Compare rivers and surface currents.

B. Surface currents are controlled by three factors: global winds, the Coriolis effect, and continental deflections. surface create surface currents in the ocean. Different winds cause currents to flow in different directions. objects from a straight path due to the Earth's rotation

It should be at the center of any map going vertically: the prime meridian, as it passes through greenwich,  england, is considered 0 degrees longitude