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. So many plants and animals disappeared that scientists call it one of the “Big Five” worst mass extinctions ever.

Almost all sea animals died — about 81% of marine species vanished. On land, 70% of vertebrate species, including many reptiles and amphibians, disappeared. Even most insects died out. It was a tough time for life on our planet.

Scientists think huge volcanic eruptions in what is now Siberia caused this disaster. These eruptions poured out lots of sulfur dioxide and carbon dioxide, heating up the planet and making the oceans sour and low in oxygen. 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

Previously, scientists thought it was hard to figure out exactly when the Permian–Triassic extinction happened. But now, they can date it very precisely. By studying volcanic ash layers from the extinction site in Meishan, China, scientists have created a detailed timeline. This helps us understand how changes in the environment, like shifts in carbon levels, affected life on Earth.

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, which helps scientists spot this event in rocks. 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 faced huge losses 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 dramatically. 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 massive extinction event, life on Earth began to recover and change in significant ways. In the oceans, older sea creatures declined, while newer groups like bivalves, snails, and sea urchins became more common. On land, important new groups such as dinosaurs began to appear.

The recovery took different amounts of time in different places and for different types of organisms. Some sea creatures bounced back relatively quickly, while others took millions of years. Scientists are still learning about how life rebuilt itself after this difficult time.

Hypotheses about cause

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

Scientists have proposed several mechanisms that might have caused the extinction. These include large impacts from space, increased 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 major hypothesis focuses on the huge volcanic eruptions known as the Siberian Traps. These eruptions released large amounts of carbon dioxide into the atmosphere, leading to rapid global warming. This warming disrupted ecosystems both on land and in the ocean, contributing to the mass extinction.

Comparison to present global warming

The Permian-Triassic extinction event has been compared to today's anthropogenic global warming and the Holocene extinction. Both events involve rapid increases in carbon dioxide, which can harm oceans and plants. While today’s carbon emissions are faster, the ancient event happened in short bursts. Scientists warn that if we do not reduce carbon dioxide, we might face similar ecological problems.

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