The world revealed by Algeos research sounds horrific and alien  a devastated landscape, barren of vegetation, scarred by erosion from showers of acid rain, huge dead zones in the oceans and runaway greenhouse gases leading to sizzling temperatures. This was Earth, 251 million years ago.

The more famous K-T extinction between the Cretaceous and Tertiary periods  in which the dinosaurs went extinct  was triggered by a large meteoroid or bolide striking the Earth. The Great Dying, between the Permian and Triassic periods, has another culprit.

The Permian-Triassic extinction event is still not fully understood, Algeo said. It took some time, but it finally dawned on the geologic community that this was not caused by a bolide.

Algeo and his colleagues from around the world are building a better understanding of the events that all but erased life from our planet. The work involves five principal investigators in addition to Algeo. The National Science Foundation has provided several substantial grants to support the research.

The evidence Algeo and his colleagues are looking at points to massive volcanism in Siberia. A large portion of western Siberia reveals volcanic deposits five kilometers (three miles) thick, covering an area equivalent to the continental United States.

It was a massive outpouring of basaltic lava, Algeo said. And, the lava flowed where it could most endanger life, through a large coal deposit.

Algeo noted that the dinosaur-killing bolide was lethal because it vaporized sulfur-rich sediments, resulting in extremely acidic rainfall. The effects of the Siberian lava eruption were likewise amplified by the coal deposit.

The eruption released lots of methane when it burned through the coal, he 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 be thousands of years, maybe tens of thousands of years.