Final answer:
Mount Rainier is located above a convergent plate boundary where the Juan de Fuca plate is subducting beneath the North American Plate, leading to the formation of the Cascade Range.
Step-by-step explanation:
Mount Rainier is located above a convergent plate boundary. Specifically, it sits above the boundary where the Juan de Fuca plate is subducting beneath the North American Plate. This tectonic setting is responsible for the formation of the Cascade Range, which includes Mount Rainier and other prominent volcanoes like Mount St. Helens. The relative movement along this boundary involves the oceanic Juan de Fuca Plate moving towards and being forced under the continental North American Plate, a process known as subduction.
The ultimate fate of the Juan de Fuca plate is complete subduction beneath the North American Plate, with the subducted material eventually melting and contributing to the magma that can fuel volcanic eruptions such as those seen in the Cascade Range. The tectonic processes that formed the Cascade Range involve the subduction of the Juan de Fuca Plate, leading to the melting of the mantle and crust which produces magmatic activity and has given rise to the volcanic mountains in this region.