The Permian Mass Extinction

The largest mass extinction marks the end of the Paleozoic era in earth’s history. The Paleozoic era had two smaller mass extinctions,  but these were not as large as the Permian Mass Extinction, also known as the  Permian-Triassic Extinction Event. It is estimated that 96% of marine species and 70% of land-dwelling (terrestrial) vertebrates went extinct. Many famous organisms, like sea scorpions and trilobites, were never seen again in the fossil record.

What caused such a widespread extinction event? The exact cause is still debated, though the leading idea relates to extensive volcanism associated with the Siberian Traps, one of the largest deposits of flood basalts known on Earth, dating to the time of the extinction event. The eruption size is estimated at over 3 million cubic kilometers, a continuous eruption approximately 4,000,000 times larger than the famous 1980 Mt. St. Helens eruption in Washington.

The unusually large volcanic eruption would have contributed many toxic gases, aerosols, and greenhouse gasses into the atmosphere. Further, some evidence suggests that the volcanism burned vast coal deposits, releasing methane (a greenhouse gas) into the atmosphere. As discussed, greenhouse gases cause the climate to warm. This extensive addition of greenhouse gases from the Siberian Traps may have caused a runaway greenhouse effect that rapidly changed the climate, acidified the oceans, disrupted food chains, disrupted carbon cycling, and caused the largest mass extinction.