Since about 1970, Plate Tectonics - the notion that Earth?s surface is comprised of large, rigid plates that are created at mid-ocean ridges and consumed at trenches - has been the ?standard model? for how the Earth works. Plate motions are known to be a manifestation of thermal convection ? flow driven by high temperatures - but the details of this fundamental process remain poorly understood. The very novel hypothesis that inspires this project is that the uppermost mantle of the Earth, just beneath the plates has been flooded by hot, fluid material supplied by plumes rising from the lower mantle. The project will use 3D numerical experiments to assess the plume fed asthenosphere model (PFA) and its various implications for a wide range of processes. In addition to its contribution to our understanding of Earth processes at the most fundamental level, the broader impacts of this project include contributions to other, related research topics, the development of new computer codes, training a graduate student and participation by undergraduate students.