Anything that causes water to move can cause a wave: earthquakes, underwater landslides, changes in atmospheric pressure, underwater volcanic eruptions, the movement of ships, or even a fish jumping. The most common cause of surface waves in the ocean, however, is the wind blowing across the water. Once set in motion by the wind, as long as the wave is in deep water, the energy of the waves is passed from water particle to water particle without the water actually moving. The size of a wave depends on how long the wind blows, the strength of the wind, and the distance the wind blows, known as the fetch.
Tides are huge “waves” that are caused by the gravitational attraction between the earth, the moon and, to a lesser extent, the sun. High tide is the crest of the wave and low tide is the trough of the wave. All objects have a gravitational attraction to each other. The amount of gravitational attraction between two objects depends on how close together they are and how large they are. Because the moon is closer to the earth it has a greater effect on the earth’s tides than the sun does, even though the sun is much larger.
Currents are rivers of water in the ocean. The two major types of currents are surface currents and density currents.
Surface currents are driven by the wind. Friction between the wind and the water sets these currents in motion. The winds that drive surface currents are the Westerlies that blow west to east at 40 degrees to 50 degrees latitude and the trade winds that blow east to west at 20 degrees latitude.
The beach forms at the edge of an island between the ocean and the sand dunes. The sand is deposited by waves and currents and is then blown around by the wind to create dunes. The beaches of Georgia’s undeveloped islands are made mostly of fine-grain sand. The beaches are fairly wide and slope gently toward the ocean. This harsh environment is a moderate energy area because the waves from distant storms release their energy as they roll up onto the beach. Winds keep sand in constant motion. In the summer the prevailing winds along the east coast blow from the southwest and in the winter from the northwest. The profile of the beach changes from a broad flat beach in the summer to a narrower and steeper beach in the winter.