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Updated: Jul 19, 2026

Evolution of Staircase Structures in Diffusive Convection
Published on: September 5, 2018
Geodynamic and seismic constraints on the thermochemical structure and dynamics of convection in the deep mantle
Alessandro M Forte1, Jerry X Mitrovica, Aude Espesset
1Department of Earth Sciences, University of Western Ontario, London, Canada.
Abstract:
We revisit a recent study by Forte & Mitrovica in which global geophysical observables associated with mantle convection were inverted and the existence of a strong increase in viscosity near a depth of 2000 km was inferred. Employing mineral-physics data and theory we also showed that, although there are chemical anomalies in the lowermost mantle, they are unable to inhibit the dominant thermal buoyancy of the deep-mantle mega-plumes below Africa and the Pacific Ocean. New Monte Carlo simulations are employed to explore the impact of uncertainties in current mineral-physics constraints on inferences of deep-mantle thermochemical structure. To explore the impact of the high-viscosity peak at a depth of 2000 km on the evolution of lower-mantle structure, we carried out time-dependent convection simulations. The latter show that the stability and longevity of the dominant long-wavelength heterogeneity in the lowermost mantle are controlled by this viscosity peak.
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