Dynamics of longitudinal Hawaiian hotspot motion and the formation of the Hawaiian-Emperor Bend

Formation of the Hawaiian-Emperor Bend has been a key geological puzzle that involves both plate tectonics and plume dynamics. Constrained by paleomagnetic data, southward hotspot motion has been considered a major contributor to the formation of the bend, but the role of longitudinal hotspot motion remains largely overlooked. Here, using geometric analysis with constraints from plate kinematics, we show a significant longitudinal hotspot motion is required to fit the Hawaiian-Emperor Chain. Further application of global mantle convection models reveals a westward (by ~6°) and then an eastward (by ~2°) hotspot drift in addition to the southward motion before and after the bend, with the westward motion primarily controlled by the intraoceanic subduction in Northeast Pacific. While both the westward and southward motion are required to fit the seamount chain, the former contributes ~20 degrees to the bend angle, larger than the later, challenging traditional views. Combining geodynamically-predicted Pacific Plate motion change at 47 Ma, our model provides a nearly perfect fit to the seamount chain, suggesting plate-mantle reorientation as the ultimate cause. It also suggests that the Hawaiian plume conduit is tilted towards the southwest, solving the long-lasting debate on the source of the Hawaiian plume among seismological studies.