The depths of the 410 and 660 km discontinuities beneath the Yellowstone hotspot are constrained using common conversion point imaging of P-wave receiver functions. The mean depth of the 410 and 660 is 411 ¿ 1.5 km and 656 ¿ 1.6 km, with 36--40 km of peak to peak topography. This topography is spatially uncorrelated, providing no evidence for a lower mantle plume currently beneath the hotspot. The topography suggests that ¿200¿C thermal anomalies exist with respect to an average mantle adiabat. Two warmer than normal regions are found: at the 410 to the NNW of the hotspot and at the 660 to the NE. Colder temperatures exist at the 410 under central Wyoming. Upper mantle convection and/or intermittent heat and mass transfer across the 660 may be responsible for the uncorrelated topography. Three negative arrivals about the 410 and 660 are observed that display correct Pds moveout.