250-bn-yr-old Siberian volcanism ‘may have caused The Great Dying’

Friday, October 29, 2010

WASHINGTON - University of Cincinnati geologists have found what led to ‘The Great Dying’ - the sudden death of around 90 percent of all living species 250 million years ago at the end of the Permian period.

Thomas J. Algeo and his colleagues have looked at evidence that points to massive volcanism in Siberia. A large portion of western Siberia reveals volcanic deposits five kilometers (three miles) thick.

And, the lava flowed where it could most endanger life, through a large coal deposit. The effects of the Siberian lava eruption were amplified by the coal deposit.

“The eruption released lots of methane when it burned through the coal. Methane is 30 times more effective as a greenhouse gas than carbon dioxide. We’re not sure how long the greenhouse effect lasted, but it seems to be thousands of years, maybe tens of thousands of years,” said Algeo.

A lot of the evidence ended up being washed into the ocean, and that is where Algeo and his colleagues look for it.

However, the Siberian lava eruption may not have been the only agent of global death during the late Permian. While most rocks deposited during the extinction show increased concentrations of total organic carbon and higher organic carbon accumulation rates, the Chinese samples show the opposite effect.

“It may be that the combined effects of this local volcanism and global climate change were especially lethal,” Algeo said.

He believes that chemical weathering by acid rain and similar processes also contributed. When erosion seven times the normal rate sent large flows of nutrients into the ocean, it created conditions much like the over-fertilization we see today near the outlets of large rivers. As it does today, this condition led to a microbial feeding frenzy and the removal of oxygen - and life - from the late Permian ocean.

“It is a reminder that things can get out of whack pretty quickly and pretty seriously. We are used to a stable world, but it may not always be so stable.” (ANI)

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