GEOLOGY: Superplume in Silico

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Science  02 Mar 2007:
Vol. 315, Issue 5816, pp. 1194c
DOI: 10.1126/science.315.5816.1194c

Rising beneath South Africa from the base of Earth's mantle is a giant plume of hot material: the African superplume. This feature has distinct edges and rises buoyantly like a plume of smoke from the core/mantle boundary, reaching a height of 1500 km beneath the continent. Simmons et al. have constructed a theoretical model of the African superplume incorporating seismic observations, motions of the overlying tectonic plates, and the elongated shape of the core/mantle boundary, as well as detailed mineral physics. They find that temperature effects can reproduce most of the plume's properties, but there remain some anomalies that must be due instead to chemical differences. Notably, a denser material seems to lie in the mid-mantle region of the plume, 1000 km above the core/mantle boundary, which is also the site where the temperature is highest. Thus, this density anomaly counteracts the density drop that the heat would naturally produce. This anomaly may be the remnant of a pile of dense material entrained from the superplume's base. — JB

Geophys. Res. Lett. 33, 10.1029/2006GL028009 (2007).

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