Extent of correlated dislocation avalanches in the asthenosphere

Determine how large spatiotemporally correlated dislocation avalanches may become in olivine within Earth’s asthenospheric upper mantle under high-temperature, low–strain-rate conditions, including the maximum spatial scale and potential propagation beyond individual grains given the large system size and long available timescales.

Background

The paper applies the mild-to-wild plasticity framework to olivine, demonstrating measurable wildness at room temperature via nanoindentation and predicting that wildness should increase with depth due to reduced lattice resistance in the asthenosphere. Under these conditions, plasticity is expected to be extremely wild, with dislocation avalanches likely occurring at least up to grain size.

Drawing an analogy to ice—the wild endmember where avalanches are confined to grains but exhibit correlations beyond grain size—the authors highlight that in the asthenosphere the system size and timescales are large. This motivates the unresolved question of the upper bound on the size and correlation extent of dislocation avalanche cascades in asthenospheric olivine.

References

It remains an open question as to how large these correlated dislocation avalanches may become in the asthenosphere, where the system size is large and long timescales are available to capture low-probability events.

— Mild-to-wild plasticity of Earth's upper mantle  (2406.10092 - Wallis et al., 2024) in Section “Mild-to-wild plasticity in the upper mantle,” paragraph following Fig. 4 (approx. page 9)