The trace of the Snake River-Yellowstone hot spot is the world's best example of a mantle plume that has been overridden by continental lithosphere. The "standard model" calls for the plume head to rise under northern Nevada and be forced northward to form basalts of the Columbia Plateau; subsequent movement of North America to the southwest over the plume tail created a hot spot trace on the surface. We present a new conceptual model for the origin of this feature that resolves inconsistencies in the current standard model and explains the recent documentation of a thermal anomaly in the mantle below Yellowstone today that plunges ∼ 65° WNW. Our model implies that the plume tail was forced beneath thinned cratonic lithosphere to the SE along with part of the plume head and has remained in this orientation for the last 12 Ma. We infer that almost all of the voicanism in SE Oregon and SW Idaho prior to 12 Ma results from overriding the southern extension of the plume head, not the plume tail, and that a distinct plume tail hot spot track was not established until formation of the Bruneau-Jarbidge eruptive center around 12 Ma. The plume tail track may also be controlled by a preexisting structural boundary in lithosphere that is thinner than adjacent lithosphere. This model demonstrates the potential importance of lithospheric topography on controlling the surface manifestation of plume volcanism and the complexity that may arise when lithospheric thickness is nonuniform.
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