CO2, an unexpected driver of deep earthquakes beneath ocean ridges
A team from the Institut de Physique du Globe de Paris (IPGP) has revealed the role of CO2 degassing in deep earthquakes beneath the Mid-Atlantic Ridge. Their work, published in Nature Communications on 10 January 2025, opens up new perspectives on the dynamics of the Earth's mantle.
Ocean bottom seismometers used during the SMARTIES Experiment
Publication date: 10/01/2025
Research
Volatile substances such as carbon dioxide (CO2) and water (H2O) play a key role in the melting of the Earth’s mantle beneath ocean ridges, where tectonic plates move apart and create new oceanic crust. However, their influence on the moving magma has remained a mystery until now. A recent study by Satish Singh’s team at the Institut de Physique du Globe de Paris (IPGP) sheds new light on this phenomenon.
Using seafloor seismometers (OBS) installed during the SMARTIES campaign in 2019, the researchers recorded surprising micro-earthquakes deep beneath the axis of the equatorial Mid-Atlantic Ridge (MAR), a region of slow spreading. These tremors, detected between 10 and 20 km below the ocean floor, occur in the warm mantle, well below the boundary between the rigid lithosphere and the ductile mantle, known as the BDB (brittle-ductile boundary).
Analysis of basaltic rocks collected nearby revealed exceptionally high concentrations of CO2 in the primary magma (around 0.4 to 3.0% by weight). The researchers suggest that the degassing of this CO2, by causing rapid changes in the volume of the magma, could trigger these deep earthquakes. In other words, the magma could stagnate at these depths, where it continues to evolve before rising to form the oceanic crust.
These discoveries are crucial: they show that volatile substances can influence not only the formation of oceanic crust, but also deep seismic mechanisms. A high CO2 content could even allow the presence of magma at lower temperatures than expected beneath the boundary between the lithosphere and the asthenosphere, increasing heterogeneities within the lithosphere.
This study opens up new perspectives on the Earth’s internal dynamics and the little-known role of outgassing in seismic processes. It was carried out with the support of the European Research Council.
Contact details :
Pr Satish Sighn, IPGP :
