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Richard O’Connell
Harvard University
Abstract:
A recent analytic boundary layer model of convection with layered viscosity and tectonic plates
has revealed the existence of multiple convective modes, with transitions and hysteresis. Modes
include ‘classical’ plate tectonics, a sluggish plate mode and a foundering plate mode. Analytic
results compare well with numerical convection calculations. When applied to the thermal
evolution of the Earth the model predicts possible transitions between modes during Earth
history, depending on the evolution of lower mantle viscosity. Such models can reconcile the
apparent discrepancy between the current terrestrial heat flow and the esitmated concentration of
heat sources in the Earth (the Urey ratio). The model allows the efficient investigation of the
tectonic and thermal evolution of terrestrial planets and exo-planets.