Did Methane Cause the Mass Extinction That Made Way for the Dinosaurs?

By Veronique Greenwood | July 25, 2011 9:51 am

triassic

What’s the News: Two hundred million years ago, half of the Earth’s species vanished in the blink of a geological eye, clearing the way for rise of the dinosaurs in the Jurassic. The cause of that mass extinction, a new study suggests, may have been gigatons of methane released from the sea floor after a slight rise in the earth’s temperature, triggering much greater warming. And if that sounds familiar, it’s because scientists are worried the same thing will happen today.

What’s the Context:

  • The primary theory as to what went wrong at the end of the Triassic period, when this extinction took place, holds that tons of carbon dioxide released during the breakup of the supercontinent Pangaea ratcheted up global temperatures to deadly levels over the course of several hundreds of thousands of years.
  • But these researchers’ work seems to indicate that the change took place even more quickly than that. In a previous study looking at limestone, which is the remains of ancient sea creatures, this team found that it disappeared from the geological record quite suddenly—a mere 20,000 years after the extinction event began.
  • For this study, they turned their attention to the cause of that extinction, looking into whether higher levels of methane could have been behind the warming event.
  • Methane is a much more potent greenhouse gas than carbon dioxide, and although most of the planet’s reserves are presently locked up in the seafloor (as methane hydrate), it does gradually bubble up. Should rising temperatures melt the permafrost layers that keep arctic seafloor methane from escaping, we could see large amounts of methane leaking into the atmosphere very rapidly.
  • In fact, researchers have already the blame for other rapid warming events on oceanic methane, notably the most extreme known climate event, the Paleocene-Eocene Thermal Maximum.

How the Heck:

  • The researchers examined the remains of plants from that 20,000-year period, deposited on the shores of the ancient Tethys Sea. With a technique that determines whether a plant’s carbon molecules were originally from carbon dioxide and methane, they looked for signs of each gas’s presence in the atmosphere.
  • What they found was first a spike in carbon dioxide, then a massive amount of methane, supporting the idea that methane may have been released after a warming caused by carbon dioxide from seismic activity.

The Future Holds:

  • The team’s findings are intriguing. Much is still unclear, though, about how such a carbon dioxide-methane loop would work. How hot would the atmosphere have to get before the permafrost layer melts? How much methane is there really in the seafloor? What other factors have to coincide with warming to have this effect? More research, likely with computer models, is needed on this topic to establish how such methane release might have worked at the end of the Triassic—and how it relates to our situation today.

Reference: Ruhl, et al. Atmospheric Carbon Injection Linked to End-Triassic Mass Extinction. Science 22 July 2011, DOI: 10.1126/science.1204255

Image credit: Alfred F. Harrell (Smithsonian Institution), via flickr user public.resource.org

(via Wired Science)

CATEGORIZED UNDER: Environment, Top Posts
  • Babygirl

    Dino farts are the answer to extinction. Sooooo simple..

  • Dave L

    Methane is lighter than air, so a giant release may kill animals near waterways, but I would expect for it to rise into the upper atmosphere before making its way to far reaches in land keeping animals farther inland safe from being gassed. Methane is so light that it can be used as a substitute for Helium in a balloon. While a giant release might make the place not smell too well, I can only envision animals along a mile or so from the ocean shore taking in a lethal inhailation, while the majority of it rises to upper atmosphere.
    I am still in agreement with the meteor crater in AZ as the best likely cause that has evidence related to it scattered around the planet. And another possible cause that I have hypothetically come up with, with no supporting evidence which is a super virus that spread like a plague. And with the majority of the species reptilian even the bird like creatures, a reptilian virus would spread faster than fire, and it is possible that at this point in time just before mammals a species became warm blooded to fight off the virus with an advanced type of immune system like that of all mammals today, such as humans.

  • ganesh

    @Dave L:
    I believe the danger from increased methane isn’t the possibility of mass suffocation along the coast. The danger comes from the fact that, as you state, the gas will rise to the upper atmosphere where it serves as an even more potent greenhouse gas than CO2. It is the accelerated warming associated with increased atmospheric methane that leads to habitat destruction and species death.

