Alaska's Pavlof Volcano. Credit: NASA Goddard Space Flight CenterResearchers from NTU Singapore and Cambridge University have discovered that the slow-motion collisions between tectonic plates can drag more carbon into Earth’s interior than previously believed.The researchers found that carbon from subduction zones, where tectonic plates collide with each other and enter the Earth's interior, tends to remain at depth rather than resurfacing as volcanic emissions.The findings were published in Nature Communications. They found that only around a third of carbon from beneath volcanic chains is returned to the surface by recycling. This contrasts with previous theories that most carbon that goes down comes back up.The solution to climate change is to decrease the amount of carbon dioxide in the atmosphere. Scientists can learn more about the carbon dynamics in the deep Earth. This is where the vast majority of the planet's carbon lives.The most well-understood components of the carbon cycle are located at or near the Earth's surface. However, deep carbon stores play an important role in maintaining our planet's habitability by controlling atmospheric CO2 levels. Lead author Stefan Farsang, a PhD student at Cambridge's Department of Earth Sciences, said that while we have a good understanding of the carbon cycle's surface reservoirs and fluxes, we don't know enough about the Earth's inner carbon stores. This is what Stefan Farsang did during his research.While there are many ways carbon can be released to the atmosphere (asCO 2 ), there is only one way it can go back into the Earth's interior. That's via plate subduction. This is where surface carbon, such as in the form micro-organisms and seashells that have trapped atmospheric CO2 into their shells are channeled into Earth’s interior. Scientists believed that much of this carbon was returned to the atmosphere via volcanic emissions. The new study shows that some carbon is trapped in rocks and sent deeper into the Earth's interior by chemical reactions.The European Synchrotron Radiation Facility was used to conduct the experiments. Simon Redfern, co-author and Dean of NTU Singapore's College of Science, said that the facility could measure extremely low levels of metals under high pressure and temperatures. They used a heated "diamond anvil" to replicate the extreme pressures and temperatures in subduction zones. This is where two small diamond anvils are pressed against the sample to create the highest pressures.This work confirms growing evidence that carbonate rocks with the same chemical composition as chalk become less calcium-rich, and more magnesium rich when they are channeled into the mantle. This chemical transformation makes carbonate more insoluble, meaning it can't be drawn into fluids that supply volcanic eruptions. Instead, most of the carbonate sinks into the mantle and may one day become diamond.Farsang stated that there is still much research to be done in this area. "In the future we plan to improve our estimates by studying carbonate solubilitiy in a wider temperature and pressure range, as well as in various fluid compositions."These findings can also be used to better understand the role of carbonate formation within our climate system. Redfern stated, "Our results demonstrate that these minerals can lock up CO2 from the atmosphere into solid forms that could lead to negative emissions." Redfern and his team are investigating similar carbon capture methods that move atmospheric CO2 into rocks for storage.These results will help us to understand how carbon can be locked into the Earth's solid Earth and out of the atmosphere. Redfern stated that if we can speed up this process more quickly than nature does it, it could be a way to solve the climate crisis."See more Video: Carbon countingFurther information: Stefan Farsang and colleagues, Deep carbon cycle constrained due to carbonate solubility. Nature Communications (2021). Information from Nature Communications Stefan Farsang and colleagues, Deep carbon cycle restricted by carbonate solubility (2021). DOI: 10.1038/s41467-021-24533-7
