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Permian-Triassic Extinction took only 20,000 years Rate of CO2 rise in Atmosphere less than today

The end-Permian extinction occurred 252.2 million years ago, decimating 90 percent of marine and terrestrial species, from snails and small crustaceans to early forms of lizards and amphibians. “The Great Dying,” as it’s now known, was the most severe mass extinction in Earth’s history, and is probably the closest life has come to being completely extinguished.

An MIT-led team of researchers has now established that the end-Permian extinction was extremely rapid, triggering massive die-outs both in the oceans and on land in less than 20,000 years — the blink of an eye in geologic time. The researchers also found that this time period coincides with a massive buildup of atmospheric carbon dioxide, which likely triggered the simultaneous collapse of species in the oceans and on land.

With further calculations, the group found that the average rate at which carbon dioxide entered the atmosphere during the end-Permian extinction was slightly below today’s rate of carbon dioxide release into the atmosphere due to fossil fuel emissions. Over tens of thousands of years, increases in atmospheric carbon dioxide during the Permian period likely triggered severe global warming, accelerating species extinctions.

The researchers also discovered evidence of simultaneous and widespread wildfires that may have added to end-Permian global warming, triggering what they deem “catastrophic” soil erosion and making environments extremely arid and inhospitable.

The group collected clay samples from ash beds both above and below rock layers from the PTB. In the lab, they separated out zircon, a robust mineral that can survive intense geological processes. Zircon contains trace amounts of uranium, which can be used to date the rocks in which it is found. Bowring and his colleagues analyzed 300 of the “best-looking” grains of zircon, and found the rocks above and below the mass-extinction period spanned only a 20,000-year phase.

The group also analyzed carbon-isotope data from rocks in southern China and found that within the same period, the oceans and atmosphere experienced a large influx of carbon dioxide. Dan Rothman, a professor of geophysics in EAPS, calculated the average rate at which carbon dioxide entered the oceans and atmosphere at the time, finding it to be somewhat less than today’s influx due to fossil fuel emissions.

http://web.mit.edu/newsoffice/2011/mass-extinction-1118.html

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