The asteroid that slammed into the ocean off the coast of Mexico some 66 million years ago killed off the dinosaurs and probably rang the Earth like a bell, triggering volcanic eruptions around the globe that may have contributed to the destruction, according to a team of University of California, Berkeley, geophysicists.
Specifically, the researchers argue that the impact likely triggered most of the immense eruptions of lava in India known as the Deccan Traps, explaining the "uncomfortably close" coincidence between the Deccan Traps eruptions and the impact, which has always cast doubt on the theory that the asteroid was the sole cause of the end-Cretaceous mass extinction.
"If you try to explain why the largest impact we know of in the last billion years happened within 100,000 years of these massive lava flows at Deccan...the chances of that occurring at random are minuscule," said team leader Mark Richards, UC Berkeley professor of Earth and planetary science, according to a press release. "It's not a very credible coincidence."
Michael Manga, a professor in the same department, has shown over the past decade that large earthquakes -- equivalent to Japan's 9.0 Tohoku quake in 2011 -- can trigger nearby volcanic eruptions. Richards calculates that the asteroid that created the Chicxulub crater might have generated the equivalent of a magnitude 9 or larger earthquake everywhere on Earth, sufficient to ignite the Deccan flood basalts and perhaps eruptions many places around the globe, including at mid-ocean ridges.
"It's inconceivable that the impact could have melted a whole lot of rock away from the impact site itself, but if you had a system that already had magma and you gave it a little extra kick, it could produce a big eruption," Manga said, according to the press release.
Richards, Renne and graduate student Courtney Sprain, along with Deccan volcanology experts Steven Self and Loÿc Vanderkluysen, visited India in April 2014 to obtain lava samples for dating, and noticed that there are pronounced weathering surfaces, or terraces, marking the onset of the huge Wai subgroup flows. Geological evidence suggests that these terraces may signal a period of calm in Deccan volcanism prior to the Chicxulub impact.
"This was an existing massive volcanic system that had been there probably several million years, and the impact gave this thing a shake and it mobilized a huge amount of magma over a short amount of time," Richards said, according to the press release. "The beauty of this theory is that it is very testable, because it predicts that you should have the impact and the beginning of the extinction, and within 100,000 years or so you should have these massive eruptions coming out, which is about how long it might take for the magma to reach the surface."
Since the team's paper was accepted for publication, a group from Princeton University published new radioisotopic dates for the Deccan Traps lavas that are consistent with these predictions. Renne and Sprain at UC Berkeley also have preliminary, unpublished dates for the Deccan lavas that could help solidify Richards' theory, Renne said.
Reference:
"Triggering of the largest Deccan eruptions by the Chicxulub impact," Mark A. Richards et al., GSA Bulletin, 30 April 2015 [https://gsabulletin.gsapubs.org/content/early/2015/04/30/B31167.1.abstract].
Co-authors of the paper, in addition to Richards, Renne, Manga and Sprain, are Walter Alvarez, a UC Berkeley professor emeritus of Earth and planetary science and the co-originator of the dinosaur-killing asteroid theory; Stephen Self, an adjunct professor in the same department at UC Berkeley; Leif Karlstrom of the University of Oregon; Jan Smit of Vrije Universeit in Amsterdam, the Netherlands; Loÿc Vanderkluysen of Drexel University in Philadelphia, Pennsylvania; and Sally A. Gibson of the University of Cambridge in the United Kingdom.
