Strength Profile:
The strength of lithospheric material depends on (1) the nature of the deformation (material are stronger when they are squeezed, weaker when they are stretched), (2) the mineralogical composition, and (3) the geotherm (the strength decreases when temperature increases).
The continental crust is characterised by a strong brittle upper crust and weak ductile lower crust
The upper mantle is strong as long as the temperature at the Moho does not exceed 650ºC. It is weak when the temperature at the Moho is close to 700ºC and above. The lower lithospheric mantle is extremely weak which explains why the lower part of the lithospheric mantle can be dragged into the convecting asthenosphere. The asthenosphere is very weak.