This relatively slim Special Publication covers a broad topic in rock deformation: why some deformation is distributed through large rock volumes and other deformation is localized in narrow zones. The focus of the 12 collected papers is on the upper crust. Deformation here is classically envisaged as ‘brittle’ rather than ‘ductile’, though the volume shows that this view is over-simplified. There are few definitive answers in this collection to problems of upper crustal deformation, but some stimulating papers that better define some good questions to ask.

A number of themes recur through the volume. The scale-dependency of ‘damage’ and ‘localization’ is most problematic, with localized deformation at one scale typically comprising a distributed damage zone at a smaller scale. Mechanistically, an important theme is the distinction between materials that strain harden, and therefore distribute damage, or strain soften and therefore localize it. One important control on such behaviour is whether a rock needs to dilate during deformation or whether it can compact due to an initially loose grain packing. A major theme is that texture and mechanical behaviour of materials evolves during deformation, so that deformation is non-linear. If there is a unifying theme through the volume, it is that this non-linearity allows deforming rocks to be seen as self-organizing systems, striving to achieve some least work condition.

Collections of papers into thematic volumes too often suffer from too much diversity and not enough cohesion. That risk in this collection is averted by an excellent introduction by the editors. Such introductions can sometimes be little more that a linked list of contributing authors. Instead, Couples and Lewis provide a thoughtful and incisive review, clearly outlining the problems of damage and localization and signposting future research directions. Supported by a strong set of papers, this volume is therefore a useful addition to the literature on rock deformation.