Thin regions sitting on top of the core-mantle boundary (CMB) with P-and S-wave velocity reductions as large as 25%-45% respectively, known as ultralow-velocity zones (ULVZs) have been investigated using seismic techniques for nearly three decades. Evidence continues to accumulate that some of the ULVZs discovered may be linked to deep seated roots of whole mantle plumes that give rise to hot spot volcanism. Seismic waveform modeling has inferred large-scale ULVZs beneath hot spots such as Hawaii (Cottaar &