Earth’s hidden conveyor belts : linking earthquakes, volcanoes, and deep Earth recycling

Recent research in subduction zones highlights how earthquakes, volcanism, and the deep recycling of Earth’s materials are part of a single connected system. At subduction zones, one tectonic plate sinks beneath another, driving most of the planet’s large earthquakes while also transporting water, carbon, and rocks back into the mantle.



Figure 2. Upper part of a subduction zone showing the link between seismic activity, fluid pathways and metasomatism and ore formation


Figure 1. 3D schematic of the two main types of subduction zones, highlighting key features : the deep-sea trench, the magmatic arc, the Wadati–Benioff seismic zone (earthquakes shown as black crosses), and the high-velocity slab extending into the mantle transition zone (after Schellart).



Until recently, observations were mainly limited to land-based networks, leaving offshore fault systems, where the largest earthquakes occur, poorly constrained. This is now changing with the development of ocean-bottom seismometers and the use of submarine fiber-optic cables as seismic sensors. These new approaches are revealing deformation processes directly on the seafloor in near real time.

One of the most important findings of recent decades is that fault motion is not only sudden. In many subduction zones, the crust also slips slowly over days to months, in so-called “slow slip events,” often accompanied by faint tremors. These observations point to a complex system where friction, deformation, and fluid migration are tightly coupled, although the relationship between slow slip and large earthquakes remains uncertain.

Fluids released from the descending plate appear to play a central role. As rocks are pushed deeper into the mantle, they release water and carbon dioxide, which migrate upward, weakening rocks, generating magma, and feeding volcanic arcs. Geochemical signatures preserved in volcanic rocks and deep mantle samples show that surface materials are continuously recycled into Earth’s interior.

Some evidence suggests that part of this volatile-rich material may be transported deeper than previously thought, potentially reaching the mantle transition zone. However, the timing and nature of the onset of global plate tectonics remain debated, with competing hypotheses ranging from very early subduction-like processes on the early Earth to a later development of modern-style plate tectonics.

To better understand these systems, new approaches are emerging, including “digital twins” of subduction zones. These are virtual models that integrate seismic, satellite, oceanographic, and geological data into continuously updated simulations of Earth’s behavior. The goal is to better understand earthquake and tsunami processes within a unified physical framework.

In this view, subduction zones are not simply tectonic boundaries, but dynamic systems that connect Earth’s surface and deep interior, controlling both catastrophic events and the long-term evolution of our planet.


The full study is published in : Critical Insights in Geochemistry and Geophysics


References :

Schellart, W.P. (2023) Subduction zones : a short review. In : Duarte, J.C. (ed.) Dynamics of plate tectonics and mantle convection. Elsevier, Amsterdam, 321–355.

Ricard, Y. & Vigny, C. (1989) Mantle dynamics with induced plate tectonics. Journal of Geophysical Research 94(B12), 17543–17559.

Dascher-Cousineau, K., Bürgmann, R., Frank, W.B., et al. (2024) Global subduction slow slip events and associated transient deformation. Science Advances 10(35), 2191.

Scientific contact :

  • Stéphane Guillot – ISTerre, Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, Univ. Gustave Eiffel, Grenoble, France