During earthquakes, cobwebs of disturbances open underground, allowing gases deep into our planet to penetrate upward. Scientists have now compiled the first long-term record showing the relationship between earthquakes and the release of carbon dioxide gas.
While the amount of carbon dioxide released by tectonic activity is poor compared to the billions of tons that human activity draws into the atmosphere each year, research published Wednesday in Science Advances sheds light on the planet’s carbon cycle controlling climate.
“It’s a modulation of the Earth̵7;s climate on geological time scales,” said James Muirhead, a geologist at the University of Auckland in New Zealand, who did not participate in the research and praised the data set collected by a team of Italian scientists.
The results could also potentially pave the way for predicting seismic activity.
The region around the central Italian Apennines, about an hour east of Rome, is full of bugs. The area was repeatedly hit by devastating earthquakes, including the L’Aquila earthquake in 2009. The wave, which killed hundreds of people, made headlines again in 2012, when a judge ruled that seven Italian earthquake experts were guilty of manslaughter. because they warned residents near the potential risk. Seismic activity in this area was associated with carbon dioxide leakage.
Giovanni Chiodini, geochemist at the National Institute of Geophysics and Volcanology in Bologna, and his colleagues analyzed the carbon content of groundwater in the Apennines. From April 2009 to December 2018, scientists collected hundreds of water samples from 36 different springs. They calculated the concentration of carbon dioxide in each sample after deducting the contributions from rainwater and soil.
The researchers estimated that tectonic activity in the study area emitted about 1.7 million tons of carbon dioxide in ten years. This is roughly equivalent to the carbon dioxide emitted by a single volcanic eruption.
The real surprise came when Dr. Chiodini and his colleagues compared their data with the records of about 17,000 earthquakes that occurred nearby. The researchers found that seismic activity and carbon dioxide degassing were clearly observed at times – periods of high earthquake activity associated with peaks in gas release. For example, the concentration of carbon dioxide measured in the months following the earthquake in L’Aquila was about twice as high as in 2013, a period of low earthquake activity. High concentrations were again measured in September and November 2016, just a few months after several large earthquakes shook the area.
Scientists suggest that this connection makes sense based on what is happening miles below the surface. The central Apennines sit at the top of the subduction zone, where plates of carbon-rich rocks are constantly sinking downwards. As these rocks sink, they are exposed to increasingly hot conditions until they melt and release gases, Dr. Chiodini said. “One hundred kilometers below the Apennines, you have a huge source of carbon dioxide,” he said. When pressure builds up underground, the bark eventually breaks, leading to earthquakes.
Scientists claim that the earthquake itself may also cause further degassing of carbon dioxide. This is because the movement of the earth can cause gas bubbles to form deep underground, similar to shaking a bottle of champagne, Dr. Chiodini said. Scientists suggest that this feedback loop explain the shocks in the Apennine Peninsula.
The big question is what will happen first, an earthquake or the degassing of carbon dioxide.
“If carbon dioxide emissions lead to large earthquakes in time, perhaps these methods could be used in conjunction with tools other than earthquake indicators,” said Dr. Muirhead.
However, he said much more observations would be needed – with measurements spaced closer together – and then it would still be a major effort to predict seismic activity. “Uncertainties are still too high and the consequences too great,” he said.