Science

Scientists suggest that the double impact of an asteroid and a volcano doomed the dinosaurs to death.

Major volcanic eruptions may have caused mass extinctions throughout Earth’s history, including the one that wiped out the dinosaurs about 66 million years ago.

Currently, the leading theory to explain the mass extinction that ended the dinosaurs suggests that it was caused by a massive asteroid colliding with Earth in what is now the Chicxulub region in the Gulf of Mexico. However, a new study suggests that the asteroid may have had an accomplice in this extinction in the form of volcanic activity.

This new study, which revised volcanic explosions in terms of the amount of lava they erupt, provides the most compelling evidence that there is no correlation between volcanic activity in the geological record and the death of many species in the blink of an eye of the geologic eye. coincidence.

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“Our results do not allow us to ignore the role of volcanism in the extinction,” Brenhin Keller, associate professor of earth sciences at Dartmouth University, said in a statement. (will open in a new tab)

The fossil record contains traces of five major mass extinctions, the most famous of which occurred during the Cretaceous period, lasting from 145.5 to 65.5 million years ago, which killed dinosaurs and about 76% of all species on Earth. .

Keller and his team found evidence of a volcanic imprint called flood basalt consistent with the Cretaceous mass extinction and three of the five other mass extinctions recorded in the Earth’s geological record.

Flood basalts are left behind when either a series of small volcanic eruptions or a single giant eruption quickly floods vast areas of land with lava. This process creates vast staggered areas of igneous rock called “large igneous provinces” that contain at least 100,000 cubic kilometers of magma.

Earth’s history already suggests that volcanic eruptions of this magnitude could trigger a mass extinction.

A series of eruptions in Siberia around 252 million years ago triggered one of the worst mass extinctions ever discovered, the Great Permian Extinction. During these eruptions, huge amounts of carbon dioxide were released into the atmosphere, killing 90% of all species and causing an ecological disaster.

Evidence of this violent and destructive volcanic activity has been recorded in the Siberian Trap, a large area of ​​volcanic rock the size of Australia.

Around the time of the Cretaceous mass extinction, the Indian subcontinent was rocked by volcanic eruptions that created the Deccan Plateau, 7,000 feet (2,000 meters) of flat basaltic lava flows that cover an area of ​​almost 190,000 square miles (500,000 square kilometers) in west-central India. .

Like the impact of the Chicxulub impactor, this could have had far-reaching global repercussions and could have filled Earth’s atmosphere with sunlight-blocking dust and toxic fumes, suffocating dinosaurs and other Cretaceous species.

A high-resolution topographic map of the Yucatan Peninsula created from data collected by the Shuttle Radar topographic mission and released in 2003. A faint dark green arc is visible in the upper left of the peninsula, indicating the remnants of the Chicxulub impact crater. (Image credit: NASA/Getty Images) (will open in a new tab)

The actual cause of the dinosaurs’ extinction has been hotly debated for some time, but the discovery of the Chicxulub crater in the Gulf of Mexico, and the violent impact that gave rise to it, has become the “smoking gun” dominating all other proposals.

“All other theories that tried to explain what exactly killed the dinosaurs collapsed when the asteroid crater was discovered,” Keller said. “But there is very little evidence of similar collisions coinciding with other mass extinctions, despite decades of research.”

In addition to correlating the best available estimates of flood basalt eruptions with periods of dramatic extinction, including but not limited to five mass extinctions, the team also created randomly generated timelines to test 100 million of these patterns.

They found that less than 1% of the simulated time frames were consistent, as well as actual flood and extinction data, suggesting that the link between massive volcanic eruptions and the mass extinction is no coincidence.

These new finds could tip the balance in favor of massive volcanic activity, but when it comes to the Cretaceous extinction event, the team thinks both the Deccan eruption and the Chicxulub impactor could have acted as a “double whammy” to wipe out the dinosaurs.

An article detailing the group’s findings was published in Proceedings of the National Academy of Sciences. (will open in a new tab)

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