Final answer:
The direction of the longshore current along the coastlines of the Fuca is influenced by the angle at which waves approach the shore and the prevailing wind direction, with potential effects from the northward movement of the Pacific tectonic plate.
Step-by-step explanation:
The direction of the longshore current along the coastlines of the Fuca would likely be determined by the prevailing wind direction and the angle of wave approach. Longshore currents are generated when waves hit the shore at an angle, moving water and sediment down the coastline. In the case of the Pacific, where storms in the South Pacific can generate large waves, the longshore current would depend on these specific wave angles as they reach the coastline. Considering the Pacific tectonic plate's northward movement, it's possible that some of the longshore currents along the Fuca could follow this general direction, but local wind conditions and coastal geometry would also be significant factors.