It has long been assumed that basal dislocations were responsible for the deformation of layered, crystalline solids. Herein we make the case that, with the notable exception of some metals that kink, ripplocations - not basal dislocations - are the operative micromechanism. The reasons are: i) clear evidence for c-axis strain at multiple length scales including in transmission electron microscopy images; ii) strong influence of confining pressure on the compressive strengths of poly-, and especially single crystals; iii) ripplocations are a topological imperative if the layers are to move relative to each other, without breaking the in-plane bonds. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
