January 24, 2011

The ‘Smoking Gun’ Of World’s Largest Extinction

After a volcanic eruption that occurred around 250 million years ago, hundreds of millions of years before dinosaurs were wiped off the face of the planet, almost 95 percent of all primitive life living in the ocean and 70 percent of all animals evolving on land were wiped out.

Researchers at the University of Calgary in Alberta, Canada have discovered evidence suggesting that massive volcanic eruptions at the time burnt significant levels of coal, producing suffocating clouds of ash and dust that greatly impacted the world, and may explain the massive devastation that occurred with the Permian Extinction.

"This could literally be the smoking gun that explains the latest Permian extinction," said Dr. Steve Grasby, adjunct professor in the University of Calgary's Department of Geoscience and research scientist at Natural Resources Canada.

Grasby and colleagues, publishing their findings in Nature Geoscience, discovered layers of coal ash in rocks from the extinction boundary in Canada's High Arctic that give the first concrete proof to support this.

"Our research is the first to show direct evidence that massive volcanic eruptions -- the largest the world has ever witnessed --caused massive coal combustion, thus supporting models for significant generation of greenhouse gases at this time," said Grasby.

Unlike the extinction of the dinosaurs 65 million years ago, where the most popular belief is that the impact of a meteorite led to their demise, it has been unclear what caused the late Permian Extinction. Previous studies have suggested massive volcanic eruptions through coal beds in Siberia would generate significant greenhouse gases causing massive global warming.

At the time of the extinction -- often referred to as "the Great Dying" -- the Earth contained one big land mass, a supercontinent called Pangaea.

The volcanoes, known as the Siberian Traps, are found in northern Russia, centered around the Siberian city of Tura and encompass Yakutsk, Noril'sk and Irkutsk. They cover an area of about 1,250,000 square miles. The ash plumes from the eruption of the large chain of volcanoes traveled to Canada's arctic where Grasby and colleagues found the coal-ash layers.

"We saw layers with abundant organic matter and Dr. Hamed Sanei [a fellow researcher] immediately determined that they were layers of coal-ash, exactly like that produced by modern coal burning power plants," wrote Dr. Benoit Beauchamp, also from the University of Calgary, in a statement.

The authors suggest the ash may have caused even more trouble for a planet that was already heating up, with its oceans starting to choke due to decreasing oxygen levels.

"It was a really bad time on Earth. In addition to these volcanoes causing fires through coal, the ash it spewed was highly toxic and was released in the land and water, potentially contributing to the worst extinction event in earth history," said Grasby.

The model used in Grasby and colleagues' study focused on the Siberian Traps. Not all the eruptions the area saw over its million-year-plus formative period were deadly on a mass scale. The, about 500,000 to 750,000 years before the extinction event, magma swelled up underground and hit a layer of coal. The mix was an explosive combination and it ripped through Earth's surface.

"The magma went through a juicy bit of crust that it can release a lot of nasty things from," said Paul Wignall, a paleontologist at the University of Leeds, UK, who studies mass extinction events.

Once the mixture hit the atmosphere, huge clouds of gas and fly ash mushroomed into the sky. The thick black clouds caught the westerly winds and ash rained down on the Buchanan Lake in the Sverdrup Basin of the Arctic, where Grasby and colleagues found their samples. This happened three times over a period of 500,000 to 750,000 years. The final fly-ash layer found by the team was laid down just before the extinction event.

This may have been the tipping point, said Wignall. Studies suggest the volcanoes released more than 3 trillion tons of carbon, enough to trigger massive climate change. The eruptions also caused acid rain and emitted sufficient halogens to create an ozone hole, he said. Toxic fly ash, on top of all this, may have been the final blow.

"I can't suggest that this is the answer to the mass extinction story, but it is a new component to it," said Wignall. "It is like throwing the kitchen sink at the world." 

Image 2: The coal"℠ash particle on the left is from the latest Permian extinction boundary at Buchanan Lake. Nunavut, the particle on the right is from a modern power plant. Credit: Hamed Sanei, NRCan/University of Calgary

Image 3: Dr. Stephen Grasby at Buchanan Lake, Axel Heiberg Island, Nunavut, where recent discovery of coal ash layers provide the first direct evidence of significant coal fires at the Latest Permian Extinction. Credit: University of Calgary


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