Fig. 3

Morphology and distribution ULVZs caused by compositionally distinct ultradense material. a Distribution of ultradense material (red isosurface) beneath large-scale thermochemical piles (partially transparent green isosurface). The lateral length-scale of accumulations of ultradense material at locations A and B is ~1000 and ~100 km, respectively. The exposed Earth’s core in downwelling regions is shown by light gray color. b A zoom-in of panel a along with the locations of 3 cross-sections. The effective buoyancy ratio field at 5 km above CMB show the locations of ultradense material (white to red color). The yellow arrow points to the region with relatively low-effective buoyancy ratio (whitish color) caused by stirring of ultradense material with pile material. c Same as in b but with the thickness of accumulations of ultradense material shown. d–f Cross-section at locations marked by gray lines in b. The temperature field is shown by dark blue to red color, the thermochemical piles are shown in green color in the lowermost mantle and the ultradense material is shown by orange-red color at the base of piles. The yellow arrow in e points to ultradense material that has been viscously entrained up to the top of the pile along the pile edges, and later sank to the bottom of the pile. Beneath each panel is a zoomed-in region outlined by the black box at the edges of piles. All panels a–f are shown at 227 Myr