Patterns of intraplate volcanism controlled by asthenospheric shear

Abstract

Volcanism observed far from plate boundaries, in the interior of oceanic and continental plates, may result from flow in the underlying mantle. Comparison between a numerical model of mantle flow and the spatial distribution of intraplate volcanism indicates that rapid shear motion in the mantle may drive melting that causes intraplate eruptions. Most of Earth’s volcanism occurs at plate boundaries, in association with subduction or rifting. A few high-volume volcanic fields are observed both at plate boundaries and within plates, fed by plumes upwelling from the deep mantle1. The remaining volcanism is observed away from plate boundaries. It is typically basaltic, effusive and low volume, occurring within continental interiors2,3,4,5,6,7 or creating seamounts on the ocean floor8,9,10,11. This intraplate volcanism has been attributed to various localized processes12 such as cracking of the lithosphere8,13,14, small-scale convection in the mantle beneath the lithosphere15,16,17 or shear-induced melting of low-viscosity pockets of asthenospheric mantle that have become embedded along the base of the lithosphere18. Here we compare the locations of observed intraplate volcanism with global patterns of mantle flow from a numerical model. We find a correlation between recent continental and oceanic intraplate volcanism and areas of the asthenosphere that are experiencing rapid shear due to mantle convection. We detect particularly high correlations in the interior of the continents of western North America, eastern Australia, southern Europe and Antarctica, as well as west of the East Pacific Rise in the Pacific Ocean. We conclude that intraplate volcanism associated with mantle convection is best explained by melting caused by shear flow within the asthenosphere, whereas other localized processes are less important.