The Mother of Mass Extinctions: How Life on Earth Nearly Ended 250 Million Years Ago
Douglas Erwin, Professor, Santa Fe Institute
July 12, 2006
During the greatest biodiversity crisis in the history of life some 250 million years ago, over 90% of all the species in the oceans died off in just a few hundred thousand years. Douglas Erwin, author of the new book Extinction: How Life on Earth Nearly Ended 250 Million Years Ago discusses his research in China, South Africa and the western US in search of the causes and consequences of this great mass extinction.
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The Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252 million years ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras. It is the Earth’s most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years.
Researchers have variously suggested that there were from one to three distinct pulses, or phases, of extinction. 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 impact events, increased volcanism, coal/gas fires and explosions from the Siberian Traps, and sudden release of methane from the sea floor; gradual changes include sea-level change, increasing aridity, and a shift in ocean circulation driven by climate change.