Earth Science: THE MOVEMENT OF OCEAN WATERS

1. WAVES

• The highest point of a wave is the CREST, and the lower point, the TROUGH.

• The length of a wave is the distance from one crest to the next crest, or from one trough to the next trough.

• The stronger the winds blow, the bigger the waves formed

• In open ocean, the longer distance the waves travel, the higher and longer they become.

• A Mass or rocks and soil that slides into thw ater from the edge of land disturbs the water and forms waves. This is a LANDSLIDE into the sea.

• The larger the mass of the rocks hitting the water, the larger the waves formed.

• In May 1960, giant waves from the Pacific Ocean hit the shores of Polollo Island off Quezon province. In August, 1976 giant waves destroyed the coastal towns of Cotabato and Davao. Undersea earthquakes were reported as the cause in both events.

• TSUNAMI refers to the giant waves formed by undersea earthquakes, volcanic eruptions and landslide.

• Tsunami are about 150 km long, traveling at about 800 km/h. They increase in height while traveling, rising as high as 30 m as they approach shore.

2. OCEAN SURFACE CURRENTS

• Flowing water carries floating objects away. The flow of the surface water of seas and oceans is known as surface currents. Surface currents mix and redistribute water in the oceans.

• Records of sailing ships and data from observations made by oceanographers show that ocean surface waters flow in large circulating currents. These circulating currents maintain their directions.

• Surface currents are driven mainly by winds. The easterly winds pushing surface water toward the equator form the equatorial currents.

• The presence of land in the path of the equatorial currents turn them to the right in the northern hemisphere and to the left in the southern hemisphere. Beyond the 30 N ans S latitudes the westerly winds push the currents. The turning to the right in the northern hemisphere and to the left in the southern hemisphere is called the Coriolis effect which is caused by the earth's rotation.

• The Gulf Stream of the North Atlantic Circulation is the fastest and strongest of the major currents. Part of the Benguela Current from the South Atlantic Circulation joins the Gulf stream and adds to its volume and speed.

• The current in the Indian Ocean is the only one which changes direction with the monsoon seasons. When the southwest monsoon wind blows, the Indian Ocean Current flows eastwest monsoon wind blows, the Indian Ocean season Current flows eastward. When the northern monsoon wind blows, the current flows westward.

• The Antarctic Circumpolar Current flows in a west to east direction around the Antarctic Continent. There are no land masses block and turn it. Being driven by winds coming from the west, it is also called the West Wind Drift.

• In the middle of each circulation is calm water. The best known of them is the Sargasso Sea in the North Atlantic Circulation. The name Sargasso is taken from the brown seaweed Sargassum growing abundantly in its calm water. Once caught there, they had to wait long for strong winds to push their sails and get them out.

• Surface currents are still useful today in water transportation. Although modern ships run on fuel, they move faster on less fuel by following the currents.

3. DENSITY CURRENTS (to be continued)