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Science 24 June 1994:
Vol. 264. no. 5167, pp. 1904 - 1907
DOI: 10.1126/science.264.5167.1904
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Articles

Asymmetric Phase Effects and Mantle Convection Patterns

Mian Liu 1

1 Department of Geological Sciences, University of Missouri, Columbia, MO 65211, USA.

Recent high-pressure experiments and thermodynamic calculations have shown that the Clapeyron slope of the spinel-perovskite phase transition at a depth of 660 kilometers in the Earth's mantle changes from negative to positive at temperatures above 1700° to 2000°C. In numerical experiments that account for this phase behavior, cold downwelling flows were impeded at the phase boundary, but hot plumes ascended to the upper mantle with ease. The resultant mantle convection was partially layered and strongly time-dependent. Mantle layering was weaker when the mantle was hotter and when the Rayleigh number was larger.

Submitted on February 8, 1994
Accepted on May 10, 1994


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