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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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The Last Gasp of the Permian
22 August 2003 (All day)
The biggest mass extinction of all time, at the end of the Permian era 251 million years ago, wiped out the vast majority of species. Now, two papers lay out scenarios for how deadly gas might have killed most land animals--and why some survived. One sketches an apocalyptic vision of methane erupting from the sea floor, forming vast clouds and exploding. In the other, paleontologists propose that at least one creature escaped the suffocating gases because it was already adapted to thin air.
The idea that methane contributed to the Permian mass extinction is not new. The anoxic oceans at that time could have stored massive amounts of methane, either dissolved in bottom waters or frozen solid. Most geologists imagined the methane gradually seeping into the atmosphere over 10,000 years or so. Gas can escape much more quickly, though, as it did at Lake Nyos, Cameroon, in 1986, when clouds of lethal carbon dioxide suddenly bubbled out of the waters.
Chemical engineer Gregory Ryskin of Northwestern University in Evanston, Illinois, wondered if that type of eruption might have happened on a larger scale during the Permian extinction. He calculated that the oceans could easily hold a whopping 10,000 gigatons of methane. After a disturbance, such as an earthquake, bubbles would form. This would lower the pressure of the water, which would then release even more dissolved gas. "It's a real kind of snowball effect," Ryskin says. Over days, massive amounts of methane would enter the atmosphere and form an explosive mixture with air, Ryskin argues in the September issue of Geology. Blown inland, the deadly clouds would be detonated by lightning. The smoke and soot from widespread fires might lead to a nuclear winter, or the gases might cause global warming; it's hard to predict which, Ryskin says.
Greg Retallack of the University of Oregon, Eugene, also believes that massive amounts of methane left the ocean, but not as catastrophically. Still, the gas would also have immediate impact. With the relative amount of oxygen in the air lowered to something akin to that at 4000 meters, animals would suffer from pulmonary and cerebral edema. "The reptiles died of mountain sickness," he says. Retallack and colleagues noticed that surviving animals had traits that would help deal with low oxygen, such as thick ribs and a barrel chest for efficient breathing.
The paper, which appears in next month's issue of the Geological Society of America Bulletin, is winning points for originality. "I think it's a really neat story," says Christian Sidor, a paleontologist at the New York College of Osteopathic Medicine in Old Westbury, who considers it a plausible explanation. Some scientists who study the Permian oceans have trouble imagining Ryskin's conflagration, however. "I just don't find compelling evidence that the methane levels needed were present in the Permian ocean," says geochemist Lee Kump of Pennsylvania State University, University Park.