A supercontinent with a keel down to the mantle transition zone (~400 km) is assumed to have existed during the early Archean (~4. 0 Ga). The supercontinent (Rodinia?) was thinned and finally split into fragments with highly variable thicknesses (150~350 km) and sizes (1×106~17 ×106 km2) during the early and middle Proterozoic. Each fragment or craton is characterized by a thick Archean lithosphere surrounded by thin Proterozoic mobile belts. It is emphasized that the lithospheric thickness is a more complicated concept than has been generally considered. The lithospheric thicknesses determined using different techniques (e. g., petrology, geochemistry, S-wave tomography, wave receiver functions, low velocity zone, geothermal data, rheology, electrical conductivity, and water content) can contradict each other. Any conclusion about the lithospheric thinning obtained from a single technique should be cross-checked by other methods.
