Viscosity-depth profiles according to the Ree-Eyring viscosity relations

The relative viscosity ηr, referred to the viscosity η(0) for surface conditions (p = 0, T ∼ 300°K), was computed as a function of depth z from the Ree-Eyring viscosity relations assuming chemical uniformity in the crust and mantle, the Jeffreys-Gutenberg p-T-z relations for the earth, and various values of the heats and volumes of activation, ΔH≠ and ΔV≠, respectively. The calculated (depth) average relative viscosity 〈ηr〉 averaged over the crust and upper mantle to 1000-km depth was 10−3 to 10−4 for an allowable lower limit of ΔH≠; this indicates that most of the resistance to plastic flow in crustal uplifts occurs in the crust itself. The Kee-Eyring theory indicates a relative viscosity ηr( = η/η (0)) of about 10−12 at 35 km depth and 10−15 at about 150 km depth. It also predicts a maximum fluidity in the mantle at a depth of about 150 km for a reasonable value of ΔV≠ (1.0 to 10 cm3/mole). The average viscosity obtained from the Fennoscandia and Canadian uplifts (∼1022 poises) is interpreted from these results to mean that η(0) is about 1025 to 1026 poises, η(35 km) about 1014 poises, and η(150 km) about 1011 poises.