The Causes & Effects of a Tsunami

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  • 0:05 What Is a Tsunami?
  • 1:11 What Causes a Tsunami…
  • 2:41 Effects of a Tsunami
  • 4:21 Lesson Summary
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Lesson Transcript
Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Expert Contributor
Maria Airth

Maria has a Doctorate of Education and over 20 years of experience teaching psychology and math related courses at the university level.

A tsunami is a powerful series of waves that result due to an abrupt disturbance, such as an earthquake. Learn how tsunamis form and grow and discover the devastating effects they can have on people and the environment.

What Is a Tsunami?

Imagine a giant wall of water growing out of the ocean, big enough to wipe out entire coastal towns and capable of killing hundreds of thousands of people caught in its path. This is the power created by a tsunami, which is a series of waves caused by an earthquake, underwater volcanic eruption, landslide or other abrupt disturbance. Tsunamis are capable of creating massive devastation when they hit land. In this lesson, you will learn how tsunamis are created and the effects they have on people and the environment.

The word tsunami comes from the Japanese language. The prefix 'tsu' means 'harbor' and the suffix 'nami' means 'wave.' Therefore, the word literally means 'harbor wave.' In March of 2011, Japan was hit by a powerful tsunami that was triggered by a 9.0 magnitude earthquake. The tsunami killed more than 15,000 people and caused billions of dollars of damage, including damage to several nuclear reactors.

What Causes a Tsunami and How Do They Form?

Tsunamis, like the one that hit Japan, can be caused by any action that creates an abrupt disturbance underwater. This can include a volcanic eruption or landslide, and even a meteorite or nuclear explosion, although these last two examples are rare. The most common cause of a tsunami is an earthquake, which is a sudden shifting of the earth's crust, which releases energy. If an earthquake happens underwater, the seafloor lifts and then drops back down, causing the overlying water to be displaced and triggering waves of water.

A tsunami wave that begins in the vast ocean has a very small wave height. For this reason, tsunamis in open ocean waters may go unnoticed. In fact, a fisherman out on the ocean may only experience a small swell as a tsunami wave passes below. Even though tsunamis are not big in height while out at sea, they can be very wide, spanning more than 1,000 football fields across.

They also travel very quickly in deep ocean waters, reaching speeds as fast as a jet plane. As the tsunami approaches the coastline and shallow water, it slows in speed but builds in height. When the tsunami comes ashore, it brings with it a tremendous amount of energy and waves that can reach heights of over 100 feet.

Effects of a Tsunami

So you can image that when a huge wall of water comes ashore, there are some devastating effects of a tsunami. As mentioned earlier, a particularly devastating effect of a tsunami reaching land is a loss of life, which can grow into the hundreds of thousands. Because tsunamis are triggered by sudden events, such as earthquakes, and because they move so quickly over deep ocean waters, there may be little time to warn coastal residents of its arrival.

As the massive wall of water crashes onshore, it can cause severe coastal erosion, which is the wearing away of coastal land or beaches. The power of the water can also wash away vegetation, making it hard to reestablish the shoreline.

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Additional Activities

Recreate the Causes of a Tsunami

In this activity, students will build tsunami simulators and observe the causes and effects of tsunamis firsthand.


  • New cat litter trays (or other deep, large and water-proof containers)
  • Art sand (or clean dirt)
  • Small figurines and/or blocks to act as buildings
  • Water
  • Small rocks
  • Index card

Instructions-Build the Ocean Front

  • Depending on the number of students and the available supplies, allow students to work independently or in small groups.
  • First students should build a simulated beach front.
    • Pour sand over a quarter of the tray tapering the sand from the height of the tray itself to practically flat by the time the sand is at the halfway point of the tray. This is the beach.
    • Now, gently pour water into the tray starting at the opposite side of the tray from the sand (the water should be hitting the tray bottom and not sand). Pour gently, especially as the water rises up the sand.
    • Stop pouring water when the simulated ocean reaches about halfway up the sand pile.
    • Add small figurines, toy houses and or blocks to simulated a development on or near the beach.

Instructions - Create a Tsunami

  • After building the simulated oceanfront scene it is time to create a tsunami.
  • Attempt to recreate as many of the causes listed for tsunamis as possible. For example:
    • Use a small (or medium sized) rock to simulate a meteorite hitting the ocean.
    • Use hands to shake the tray, simulating an earthquake.
    • Use an index card to shove a large amount of sand into the water quickly to simulate a landslide.
  • Observe what happens to the water and the objects on land with each of these simulations.

Instructions - Reflection

  • After the simulation phase of the activity, students should write a brief essay summarizing the results of each simulation. The essay should answer the following questions:
    • How did the water move?
    • What happened to the sand?
    • What actions cause the most impact?
    • What can humans do to protect against tsunami damage?

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