Superpiles: The Impact of Mantle Cooling on Large Low Velocity Provinces

Among the most prevalent features in Earth’s deep mantle are the Large Low Velocity Provinces (LLVPs), hypothesized to be hotter and compositionally distinct from the surrounding mantle ^1–4 . LLVPs have previously been viewed as either active superplumes rising through the mantle or passive piles shaped by large scale convection ^5–10 . Recent tomography models suggest LLVPs may exhibit a plume-shaped morphology ¹¹ . Geodynamic experiments offer insights into the formation, characteristics, and evolution of mantle structures. This study investigates whether LLVPs are active drivers of mantle convection or passively shaped by the convection of the surrounding mantle. Here we show LLVPs can form passive piles with plume-shaped morphology, even with small intrinsic density differences. Our results reveal that an initially warm, cooling mantle supports the formation of passive superpiles with intrinsic density differences smaller than previously thought. We refer to these as superpiles. This indicates that the background mantle temperature plays a crucial role in determining LLVP morphology. These findings suggest that the observed plume-like shapes of LLVPs in recent tomography models that have been thought to be superplumes could be superpiles.