ISTerre seminar

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Ancient geodynamo driven by lunar tides beneath a basal magma ocean

Thursday 17 July 2025 - 14h00

Professor Richard Katz - University of Oxford, Dept of Earth Sciences
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Earth's magnetic field is generated by dynamo action in the liquid part of the core. There is evidence of an intense field dating back to at least 3.4 billion year ago (Ga). However, prior to nucleation of the inner core at about 1 Ga, the driver of the geodynamo is unknown. During this early interval, the bottom of the silicate mantle, enclosing the core, may have been fully molten. We hypothesise that the boundary between this basal magma ocean and the immiscible liquid core was susceptible to tides driven by the Moon's gravity. Using a model of fluid dynamics and gravitation, we predict the laminar part of this tidal flow. We show that tidal resonance with the basal magma ocean supplied ample energy to generate the turbulent, magnetic induction required for dynamo action. We conclude that the Moon played a role shielding early Earth from solar radiation, enabling the emergence of life on this planet.

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Organizing team : Géodynamo

Salle Dolomieu, Maison des Géosciences, 38400 Saint Martin d'Hères

Informations de visio :

https://univ-grenoble-alpes-fr.zoom.us/j/91690538748?pwd=buNDS0rAZw9rG4vS1rWxX53zHYdQaw.1