| Summary: | Ph.D. Two plates converge at oceanic trenches with the expected result that the denser plate descends into the upper mantle beneath the less dense plate in a process known as subduction. However, when anomalously thick oceanic material, such as an oceanic plateau, begins subduction, the exact nature of how the oceanic plateau affects the subducting slab and upper plate is not well understood. If the oceanic plateau is positively buoyant it will tend to resist subduction which may cause a reduction in subducting plate speed; in some cases, slab break-off followed by accretion of the plateau to the upper plate or a reversal in subduction polarity. Depending on the subduction system, plateau dimensions and density structure, oceanic plateaus can subduct, which may lead to changes in slab morphology, changes in plate motion, and may drive far-field deformation in the overriding plate. The convergent margin in south-central Alaska is marked by oblique flat slab subduction of the Pacific plate and Yakutat oceanic plateau beneath the overriding Wrangell block forearc sliver and the North American plate. Both flat slab subduction of young seafloor and subduction of an oceanic plateau can cause an overall increase in slab buoyancy that may lead to an increase in coupling to the base of the overriding plate and significant upper plate deformation.
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