Acid rain, ozone depletion tagged as cause of ancient species die-offs

Nov. 22, 2013 at 5:37 PM
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CAMBRIDGE, Mass., Nov. 22 (UPI) -- Acid raid and ozone depletion fueled an ancient extinction of 90 percent of marine species and 70 percent of terrestrial species, U.S. researchers say.

The event 250 million years ago -- a severe mass extinction that set the stage for the emergence of the dinosaurs -- has long been attributed to volcanic eruptions in a large area of modern-day Russia known as the Siberian Traps.

A research team led by Benjamin Black of the Massachusetts Institute of Technology used computer models to predict the impacts of gases released from the Traps on the atmosphere at the end of the Permian period.

Their results suggest volcanic releases of both carbon dioxide and sulfur dioxide could have created highly acidic rain, potentially leaching the soil of nutrients and damaging plants and other vulnerable terrestrial organisms, while the release of halogen-bearing compounds such as methyl chloride could also have resulted in global ozone collapse.

Writing in the journal Geology, the researchers from MIT, the Carnegie Institution and the National Center for Atmospheric Research said the volcanic activity was likely episodic, producing repeating waves of acid rain and ozone depletion.

The resulting drastic fluctuations in acidity and ultraviolet radiation, accompanied by an overall temperature increase from greenhouse gas emissions, could have contributed to the end-Permian mass extinction on land, they said.

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