the layer of the earth where mantle convection occurs and on which the earth's crust rests is the
The asthenosphere is the highly viscous mechanically weak ductility-deforming region of the upper mantle of the Earth. It lies below the lithosphere, at depths between 100 and 200 km (~62 and 124 miles) below the surface, but perhaps extending as deep as 700 km (~435 miles).The asthenosphere is a portion of the upper mantle just below the lithosphere that is involve in plate tectonic movements and isostatic adjustments. In spite of its heat, pressures keep it plastic. Hope this helps.