Sunday, October 11, 2015

Asteroid that killed dinosaurs also intensified volcanic eruptions - study

Asteroid that killed dinosaurs also intensified volcanic eruptions - study

The asteroid that slammed into Earth and heralded the doom of the dinosaurs triggered a surge in volcanic eruptions that made the catastrophe even worse, researchers claim.
Scientists analysed prehistoric lava flows in India and found that soon after the massive impact, volcanic eruptions became twice as intense, throwing out a deadly cocktail of sulphur dioxide and carbon dioxide.
The shockwaves produced when the space rock thumped into Earth likely shook up volcanic plumbing systems around the world, creating larger magma chambers that spewed out more material when they erupted.
Combined with the hefty impact, the increase in volcanic activity would have pumped enough dust and noxious fumes into the atmosphere to blanket the Earth and drive many species to extinction.
The asteroid or comet that crashed into Earth 65m years ago was likely more than six miles (10km) in diameter. When it struck, it released more energy than a billion of the nuclear bombs that destroyed Hiroshima. The impact left its mark at Chicxulub in Mexico in the form of an enormous crater 110 miles (180km) wide.
The impact threw dust into the atmosphere and could have set off magnitude 9 earthquakes around the globe.“We’re not debating the importance of the impact at Chicxulub, it was a very traumatic event, but extensive volcanism would have made it very difficult for ecosystems to recover,” said Loÿc Vanderkluysen at Drexel University, who took part in the study. 
The scientists examined layers of ancient lava that are exposed by a cliff face east of Mumbai in India. Known as the Deccan Traps, the lava flows sit like a layer cake, and cover an immense area, roughly the size of Spain. “It’s one of the few very large volcanic provinces we have. It is hard to grasp the scale,” said Vanderkluysen.Tests on different parts of the lava flows put more precise dates on when they formed, and showed that a massive rise in the eruption rate came soon after the giant impact. The volcanoes, in what is now India, were likely the most dramatic on Earth at the time, but the blast and shockwaves unleashed by the asteroid will have ignited other volcanoes around the world.The researchers used a dating technique that placed the surge in eruptions no more than 50,000 years after the impact, a mere blink of the eye in geological terms. “It would be a coincidence for these two things to be happening so close to one another. It’s unlikely to be random,” Vanderkluysen told the Guardian. Details of the study are published in the journal, Science.
For much of life on Earth, the consequences were terrible. The impact, followed by a prolonged surge in eruptions, laid waste to the ecosystem and prevented it from bouncing back for more than 500,000 years. “The biodiversity and chemical signature of the ocean took about half a million years to really recover, which is about how long the accelerated volcanism lasted,” said Paul Renne, a geologist at the University of California, Berkeley, and lead author on the study. “Our data don’t conclusively prove that the impact caused these changes, but the connection looks increasingly clear.”
Scientists have argued for years about the impact of the fatal blow that wiped out the dinosaurs. While some pointed to the Chicxulub crater, and said the asteroid was the main driver for the mass extinction, others claimed that the huge volcanic eruptions that gave rise to the Deccan Traps were to blame.
“If our high-precision dates continue to pin these three events – the impact, the extinction and the major pulse of volcanism – closer and closer, people are going to have to accept the likelihood of a connection among them,” said Mark Richards, a co-author on the study.

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