Three-Dimensional Instabilities of Mantle Convection with Multiple Phase Transitions

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Science  26 Feb 1993:
Vol. 259, Issue 5099, pp. 1308-1311
DOI: 10.1126/science.259.5099.1308


The effects of multiple phase transitions on mantle convection are investigated by numerical simulations that are based on three-dimensional models. These simulations show that cold sheets of mantle material collide at junctions, merge, and form a strong downflow that is stopped temporarily by the transition zone. The accumulated cold material gives rise to a strong gravitational instability that causes the cold mass to sink rapidly into the lower mantle. This process promotes a massive exchange between the lower and upper mantles and triggers a global instability in the adjacent plume system. This mechanism may be cyclic in nature and may be linked to the generation of superplumes.