Scientists find smoking gun of Permian–Triassic extinction

The Permian–Triassic extinction is sometimes called “the Great Dying” or “the mother of all mass extinctions.” It happened about 250 million years ago – before dinosaurs came to rule the Earth. If you imagine millions of coal-fired power plants burning all at once – suddenly and in a single location – then you’re close to envisioning the world just before this extinction event, according to an article released on Sunday in Nature Geoscience.

Stephen Grasby, a geochemist at the Geological Survey of Canada, writes that fly ash – a microscopic carbon-rich soot generated by modern-day power plants – was a probable trigger of the Permian–Triassic extinction.

Is he suggesting that there were power plants in the ancient world? No.

He’s speaking of volcanoes, one volcano in particular, which happened to sit in Russia’s Siberian Traps on top of a major coal deposit. This volcano was a coal combustion machine, and it manufactured fly ash. Dr. Grasby believes it was this uniquely situated volcano that caused mass extinctions on Earth 250 million years ago. As Gayathri Vaidyanathan explains in Nature‘s blog:

One trigger for the near-apocalyptic ‘great die-off,’ which killed 96% of marine species and 70% of land-based vertebrate organisms, was a volcanic explosion in coal and shale deposits in Siberia. Within days, ash from the eruption, raining down onto the Canadian Arctic, sucked oxygen from the water and released toxic elements.

Dr. Grasby’s paper details his discovery of 3 distinct layers of fly ash in the Canadian Arctic. He says the top layer indicates that a gigantic, coal-combustive volcanic eruption occurred in Siberia just before the Permian-Triassic extinction. (The remaining layers of fly ash show that two smaller volcanoes preceded “the big one”.) Again, writer Gayathri Vaidyanathan paints the scene.

Once the [volcanic] mixture hit the oxygen-laden air, huge clouds of gas and fly ash mushroomed into the stratosphere. The black clouds caught the westerly winds and ash rained down on the Buchanan Lake in the Sverdrup Basin of the Arctic, where Grasby and his team found their samples. This happened three times over a period of 500,000 to 750,000 [years].

While volcanoes, on their own, can blow lots of nasty gas and ash into the air, throwing coal into the mix is even more deadly. The fly ash burning coal creates is extremely polluting stuff. Even today, when released from coal plants, fly ash contains toxins – such as arsenic, beryllium and lead.

But 250 million years ago, the situation was even worse. There was so much fly ash in the air that it sucked oxygen out of Earth’s seas (carbon-rich ash is very attractive to oxygen molecules). And that’s why, according to Grasby’s team, even though lots of species on land died during the Permian–Triassic extinction, marine life took an even bigger hit.

Studies have suggested the [Siberian] volcanoes released 3 trillion tonnes of carbon, enough to trigger massive climate change. The eruptions also caused acid rain and emitted sufficient halogens to create an ozone hole, he says. Toxic fly ash, on top of all this, may have been the final blow.

It’s interesting to think that, when we humans burn coal today, we might be creating a similar environmental impact, on a smaller scale perhaps, and in slower motion.

The end of cheap coal worldwide might be less than ten years away

January 25, 2011

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Beth Lebwohl

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