≡ Menu

A Volcanic Cause of Dinosaur Extinctions?

The Chicxulub crater in the Yucatan gets plenty of press whenever the subject of asteroid deflection comes up, it being the supposed evidence of the ‘dinosaur killer’ that changed life on Earth forever some 65 million years ago. But other factors may have played a role in the dinosaur extinctions, among them geological events in India, now studied in the form of the so-called ‘Deccan Traps,’ immense lava beds that show the ancient flow of lava from the same era over an area of hundreds of miles.

The Deccan lava fields

If current work is correct, the main phase of these eruptions released ten times the amount of climate-altering gases into the atmosphere as Chicxulub itself, which would have occurred more or less at the same point in geological history. And if iridium deposits were an early clue to what happened in the Yucatan, marine sediments and microscopic marine fossils point to the power of the volcanoes. The life forms that created these fossils are known to have evolved just after the extinction event.

Image: A vertical mile of Deccan lavas visible from Arthur’s Seat at Mahabaleshwar. Are we looking at the epicenter of the event that killed the dinosaurs? Credit: Mike Widdowson.

The era we’re talking about is defined by the Cretaceous-Tertiary (or K-T) boundary. The problem has been narrowing the date of the possibly causative eruptions to this chronological window. The microfossils help because they associate the primary eruptions with the immediate aftermath of the mass extinction event. The same microfossil formations were found 1000 kilometers from the center of the Deccan Traps at a place called Rajahmundry, where two lava traps contain four layers of lava each. Sediment with the microfossils is found just above the lower trap, the one involved in the primary phase of the Deccan eruptions.

Gerta Keller (Princeton University), who presented these results at the annual meeting of the Geological Society of America in late October, sees the findings as an indicator that Chicxulub may have to be demoted:

“Our results are consistent and mutually supportive with a number of new studies, including Chenet, Courtillot and others (in press) and Jay and Widdowson (in press), that reveal a very short time for the main Deccan eruptions at or near the K-T boundary and the massive carbon dioxide and sulfur dioxide output of each major eruption that dwarfs the output of Chicxulub. Our K-T age control combined with these results strongly points to Deccan volcanism as the likely leading contender in the K-T mass extinction.”

Thus the main Deccan volcanic events seem to have ended at the same time as the K-T boundary, offering powerful evidence for this interesting theory. The slow recovery of marine species over a period of 300,000 years following the extinction event may also be explained by subsequent Deccan eruptions, the last of which occurred 280,000 years later.

These findings introduce yet another argument for not restraining the human species to a single, fragile world, one menaced not only by Earth-crossing asteroids and comets but by geological processes that are, if anything, much more beyond our technological control. A robust human expansion into nearby space continues to be good long-term insurance, as the fractious history of Earth continually insists.

Three abstracts are available: Keller, “Main Deccan Volcanism Phase Ends At K-T Mass Extinction: Evidence from the Krishna-Godovari Basin, SE India” (here); Adatte, “Paleoenvironment After Main Deccan Volcanism Ended at K-T Mass Extinction: Evidence From The Krishna-Godavari Basin, SE India” (here), and Keller, “Age and Paleoenvironment of Deccan Volcanism and the K-T Mass Extinction” (here). This Geological Society of America news release has more.

Addendum: Will Baird offers quite an interesting take on all this, contrasting the Permian extinction with the K-T event on his blog The Dragon’s Tales. Be sure to read the whole thing, and note this:

The fact of the matter is that these two extinctions killed in very different ways. These two extinctions effected organisms of different types. They cannot be caused by the same mechanism. Extinction events are not just something that has a geochronologically convenient ‘explanation.’ That explanation has to fit the pattern of that extinction as well as the time frame.

Comments on this entry are closed.

