Rheology of the Mantle

There have been two main avenues of investigation of the rheology of the mantle: theoretical and laboratory studies of the mechanical behavior of solids and direct estimates obtained by comparing geologic observations with model calculations in which rheological parameters are the principal variables. Studies of large-scale mantle flow, such as convection, might also put some constraints on mantle rheology, although at the present better knowledge of the rheology is needed to specify suitable models for investigation. The main advances of the last 4 years in our understanding of mantle rheology have been in the realization that the lower mantle may be less resistant to creep than was previously believed and in the realization and preliminary investigation of the complexities of the convection problem