EXTINCTIONS
The Great Dying: Permian Extinction
~252 million years ago
Phanerozoic · Paleozoic · Permian
The end-Permian extinction is the most severe extinction on record, set off about 252 million years ago when the Siberian Traps, a vast volcanic province, erupted through coal beds and released carbon for perhaps a million years.
The end-Permian extinction is the most severe extinction in the fossil record: about nine marine species in ten died. The Siberian Traps erupted in Siberia through coal beds and released carbon for perhaps a million years. The sea warmed, lost its oxygen and acidified, and on land the forests disappeared. The whole crisis falls within 200,000 years, an interval that counts as instantaneous in geology. The extinction killed selectively, and Penn and colleagues (2018) used this selectivity as a test. If warming combined with oxygen loss was the cause, tropical species, already adapted to warm and oxygen-poor water, should have fared better than polar ones. The fossil record confirms this prediction.
Why it matters
Life came closer to being extinguished in the end-Permian extinction than at any other time. The scale of the loss implies that every ecosystem was reconstituted from the survivors, which were not the previously dominant organisms. The extinction separates the Palaeozoic era from the Mesozoic era that follows it. The lineages leading to dinosaurs and to mammals both begin after the extinction.
Dating & uncertainty
The extinction is dated to 251.9 million years ago and lasted under 200,000 years. Both figures come from uranium-lead dating, which measures the decay of uranium into lead, of volcanic ash beds in South China, and they are among the most precise in deep time, the distant geological past. The kill mechanism is less well established. Besides warming and deoxygenation of the sea, acidification, the toxic gas hydrogen sulfide and damage to the ozone layer have each been proposed, and none excludes the others.
Earth history as one day
22:40:041 h 20 min before midnight
if Earth’s 4.54 billion years were compressed into a single day