  • JD November 1, 2007, 15:02

    Trying to remember here. I believe there was a theory, a few years ago, that the impact event could have triggered or greatly intensified the Deccan eruptions. The main point of the theory was converging seismic stresses, circling the globe from the Chicxulub impact point. It seemed persuasive since the Deccan region is roughly opposite the Chicxulub impact point and a similar theory is used to account for tidal wave damage on the leeward side of islands. I can’t remember the proponents name or other information. I’m also uncertain if more accurate dating precludes or supports such a theory. Just thought I’d throw it out for discussion.

  • andy November 1, 2007, 15:43

    The volcanic eruption hypothesis also has a bearing on the even larger Permian-Triassic mass extinction, which seems to have occurred at the same time as the eruption of the Siberian Traps.

    This may have a bearing on what is found when measurements are made of the atmospheres of habitable zone planets: would the gases produced by such massive eruptions be detectable, and would we be able to distinguish this scenario from pollution produced by a technological civilisation?

  • Pradeep November 2, 2007, 2:57

    Indian papers have been reporting this and some of them have added a very silly line: Looks like the extinction of dinosaurs just got outsourced to India.

    I live on the Western Ghats in the aforementioned Deccans. It has been really quite for really long down here. Earlier this month though, we felt a lot of tremors. Although its volcanic soil might indicate to an active volcanic past. Am watching this to see if anything interesting comes out of it. I think we’d be proud of the honour of single-handedly (without help of comets and meteors) destroying the dinosaurs. But that might also put into question our peaceful existence so far.

  • Administrator November 2, 2007, 8:36

    I hadn’t heard of new tremors in your area, Pradeep, but let’s hope they calm back down. I’ve seen that ‘outsourcing’ headline you mention over here as well, perhaps the result of a copywriter who was having a very unimaginative day!

  • ljk November 2, 2007, 9:10

    Or one who had been previously outsourced. :^)

  • dad2059 November 2, 2007, 9:14

    The study of the Deccans can prove to be useful in the area of super-volcano research such as the Yellowstone Park caldera, which seems to have an eruption cycle of 600,000 to 1,500,000 years.

    And to answer JD, yes there is a theory about Chicxulub and volcanos: http://www.astronomy.com/asy/default.aspx?c=a&id=4602

    The Deccans are mentioned in this also.

  • andy November 2, 2007, 9:30

    dad2059: as far as I am aware, “supervolcanoes” such as Yellowstone are a different type of eruption: they are very large explosive events, and the amount of material produced is on the order of 100-1000 km^3. Large Igneous Provinces, such as the Deccan traps are not thought to be explosive, but produce many orders of magnitude more material: 10^5-10^6 km^3, and erupt over timescales of millions of years.

  • James Nicoll November 2, 2007, 11:10

    The Dragon’s Tales had a post on PT/KT extinctions:


  • Administrator November 2, 2007, 13:51

    That’s a good post you’ve pointed us to, James, and I’ve just inserted a pointer to it as well in the original article here.

  • Will Baird November 2, 2007, 18:34

    Wow. My post got noticed earlier than I thought it would! tres kewl! I was going to throw out for the Boneyard blog Carnival (http://boneyardcarnival.wordpress.com/), but its kewl that it got noticed all the same. CD has a bigger readership at this point than BY does. :)

  • Administrator November 2, 2007, 19:48

    It was an excellent post, Will, and now that I’m familiar with your site, I’ll know where to look when the next flurry of speculation on the K-T culprit hits.

  • Pradeep November 3, 2007, 7:59


    The tremors were quite light. Nothing major – http://www.hindu.com/2007/10/07/stories/2007100752730400.htm – but they were continued over a few weeks.

  • ljk January 7, 2008, 10:54

    Were the dinosaurs wiped out by insects?

    The Guardian, 7 January 2008


    James Randerson, science correspondent

    They were the most imposing and terrifying creatures
    that have ever walked on the surface of the Earth, but
    according to a new theory the dinosaurs may have been
    pushed towards extinction 65m years ago by humble

    During the later part of the dinosaurs’ dominion over the
    land, insects underwent an explosion in diversity and in
    the process dealt a double whammy to the lumbering
    giants – they spread disease and contributed to a
    transformation of vegetation which the plant-eating
    reptiles failed to adapt to.

