Triassic–Jurassic extinction

The Triassic–Jurassic (Tr-J) extinction event, often called the Triassic–Jurassic mass extinction (TJME) or end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, 201.4 million years ago. It was one of five major extinction events during the Phanerozoic, and it changed life on Earth forever.

In the oceans, many types of sea creatures died out. About 23–34% of marine genera disappeared. Groups like corals, bivalves, brachiopods, bryozoans, and radiolarians lost many of their species, and conodonts disappeared completely. On land, most large reptiles called archosauromorphs went extinct, except for crocodylomorphs, dinosaurs, and pterosaurs. These survivors became the main land animals for the next 135 million years. Plants also changed greatly during this time.

Scientists believe the main cause of this extinction was huge volcanic eruptions in the Central Atlantic magmatic province (CAMP). These eruptions poured lots of carbon dioxide into the air, leading to strong global warming and ocean acidification. They also released toxic mercury. Some older ideas suggest climate changes, sea level shifts, or asteroid impacts might have played a role, but the volcanoes are thought to be the main reason.

Research history

Early studies of the Triassic-Jurassic extinction in the mid-20th century often focused on gradual changes in the environment, influenced by the belief that Earth's history unfolded slowly over time. A well-known scientist, Edwin H. Colbert, thought changes in rainfall and sea levels gradually reduced land area, leading to the extinction.

Later, in the 1980s, researcher Jack Sepkoski recognized this event as one of the five major mass extinctions in Earth's history. After learning that an asteroid impact caused the end of the dinosaurs, some scientists suggested a similar impact caused the Triassic-Jurassic extinction. However, today most experts believe massive volcanic eruptions in the Central Atlantic magmatic province played the biggest role, especially after similar volcanic activity was linked to another ancient extinction, the Permian-Triassic extinction event.

Effects

The Triassic-Jurassic extinction was a major event that changed life in the oceans and on land about 201.4 million years ago. In the seas, many types of marine life disappeared, including about 23–34% of marine genera. Corals, bivalves, brachiopods, and bryozoans lost a lot of their diversity, and conodonts completely vanished. However, marine vertebrates like fish and some types of shellfish were less affected.

On land, the extinction had a big impact on animals and plants. Many amphibians and reptiles that were common in the Triassic did not survive into the Jurassic. Dinosaurs, however, began to thrive and fill the places left empty by the extinct species. Plants also saw changes, with some types disappearing while others, like certain ferns, became more common. Overall, this extinction event shaped the kinds of animals and plants that would dominate the Earth in the following millions of years.

Possible causes

The leading explanation for the Triassic–Jurassic extinction is massive volcanic eruptions from the Central Atlantic Magmatic Province (CAMP). These eruptions were some of the largest known in Earth's history, spreading across parts of Europe, Africa, South America, and North America. Evidence shows these eruptions happened around the same time as the extinction, with changes in carbon in ancient soils and ocean sediments linking the two events.

These volcanoes released huge amounts of carbon dioxide, a gas that traps heat and warms the planet. Before the extinction, carbon dioxide levels were about 1,000 parts per million. During the extinction, they jumped to 1,300 parts per million and then rose even more. This rapid warming changed climates quickly, making life difficult for many species. The warmth also caused other problems, like more wildfires and less oxygen in the oceans, which helped cause the extinction.

Comparisons to present climate change

Scientists have noticed that the huge amount of carbon released during a period of intense volcanic activity, called the CAMP volcanism, caused rapid climate change about 201.4 million years ago. This event led to a major loss of many sea creatures.

Today, human activities are putting carbon dioxide into the air at a very fast rate, similar to what happened back then. This is causing the Earth's climate to warm up quickly. Some scientists worry that if we keep adding carbon dioxide like we are now, it could harm many ocean animals, especially coral reefs, just like it did a long time ago. They say it is very important to cut down on carbon emissions to protect our planet.