Volcanoes Aren’t Solely to Blame for the Extinction 252 Million Years Ago

Long before the dinosaurs went extinct 66 million years ago, an event known as the End-Permian extinction wiped out over 95% of marine species and about 70% of land species. A widely accepted explanation for this extinction, which occurred 252 million years ago, is that ancient volcanic eruptions released massive amounts of carbon, causing global warming.

But new research suggests that it would have been very hard for the volcanoes alone to change the atmosphere’s carbon profile. Something else must have been at play, according to the study in Earth and Planetary Science Letters. The paper’s lead author, Ellen Gales, did the research for her master’s degree thesis at The City College of New York, working with co-author Professor Benjamin Black (CCNY, The Graduate Center) and a colleague from Arizona State University.

Scientists have a record of how the carbon “fingerprint” in Earth’s atmosphere changed during mass extinctions. But we don’t have a good record of what was actually spewed out by volcanoes. Gales and Black developed a new way to estimate the carbon isotope ratios of eruptions by studying igneous rocks left by ancient volcanic activity in Siberia. They found that the carbon profile from the eruptions differed from what’s known about carbon in the atmosphere during the extinction period.

Siberian Traps, a large region of volcanic rock in Siberia, Russia

Siberian Traps, a large region of volcanic rock in Siberia, Russia

“Ellen’s work is new in that scientists have previously guessed what the geochemical fingerprint of CO2 from these giant eruptions might be, but our findings are some of the first direct measurements of this fingerprint,” Black told CCNY. “The key finding of our research is that carbon from massive, ancient volcanic eruptions does not line up well with the geochemical clues that tell us about how some of Earth’s most profound mass extinctions occurred.”

So what else could have contributed?

“One possibility is that the magmas could have heated up the surrounding crust, releasing even more carbon from rocks like limestones and coals,” Black said. Alternatively, the warmer climate caused by carbon from the eruptions could have triggered more carbon release, from methane clathrates, a compound found on ocean floors.

 “These results contribute to our knowledge of how carbon, a key ingredient for life and climate, cycles around our planet, and the role of enormous volcanic eruptions in this cycle,” Gales said. “These rare events released large quantities of carbon dioxide into the atmosphere, analogous to the carbon emissions of human beings. Understanding how the environment responded to this scale of CO2 release in the past is important for predicting how the climate might change in the future.”