Grain to grain variations in elastic moduli cause stress to percolate in polycrystalline materials much as is observed in granular materials. The presence of percolation causes shear localization and also provides a template for foliation development in metamorphic rocks. In addition, stress percolation provides a framework for modeling aggregate behavior over multiple-length scales based on single-crystal properties.
The figure shows variations in the direction and magnitude of the principle components of the stress tensor. The most compressive stress is blue, the least compressive stress is orange.
Hunt, et al., 2012, EPSL,v. 319-320, p. 96-103
Non-dimensional temperature difference between simulations when thermal diffusivity of post-perovskite is doubled; red: hotter and blue: colder. Grey area shows the change in extent of the post-pervoskite lens when thepost-perovskite thermal diffusivity is twice that of perovskite.