Mantle Viscosity: What are We Exactly Looking for?
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Any rheological law must obey the principles of local action, objectivity, and macroscopic determinism, with possible hidden intrinsic variables, as are the lapse of time since loading or unloading, or the past load. Among ten different microscopic processes of creep that are reviewed, non-linear creep by motion of dislocations with dynamic recrystallization is the most plausible. It includes transient creep, that has been studied in rock ice: Andrade’s creep on loading, and reverse logarithmic creep on unloading. Only part of the extra strain on loading is recoverable. After a change in one component of stress, transient creep is observed on all the components. Similarly, the mantle should not be a linear visco-elastic body. When it is modelled as such, the analyses of isostatic adjustments allow to determine apparent visco-elastic parameters at a given instant, but they change with time and have no predictive value.
KeywordsSlip System Deviatoric Stress Simple Shear Lower Mantle Mantle Convection
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A good short introduction to the subject might be:
The extensive literature on the subject is quoted in:
- Peltier, W.R. ed. (1989) Mantle convection, plate tectonics and global dynamics, Gordon and Breach Sci. Publ., New York.Google Scholar
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