 Thus, Daly's asthenosphere was inferred to be 120 to 400 km thick.According to Daly, the base of the solid earth mesosphere could extend to the base of the mantle (and, thus, to the top of the core).Isacks, Oliver, and Sykes (1968) applied lithosphere and asthenosphere to their conception to the “New Global Tectonics” or what subsequently became known as plate tectonics.