On Dislocation Climb as an Important Deformation Mechanism for Planetary Interiors

An understanding of the rheological behavior of the solid Earth is fundamental to provide a quantitative description of most geological and geophysical phenomena. The continuum mechanics approach to describing large-scale phenomena needs to be informed by a description of the mechanisms operating at the atomic scale. These involve crystal defects, mainly vacancies and dislocations. This often leads to a binary view of creep reduced to diffusion creep or dislocation creep. However, the interaction between these two types of defects leading to dislocation climb plays an important role, and may even be the main one, in the high-temperature, low strain rate creep mechanisms of interest to the Earth sciences. Here we review the fundamentals of dislocation climb, highlighting the specific problems of minerals. We discuss the importance of computer simulations, informed by experiments, for accurately modeling climb. We show how dislocation climb increasingly appears as a deformation mechanism in its own right. We review the contribution of this mechanism to mineral deformation, particularly in Earth's mantle. Finally, we discuss progress and challenges, and we outline future work directions. ▪ Dislocations can be sources or sinks of vacancies, resulting in a displacement out of the glide plane: climb. ▪ Dislocation climb can be a recovery mechanism during dislocation creep but also a strain-producing mechanism. ▪ The slow natural strain rates promote the contribution of climb, which is controlled by diffusion. ▪ In planetary interiors where dislocation glide can be inhibited by pressure, dislocation climb may be the only active mechanism.