Mass Extinction Event Triggered by Earth's Acidic Oceans

A mass extinction event that may have been the largest in all of Earth's history may have been triggered by changes in the planet's oceans. Scientists have found that the amount of carbon added to the atmosphere that triggered the event caused the oceans to become acidic.

The mass extinction event occurred about 252 million years ago. During the event, more than 90 percent of marine species and more than two-thirds of the animals living on land were wiped out. Volcanic eruptions spewed huge amounts of carbon dioxide into the atmosphere at the time, which were then absorbed by the ocean.

In order to learn a bit more about this extinction event, the researchers analyzed rocks which were present on the ocean floor during the event. This allowed them to develop a climate model to work out what drove the extinction. The rocks preserved a detailed record of changing oceanic conditions at the time.

In the end, the researchers found that the carbon was released at rates similar to modern emissions. This fast rate of release was a critical factor driving ocean acidification. The acidification of the oceans lasted for about 10,000 years. In addition, the rate of release changed the very chemistry of the oceans.

"Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now," said Matthew Clarkson, one of the researchers, in a news release. "This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions."

The findings are published in the journal Science.

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