Yellowstone Plume Conduit Tilt Caused by Large-Scale Mantle Flow

Mantle plumes are hot upwellings of rock thought to originate at the core-mantle boundary. As they rise through the mantle, their conduits may become tilted due to lateral large-scale mantle flow. Recent tomographic images have revealed a strongly tilted plume conduit starting at the core-mantle boundary beneath northern Baja California rising toward the Yellowstone hot spot from the southwest. Here we perform numerical computations of plumes deflected in large-scale mantle flow with the aim of finding if realistic model parameter ranges exist that yield a good fit with the tomographically observed conduit. We restrict ourselves to models that yield reasonable results for plume conduit tilt and hot spot motion globally. These models require high viscosity approximate to 10(23) Pa s at some lower mantle depths. For a plume head reaching the surface 17 Ma, corresponding to the start of the Columbia River Basalts, our models require rise times approximate to 80 Myr or longer to match the tilt of the conduit observed by tomography. We used several tomography models to determine mantle density with almost all models predicting southwestward flow in the lowermost mantle beneath the western United States. Exact details of the shape of the predicted conduit's southwesterly tilt vary, depending on the density and viscosity structures we used. In many cases we find comparatively strong tilts in two depth ranges, in the upper and lower portions of the mantle, which is also a characteristic of the tomographically observed conduit. We expect that future models may help to constrain large-scale flow by matching these corresponding depth ranges.