Fig. 2

The lateral variations in the surface heat flow and convecting flow structure. a The distribution of the inverse square of the surface heat flow shown in both colour and white contour lines. b The plot of the inverse square of heat flow at the surface as a function of the distance L from the divergent plate boundary (ridge) along a horizontal track indicated by the dashed line in a. Also shown by the dash-dotted line is the theoretical prediction from the half-space cooling for small L, while by the dashed line is the deviation from it for large L. c The distribution of vertical component of velocity \(V_z\) on the horizontal plane at the height of \(z=0.672\)