Evolution of congested subduction zones and their influence on the Cretaceous and Neogene tectonics of New Zealand WILLISDAVID MICHAEL 2017 The movement of tectonic plates over the surface of the Earth is driven by subduction. Subduction returns oceanic crust into the mantle, producing earthquakes, magmatism, and deformation driving mountain building, or basin formation in the adjacent plate. Areas where the oceanic crust is anomalously buoyant are associated with increased uplift, and mountain building processes. This thesis uses numerical models to explore why subduction of buoyant oceanic crust is uplift is associated with uplift and mountain building, and applies the results to mountain building processes in New Zealand.