Plume-Tree Structure Induced by Low-Viscosity Layers in the Upper Mantle

Previous seismological results and geodynamic modeling showed that mantle plumes have thin tails. However, the latest geophysical observations reveal the presence of broad and bifurcate plumes in the lower and upper mantle, providing a new challenge to further understand the evolution of plume morphology. Here, developing 3-D numerical models, we demonstrate that a plume shaped like a tree, derived from the mantle transition zone, branches up to surface volcanoes due to the combined influence of weak layers in the asthenosphere and the mantle transition zone. Clusters of mantle plumes likely explain the simultaneous occurrence of multiple subparallel hot spot tracks in the Pacific and Atlantic Oceans. Meanwhile, the mantle plume wandering at a rate of similar to 1.5 cm/year in the upper mantle without a strong mantle wind provides a new mechanism for hot spot motions. Thus, our model represents a significant advance for linking plume studies in seismology, geochemistry, and plate reconstruction.