The oceanic trench which marks the boundary between the N. American Plate and the Pacific Plate. The subduction of the Pacific Plate changes from normal to oblique from west to east along the trench, with the boundary becoming a transform fault before subduction continues in the Kuril Trench. Towards the eastern end of the Aleutian Trench there is an increasingly wide accretionary wedge, and an absence of andesitic volcanoes.