A physical basis for the sharp bend that characterizes the geometry of the Hawaiian-Emperor hotspot track in the north Pacific Ocean is presented in a study published in Nature this week. Volcanoes that form away from tectonic plate boundaries are thought to be the surface manifestation of mantle plumes - hot magma rising from deep within the Earth. As tectonic plates move over these ‘hotspots’, new volcanoes progressively form.

Several mechanisms have been proposed to explain the peculiar bend in the Hawaiian-Emperor hotspot track in the north Pacific, but the underlying mantle flow dynamics have remained enigmatic.

Dietmar Muller and colleagues followed the trajectory and tilt of mantle plumes over the past 230 million years using numerical models of mantle convection. They find that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 and 50 million years ago and that this occurred as a consequence of long-lasting subduction systems (whereby one plate dives below another plate). Their models suggest that the sharp bend in the Hawaiian-Emperor hotspot track can be explained by the interplay between plume tilt and the lateral migration of plume sources.