Fig. 3

Time snapshots of temperature field at 1 Gyr from mantle convection models (A) with and (B) without a continuous proto-LLVP layer at the core–mantle boundary. The basal layer (A) acts as a thermal blanket and physical barrier, leading to reduced heat transfer from the core and inhibits strong plume formation, while the (B) model without a basal layer shows vigorous upwellings (red arrows) and complex convection patterns. Blue arrows are velocity vectors of mantle flow scaled by magnitude; the scale factor is identical in (A) and (B). For both the models, core–mantle boundary temperature (T_CMB) is 4500 K, and mantle potential temperature (T_P) is 1430 ℃. The internal radiogenic heating ratio \(\:\left(\frac{{H}_{LLVP}}{{H}_{Mantle}}\right)=1\) applies to (A).