Among the most exciting and unexpected findings related to plate tectonics was the discovery of the hydrothermal vents that populate the earth?s mid-ocean ridge system. Not only do these deep hot springs support a variety of exotic life forms, they are now known to be a primary means by which heat is extracted from the earth?s interior and to be a primary means of chemical exchange between the seafloor and the oceans. But just how heat is supplied to these systems, and how they relate to the tectonic environment remains poorly understood. This project will employ a combination of 3D and 2D high resolution seismic tomography, 2D multichannel reflection and micro-earthquake modeling define the relationship between magmatism, faulting, substrate lithology (rock types) and hydrothermal circulation at the Rainbow Hydrothermal Field on the Mid Atlantic Ridge. This integrated approach is designed to test several hypotheses related to hydrothermal activity and its relationship to the geological environment. Broader impacts include a substantial contribution to international studies of the mid-ocean ridge system, support for two Ph.D. thesis projects and experience for undergraduate interns.