What may have caused the Permian extinctions?. Earth & Marine Sciences

The Permian mass extinction event led to the extinction of ~96% of marine animal species. A possible cause for this event is extensive volcanism in Siberia, which could have caused an increase in global temperatures. This climate change could have slowed ocean circulation (which is driven by the difference in temperature between equatorial & polar waters), which in turn would have decreased oxygen in the oceans and resulted in massive deaths of marine organisms. Other theories include widespread glaciations accompanied by a lowering of sea levels, and severe climatic fluctuations.