Propagating compaction bands in confined compression of snow

Some materials are strong in response to a slowly applied deformation, yet weak when subject to rapid deformations-a materials property known as strain-rate softening(1). Snow exhibits such behaviour: it is comparatively strong at lowdeformation rates, where it is quasi-plastic, but weak at high rates, where it deforms in a quasi-brittle manner(2). During deformation, strain-rate-softening materials ranging from metals(3,4) to micellar systems(5) exhibit complex spatio-temporal deformation patterns, including regular or chaotic deformation-rate oscillations and travelling deformation waves(6). Here we report a systematic investigation of such phenomena in snow and showthat snowcan deform with the formation and propagation of localized deformation bands accompanied by oscillations of the driving force. We propose a model that accounts for these observations. Our findings demonstrate that in snow, strain localization can occur even in initially homogeneous samples deforming under homogeneous loads.