Press Trust of IndiaFeb 26, 2019 12:48:13 IST
The asteroid impact that wiped off dinosaurs from the face of Earth 66 million years ago may have also reignited massive volcanic eruptions in India, half a world away from the impact site, a study has found.
The research, published in the journal Science, obtained more precise dates for the Deccan Traps volcanic lava flows, linking peak activity more closely to the asteroid or comet impact 66 million years ago and the coincident mass extinction.
However, it leaves unclear to what degree the two catastrophes contributed to the near-simultaneous mass extinction that killed off the dinosaurs and many other forms of life.
The research sheds light on huge lava flows that have erupted periodically over Earth's history, and how they have affected the atmosphere and altered the course of life on the planet.
Scientists from the University of California (UC) Berkeley in the US showed that the most precise and accurate dates yet for the intense volcanic eruptions in India that coincided with the worldwide extinction at the end of the Cretaceous Period, the so-called K-Pg boundary.
The million-year sequence of eruptions spewed lava flows for distances of at least 500 kilometers across the Indian continent, creating the so-called Deccan Traps flood basalts that in some places are nearly two kilometers thick.
"Now that we have dated Deccan Traps lava flows in more and different locations, we see that the transition seems to be the same everywhere," said Paul Renne, from UC Berkeley.
"I would say, with pretty high confidence, that the eruptions occurred within 50,000 years, and maybe 30,000 years, of the impact, which means they were synchronous within the margin of error," said Renne.
"That is an important validation of the hypothesis that the impact renewed lava flows," he said.
The new dates also confirm earlier estimates that the lava flows continued for about a million years, but contain a surprise: three-quarters of the lava erupted after the impact.
Previous studies suggested that about 80 percent of the lava erupted before the impact.
If most of the Deccan Traps lava had erupted before the impact, then gases emitted during the eruptions could have been the cause of global warming within the last 400,000 years of the Cretaceous Period, during which temperatures increased, on average, about 8 degrees Celsius.
During this period of warming, species would have evolved suited to hothouse conditions, only to be confronted by global cooling from the dust or by climate cooling gases caused by either the impact or the volcanos.
The cold would have been a shock from which most creatures would never have recovered, disappearing entirely from the fossil record.
However, researchers said if most of the Deccan Traps lava emerged after the impact, this scenario needs rethinking.
"This changes our perspective on the role of the Deccan Traps in the K-Pg extinction," said Courtney Sprain, a former doctoral student at UC Berkeley.
"Either the Deccan eruptions did not play a role — which we think unlikely — or a lot of climate-modifying gases were erupted during the lowest volume pulse of the eruptions," said Sprain, who is now at the University of Liverpool in the UK.
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