Final answer:
The largest lithospheric plates have various movement directions, shaped by the type of plate boundaries. The Juan de Fuca Plate, in a convergent boundary with the North American Plate, is subducting beneath it, leading to volcanic activity and the formation of the Cascade Range.
Step-by-step explanation:
The largest lithospheric plates include the Pacific Plate, North American Plate, Eurasian Plate, African Plate, Antarctic Plate, Indo-Australian Plate, and the South American Plate. These plates exhibit movement in various directions: the Pacific Plate is moving northwest, the North American Plate is moving west-southwest, and others each have their distinctive movement patterns based on their interactions at plate boundaries.
Along the West coast of North America, we find several types of plate boundaries. Starting from the Gulf of California and moving northward to British Columbia, there are transform boundaries marked by the San Andreas Fault system, divergent boundaries exemplified by the spreading center in the Gulf of California, and convergent boundaries illustrated by the subduction zone where the Juan de Fuca Plate is being pushed beneath the North American Plate.
As for the Juan de Fuca Plate, it is sitting in a convergent plate boundary and is moving east-northeast towards the North American Plate. Given this movement, the ultimate fate of the Juan de Fuca Plate is to be fully subducted beneath the North American Plate, which could potentially lead to the formation of new mountain ranges or volcanic activity in the region. This subduction process is also responsible for the formation of the Cascade Range, which includes volcanic mountains such as Mt. St. Helens, due to the upward movement of melted mantle material that forms magmas and consequent volcanic eruptions.