Permian–Triassic extinction event

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The Permian–Triassic (P–Tr) extinction event, informally known as the Great Dying,[1] was an extinction event that occurred 251.4 million years ago,[2][3] forming the boundary between the Permian and Triassic geologic periods. It was the Earth's most severe extinction event, with up to 96% of all marine species[4] and 70% of terrestrial vertebrate species becoming extinct[5] It is the only known mass extinction of insects.[6][7] Some 57% of all families and 83% of all genera were killed. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after other extinction events.[4] This event has been described as the "mother of all mass extinctions".[8]

Researchers have variously suggested that there were from one to three distinct pulses, or phases, of extinction.[2][5][9][10] There are several proposed mechanisms for the extinctions; the earlier phase was likely due to gradual environmental change, while the latter phase has been argued to be due to a catastrophic event. Suggested mechanisms for the latter include large or multiple bolide impact events, increased volcanism, and sudden release of methane clathrate from the sea floor; gradual changes include sea-level change, anoxia, increasing aridity,[11] and a shift in ocean circulation driven by climate change.


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