Earth's mantle plasticity explained
Earth's mantle is a solid layer that undergoes slow, continuous convective motion. But how do these rocks deform, thus making such motion possible, given that minerals such as olivine (the main constituent of the upper mantle) do not exhibit enough defects in their crystal lattice to explain the deformations observed in nature? A team led by the Unité Matériaux et Transformations has provided an unexpected answer to this question. It involves little known and hitherto neglected crystal defects, known as 'disclinations', which are located at the boundaries between the mineral grains that make up rocks. Focusing on olivine, the researchers have for the first time managed to observe such defects and model the behavior of grain boundaries when subjected to a mechanical stress. The findings, which have just been published in Nature, go well beyond the scope of the geosciences: they provide a new, extremely powerful tool for the study...
