What is the primary cause of ocean currents?

The primary cause of ocean currents is the wind, which creates friction on the surface of the ocean. As the wind blows across the water, it transfers energy to the water molecules, causing them to move in the same direction as the wind. This movement generates surface currents, which can be further influenced by the Earth's rotation (through the Coriolis effect), landmasses, and variations in water temperature and salinity.

While the moon's gravitational pull influences tides, it does not primarily drive the consistent flow of currents in the ocean. Ocean salinity variations do affect water density, which can create currents, but these thermohaline currents are secondary to the wind-driven surface currents. Underwater volcanic activity can create localized currents but is not a primary driver of the larger ocean currents that are mainly influenced by surface wind patterns.