Accurate models for the incision of the Grand Canyon must includecharacterization of tectonic influences on incision dynamicssuch as active faulting and mantle to surface fluid interconnections.These young tectonic features support other geologic data thatindicate that the Grand Canyon has been carved in the past 6Ma. New U-Pb dates on speleothems are reinterpreted here interms of improved geologic constraints and understanding ofthe modern aquifer. The combined data suggest that Grand Canyonincision rates have been relatively steady since 3-4 Ma.Differences in rates in the eastern (175-250 m/Ma) andwestern (50-80 m/Ma) Grand Canyon are explained by Neogenefault block uplift across the Toroweap-Hurricane system. Mantletomography shows an abrupt step in mantle velocities near theColorado Plateau edge, and geodynamic modeling suggests thatupwelling asthenosphere is driving uplift of the Colorado Plateaumargin relative to the Basin and Range. Our model for dynamicsurface uplift in the past 6 Ma contrasts with the notion ofpassive incision of the Grand Canyon due solely to river integrationand geomorphic response to base-level fall.