500 and 4,000 prior to the extinction event to around 8,000 after the extinction. As carbon dioxide levels shot up, extreme temperature rise would have followed. In a 2020 paper, scientists reconstructed the mechanisms that led to the extinction event in a biogeochemical model, showed the consequences of the greenhouse effect on the marine environment, and concluded that the mass extinction can be traced back to volcanic CO emissions. Further evidence – based on paired coronene-mercury spikes – for a volcanic combustion cause of the mass extinction was published in 2020. The Siberian Traps had unusual features that made them even more dangerous. The Siberian Traps eruptions released sulphur-rich volatiles that caused dust clouds and the formation of acid aerosols, which would have blocked out sunlight and thus disrupted photosynthesis both on land and in the photic zone of the ocean, causing food chains to collapse. These volcanic outbursts of sulphur also induced brief but severe global cooling, leading to glacio-eustatic sea level fall. The eruptions may also have caused acid rain as the aerosols washed out of the atmosphere. That may have killed land plants and mollusks and planktonic organisms which had calcium carbonate shells. Pure flood basalts produce fluid, low-viscosity lava, and do not hurl debris into the atmosphere. It appears, however, that 20% of the output of the Siberian Traps eruptions was pyroclastic (consisted of ash and other debris thrown high into the atmosphere), increasing the short-term cooling effect. When all of the dust and ash clouds and aerosols washed out of the atmosphere, the excess carbon dioxide emitted by the Siberian Traps would have remained and global warming would have proceeded without any mitigating effects. The Siberian Traps are underlain by thick sequences of Early-Mid Paleozoic aged carbonate and evaporite deposits, as well as Carboniferous-Permian aged coal bearing clastic rocks. When heated, such as by igneous intrusions, these rocks are capable of emitting large amounts of greenhouse and toxic gases. The unique setting of the Siberian Traps over these deposits is likely the reason for the severity of the extinction. The basalt lava erupted or intruded into carbonate rocks and into sediments that were in the process of forming large coal beds, both of which would have emitted large amounts of carbon dioxide, leading to stronger global warming after the dust and aerosols settled. The timing of the change of the Siberian Traps from flood basalt