Fig. 2.

Distance of ULVZs from thermochemical pile edges. For each distance in the horizontal axis, the corresponding vertical axis shows the areal fraction of hottest regions or accumulations of ultradense material at this distance. Here, the hottest regions refer to candidate regions for melting (e.g., Fig. 1b–e), the regions with accumulations of ultradense material refer to places where the effective buoyancy ratio (B ^eff) is larger than 1.5, and the edges of piles are identified at locations with B ^eff = 0.1. The distances are calculated at 4 depths of 5, 20, 40km and 68 km above the CMB