooled Earth's climate, possibly responsible for the mass extinction.  A layer of iridium-rich rock known as the K-pg boundary is believed to be the remnant of the impact debris.

Did the asteroid really kill the dinosaurs? (Getty)

About 66 million years ago, a giant asteroid slammed into our planet, unleashing a terrible firestorm that obliterated the sun and .

Or is it? A new study has cast doubt on the theory that the dinosaurs were actually wiped out by one — and instead pointed the finger at volcanoes.

Researchers believe giant, continent-spanning “tidal basalt” eruptions caused the mass extinction — and others in Earth’s history.

The presence of an asteroid only made matters worse, the researchers say.

The study, published in the Proceedings of the National Academy of Sciences (PNAS), reports that volcanic activity appears to have been the main reason for the mass extinction.

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In fact, a certain type of volcanic activity could also explain other mass extinctions in history, the researchers believe.

Co-author Brenhin Keller, assistant professor of earth sciences at Dartmouth, says: “All other theories that tried to explain what killed the dinosaurs, including volcanism, were overwhelmed when the Chicxulub impact crater was discovered,” he says.

But Keller points out that despite decades of exploration, there is very little evidence of similar impact events coinciding with the other mass extinctions.

Keller says, “While it is difficult to determine whether a specific volcanic eruption caused a specific mass extinction event, our findings make it difficult to ignore the role of volcanism in the extinction event.”

The researchers found that four out of five mass extinctions occurred simultaneously with a type of volcanic outpouring called flood basalt, the researchers say.

These eruptions flood vast areas – even an entire continent – with lava in the geological blink of an eye of a million years.

As evidence, they leave huge fingerprints — vast regions of step-like igneous rock (solidified by the erupted lava) that geologists call “great igneous provinces.”

To be considered “large,” a large magmatic province must contain at least 100,000 cubic kilometers of magma.

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For context, the 1980 Mount St. Helens eruption involved less than a cubic kilometer of magma.

A series of eruptions in present-day Siberia triggered the most devastating mass extinction about 252 million years ago, releasing a gigantic burst of carbon dioxide into the atmosphere and suffocating almost all life.

Witnessed by the Siberian Traps, a large region of volcanic rock roughly the size of Australia.

Volcanic eruptions also rocked the Indian subcontinent around the time of the great dinosaur extinction, creating what is now known as the Deccan Plateau. Similar to the asteroid impact, this would have had far-reaching global effects, blanketing the atmosphere with dust and noxious fumes, choking out dinosaurs and other life, and altering the climate for long periods of time.

Researchers compared the best available estimates of flood basalt eruptions to periods of drastic species extinctions on the geologic timescale, including but not limited to the five mass extinctions.

Paul Renne, Professor-in-Residence of Earth and Planetary Sciences at the University of California, Berkeley, says: “Our results indicate that there would have been, in all likelihood, a large-scale Cretaceous-Tertiary extinction event that whether or not there has been an impact that can now be shown more quantitatively.

“The fact that there was an impact undoubtedly made matters worse.”

The eruption rate of the Deccan Traps in India suggests the stage was set for widespread extinctions even without the asteroid, Green says.

The impact was the double whammy that loudly rang the death knell for the dinosaurs, he adds.

Flood basalt outbursts are not common in the geologic record, Green says. The last of comparable, but much smaller scale, occurred about 16 million years ago in the Pacific Northwest.

“While the total amount of carbon dioxide released into the atmosphere with modern climate change is still very much less than the amount emitted by a large volcanic province, fortunately we are emitting very rapidly,” says Keller, “and that’s a reason to be concerned.”

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