The PI will investigate hotspots and mid-oceanic ridges to constrain their underlying physical processes, mainly heat and mass transfer. His investigation of hotspots has confirmed that these features are produced by mantle plumes. In particular, the shape of hotspots swells, such as that hear Hawaii, is simply related to the kinematics of flow from plumes. He has constrained the heat and mass fluxes of plumes globally. He will now extend this work to learn more about how plumes work and about the dynamics of heat transfer between the plume and the lithosphere. Some variations in the mantle temperature beneath ridge axes may be related to ambient temperature variations at mid-mantle depths, not plumes. His studies of ridge axes will concentrate on modeling features affected by temperature variations associated with hotspots, such as central rifts. He will continue to study temperature variations associated with hydrothermal circulation with emphasis on the downwelling parts of the circulation nearest to the ridge axis. He will reprocess multichannel seismic data from the back-arc Valu Fa ridge near Tonga to constrain the location of the crustal magma chamber, including one line across an overlapping spreading center.
