A research team has found that ancient volcanoes, contrary to what we previously believed, continued to release carbon dioxide from deep within the Earth long after their last eruptions.
An international research group led by a volcanologist at Rutgers University-New Brunswick has made an exciting discovery: ancient volcanoes continued to emit carbon dioxide into the atmosphere from deep within the Earth long after they had last erupted, defying current scientific beliefs.
This research helps clarify a longstanding mystery regarding the causes of extended warming periods during key events in Earth’s climate history. The findings are published in the journal Nature Geoscience.
According to Benjamin Black, the study leader and associate professor in the Department of Earth and Planetary Sciences at Rutgers, “Our discoveries are significant as they uncover a concealed source of CO2 in the atmosphere at times when the climate has rapidly warmed and remained warm longer than we anticipated.” He added, “We believe we’ve identified a crucial piece of the puzzle regarding how Earth’s climate was disrupted, and equally important, how it managed to recover.”
Currently, human activities are generating a far larger amount of carbon dioxide than all active volcanoes combined. However, these new findings could provide insight into how the planet’s climate might rebound if human emissions eventually decline. “Earth has natural climate regulation systems, much like a thermostat in your home,” Black explained. “The pressing question is whether there are limits beyond which these climate regulation systems fail, making recovery much more difficult.”
For many years, researchers have been puzzled by climate records that show Earth’s atmosphere failed to recover as swiftly as expected after the end-Permian mass extinction event that occurred 252 million years ago—the most severe biodiversity loss known in Earth’s history. This mass extinction has been associated with significant volcanic activity in Siberia. Astonishingly, even after the eruptions stopped, it took nearly 5 million years for Earth’s climate to stabilize.
Black remarked, “This delayed recovery has confused scientists. It appears that Earth’s natural thermostat malfunctioned during and after this event. We noticed that a similar trend seemed to have been evident during other notable periods in Earth’s history characterized by extensive volcanic activity, and we set out to understand why.”
In their research, Black and his international colleagues investigated historical records and discovered signs of carbon dioxide emissions from volcanic regions lasting millions of years after most surface eruptions had concluded. They conducted chemical analyses of the lavas, created computer simulations of melting processes within the Earth, and compared the outcomes to climate records found in sedimentary rocks.
The analyses revealed that these enormous ancient volcanic regions took a long time to shut down completely. While surface eruptions may have stopped, deep within the Earth’s crust and mantle, magma continued to release carbon dioxide, resulting in prolonged climate warming.
Black referred to this subsurface carbon dioxide from magma as “cryptic carbon,” as it originates from magmas located deep within the Earth’s structure. “It’s akin to the volcanoes still discharging carbon long after they’ve become dormant,” he said.
The significance of this new study lies in its identification of a hidden source of atmospheric carbon dioxide during periods of sudden climate warming. If these volcanoes were “turning the temperature up,” it suggests that Earth’s climate regulation systems might function better than scientists previously believed.
If this is indeed the case, it offers hopeful news for Earth’s recovery following human-induced climate change. According to Black, “This means that if we halt the increase in temperature, over geological periods of hundreds of thousands to millions of years, the climate could rejuvenate.”
Nonetheless, Black stressed that cryptic carbon from volcanoes cannot account for contemporary climate change. “The specific type of volcanism we are examining is quite rare, capable of producing enough magma to flood the continental United States to a depth of half a kilometer,” he pointed out. “This kind of activity hasn’t taken place for 16 million years. Currently, all volcanic activity worldwide contributes to less than one percent of the carbon dioxide released by human activities.”
Nevertheless, scientists are eager to glean insights from these historical eruptions to better understand current and future climate dynamics. “These ancient eruptions are among the few occurrences in Earth’s past that released carbon on a scale comparable to current human activities,” Black noted. “Thus, studying these past eruptions may provide valuable information on how Earth’s climate systems respond to substantial carbon emissions.”
This research represents merely the starting point of a multi-year project, funded by the National Science Foundation, aimed at investigating how cryptic carbon affects recovery following major climatic disruptions. This summer, the research team traveled to northeastern Oregon, an area where significant volcanic activity has been linked to climate warming that occurred around 16 million years ago. The scientists focused on the Wallowa Mountains, which are characterized by vast flat sheets of magmatic dikes formed when molten rock filled cracks and solidified. Due to erosion, this region, referred to as the “Alps of Oregon,” exposes rocks that were once magma deep inside the Earth.
Members of the team, including Black, colleagues, and graduate students from Rutgers and other universities involved in the National Science Foundation-funded project, trekked into the mountains, reaching altitudes of 5,000 to 9,000 feet, to collect samples of the glassy materials found at the edges of the dikes. These formed when magma interacted with cooler surrounding rocks. Back in their laboratories, the researchers are searching for signs of ancient carbon dioxide and other gas emissions within these glassy rocks.
Other contributors to the study included: Leif Karlstrom from the University of Oregon; Benjamin Mills from the University of Leeds, UK; Tamsin Mather from the University of Oxford, UK; Maxwell Rudolph from the University of California-Davis; Jack Longman from Northumbria University, UK; and Andrew Merdith from the University of Adelaide, Australia.
