Are hotspot plumes rooted at the core-mantle boundary?
In plain words
Volcanic hotspots like Hawaii and Iceland may be fed by hot columns rising from the bottom of the mantle. Seismic images are blurry, so how deep these columns go and how many exist is uncertain.
Precise statement
Determine which hotspots are fed by continuous low-velocity conduits from the core-mantle boundary, their widths and excess temperatures, and the fraction of hotspots with deep roots. An answer is a resolution-tested tomographic catalog of plume conduits with depth extent and temperature anomalies.
What would settle it
Full-waveform tomography with ocean-bottom seismometer coverage and formal resolution analysis around major hotspots.
Status in the literature
Full-waveform tomography in 2015 (French and Romanowicz, Nature) imaged broad deep-rooted conduits beneath several major hotspots; the fraction and their dynamics remain open.