Three-dimensional modeling of upper-mantle anelastic structure reveals that thermal upwellings associated with the two superplumes, imaged by seismic elastic tomography at the base of the mantle, persist through the upper-mantle transition zone and are deflected horizontally beneath the lithosphere. This explains the unique transverse shear wave isotropy in the central Pacific. We infer that the two superplumes may play a major and stable role in supplying heat and horizontal flow to the low-viscosity asthenospheric channel, lubricating plate motions and feeding hot spots. We suggest that more heat may be carried through the core-mantle boundary than is accounted for by hot spot fluxes alone.  Science, 296,  p513-516, 2002
 
 

Top panels: Map views of  QRLW8 centered on the low Q minima in the Pacific (left) and Africa (right). Bottom panels: Depth cross-sections along profiles indicated in the top panels showing,  Q distribution in the upper mantle, and VSH distribution in the lower mantle.  Note the position of the low Q regions in the transition zone above the lowermost mantle low velocity minima in all cases.
 

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