Mass extinction: Largest ecological catastrophe might have begun with volcanic winter

The end-Permian mass extinction 252 million years ago might have begun when eruptions triggered a volcanic winter

By Cameron Duke

For decades, we have been trying to unravel the causes of the end-Permian mass extinction, the most devastating extinction event in our planet’s history. The prevailing view is that global warming played a part, but now there is evidence that the warming was preceded by a volcanic winter – a long, global cold spell called by volcanic activity that would have destabilised ecosystems.

About 252 million years ago during the end-Permian extinction, life on Earth came dangerously close to a terminal collapse. In the geologic blink of an eye, roughly 85 per cent of the species on the planet vanished. This is thought to have begun when lava oozed across modern-day Siberia in a series of eruptions that pumped enough carbon dioxide and methane into the atmosphere to raise global temperatures and starve the oceans of oxygen.

Now, a study suggests that the so-called Siberian Traps aren’t the only eruptions to blame for the extinction.

“In southern China, there are unusual levels of copper and mercury embedded in ash layers right at the mass extinction boundary,” says Michael Rampino at New York University, one of the authors of the study. The ash layers are also rich in sulphur, which hints at the style of volcanic eruption: “This suggests explosive volcanism in the region,” he says.

These explosive eruptions – which were distinct from the non-explosive Siberian eruptions – were catastrophic enough that the ensuing ash cloud likely heralded the beginning of what Rampino refers to as a “volcanic winter”, a rapid period of global cooling that the researchers think may have preceded the warming caused by the Siberian Traps.

“There would have been global effects on climate as material from the eruptions would have been carried around the globe by stratospheric winds,” says Rampino.

The geology also shows that the ash clouds correlate with large, local extinctions of land-based life, hinting that the explosive eruptions were large enough to have a severe impact on the biosphere.

If this conclusion is correct, it suggests that the end-Permian extinction might have been caused by the one-two punch of geologic activity. “Organisms [would have been stressed] with a rapid period of cooling followed by a long period of warming,” says Rampino.

Journal reference: Science Advances, DOI: 10.1126/sciadv.abh1390

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