The core-mantle boundary (CMB) is a crucial interface within the Earth, marking the boundary between the outer core and the lower mantle. For the past two decades, seismological studies have identified anomalous low-velocity zones above the CMB, such as the large low-shear-velocity provinces (LLSVPs) beneath Africa and the Pacific. Smaller ultralow-velocity zones (ULVZs) have been detected in these regions, characterized by significantly lower seismic wave speeds and higher densities compared to the surrounding mantle.