Claudio Faccenna on the Dynamics of Subduction Zones
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Subduction zones can be very long-lived, persisting for tens of even hundreds of millions of years. During that time they rarely stay still, but instead retreat, advance, move laterally, or reverse direction. In the podcast, Claudio Faccenna discusses the processes that govern these movements. It turns out that these depend not only on the properties of the subducting slab, but also on the environment, including the proximity of other subduction zones.
Faccenna has been studying how convergent margins evolve for over 30 years, concentrating particularly on the Mediterranean region. He is Head of the lithospheric dynamics section at the Helmholtz Center for Geosciences at GFZ in Potsdam in Germany and also a Professor at the Department of Science at Roma Tre University.
Podcast Illustrations
Images courtesy of Claudio Faccenna unless otherwise noted.
Top: map of subduction zone locations. Bottom: depth profiles of Pacific subduction zones. Western Pacific subduction zones, which subduct toward the west, are drawn in blue, and eastern Pacific subduction zones, which subduct toward the east, are drawn in red. Dashed lines indicate depths of 410 km and 660 km, which correspond to mantle transition zones where the seismic velocity, mineral phases, and density change. Zero on the distance scale corresponds to proximity to the coastline. The figure shows that the shapes of the subducting slabs vary considerably. This is thought to result from the interaction of several interacting factors, including the slab's properties, the mantle's characteristics, and forces on the plate.
Becker, T and Faccenna, C. (2025), Tectonic Geodynamics, Princeton University Press
Subduction zones along the western Pacific and Indonesia. The figure shows sections of P-wave tomography anomalies along the yellow lines on the map (Fukao & Obayashi, 2013), seismicity (orange dots on profiles; Engdahl et al., 1998), plate velocities (orange vectors; Argus et al., 2011), and volcanoes (cyan inverted triangles; Siebert & Simkin, 2023).
Becker, T and Faccenna, C. (2025), Tectonic Geodynamics, Princeton University Press
Subduction zones along the west coast of the Americas. In the podcast, Faccenna described how the slab subducting below the Andes has entered the lower mantle where it lateral movement is restricted by the higher viscosity there.
Becker, T and Faccenna, C. (2025), Tectonic Geodynamics, Princeton University Press
Geodynamics of a subduction zone, including a subducting plate, an overriding plate and the asthenosphere, with driving and resisting forces and the typical mantle flow pattern created by the descending slab (modified after Forsyth and Uyeda, 1975; Magni et al., 2024). Driving forces (white arrows): Frp, ridge push; Fsp, slab pull; Fnb, negative buoyancy of the subducting lithosphere; Fts, trench suction. Resisting forces (yellow arrows): Rd (c/o), mantle drag; Rs-c, resistance at the subduction interface; Rb, bending resistance; Rs, mantle resistance along the slab; Ra: resistance force due to dynamic pressure, Rr, mantle resistance on the ridge.