'One-Two' Punch of Asteroid and Volcanic Eruptions May Be to Blame for Dinosaur Extinction

By Kevin Byrne, AccuWeather.com Staff Writer

November 4,2015; 10:24PM,EST

 

 

Researchers have presented new evidence that suggests that the asteroid that struck Earth 66 million years ago also caused an increase in global volcanic eruptions, creating a "one-two" punch that led to the extinction of the dinosaurs and other species.
In a study published last month in the journal Science, the research group said the strong ecologic recovery may have been impossible for up to 500,000 years after the increase in volcanism. Faculty from the University of California Berkeley, Drexel University in Philadelphia and the Indian Institute of Technology Bombay in Mumbai, India, contributed to the research.
Lead researcher Paul Renne, director of the Berkeley Geochronology Center at UC Berkeley, said that according to the team's high-precision isotope dating of the lava flows, the impact and volcanism occurred within 50,000 years of the extinction, making it hard to distinguish which event was the primary cause. Specifically, they discovered that the Deccan Traps lava flows in India doubled in output.
Layered lava flows of the Deccan Traps east of Mumbai, India. (Photo/Mark Richards UC Berkeley)
"It is going to be basically impossible to ascribe actual atmospheric effects to one or the other. They both happened at the same time," he said in a news release.
"Both the impact and the volcanism would have blanketed the planet with dust and noxious fumes, drastically changing the climate and sending many species to an early grave," the release states.
The study proposes that the impact caused a shift in the Earth's underground plumbing, which produced changes in the frequency and chemistry of the eruptions.
Smaller magma chambers before the impact became larger, which means they took longer to fill but spewed more lava when they did erupt, according to Renne. The analysis, done earlier this year after collections were taken in India, examined lava flows from time periods at the beginning of the extinction as well as hundreds of thousands of years before and after it took place.
The asteroid impact is known as the Chicxulub crater, which is located off Mexico's Yucatan Peninsula.
Ben Black, a postdoctoral scholar in the Department of Earth and Planetary Science at UC Berkeley, told AccuWeather an increase in Deccan volcanism 66 million years ago likely corresponded to more gases, such as sulfur and carbon dioxide, going into the atmosphere.
"Sulfur can cause temporary cooling of climate and acid deposition," Black said. "Carbon dioxide can cause longer-term warming of climate and ocean acidification; halogens can cause ozone depletion."
"Consequently, I expect that [the] global climate warmed somewhat, perhaps with episodes of cooler temperatures just when pulses of magma erupted," he said.
In the deep past, volcanic carbon dioxide may have even helped Earth develop from a "snowball state," Black said. Today, volcanoes may even respond to climate conditions with increased or decreased rates of activity, he added.
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Whether it was the asteroid or volcanism that was largely responsible for the extinction has long been a hotly contested debate.
Study co-author Mark Richards said that if they can continue to pin the impact, extinction and volcanism closer together, people will have to accept the likelihood of a connection among them.
"The scenario we are suggesting, that the impact triggered the volcanism, does in fact reconcile what had previously appeared to be an unimaginable coincidence," Richards said.
Carbon isotopes, fossils and sedimentary and volcanic rocks are all key clues for geologists and paleontologists to lean on when researching and evaluating what happened in this environmental catastrophe tens of millions of years ago.
"The challenge and also the reward for geologists is to continue assembling these clues in order to put together the complete story of what happened," Black said.
"Clearly this was a time of dramatic upheaval," he said.

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