A recent finding in the South Atlantic has revealed a silent yet decisive climate mechanism: volcanic debris on the seabed can store up to 40 times more carbon than solid rocks.
This discovery, led by the University of Southampton, provides a key piece to understanding the deep carbon cycle and the hidden role of the oceans in the Earth’s climate regulation.
Volcanic debris: true mineral sponges
The fragmented lava debris, known as volcanic breccias, act as true sponges capable of retaining carbon dioxide for millions of years.
- Seawater slowly filters through the gaps in the fractured material.
- The ions present react with the rock and promote the formation of carbonate minerals.
- The CO₂ is sealed within the stone, forming a long-term geological archive.
Researcher Rosalind Coggon, the principal investigator of the study, highlighted that the novelty was recovering for the first time complete cores of these breccias, after tens of millions of years of travel with the oceanic plate. This allowed observing how these deposits evolve over time.
Comparison with solid basalt
Intact basalt can also retain carbon, but it does so more slowly:
- Its internal surface is limited.
- Fluids take longer to access fresh areas to initiate reactions.
Volcanic breccias, on the other hand, are born already fragmented, with a multitude of gaps that facilitate water circulation and multiply reaction opportunities.
The new data confirm that these breccias store between two and forty times more carbon than the compact lavas previously analyzed.
The deep carbon cycle
The deep carbon cycle regulates the Earth’s climate in the long term:
- At ocean ridges, the movement of plates generates new volcanic crust and releases CO₂ into the ocean and atmosphere.
- When the crust cools and moves away from the ridge, it begins to act as a chemical filter, trapping carbon within.
This process, although invisible and slow, has been crucial for stabilizing the climate in past eras.
Implications of the finding
The discovery does not offer an immediate solution to the current climate crisis, as the processes involved advance at the pace of tectonics and mineralization, far below human scales. However, it provides valuable information to:
- Reconstruct ancient levels of atmospheric CO₂, key to assessing Earth’s climate sensitivity.
- Improve global climate planning models, integrating the role of the oceanic crust.
- Design carbon storage strategies based on natural processes.
Potential applications
The finding opens new avenues for innovation:
- Rapid mineralization: leverage basalt formations on land to fix CO₂ in a few years.
- Marine geological protection: preserve seamounts and ridges for their role in the carbon cycle.
- Research in oceanic geochemistry: better understand how these deposits evolve to optimize mitigation strategies.
The ocean not only regulates the climate through currents, ice, or direct CO₂ absorption. It also does so from below, from the oceanic crust, through invisible processes that work tirelessly. Recognizing this hidden role is essential to imagine a more balanced future and to design climate policies that integrate the planet’s geological dynamics.
