Fig. 1
From: Crystal plasticity as an indicator of the viscous-brittle transition in magmas
Schematic representation of a dislocation in a crystal lattice. Here an edge dislocation forms and propagates through the lattice for simplicity, but screw dislocations are also common. The stages show: a isostatic stress conditions, and no deformation; b differential stress applied, leading to elastic strain; c yielding occurs under applied stress, creating a dislocation; d the dislocation migrates under differential stress conditions; e the dislocation passes through, resulting in distortion and f upon return to isostatic stress conditions, elastic strain is recovered. Dislocations that have passed through as in f leave a shape change but no internal distortion, however, significant densities of dislocations stranded within the lattice at stages c–d give rise to macroscopic lattice distortion as documented here
