Seismic Imaging of Deep Mantle Plumes

The plume model has been the leading hypothesis for hotspot volcanism for five decades. Whereas experiments have clarified how plumes form and rise, the onus has been put on seismologists to find plumes in Earth. Seismic evidence has almost always been contentious because plumes perturb waves slightly and interpretations are inherently nonunique. Using simulations of convection and experimental constraints, we show that traveltime delays of teleseismic shear waves are less than a second and that it is difficult to resolve the plume conduit in the lower mantle using teleseismic traveltime tomography. We discuss the effects of plumes on the transition zone and review analyses of wave diffraction around plumes in the deep mantle, which indicate that plume stems may leave a detectable imprint on the seismic wavefield. We anticipate significant progress in the imaging of deep mantle plumes if seismologists continue their commitment to the deployment of seismic instrumentation in the oceans. Seismic studies will continue to benefit from three-dimensional waveform modeling techniques and advances in adjoint tomography. It is essential to compare seismic modeling results with the seismic signatures predicted by dynamic models and to test them against other geophysical and geological observations.