The concurrent emergence and causes of double volcanic hotspot tracks on the Pacific plate

The emergence of geographically and geochemically distinct double volcanic chains on the Pacific plate coincides with a recent azimuthal change in the motion of the plate. Double hotspot mystery Volcanic hotspots in regions that are not associated with plate tectonics are widely thought to be surface expressions of thermochemical upwellings from the deep Earth. But the emergence of the double Loa and Kea tracks of volcanism along the Hawaiian–Emperor hotspot island chain, and the systematic geochemical differences between them, remain enigmatic. Timothy Jones et al . show that the emergence of these and other double volcanic tracks on the Pacific plate coincides with a recent change in Pacific plate motion. They propose that mantle flow beneath the rapidly moving Pacific plate strongly tilts the Hawaiian plume and leads to lateral separation between high- and low-pressure melt source regions, producing the geographically and geochemically distinct volcanic chains. Mantle plumes are buoyant upwellings of hot rock that transport heat from Earth’s core to its surface, generating anomalous regions of volcanism that are not directly associated with plate tectonic processes. The best-studied example is the Hawaiian–Emperor chain, but the emergence of two sub-parallel volcanic tracks along this chain 1 , Loa and Kea, and the systematic geochemical differences between them 2 , 3 have remained unexplained. Here we argue that the emergence of these tracks coincides with the appearance of other double volcanic tracks on the Pacific plate and a recent azimuthal change in the motion of the plate. We propose a three-part model that explains the evolution of Hawaiian double-track volcanism: first, mantle flow beneath the rapidly moving Pacific plate strongly tilts the Hawaiian plume and leads to lateral separation between high- and low-pressure melt source regions; second, the recent azimuthal change in Pacific plate motion exposes high- and low-pressure melt products as geographically distinct volcanoes, explaining the simultaneous emergence of double-track volcanism across the Pacific; and finally, secondary pyroxenite, which is formed as eclogite melt reacts with peridotite 4 , dominates the low-pressure melt region beneath Loa-track volcanism, yielding the systematic geochemical differences observed between Loa- and Kea-type lavas 3 , 5 , 6 , 7 , 8 , 9 . Our results imply that the formation of double-track volcanism is transitory and can be used to identify and place