| Summary: | Deformation of anisotropic rocks, ice and metals mainly occurs by crystal-plastic mechanisms, where crystals dominantly deform by glide of dislocations in crystal slip planes. However, understanding and predicting the deformation of anisotropic rocks is not straightforward, especially because their behaviour under stress is very complex. This is mainly due to: the variety of deformation mechanisms that operate in polycrystalline materials, the range of deformation conditions (pressure, temperature, kinematics of deformation, etc.) that affect them, which in fact change the balance between deformation processes, the variety of resulting anisotropy and microstructures, which in turn alter the mechanical properties of the deforming rock Two fundamental scientific problems nowadays are: how do different deformation mechanisms operate and interact in rocks? how are the rheological properties at the micro- scale control the large-scale rock behaviour? Ice is one of the most common minerals found on the Earth’s surface. It has been widely used as an analogue for quartz- or olivine-rich rocks, as all these minerals deform following similar mechanisms resulting in non-linear flow laws. The study of polar ice gives us valuable information as we can directly link the measured strain rate in ice sheets with the microstructures observed from ice drill cores and the seismic velocities estimated in ice sheets. By numerical simulations of ice microstructure evolution during deformation and recrystallisation, we demonstrate that the mechanical anisotropy at the crystal scale is transferred to the scale of the polycrystalline rock. Mechanical anisotropy has an enormous impact on understanding and predicting localisation of deformation at different scales (Jansen et al., 2016; Llorens et al., 2016), rock strength (Llorens et al., 2017) and seismic velocity estimations (Llorens et al., 2020). These are all key for forecasting ice-sheet flow to the oceans, and for understanding past climate changes and predicting future ones. ...
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