Mass extinction linked to volcanism

Ancient global warming, which triggered a deep-sea mass extinction more than 55 million years ago, may have been caused by massive volcanic activity, scientists have said.

But they warn that this natural event does not come close to matching what humans are doing today.

In a study published in the journal Proceedings of the National Academy of Scienc es, researchers suggest ancient volcanism sent huge amounts of carbon dioxide into the atmosphere during that time, which was then absorbed by the oceans over thousands of years.

The soaring carbon dioxide levels drove temperatures up by between 5C and 8C during a time period known as the Paleocene-eocene Thermal Maximum (PETM), about 55.6 million years ago.

The researchers say the event triggered chemical reactions that caused waters to become highly acidic, killing and impairing many marine species.

They warn that current human-led emissions are introducing carbon into the oceans up to eight times faster than the volcanoes did.