Which came first, the asteroid or the Indian volcanoes?

February 28, 2019 8:55 AM

Recent studies of the Deccan Traps (Wikipedia), a very large igneous province (Wiki) located on the Deccan Plateau of west-central India make it seem increasingly likely that an asteroid or comet impact 66 million years ago reignited massive volcanic eruptions in India, half a world away from the impact site in the Caribbean Sea (Science Daily). "The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary" (UC Berkeley) and "U-Pb constraints on pulsed eruption of the Deccan Traps across the end-Cretaceous mass extinction" (Princeton; both published in Science, both abstracts only).

These studies question the causal relationship between the date of the impact that made the Chicxulub crater, which coincides with the Cretaceous–Paleogene boundary (K–Pg boundary; Wiki x2), slightly less than 66 million years ago.

From the Science Daily article:

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 (14.4 degrees Fahrenheit). 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: literally, a mass extinction.

But 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 first author Courtney Sprain, a former UC Berkeley doctoral student who is now a postdoc at the University of Liverpool in the United Kingdom. "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."

Gerta Keller, Professor of Geosciences at Princeton, has a website dedicated to her Mass Extinction studies and specifically Deccan Volcanism. Professor Keller was involved in Princeton's latest study, though it's unclear how this new information might amend the older material on her website.

posted by filthy light thief (12 comments total)

Coverage of the Asteroid vs Volcanoes debate (that I could have sworn was covered before): The Nastiest Feud in Science -- A Princeton geologist has endured decades of ridicule for arguing that the fifth extinction was caused not by an asteroid but by a series of colossal volcanic eruptions. But she’s reopened that debate. (Bianca Bosker for The Atlantic, Sept. 2018 issue)
posted by filthy light thief at 8:58 AM on February 28, 2019 [1 favorite]

ooooh awesome post, thank you FLT!!! I find this stuff fascinating and look forward to diving in once I get a chance later today!!
posted by supermedusa at 9:08 AM on February 28, 2019

Here's the previous post about Gerta Keller and the Nastiest Feud in Science
posted by theory at 9:10 AM on February 28, 2019 [3 favorites]

What irritated me about the Keller article was the framing of it as invalidating the asteroid impact, instead of reframing it in context. We have a very clear picture of how destructive that impact was and how the shutdown of photosynthesis was an enormous blow to the existing world order. The question was did it hit a system already under stress, i.e. the analyses that have suggested a high rate of extinction even before the strike, and if vulcanism (quite possibly increased by the strike) culled even more of the survivors.
posted by tavella at 9:27 AM on February 28, 2019 [3 favorites]

How would an asteroid impact trigger volcanoes? The argument seems to involve a lot of hand waving and the assumption that the eruption was about to happen anyway.
posted by Joe in Australia at 11:42 AM on February 28, 2019

The asteriod strike on one side of the earth caused a magma surge on the far side. This is a wholistic and rational view of interconnected dynamics.

There is a lake in the top of Yosemite, Tenaya, has a syncopated glitter indicative of a geophysical driver. I have always thought plate techtonics drives this "rhythm without cause." It is a ways off that bumping plate, but I think that is the cause.

Chest thumping in science is a major driver of bad science. I know woo isn't a favorite either, but scientists forget, there is no last word, you know, until there really is one, some day. Scientists forget each one of them will have a final exhale, would be nice if they contributed to understanding rather than confusion.
posted by Oyéah at 12:13 PM on February 28, 2019 [2 favorites]

The idea is that the asteroid hit one side of the Earth and the shockwave travelled around and through, with the waves interacting constructively. The technical term for this is "blorp", or at least it should be.
posted by BeeDo at 1:32 PM on February 28, 2019 [10 favorites]

This is another round in the long running feud between the Luis and Walter Alvarez camp at Berkeley and the Greta Keller camp at Princeton. This round goes to Berkeley.

The argument is around cause and effects, between volcanism and asteroid impact, and which came first. According to Keller's earlier data, the Deccan Traps volcanism started 800,000 years before the asteroid impact, so the extinction was caused by volcanism, not an impact. But this new data refines the timeline indicating that most of the volcanism occurred shortly after the impact, suggesting that the volcanism was triggered, or at least greatly accelerated by the impact.

Also mentioned in the previous Greta Keller thread was new gravimeter evidence indicating that there was a pulse of volcanism at the mid-ocean ridges coincident with the asteroid impact. So it seems that there was a burst of volcanism global wide, not just in the Deccan Traps, associated with the impact.

Keller's position is becoming less and less tenable as more data is gathered and timelines are refined.
posted by JackFlash at 10:17 PM on February 28, 2019 [3 favorites]

Sadly India wasn't antipodal to Chicxulub in the Late Cretaceous. Also, the latest thinking is that the Chicxulub event wouldn't focus enough energy at the palaeo-antipode to crack the crust open like that.
Maybe the meteor strike did "reignite" the Traps. Maybe some of the millions of tons of gypsum punched into the atmosphere by the impact landed on several hundred square kilometers of red hot lava and killed everything. Maybe nothing important has just one explanation.
posted by thatwhichfalls at 10:28 PM on February 28, 2019 [1 favorite]

An accessible account of Chixlub from the Alvarez side, T-Rex and the Crater of Doom.
posted by j_curiouser at 10:42 AM on March 1, 2019

From the PhysOrg link:
"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. "It's not a very credible coincidence."

Has an actual stats person addressed this? Because yes, that does sound unlikely on the face of it, but maybe it's not actually that unlikely, given:
(a) the length of the eruption (hundreds of thousands of years);
(b) the fact that an earlier impact would probably have been found at least as significant, if not more so;
(c) the anthropic argument: if the mass extinction and re-radiation of species at the end of the Cretaceous required coincidental catastrophes, then we wouldn't be around if the coincidence had not happened.

Even ignoring these issues, the actual odds that I've seen suggested are between 1/10 and 1/100 ("Triggering of the largest Deccan eruptions by the Chicxulub impact", pg. 2). Coincidences that that happen all the time. And, honestly, the fact that the theorists have backed down from "the impact caused the massive eruption" to "the impact exacerbated the massive eruption" makes me think that proof would require more comparisons of similar eruptions and similar impacts.
posted by Joe in Australia at 4:46 PM on March 2, 2019 [1 favorite]

I'm not a statistics person, but I do know that in the 4.5 billion years of Earth's history, some seemingly unlikely coincidences were bound to happen. Not saying it is a coincidence, just saying that it's not implausible.
posted by ambulocetus at 6:40 AM on March 3, 2019