mantle is 24.0 GPa compared to the bottom of the mantle, which is 136 GPa.

Estimates for the viscosity of the upper mantle range between 10¹⁹ and 10²⁴ Pa·s, depending on depth, temperature, composition, state of stress, and numerous other factors. The upper mantle can only flow very slowly. However, when large forces are applied to the uppermost mantle, it can become weaker, and this effect is thought to be important in allowing the formation of tectonic plate