Extensive iron-water exchange at Earth's core-mantle boundary can explain seismic anomalies.

Seismological observations indicate the presence of chemical heterogeneities at the lowermost mantle, just above the core-mantle boundary (CMB), sparking debate over their origins. A plausible explanation for the enigmatic seismic wave velocities observed in ultra-low-velocity zones (ULVZs) is the process of iron enrichment from the core to the silicate mantle. However, traditional models based on diffusion of atoms and penetration of molten iron fail to account for the significant iron enrichment observed in ULVZs.