Geologists at the Massachusetts Institute of Technology (MIT) have discovered a clay mineral found on the seafloor. smectite, It has a surprisingly high capacity sequester carbon for millions of years. This discovery opens the door to understanding a hitherto unknown way to capture CO2, the gas that threatens the planet’s climate. Scientists do not even rule out that this could be applied to reduce current global warming.
seen under the microscope, A small grain of this clay is accordion-shaped, and these folds are effective traps for capturing carbon. organic.
The MIT team showed that: Carbon-capturing clay is the result of plate tectonics: When oceanic crust collides with a continental plate, rocks come to the surface and over time they can turn into minerals, including smectite.
Over time, the clay sediment settles back into the ocean, where minerals trap parts of dead organisms in their microscopic folds. This prevents microbes from consuming organic carbon and releasing it into the atmosphere as carbon dioxide.
Help cool the planet
For millions of years, Smectite beneath oceans could influence global climate and help cool the entire planet. Through a series of analyses, the researchers showed that the smectite likely formed after several major tectonic events over the last 500 million years. During each tectonic event, the clay trapped enough carbon to cool the Earth and trigger the ensuing ice age.
In fact, this discovery shows for the first time that plate tectonics can trigger ice ages through the production of carbon-capturing smectite.
This clay can be found in some tectonically active areas today.Scientists believe that smectite continues to sequester carbon at this time, providing a natural buffer. against human activities that, although slow-acting, are warming the climate.
Scientists believe that smectite is currently sequestering carbon, providing a natural buffer against warming, albeit slowly.
“The impact of these modest clay minerals has broad implications for the habitability of planets,” says Joshua Murray, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “There may even be a modern application for this clay to offset some of the carbon that humanity has released into the atmosphere.”
Murray and Oliver Jagoutz, professors of geology at MIT, published the results of their research in the journal Natural Geology.
Ice ages and plate tectonics
The new study follows up on the team’s previous work showing that each of Earth’s major ice ages was likely triggered by a tectonic event in the tropics. Researchers discovered that Each of these tectonic events exposed oceanic rocks called ophiolites to the atmosphere.
They proposed the idea that when a tectonic collision occurs in a tropical region, ophiolites can undergo certain weathering effects, such as wind, rain, and exposure to chemical interactions, transforming rocks into various minerals, including clay.
“These clay minerals influence climate in different ways depending on the species believed to be present.”explains Murray.
At the time, it was unclear what minerals might emerge from the impact of these weathering conditions and whether and how these minerals might contribute directly to the cooling of the planet. Although there appears to be a connection between plate tectonics and ice ages, the exact mechanism by which one could trigger the other was still questioned.
With the new study, The team wanted to find out whether the proposed tropical tectonic erosion process would produce carbon-sequestering minerals.and more, in quantities sufficient to trigger a global ice age.
Checking cooling potential
The team first reviewed existing geological studies and research and collected data on the weathering of large igneous minerals over time and the types of clay minerals these weathering might produce. They then incorporated these measurements into simulations of erosion of different rock types known to undergo tectonic collisions.
“Later We look at what happens to such rocks when they break down due to erosion and the influence of a tropical environment and what minerals are formed as a result,” explains Jagoutz.
They then plugged each eroded “end product” mineral into a simulation of the Earth’s carbon cycle to see what effect a particular mineral might have by interacting with organic carbon or inorganic carbon, such as parts of dead organisms. amount of carbon dioxide in the atmosphere.
During these analyses, one mineral showed clear effects: smectite. In addition to being a naturally eroded product of tropical tectonics, clay was also very effective at trapping organic carbon. In theory, smectite seemed like a solid link between tectonics and ice ages.
However, Was there really enough clay to trigger the previous four ice ages? Theoretically, researchers should confirm this by finding smectite in ancient rock layers from every period of global cooling.
“Unfortunately, we can’t measure them directly because the clay is buried by other sediments,” Murray says. “But we can look for his fingerprints.”
It’s a slow process
The team reasoned that because smectites are a product of ophiolites, these oceanic rocks also contain characteristic elements such as nickel and chromium that may be preserved in ancient sediments. If smectite had been present in the past, nickel and chromium would have been in the same state.
To test this idea, the team examined a database containing thousands of ocean sedimentary rocks accumulated over the last 500 million years. During this period, the Earth experienced four different ice ages. Looking at rocks from each of these periods, the researchers observed large peaks of nickel and chromium and concluded that smectite must also have been present.
The carbon trapped in the clay over millions of years was enough to trigger each of the planet’s four major ice ages.
They estimate that the clay mineral may have increased the preservation of organic carbon by less than a tenth of a percent. In absolute terms this is a very small amount. But they calculated that the carbon trapped and accumulating in clay over millions of years would have been enough to trigger each of the four major ice ages.
“We found that it doesn’t take much of this material to have a big impact on the climate,” Jagoutz said.
“This clay may also have partially contributed to the cooling of the Earth over the last 3 to 5 million years.”“In the absence of humans, this clay probably makes a difference to the climate. It’s a very slow process,” adds Murray.
Possible practical application against climate change
“Jagoutz and Murray’s work is a good demonstration of how important it is to consider all biotic and physical components of the global carbon cycle,” says Lee Kump, a professor of earth sciences at Penn State University who was not involved in the study. “Feedbacks between all these components control atmospheric greenhouse gas concentrations on all time scales, from annual rises and falls of atmospheric carbon dioxide levels to greenhouse-to-greenhouse transitions over millions of years.”
Could smectites be used intentionally to further reduce the world’s carbon emissions? Murray sees some potential for supporting carbon stocks such as permafrost regions. Rising temperatures are predicted to melt permafrost and release long-buried organic carbon. If smectite could be applied to these areas, the clay could prevent this released carbon from escaping and further warming the atmosphere.
“If you want to understand how nature works, you have to understand it at the scale of minerals and grains,” says Jagoutz. “And that’s also the way to find solutions to this climate disaster. If you study these natural processes, you’re very likely to find something really useful.”
Reference work: DOI: 10.1038/s41561-023-01342-9
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