    I am also reminded about concerns of a similar nature regarding Siberian permafrost and the present warming trend.

    Regarding a viral plague and endo/exothermy, it is probably false to assume that endothermy arose in response to a global immuno-catastrophe. It is now commonly thought that many dinosaur species (but not all) were warm blooded and it is speculated that some of the exothermic species were effectively endothermic due to their great size. This is not to say that a pathogen didn’t do the deed, but considering that such a virus or bacterium would have to be adapted to thousands of species across dozens of families and hundreds of genera, it is hard to believe that such a pandemic could even be possible. Wouldn’t a pathogen of such virulence succumb to its own success before it could spread in such a way?

  • amphiox

    Methane also reacts with oxygen, and enough methane release will lower O2 levels. And there was a drop in atmosphere O2 at the time of the end-Triassic extinction, as well as the previous end-Permian one.

  • Solitha

    Dave L and ganesh… You missed the era being discussed, I think. This isn’t about the end of the dinosaurs, but the mass extinction that cleared the way for the dinosaurs to dominate.

  • IW

    Regardless of how they arose, it’s obvious why dinosaurs went extinct: some irate homemaker slapped them silly for tracking muddy footprints all over the floor….

  • Me3PO

    I don’t think ganesh got the wrong era, it was just a response to the statement made by Dave L who is most likely talking about dinosaurs.

  • Addison DeWitt

    I thought the end-Triassic “extinction” was a myth. I thought they did a more careful review of species and found that it was only in North America. We need more rocks from across the globe to assess an accurate geologic picture of the past. Until them, I’m not buying it.

  • JMW

    Hm. I believe “Under a Green Sky” by Peter Ward outlined this possibility and a possible mechanism by which the methane would be released and cause a mass extinction.

  • Barry Johnstone.

    A super-fart killed EVERYTHING! Everybody knows that. It also ties in with what is known only to creationists – who know ALL! (They just got a decimal-point slightly mis-placed)

  • Brad Arnold

    First, we will be cutting our greenhouse emissions dramatically in the near future because a revolutionary clean energy technology is emerging the last quarter of 2011. LENR using nickel – 90% cheaper than any other energy. Using LENR a gram of nickel yields an incredible 1.7 billion calories (100 times less than uranium 235, but 10,000 more than coal or oil). Here is a link to a clearing house of articles on the technology: http://peswiki.com/index.php/News:Rossi_Cold_Fusion

    Second, regardless we will have to use geoengineering to cool the Earth in the short term. “The alternative (to geoengineering) is the acceptance of a massive natural cull of humanity and a return to an Earth that freely regulates itself but in the hot state.” –Dr James Lovelock, August 2008

    Third, there is already a gigantic amount of methane ready to melt now. For instance, there is an area six times the size of Germany containing about 540 billion tons of carbon off the Siberian coast. That submarine permafrost is perilously close to thawing. Three to 12 kilometers from the coast the sea sediment is just below freezing. The permafrost has grown porous, there is a loss of rigor in the frozen sea floor, and the surrounding seawater is highly oversaturated with solute methane.

    Finally, I really don’t think many people understand what is already predicted by climate models that omit any natural greenhouse gas emissions from a warming Earth. “Few seem to realise that the present IPCC models predict almost unanimously that by 2040 the average summer in Europe will be as hot as the summer of 2003 when over 30,000 died from heat. By then we may cool ourselves with air conditioning and learn to live in a climate no worse than that of Baghdad now. But without extensive irrigation the plants will die and both farming and natural ecosystems will be replaced by scrub and desert. What will there be to eat? The same dire changes will affect the rest of the world and I can envisage Americans migrating into Canada and the Chinese into Siberia but there may be little food for any of them.” –Dr James Lovelock’s lecture to the Royal Society, 29 Oct. ’07

  • http://www.climatesoscanada.org/ Cory Morningstar
  • http://discovermagazine.com Iain

    @ Dave
    You are thinking of the wrong mass extinction event. This article was about the one that allowed dino’s to prosper, not their demise. The methane is supposed to have caused massive warming (hint hint).
    As to the dino’s extinction, the meteor crater in AZ isn’t the culprits lair, the Gulf of Mexico is.

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