Narrow, fast, and “cool” mantle plumes caused by strain‐weakening rheology in Earth’s lower mantle

The rheological properties of Earth's lower mantle are key for dynamics and planetary evolution. main rock-forming minerals in the bridgmanite (Br) smaller amounts ferropericlase (Fp). Previous work has suggested that large differences viscosity between these greatly affect bulk rock rheology. resulting effective rheology becomes highly strain-dependent as weaker Fp become elongated eventually interconnected. This implies strain localization may occur mantle. So far, there have been no studies on global-scale convection presence such strain-weakening (SW) Here, we present 2D numerical models thermo-chemical spherical annulus geometry including a new formulation materials, combining weakening healing terms. We find SW several direct indirect effects convection. most notable effect is changing weakened plume channels well formation larger thermochemical piles at base conduits act lubrication exhibit thermal anomaly. also reduces overall viscosity, terms increasing convective vigor core-mantle boundary heat flux. Finally, put our results into context with existing hypotheses style mixing. Most importantly, suggest kind explain discrepancy expected observed anomalies deep-seated plumes Earth.