Geological evidence extracted from the floor of the Atlantic Ocean affirms a long-standing theory that greenhouse gas emissions associated with volcanism drove catastrophic climate change 56 million years ago.

A new study by an international team of scientists—including University of Utah geologists—examined hundreds of core samples in search of clues to what drove rapid warming that triggered the deep sea die-off marking the transition from the Paleocene to the Eocene epoch. A paper published this month concludes that large volumes of methane—a potent greenhouse gas—escaped from hydrothermal vents on the ocean floor during a period of intense volcanic activity.

Around the time the Americas and Europe started spreading apart to form the North Atlantic, Earth’s temperatures spiked by 5 degree Celsius and ocean chemistry changed during a 200,000-year period known as the Paleocene-Eocene Thermal Maximum, or PETM. This resulted in a major extinction event that wiped out a lot of deep marine life and accelerated evolution among terrestrial creatures, with mammal species becoming more diverse.

Ancient analogue for today’s climate change

“This article provides evidence for hydrothermal venting playing a major role in the global warming event that happened during the PETM by showing vents in the North Atlantic erupted in very shallow water and coincided with the onset of the PETM,” said Sarah Lambart, a U professor of geology and geophysics. “While their origins are different, the PETM presents similarities with global warming today in that the sediments that were heated were very rich in hydrocarbons. So this event can be used as a natural analogue for how the Earth system responds to the rapid burning of fossil fuels.”

She noted that today’s anthropogenic climate change is 100 times faster than what transpired at the end of the Paleocene.

Scientists have long believed the PETM was triggered by rapid and massive releases of carbon dioxide (CO2) and methane (CH4) into the atmosphere from geological sources.

Methane is a far more powerful greenhouse gas than carbon dioxide, although it eventually breaks down in the atmosphere. Over short time frames, methane could have a major impact on the climate, and the scientific team thinks that might be the case with the PETM, which coincided with the volcanic-driven continental breakup that created the Atlantic.