Permian–Triassic extinction event

The Permian–Triassic extinction event, also called the Great Dying, was the biggest die-off in Earth's history. It happened about 251.9 million years ago (mya), when the Permian time ended and the Triassic began. Many plants and animals disappeared, making it one of the “Big Five” worst mass extinctions ever.

Most sea animals died — about 81% of marine species vanished. On land, many vertebrate species, including reptiles and amphibians, disappeared. Even many insects died out. It was a difficult time for life on our planet.

Scientists think huge volcanic eruptions in what is now Siberia caused this disaster. These eruptions released lots of sulfur dioxide and carbon dioxide, heating up the planet and changing the oceans. This made it very hard for many creatures to survive. Other ideas include burning oil and coal, natural climate changes, and maybe even a space rock hitting Earth.

Dating

Scientists now know exactly when the Permian–Triassic extinction happened. They studied volcanic ash from the extinction site in Meishan, China, and made a detailed timeline.

The extinction happened about 251.9 million years ago and lasted for around 60,000 years. During this time, there was a big drop in a special carbon measure called δ¹³C. There also was a big rise in temperature and more carbon dioxide in the air, which likely hurt many plants and animals.

Extinction patterns

Marine invertebrates lost many members during the Permian-Triassic extinction. Many sea creatures, especially those with shells made of calcium carbonate, disappeared because the oceans became more acidic. This happened when there was too much carbon dioxide in the air. Some sea animals, like brachiopods and ammonites, survived but in smaller numbers.

On land, many insects and plants also disappeared. The largest insects ever known went extinct, and forests changed a lot. Some land animals, like large herbivores, died out, while others survived but lost many members of their species. It took millions of years for life on Earth to recover fully after this event.

Biotic recovery

After the big loss of life, Earth started to heal. In the oceans, older sea creatures became less common. New groups like bivalves, snails, and sea urchins grew more numerous. On land, new groups such as dinosaurs began to appear.

The recovery took different times for different places and kinds of living things. Some sea creatures came back fairly fast, while others needed millions of years. Scientists are still discovering how life grew again after this hard time.

Hypotheses about cause

Explaining an event from 250 million years ago is hard because much evidence on land has been lost or buried, and the seafloor has changed over time.

Scientists have suggested several reasons that might have caused the extinction. These include big impacts from space, more volcanic activity, and sudden releases of methane from the seafloor. Other ideas involve changes in sea level, oxygen levels in the ocean, and dryness on land.

One big idea is about huge volcanic eruptions called the Siberian Traps. These eruptions put lots of carbon dioxide into the air, causing the Earth to warm up quickly. This warming upset ecosystems on land and in the ocean, helping to cause the mass extinction.

Comparison to present global warming

The Permian-Triassic extinction event is often compared to today's anthropogenic global warming and the Holocene extinction. Both events saw quick rises in carbon dioxide, which can hurt oceans and plants. While today’s carbon emissions rise faster, the ancient event happened in short bursts. Scientists say that if we do not cut down on carbon dioxide, we could face similar problems for nature.

Oceans today, like during the extinction, are losing pH and oxygen. Geologist Lee Kump explains that this ancient event shows what can happen when too much carbon dioxide is released quickly. He worries that human actions might cause long-term damage to nature.