ISTerre seminar

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The emergence of proto-plate boundaries from lithospheric drips with grain-damage

Wednesday 7 October 2026 - 11h00

Pr David Bercovici - Yale University
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TBThe emergence of plate tectonics in the early Earth may have started with convective downwellings or drips, which induced localized damaged zones in the lithosphere that eventually accumulated and organized into a network of weak plate boundaries. To address the question of how early downwellings might have localized into damage zones, we explore a simple theory for dripping lithosphere with two-phase grain damage. This model involves only a gravitationally unstable lithosphere overlying a relatively inviscid asthenosphere, and underlying a mobile floating layer of crust that can pile up over downwellings or thin over upwellings. The lithospheric layer has a composite rheology with dislocation creep and grain-size sensitive diffusion creep; grain-size evolves according to the theory of two-phase grain-damage with Zener pinning. Linear stability analysis of the model displays mode selection at finite wavelengths, and the peak growth rate and least-stable wavelength are strong functions of crustal mobility. Nonlinear solutions to the full model predict that, for a range of simple or random initial conditions, self-organizing and highly localized, lineated upwellings, downwellings and weak zones emerge by connecting proximal drips (or upwellings) to each other. Results suggest that essential localized weak zones leading to lineated plate tectonic boundaries can spontaneously arise from post-Hadean lithospheric drips.

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Organizing team : Géodynamo

Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères