Name: _____________________________________ Date: _________________ Period: ______
A current is a steady movement of water in a specific direction. In the ocean there are two major
types of currents; they are surface and deep currents. Surface currents move on or near the
surface of the ocean and are driven by winds. Deep currents move very slowly beneath the
surface of the ocean and are caused by differences in the density of the water.
Surface currents are controlled by three factors; the wind belts, the earth’s rotational effects, and
the location of the continents. The two wind belts that affect the surface currents the most are the
trade winds and the westerlies. The trade winds are located just north and south of the equator,
and the westerlies are located in the middle latitudes. (Page 428)
The Coriolis effect also contributes to the motion of surface currents. It is the deflection of the
earth’s winds and ocean currents caused by the earth’s rotation. As a result of the Coriolis effect
and wind belts, huge circles of moving water called gyres are formed. In the northern hemisphere
the flow of water in these circles is clockwise, and in the southern hemisphere it is
counterclockwise. (Page 428)
Deep ocean currents are very cold, dense, and slowly moving currents under the warm surface
waters. They are produced as cold, dense water of the polar regions sinks and flows beneath
warmer ocean water toward the equator. (Page 431)
Two types of currents near the shore are longshore and rip currents. A long-shore current is an
ocean current that moves parallel to shore. It is caused by swells sweeping into the shoreline at
an angle and pushing water down the length of the beach in one direction.
Longs-shore currents usually extend from the shallow waters inside the breaking waves to the
outside breakers. They vary depending on the size, strength, and direction of the approaching
swell, and the length of the beach. The more prominent the swell size and direction, and the
longer and straighter the beach is, the more powerful and swift the long-shore current will be.
A rip current is a strong, narrow surface current that flows rapidly away from the shore. Rip
currents form when excess water that has accumulated along a shore due to wind and waves
rushes back suddenly to deeper waters.