Gondwanaland was buoyant, as indicated by nonmarine facies, and Laurasia was depressed, as indicated by marine facies. As a supercontinent, Gondwanaland lasted much longer than Laurasia and was hotter from internal heat. Moreover, the Pan-African orogenic cycle, confined to Gondwanaland, augmented the heat supply, which possibly generated a permanently buoyant lower crust by underplating. A crustal layer in the Australian Proterozoic shield with subhorizontal reflectors and velocity (Vp) >7.5 km/s is interpreted as mafic underplating beneath latest Neoproterozoic flood basalt. The Pan-African terrane in East Africa also contains evidence of mafic underplating, and most of Gondwanaland (but not Laurasia) was affected by terminal Pan-African (0.5 Ga) uplift and cooling.