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Washington: Most of the
life forms wiped out in an event known as the Great Dying, 250
million years ago, came slowly from thousands of centuries of
volcanic activity.
The deadliest mass extinction of all took a long time to kill 90
percent of Earth's marine life, and it killed in stages, according
to a detailed investigation by an University of Cincinnati team,
led by professor of geology Thomas J. Algeo.
Algeo worked with 13 co-authors to produce a high-resolution look
at the geology of a Permian-Triassic boundary section on Ellesmere
Island in the Canadian Arctic, the journal Geological Society of
America Bulletin reports.
About 252 million years ago, at the end of the Permian period,
Earth almost became a lifeless planet. Around 90 percent of all
living species disappeared then in what scientists have called
'The Great Dying'.
Algeo and colleagues have spent much of the past decade
investigating the chemical evidence buried in rocks formed during
this major extinction, according to a Cincinnati statement.
The world revealed by their research is horrific and alien -- a
devastated landscape, barren of vegetation and scarred by erosion
from showers of acid rain, huge "dead zones" in the oceans, and
runaway greenhouse warming leading to sizzling temperatures.
The evidence that Algeo and colleagues are looking at points to
massive volcanism in Siberia. A large portion of western Siberia
reveals volcanic deposits up to five km (three miles) thick,
covering an area equivalent to the continental US. And the lava
flowed where it could most endanger life, through a large coal
deposit.
What appears to have happened, according to Algeo and his
colleagues, is that the effects of early Siberian volcanic
activity, such as toxic gases and ash, were confined to the
northern latitudes. Only after the eruptions were in full swing
did the effects reach the tropical latitudes of the Tethys Ocean.
"The eruption released lots of methane when it burned through the
coal," Algeo said. "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 have been tens or
hundreds of thousands of years."
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