Geophysical evidence for the scale of mantle convection

Evidence from high resolution seismic tomography. A critical issue for geochemical mantle models is the extent of mantle mixing by convection and the potential for maintaining separate reservoirs. The most direct information on the scale of 

Some volcanic centers, however, are better explained by either local melting anomalies (Hofmann 1997), comparatively broad upwellings associated with plate-scale flow (e.g., Darwin and African Rises Sleep 1990), or a plume of shallow origin (e.g., Tahiti Steinberger 2000). In order to determine the plume flux from the deep mantle, the proportion of the ocean island hotspots that are derived from the CMB, as well as the number of plumes beneath continental regions (e.g., Ritter et al. 2001), must be better constrained. 

In defining the total flux of material from the deep mantle into or through the upper 

10 g/yr. At this rate, the mass of the upper mantle is exchanged in 

1998) and are limited to proscribed behavior. Additional avenues of investigations using numerical models include assessing the survivability of highly viscous blobs in the 

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