X-ray Topographic Observations of Edge Dislocation Glide on Non-basal Planes in Ice

White synchrotron X-radiation topography has been used to observe the motion of dislocations in single crystals of ice under a compressive stress in the [1 1 00] direction, for which there is no resolved stress on the basal plane. Dislocations with [1 2 10] and [ 2 110] Burgers vectors were nucleated from surface scratches, and their edge components were observed to glide on non-basal planes, which may be prismatic or may have unspecific pyramidal character. Screw components are not mobile on such planes.