Bénédicte Rey
Wed 30 October 2024
Huge underground fields of magma have been linked to four of the five big mass extinctions on Earth (MAXIM FESYUNOV) (MAXIM FESYUNOV/AFP/AFP)
Massive fields of magma underneath ancient volcanoes spewed out carbon dioxide long after eruptions on the surface had ended, potentially explaining why past global warming episodes lasted longer than expected, a study said Wednesday.
Humans are emitting far more planet-heating carbon-dioxide (C02) than all the world's volcanoes put together. But scientists hope that by studying climate change in Earth's distant past, they can understand how the world heats up -- and crucially, how it can cool down again.
Scientists have long been puzzled by how long it took Earth's atmosphere to recover from a mass extinction event 252 million years ago that ended the Permian period.
It was the most severe extinction event in our planet's history, wiping out roughly 90 percent of marine species and 70 percent of those on land.
Scientists believe the upheaval was caused by huge volcanic eruptions in Siberia. The eruptions created what are called large igneous provinces -- huge underground regions of magma and rock -- which have been linked to four of the five big mass extinctions since complex life appeared on Earth.
It took Earth's climate nearly five million years to recover.
But according to scientific models, the world should have regrouped much more quickly.
"Earth's natural thermostat seems to have gone haywire during and after this event," said Benjamin Black, a researcher at Rutgers University in the United States and lead author of a new study in the journal Nature Geoscience.
- 'This gives me hope' -
To find out more, the US-led team carried out chemical analyses of lava, used computer models to simulate inner-Earth processes and compared climate records preserved in rock.
Their results suggested that even once volcanic activity had ended during past episodes, magma kept releasing carbon dioxide deep in the Earth's crust and mantle, which continued heating the globe.
"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," Black said in a statement.
"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."
Black told AFP that the process described in the study "definitely cannot explain present-day climate change".
All the world's volcanoes currently "release less than one percent as much carbon to the atmosphere as human activities," he explained.
The type of volcanism the team investigated was last seen on Earth 16 million years ago, Black said, and was so enormous it could "cover the continental United States or Europe half a kilometre deep in lava".
But if the findings are confirmed, it could show that Earth's thermostat is working better than scientists had thought.
"This gives me hope that geologic processes will be able to gradually draw anthropogenic CO2 back out of the atmosphere," Black said.
"But it will still take hundreds of thousands to millions of years, which is obviously a long time for human beings."
ber/dl/tw
Buried Alive: 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
Rutgers University
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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.
view moreCredit: Benjamin Black/Rutgers University
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. The work is detailed in today’s issue of the journal Nature Geoscience.
“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,” said 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. “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.”
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. “Earth has natural climate control systems – sort of like the thermostat in your house,” Black said. “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 5 million years to stabilize.
“This delayed recovery has long puzzled scientists. Earth’s natural thermostat seems to have gone haywire during and after this event,” Black said. “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.”
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.
“We call this CO2 from the subsurface magma ‘cryptic carbon’ because it comes from magmas lurking deep in the system,” Black said. “It’s as if the volcanoes were releasing carbon from beyond the grave.”
Black said 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.
“If this is true, it could be good news for Earth's recovery after human-driven climate warming,” Black said. “It means that if we stop turning the thermostat up, on geologic timescales of hundreds of thousands to millions of years, climate can recover.”
Black emphasized 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 kilometer deep in lava,” Black said. “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. “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,” Black said. “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.”
These findings are just the beginning of a multi-year effort funded by the National Science Foundation to investigate how cryptic carbon could influence recovery after major disruptions of Earth’s climate. This summer, the team journeyed to northeastern Oregon, where massive volcanism has been linked with climate warming 16 million years ago. 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. Because of erosion, the area known as the “Alps of Oregon” exposes these rocks that once constituted magma deep in the Earth.
Team members, including Black and colleagues and graduate students from Rutgers and other universities that are part of the National Science Foundation-funded team, clambered into the mountains, ranging between 5,000- and 9,000-feet high, and sampled the glass-like material at the edges of the dikes. These were created when magma came into contact with colder surrounding rocks. Back at their labs, the researchers are looking for evidence in the glassy rocks of ancient emissions of carbon dioxide and other gases.
Other scientists on the study included: Leif Karlstrom of the University of Oregon; Benjamin Mills of the University of Leeds, Leeds, UK; Tamsin Mather, University of Oxford, Oxford, UK; Maxwell Rudolph, University of California-Davis; Jack Longman, Northumbria University, Newcastle Upon Tyne, UK; and Andrew Merdith, University of Adelaide, Adelaide, Australia.
Journal
Nature Geoscience
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Cryptic degassing and protracted greenhouse climates after flood basalt events
Article Publication Date
30-Oct-2024
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