Answer the following question given this paragraph: 

Like air in the atmosphere, ocean water moves in currents. A current is a stream of moving water that flows through the ocean. Surface currents are caused mainly by winds but not daily winds. Surface currents are caused by the major wind belts. These winds blow in the same direction all the time. So they can keep water moving in the same direction.


Q: What are surface currents generally caused by?


A:
major wind belts