    The hypothesis is laid out in a new book by entomologists
    George and Roberta Poinar. George Poinar is a professor
    of zoology at Oregon State University.

    “We can’t say for certain that insects are the smoking gun,
    but we believe they were an extremely significant force in
    the decline of the dinosaurs,” said Poinar. “Our research
    with amber shows that there were evolving, disease-carrying
    vectors in the Cretaceous [period], and that at least some of
    the pathogens they carried infected reptiles. This clearly fills
    in some gaps regarding dinosaur extinctions.”

    In the gut of one biting insect preserved in amber – fossilised
    tree sap – from that era, the team has found the pathogen
    that causes the parasitic disease leishmaniasis, and in another
    they found a type of malaria parasite that infects birds and
    lizards. By inspecting fossilised dinosaur faeces, the team
    also found parasitic microbes that are carried by insects.

    Apart from spreading disease, the insects were busy
    pollinating flowering plants.

    These gradually took over from seed ferns, cycads and
    gingkoes. If herbivorous dinosaurs could not adapt to this
    new diet they would have gone hungry.

    Poinar believes that the most popular theory for the
    dinosaurs’ demise – that a meteorite impact changed the
    global climate – falls short because the extinction took
    too long.

    “Other geologic and catastrophic events certainly played
    a role. But by themselves, such events do not explain a
    process that in reality took a very, very long time, perhaps
    millions of years. Insects and diseases do provide that

  • ljk January 15, 2008, 15:11

    What Bugged the Dinosaurs?

    Insects, Disease, and Death in the Cretaceous

    George Poinar, Jr. & Roberta Poinar

    To read the entire book description or the introduction, please visit:


    Millions of years ago in the Cretaceous period, the mighty Tyrannosaurus rex–with its dagger-like teeth for tearing its prey to ribbons–was undoubtedly the fiercest carnivore to roam the Earth. Yet as What Bugged the Dinosaurs? reveals, T. rex was not the only killer. George and Roberta Poinar show how insects–from biting sand flies to disease-causing parasites–dominated life on the planet and played a significant role in the life and death of the dinosaurs.

    “What Bugged the Dinosaurs tells the story of insects’ tremendous impact on Cretaceous ecosystems…There are fascinating chapters on the evolution of pathogens, what makes insects ‘the ultimate survivors,’ and the nature of extinctions…The scientific and, at times, technical, subject of this book is complemented by an often colorful narrative style…worthwhile for lay readers as well as experts.”–Aaron Brooks, ForeWord Magazine

    Cloth | $29.95 / £17.95 | ISBN: 978-0-691-12431-5

  • ljk April 27, 2009, 9:19

    April 27, 2009

    Were the Dinosaurs Really Wiped Out by an Asteroid? Possibly Not

    Written by Ian O’Neill

    In 1979, the huge Chicxulub crater, measuring about 180 km (112 miles) in diameter, was discovered on the northern Yucatan Peninsula, Mexico.

    Scientists made the obvious conclusion that something rather large had hit the Earth in this location, probably causing all kinds of global devastation 65 million years ago.

    At around the same time, 65% of all life on the face of the planet was snuffed out of existence. The dinosaurs that roamed the planet up to that point were no more.

    The timing of asteroid impact and the time of the mass extinction was too much of a coincidence to be ignored. When particles from the asteroid impact were discovered just below the Cretaceous-Tertiary (K-T) boundary, there was a strong causal link: the effects of the asteroid impact had driven the dinosaurs to extinction.

    However, a problem with this theory has come to light. It turns out the Chicxulub impact pre-dates the K-T boundary by 300,000 years…


Next post:

Previous post: