by Ann Marie Dwyer

Created on: March 22, 2007   Last Updated: November 24, 2008

Both types of ocean waves, tsunamis and surface waves, are the vertical shifting of water, but are created by totally different influences.

Surface waves are the most common. They are created by the friction of the wind as it blows across the surface of the water. The transference of energy from the wind to the water creates a column of water with valleys on either side. These are the waves which rock boats and make surfers happy.

As the wave moves in the direction of the wind, the water does not move with it. Water in the wave only moves up and down. Because waves need to draw in water to create vertical height, water at the shores are pulled toward the wave. This gives the illusion that waves move water horizontally. To prove this in your own experiment, blow across the surface of a bowl of water. Drop in a buoy, fishing bobber or cork, and it will only move up and down.

Tsunamis, from the Japanese words for "harbor wave", are mistakenly called tidal waves. The common causes of tsunamis are underwater activities: Powerful earthquakes (above 6.75 on the Richter scale), volcanic eruptions and rock slides. Occasionally, a tsunami will be caused by an asteroid or meteorite hitting the surface of the ocean.

The rapid change in the underwater terrain causes the tsunami to draw back water from the shores to create the vertical column of water. This allows tsunamis to reach much larger heights than surface waves. Tsunamis are caused by a much greater transference of energy.

The difference in the amount of energy transferred between the cause of the wave and the water determines the speed at which the wave travels and the distance between waves. Where surface waves move at the most 90 mph, the tsunami can travel at speeds closer to 400 mph. Tsunamis will be tens of thousands of feet apart, where surface waves may be only inches apart.

Tides are often mistaken for waves. Tides occur when water moves from one side of the Earth to the other. The moon has a gravitational pull on the Earth. As it orbits the Earth, it pulls. The water is lightweight and is affected by the pull of lunar gravity. No energy is transferred in the tidal process. This is why tides are not waves.

When the moon sets in the morning, it pulls the water toward it causing high tide on eastern coasts. When the moon rises at night, it pulls the water away from the beach, causing low tide on eastern shores. The opposite is true for western coasts.

Without the exchange of energy, there would be no waves!

Learn more about this author, Ann Marie Dwyer.
Click here to send this author comments or questions.