Dynamics » Continental Drift » Types of Tsunamis » Birth of a Tsunami

 These are the tsunami victims. Can you please help them?

 Fact In 1703, Japan was hit by a tsunami killing 5,233 people.
Dynamics » Birth of a Tsunami

Origin of the Word:

The word "tsunami" comes from the Japanese words tsu (harbor) and nami (waves). They are sometimes called "harbor waves".

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Anatomy of a normal wave:

The picture below shows a picture of a normal wave. The distance between the crest (highest point of the wave) and the trough (lowest point of the wave) is called the wave height. The distance (horizontal) between two consecutive wave crests is called wave length.

The time it takes for two consecutive waves to cross the same point is used to calculate the frequency of waves. This is called wave period.

Normal waves are usually caused by wind, although they can be generated by gravitational pull, atmospheric pressure and unusual activity under water. The size and speed of wind waves depend on the strength of the wind.

Normal waves usually have a wave speed of 5-60 mph (8 -100 kph), a wave period of 5-20 seconds apart and a wave length of 300-600 feet apart (100 - 200 meters apart).

Caption: Anatomy of a Normal Wave
Credit: U. S. Navy

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Anatomy of a tsunami wave:

The main differences between a tsunami wave and normal wind-generated wave are size, speed and cause. Tsunami waves usually have a wave speed of 500 -600 mph (800 -1000 kph), a wave period of 10 minutes to 2 hours apart and a wave length of 60 - 300 miles apart (100 - 500 km apart). The anatomy of a tsunami wave is otherwise similar to the wind-generated wave.

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Birth of a tsunami wave:

Tsunamis are formed when a large volume of water is displaced, either by an earthquake or by a gigantic landslide. The tsunami that happened on December 26, 2004 was triggered by an earthquake. The earthquake measure 9.0 on the Richter scale -- one of the biggest in recorded history. This earthquake happened due to a slippage between the India and Burma plates near the island of Sumatra in Indonesia. The slippage happened along a 600 mile (1000 kms) boundary between the two plates. It is a real big slippage.

When the tsunami is born, it begins as a series of waves in the ocean that can be as high as 33 feet and extend hundreds of miles long. They are nothing but giant and ferocious "walls of water" that travel at great speeds. Scientists have measured the speed of travel of the tsunamis and have found that they can travel as fast or faster than a commercial jet. For example, the December 26, 2004 tsunami was recorded to have traveled 375 miles (600 km) in approximatley 75 minutes. That's very fast -- 300 mph (480 kph). Some tsunamis have been recorded to travel up to 600 mph (965 kph) at the deepest point of water. They slow down as they approach the shore at about 40 mph (64 kph). However, at this point the energy of the tsunami's speed is transferred to height and sheer force as it approaches the shore.

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Credits

Credits: Online

Credits: Books

• Plate Tectonics by Kevin Cuff, Ian Carmichael, Carolyn Willard
• Apocalypse: a Natural History of Global Disasters by Bill McGuire (Cassell, London, 1999).
• Furious Earth: The Science and Nature of Earthquakes, Volcanoes, and Tsunamis by Ellen J. Prager.

Credits: Interactions

Ideas for team-generated interactions were conceived by reading articles from NASA and also from Creative Adventures activities.

Credits: Individuals

• Ms. Irivinti for teaching us how to use Dreamweaver for our web design, Photoshop and Fireworks for graphics as well as animating our logo. She taught us how to create different background (fading) effects, how to pick appropriate colors, and how to generate theme specific images, spacers etc. She also assisted us with all programming aspects of our website.
• Mrs. Cataldo, Ms. Irivinti and our parents for guiding us with research and content development. It was difficult to find information we needed in one place and their assistance helped us a lot in this regard.
• Mrs. Cataldo and Ms. Irivinti for reviewing and editing what we wrote. They told us when our writing needed more work and also taught us how to cite sources, obtain permission for images that we borrowed from other websites and also the proper way to credit them.

Our Interactions on Tsunamis

More Online Interactions on Tsunamis

Vocabulary on Birth of a Tsunami

• Anatomy: The basic structure.

• Boundary : Border.

• Crest: Highest point of a wave

• Displaced : To move or shift from the usual place or position.

• Frequency: The number of times a certain event occurs in a certain period.

• Gigantic: Very large.

• Richter Scale : A scale used to measure energy released by an earthquake.

• Trough: Lowest point of a wave.