Permian–Triassic extinction event
Earth's most severe extinction event / From Wikipedia, the free encyclopedia
Approximately 251.9 million years ago, the Permian–Triassic (P–T, P–Tr) extinction event (PTME; also known as the Late Permian extinction event,[3] the Latest Permian extinction event,[4] the End-Permian extinction event,[5][6] and colloquially as the Great Dying)[7][8] forms the boundary between the Permian and Triassic geologic periods, and with them the Paleozoic and Mesozoic eras.[9] It is Earth's most severe known extinction event,[10][11] with the extinction of 57% of biological families, 83% of genera, 81% of marine species[12][13][14] and 70% of terrestrial vertebrate species.[15] It is also the greatest known mass extinction of insects.[16] It is the greatest of the "Big Five" mass extinctions of the Phanerozoic.[17] There is evidence for one to three distinct pulses, or phases, of extinction.[15][18]
The precise causes of the Great Dying remain uncertain. The scientific consensus is that the main cause of extinction was the flood basalt volcanic eruptions that created the Siberian Traps,[19] which released sulfur dioxide and carbon dioxide, resulting in euxinia (oxygen-starved, sulfurous oceans),[20][21] elevating global temperatures,[22][23][24] and acidifying the oceans.[25][26][3] The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to the ocean-atmosphere system during this period.[22] Several other contributing factors have been proposed, including the emission of carbon dioxide from the burning of oil and coal deposits ignited by the eruptions;[27][28] emissions of methane from the gasification of methane clathrates;[29] emissions of methane by novel methanogenic microorganisms nourished by minerals dispersed in the eruptions;[30][31][32] and an extraterrestrial impact which created the Araguainha crater and caused seismic release of methane[33][34][35] and the destruction of the ozone layer with increased exposure to solar radiation.[36][37][38]