An international team of geoscientists journeyed to northeastern Oregon, where massive volcanism has been linked with climate warming 16 million years ago. For their study, the scientists zeroed in the Wallowa Mountains, which are laced with enormous sheets of flat magmatic dikes, created when molten rock flowed into cracks and solidified. Credit: Benjamin Black/ Rutgers University.
New study finds carbon dioxide release from magma deep beneath ancient volcanoes was a hidden driver of Earth’s past climate.
A Rutgers-led study finds ‘cryptic carbon’ from underground portions of enormous volcanic provinces contributed to climate warming during key moments in Earth’s past.
An international team of geoscientists led by a volcanologist at Rutgers University-New Brunswick has discovered that, contrary to present scientific understanding, ancient volcanoes continued to spew carbon dioxide into the atmosphere from deep within the Earth long past their period of eruptions.
In doing so, the research team has solved a long-standing mystery over what caused prolonged episodes of warming during turning points in Earth’s climate history.
Benjamin Black, who led the study and is an associate professor in the Department of Earth and Planetary Sciences at the School of Arts and Sciences, said: “Our findings are important because they identify a hidden source of CO2 to the atmosphere during moments in Earth’s past when climate has warmed abruptly and stayed warm much longer than we expected.
“We think we have figured out an important piece of the puzzle for how Earth’s climate was disrupted, and perhaps just as importantly, how it recovered.”
Natural climate control systems
In the present-day, humans are releasing vastly more carbon dioxide than all active volcanoes put together – but the new findings could shed light on how the planet’s climate will recover if and when human carbon dioxide emissions decrease.
Black said: “Earth has natural climate control systems – sort of like the thermostat in your house. The question is – are there thresholds beyond which those climate control systems start to break down, making it much harder for climate to recover?”
For decades, scientists have been baffled by climate records showing the failure of the Earth’s atmosphere to recover as quickly as expected after what is known as the end-Permian mass extinction 252 million years ago – the most severe decrease in biodiversity known to have occurred on Earth.
The mass extinction has been linked with tremendous volcanic eruptions in Siberia. Even after the eruptions ceased, Earth’s climate took nearly five million years to stabilise.
Black advised: “This delayed recovery has long puzzled scientists. Earth’s natural thermostat seems to have gone haywire during and after this event.
“We noticed that a similar pattern seemed to have occurred at multiple other times in Earth’s history with massive volcanism, and we set out to understand why.”
Evidence
Black and an international team of colleagues looked back in time and found evidence for carbon dioxide emissions from this type of volcanic province that could last millions of years after most surface eruptions had ended.
They did this by compiling chemical analyses of the lavas, developing computer models simulating melting inside the Earth, and comparing the results with records of past climate preserved in sedimentary rocks.
The analyses showed that massive ancient volcanic provinces shut down slowly. At the surface, eruptions may have stopped, but deep in the crust and mantle, magma was still releasing carbon dioxide, leading to prolonged climate warming.
Black said: “We call this CO2 from the subsurface magma ‘cryptic carbon’ because it comes from magmas lurking deep in the system. It’s as if the volcanoes were releasing carbon from beyond the grave.”
He advised the findings in the new study are significant because they identify a hidden source of atmospheric carbon dioxide during moments when the climate warmed abruptly.
If the volcanoes kept “turning the temperature up”, it could mean the Earth’s thermostat may work better than scientists thought.
Black said: “If this is true, it could be good news for Earth’s recovery after human-driven climate warming.
“It means that if we stop turning the thermostat up, on geologic timescales of hundreds of thousands to millions of years, climate can recover.”
Rare
Black emphasised that cryptic carbon from volcanoes cannot explain present-day climate change: “The type of volcanism we are investigating is rare, capable of generating enough magma to cover the continental United States half a kilometre deep in lava.
“This kind of volcanism has not occurred for 16 million years. All the volcanism taking place on the planet today releases less than one percent as much carbon dioxide as human activities.”
But scientists still hope to learn from these past eruptions about current and future climate.
Black advised: “These ancient eruptions appear to be some of the only events in Earth’s history that release carbon on the same scale as humans are doing today, so by studying these eruptions in the deep past we can learn more about how Earth’s climate systems respond to massive release of carbon to the atmosphere.”
The study is published in Nature Geoscience.
