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Tsunami: The Big Wave

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Summary of Article
A tsunami (soo-NAH-mee) is a series of gigantic waves that occur in the ocean or other large bodies of water. Formed when a large amount of water is rapidly displaced, tsunamis are often caused by an earthquake, a landslide, an exploding volcano, or even a meteorite impact. This article explains the physics behind the giant waves. It also describes the tsunami warning system and cites several examples of the destruction caused by these great waves. The article also provides tips on what to do if a tsunami is imminent.

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Suggested Age/Grade Levels
Age Level: 10 - 18
Grade Level: 7th grade - 12th grade

Related Topics
Earth Science
Discuss with students how natural occurrences, like earthquakes, have dangers that aren't visible in the area where the quake hit. Oceanography
Discuss with students how an ocean disruption in Alaska can affect Chile. Geography
Get a map of the world and lead a class discussion about which countries a tsunami would most likely hit. History
Discuss what else took place in the world during different major tsunamis.

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Objectives
After studying the article, students should be able to:

Define a tsunami and list at least two causes.
Illustrate, through labeled diagrams, the difference between a wind-generated wave and a tsunami wave.
Explain how a tsunami differs from a tidal wave.
List four major areas on Earth that are most likely to experience the effects of tsunamis.
List at least five things one should do after a tsunami warning is issued.
Describe the difference between a tsunami watch bulletin and a tsunami warning.
Name at least three tsunamis (by geographic reference) that have occurred in the 20th century.

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Classroom Activities
Ocean Wave Simulation
This activity will demonstrate how an ocean wave is formed and grows larger.

Materials needed:

500 ml plastic bottle (a 2-liter soda bottle will work)
150 ml of water
150 ml of vegetable oil
blue food coloring

Fill the plastic bottle with the 150 ml of water. Next, put three to four drops of the blue food coloring into the oil. Pour the oil into the bottle. The oil should float on top of the water. Shift the bottle from left to right, simulating an ocean wave. Notice how the wave grows larger from one end of the bottle to the other.

Wave Formation
This activity will simulate how the "small" beginnings of a tsunami can turn into a giant wave.

Materials needed:

bucket
water
small pebble
baseball bat or stick

Fill the bucket about 3/4 full of water. Put the bucket of water on a flat surface and let the water become still. Drop a small pebble in the middle of the water and watch the waves form. What happens as the waves travel farther from where the pebble was dropped?
For another experiment, after the water has become still, strike the bottom of the bucket with the baseball bat or stick. Are ripples formed in the water? Are the ripples smaller or larger on the side of the bucket where the stick hit?

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Questions for Discussion
Q: Earthquakes are one source of tsunamis. Can you think of other potential sources?
A: Other potential sources of tsunamis include landslides, volcanoes, and large meteorites hitting the ocean.

Q: Why are tsunamis difficult to detect at sea?
A: Tsunamis are difficult to detect because when a wave begins in the deep ocean waters it is very small and may look like nothing more than a gentle rise and fall of the sea surface.

Q: What would you do if you lived adjacent to a coastal beach area and just heard that you had 20 minutes before a tsunami would strike? Can you come up with a plan of action?
A: First, if you are in a dangerous area you should turn off the water, gas, and electricity and quickly move to higher ground. You should never go down to the beach to watch the waves come in, for you won't live to tell anyone about it! Also, listen to a portable radio to find out when it is safe to return home (the first tsunami wave to hit could be the smallest!).

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Quiz
Click here for a Tsunami quiz.
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Just the Facts
Tsunamis are not tidal waves. They are a series of waves of extremely long wavelength and period. They are not associated with the tides.

Tsunamis are primarily associated with earthquakes in oceanic and coastal regions.

Tsunamis can travel virtually unnoticed through the open ocean because the wave height may be only twelve inches.

There is no truly reliable early detection system for tsunamis yet.

Tsunamis can be local, regional, or ocean-wide, depending on the size of the waves and the area affected.

Tsunami wave heights when approaching a shore can reach 100 ft. or more.
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Links to Relevant Web Sites and Additional Resources

http://observe.ivv.nasa.gov/nasa/exhibits/tsunami/tsun_links.html

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Vocabulary
tsunami: (soo-NAH-mee) a series of waves that occur in an ocean or other large body of water and caused by some activity that displaces large amounts of water.

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For Fun
Just for fun, play our Tsunami Wordsearch game.
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