[AntiGuv]

I thought the Siberian Traps had been tied in to the Permian extinction, but perhaps my recollection is faulty.

[Ernest_at_the_Beach]

Reading material on that :

End Permian Volcanism

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How could the Siberian Traps cause global mass destruction?

The immediate area would be affected by such things as lava and pyrocastic flows but how does this affect the other side of the world? The real power of the Siberian Traps was the climate altering potential by the emission of ash and gases. The Siberian Traps is recognised as having a large proportion of pyroclastic deposits relative to other flood basalts. This indicates an explosive nature with much ash and gases being pumped into the atmosphere. All of this ash and gas has two main effects that, even though they are opposite to each other, act on differing timescales.

Initially sulfur aerosols and volcanic ash envelop the earths atmosphere blocking out sunlight and sending surface temperatures plunging . Ash and sulphur aerosols can remain in the upper atmosphere for 100's to 1000's of years which would be enough to cause a significant glaciation. At the end of the Permian period the biggest ever drop in sea level in history occurred. Two scientists named Holser and Magaritz in 1987 proposed that such a marine regression could be caused by a large scale glaciation.

The second major effect is the emission of greenhouse gases such as CO2, methane and also water vapour. Green house gases warm the climate by allowing sunlight to pass through, heat reflected by the Earth itself cannot penetrate the atmosphere so is retained. Greenhouse gases stay in the atmosphere much longer so their climate changing effects can last for millions of years.

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Another minor effect is the destruction of the ozone layer caused by gas emissions. Chlorine and fluorine gases are erupted from almost all volcanic eruptions and these destroy the ozone layer. Without the ozone layer, harmful UV rays can kill organisms therefore contributing to a mass extinction.

[gcruse]

From another source...

The buckyballs at the Permian-Triassic boundary contain trapped helium and argon with isotopic compositions like those in meteorites called carbonaceous chondrites, and very different from those on Earth. This led Becker and her colleagues to conclude that impact of a 9-kilometer asteroid deposited the buckyballs. An unanswered question is whether this impact caused the mass extinction by itself or did so in collaboration with the Siberian volcanism and possibly unrelated climate changes.