Scientists have analyzed lavas drilled from deep under the South Atlantic Ocean to understand how much CO₂ is captured within the rocks due to reactions between the rocks and ocean.

The research, led by the University of Southampton, found that piles of lava rubble, formed due to erosion of seafloor mountains, form geological sponges for CO₂.

It's the first time the role of lava rubble as carbon sponges has been fully appreciated, and the research reveals secrets about Earth's long-term carbon cycle.

Lead author of the research, published in the journal Nature Geoscience, Dr. Rosalind Coggon, Royal Society Research Fellow at the University of Southampton, said, "We've known for a long time that erosion on the slopes of underwater mountains produces large volumes of volcanic rubble, known as breccia—much like scree slopes on continental mountains.

"However, our drilling efforts recovered the first cores of this material after it had spent tens of millions of years being rafted across the seafloor as Earth's tectonic plates spread apart.

"Excitingly, the cores revealed that these porous, permeable deposits have the capacity to store large volumes of seawater CO₂ as they are gradually cemented by calcium carbonate minerals that form from seawater as it flows through them."

Understanding past changes in the long-term carbon cycle

The movement of carbon between Earth's interior, oceans, and atmosphere over millions of years controls how much CO₂ is in the air, which affects Earth's climate.