Identifying a killer can be difficult when it seems every murder weapon imaginable has been used in the crime, and when the victim is the entire planet. About 252 million years ago, a rich and wonderful world was annihilated in the worst mass extinction ever: the End-Permian, a catastrophe with no close competitor in Earth’s history. Volcanoes of a truly preposterous scale erupted in Siberia over many thousands of years, loosing all manner of chaos on the world. Rounding up, everything died.

Diagnosing the particular flavor of chaos responsible for this mass death has proven elusive. The Siberian Traps, now long retired as a vast swath of basalt plateaus in the far northern reaches of Russia, might have poisoned the world with mercury. Or maybe they destroyed the ozone layer by incinerating huge underground layers of ancient evaporites. Or perhaps they acidified the planet with sulfur dioxide and carbon dioxide, stripping vegetation, killing corals worldwide, and so altering the chemistry of the planet’s soil that dirt would have tasted like vanilla. Or maybe the Traps wracked the planet with brief volcanic winters, or maybe they poisoned the planet with carbon dioxide itself, or the oceans became stagnant and poisoned with toxic hydrogen sulfide. Maybe that’s what killed everything.

Or, maybe the oceans became stratified and nutrient-starved, and phytoplankton suffered. Or perhaps it was a lack of oxygen in the ocean that suffocated everything, or maybe it just got too damn hot.Some paleontologists have thrown up their hands and yielded to this overdetermination of kill mechanisms at the End-Permian, proposing an inelegant Murder on the Orient Express hypothesis of mass extinction that implicates the entire suite of killers. A new study, though, claims to pinpoint the primary killer from this murderer’s row: Among the slew of Very Bad Things implicated in the worst calamity the Earth has ever known, it was the global-warming-driven ocean anoxia that stands out as the primary agent of Armageddon. And in this reaper of the Paleozoic, the study’s authors see a future menace.

“I think this study shows the end of the road that we’re heading down,” says the lead author, Justin Penn of the University of Washington, about our modern warming, and increasingly suffocating, oceans.

As we’ve known since the 1860s, carbon dioxide is a very important greenhouse gas, and if you increase the amount of it in the atmosphere, it makes the …read more

Source:: The Atlantic – Best of

      

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A Portrait of Catastrophe in the World’s Oceans

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