Fresh-water S1 ice has been slowly compressed uniaxially across the co
lumns at -10 degrees C (T-h = 0.96). Orowan-type deformation kinks wer
e observed and cracks were detected on the kink band boundaries. Each
crack was associated with a step in the boundary. Nucleation of these
cracks is explained in terms of a Stroh-type dislocation pile-up mecha
nism.