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Did a Chicxulub oil fire kill off dinosaurs?

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An artist's rendering shows the Chicxulub asteroid crashing into the Yucatan Peninsula about 66 million years ago. New research suggests dinosaurs might have died out even if the asteroid missed Earth. Illustration: Donald E. Davis / NASA
An artist’s rendering shows the Chicxulub asteroid crashing into the Yucatan Peninsula about 66 million years ago. New research suggests dinosaurs might have died out even if the asteroid missed Earth. Illustration: Donald E. Davis / NASA

Scientists have a new theory about how the Chicxulub crater, which hit the Yucatán about 66 million years ago, caused the demise of so many creatures but not others.

Researchers from Japan argue that the six-mile-wide chunk of rock slammed into an oil field in the present-day Yucatán Peninsula and triggered an inferno that launched a massive cloud of smoke.

The resulting layer of soot that enveloped the globe would have been just the thing to kill the dinosaurs and most other land-dwelling creatures, said scientists at Tohoku University.

But the cloud would have let in enough sunlight to allow some animals to survive, they wrote in Scientific Reports.

Earlier theories

Previous studies have postulated that the asteroid sparked mass extinction by releasing high levels of sulfuric acid particles in the atmosphere. The particles would have caused complete darkness, near-freezing temperatures and acid rain.

The Japanese team collected samples of sediment along the Cretaceous-Paleogene boundary — a thin band of rock that marks the timing of the extinction of dinosaurs — in locations about 600 miles outside the crater in Haiti and about 3,700 miles away in Spain.

Samples from both locations were found to have come from the same source: Yucatán.

The researchers hypothesize that soot was slowly deposited on land in the five years following the massive collision.

Soot would have blocked about 85 percent of sunlight and cut rainfall by nearly 80 percent, creating near-drought conditions. Temperatures would have plunged by up to 60 degrees Fahrenheit.

Then plants would begin to die off, cutting off the food supply to creatures higher up the food chain — such as the dinosaurs.

What survived, and why

Crocodilians, birds, small mammals, and most ocean creatures survived because their habitats afforded them protection from the chilling temperatures, and they maintained a diet lower on the food chain.

But previous studies have shown there was a lot more going on at the time.

Other scientists point out that lava had been flowing from the Deccan traps in India for about 250,000 years before the asteroid hit, and a study published in 2015 found that the crater impact may have instigated an additional eruption there, adding a significant amount of carbon dioxide to the atmosphere.

That would have caused temperatures to rise, not fall, adding to difficulty of holding to any one scientific theory.

With information from the Los Angeles Times, phys.org

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