Snow as a foam of ice: Plasticity, fracture and the brittle-to-ductile transition

At strain rates lower than 10−4 s−1. snow deforms plastically and fractures in a ductile manner; at higher strain rates it is brittle. The brittle-to-ductile transition has an activation energy of 0.6 ± 0.1 eV. Plasticity preceding fracture is characterized by an activation energy of 0.6 ± 0.05 eV for temperatures below –6°C. and about 2.7 ± 0.4eV above. The basic deformation mechanism of snow. an ice foam, is power-law creep of ice. As in silicon, the activation energy of the brittle-to-ductile transition is the lowest of the activation energies of all deformation processes available, but in ice these are the same, 0.6eV, for dislocation glide diffusion and sublimation.