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Earth's Biggest Extinction Due to Climate, Volcanoes: Researchers

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Scientists may have found the smoking gun that ties massive volcanic eruptions in Siberia to the huge Permian extinction, known as the Great Dying. Researchers have discovered that chemicals pumped out of the volcanoes created acid rain that led to the death of some 70 percent of life on land and 90 percent of sea life, according to the study published in Geology.

The link between volcanic activity and extinctions may go further than just the Permian period: scientists have found major eruptions coincided with all five great extinctions, including that of the dinosaurs, which has in the past been attributed to an asteroid collision. All of this could be seen as a warning of what can happen if the climate gets too out of whack, since man-made pollution can produce similar effects, scientists say.

To get a closer look at what happened at the end of the Permian Period, around 250 million years ago, an international team of scientists pored over samples from rock cliffs in the Italian Dolomites, which contain a clear historical record of life before, during and after the Great Dying.

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“At the time, the supercontinent Pangaea was trying to split apart,” says the new study’s lead author, Mark Sephton, a professor of organic geochemistry in the department of earth science and engineering at Imperial College London. “The basalts that poured out are now called the Siberian Traps and are some of the largest of their type. The Siberian eruptions were particularly nasty because they intruded into a large sedimentary basin containing coals and salts which were cooked by the heat to produce a range of gases.”

When the forests died out, the soils beneath them eroded and eventually made their way to the shallow ocean waters nearby. As Pangaea split up, the sediments were uplifted and became part of a mountain chain, some of which is now exposed in the Italian cliffs.

Sephton and his team hoped that the sedimentary layers would hold the key to explaining the Great Dying. When they examined the end-Permian rock samples, they found a compound called vanillin.

“We didn’t go looking for it,” Sephton says. “It just jumped out at us when we analyzed the rocks. Vanillin is a breakdown product of wood. It also happens to be a flavoring agent in the food industry.”

The team learned from food researchers that vanillin will oxidize to vanillic acid when the pH is neutral or high. If the surrounding environment is acidic, meaning the pH is low, then the vanillin won’t oxidize into vanillic acid. So, if the rocks had much more vanillin than vanillic acid, that would mean that the surrounding soils were highly acidic.

As it turns out there was plenty of vanillin in the samples. “The acidity of end Permian soils appears to have been similar to vinegar or lemon juice,” Sephton says. “Acidity placed the end Permian forests under stress. Eventually, rooted vegetation would have succumbed to the increased acidity. Because the roots could no longer bind the soil, erosion would have occurred stripping the land of its surface cover. With the base of the food chain gone, the ecosystem would have collapsed.”

If you think it couldn’t happen now, Sephton points to the die-off of forests in the Black Triangle of the Czech Republic. “Prior to the 1990s the industrial use of brown coal led to sulfur dioxide emissions and acid rain,” he says. “The local trees died providing a modern-day example of how the Permian catastrophe must have looked.”

Linda Elkins-Tanton, who coauthored a study on the Siberian Traps last year, says the new research dovetails nicely with her team’s findings. In that study, researchers measured the amount of sulfur spewing out of the volcanoes during the end-Permian Period and then plugged it into a global climate models. The result: a prediction of acid rain with a pH comparable to vinegar or lemon juice.

“There was another exciting discovery,” says Elkins-Tanton, director of the school of earth and space exploration at Arizona State University. “These magmas had enough naturally occurring chlorine and fluorine—naturally occurring chlorofluorocarbons—to destroy the ozone layer. It would have been 70 percent worse than the modern-day ozone hole at its worst. It blew my mind that there could be naturally occurring chlorofluorocarbons, the same as the ones we banned. Turns out the earth can make them, too.”

Many geoscientists are beginning to think that eruptions like the one in Siberia might be at the root of all the mass extinctions, including that of the dinosaurs, Elkins-Tanton says, noting that the Deccan flood basalts occurred at the same time as the extinction.

“There’s a big battle going on right now over which mechanism [the asteroid or the volcanism] is closest to the extinction,” she says. “All five big extinctions are associated with flood basalts.”

We might be able to learn something about the worst-case climate change scenario by studying the end-Permian extinction, Sephton says.

“The influences we are recording are pulses of acid rain which repeatedly hit the biosphere hard,” Sephton said. “Life on Earth struggled to resist the harsh conditions produced. Current climate change is driven by increasing levels of carbon dioxide in the atmosphere. That may well have been the case for the end Permian as well because the Siberian Traps emitted carbon dioxide in addition to sulfur dioxide. Once rooted vegetation was lost on land, the soil organic carbon would have been eroded and oxidized to release more carbon dioxide. Therefore, the end-Permian is a good place to look for predicting the consequences of a rapidly warming word.”

Elkins-Tanton agrees. “The only thing that comes close to what happened then is what we are doing now,” she says.

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