Fred Jaicks   Written and compiled by Fred Jaicks.


The Causes and Effects of Tsunamis

The word tsunami is derived from the Japanese and the literal translation is “harbor wave.” Tsunamis are a type of natural disaster that often occur quickly and with little warning. Although there is a general impression that a tsunami is a giant wave in the ocean, it is actually made up of many waves that quickly move together. It is important to note that during a tsunami, the water does not only move forward but it also moves upwards. This is why during a tsunami, the waves look far larger than normal.

What Causes a Tsunami?

Tsunamis are usually provoked by large explosions or disturbances deep under the Earth’s surface. For example, an underwater volcano or an earthquake, or even a man-made explosion can cause a tsunami. In different circumstances, a landslide occurring along the sea floor can displace water and cause a rush of waves that form a tsunami. In some rarer cases, debris, such as meteoroids falling from space can also force the water to create a tsunami by causing a deep and massive splash.

In the case of a volcano, the eruption underwater simply causes the water to be pushed forcefully into a succession of strong waves. On the other hand, an underwater earthquake can make the ocean bed rise or shake back and forth. This affects the water above it, forcing waves to move higher and faster. To see this principle occur on a small scale, take a glass of water and quickly move it back and forth. You will see that the water in the glass creates waves that move high up against the sides of the glass. Similarly, if objects in the glass collide (in the way that tectonic plates may push against each other), the water will rock back and forth and rise up again. In real life however, there aren’t any sides of the glass to contain the water, so instead the waves end up crashing on land. In particular, subduction earthquakes, where shifts occur over or across fault lines, are known for triggering tsunamis.

What Happens When a Tsunami Occurs?

Tsunamis are incredibly powerful natural events and they can cause widespread damage and even fatalities among unprepared communities. When tsunami waves hit land, they do so very strongly and at first any buildings, vehicles and other items can easily be destroyed. When the waves recede, they draw loose objects back into the water. In this way, many people sadly end up drowning. At this point the water contains plenty of debris, and when the waves hit land again, the debris is washed ashore, creating further damage and havoc. Apart from destroying material objects, tsunamis can also demolish farm land, plant life and animals that are in its path. Those people who do not lose their lives may instead lose their homes and livelihoods. Very often, after a tsunami, the remaining still water becomes contaminated and can bring on water-borne diseases such as malaria. It takes a long time for the natural ecosystem and human communities to recover after a tsunami. 

Learn More About Tsunamis

  • Tsunami Class Resources – Browse through some interesting projects and websites all about tsunamis.
  • Tsunamis Caused by Earthquakes – Read about real underwater earthquakes that occurred and how they triggered tsunamis.
  • What Does a Tsunami Look Like? – Have a look at some photographs captured of a tsunami that occurred in 2004. Here you can see that many of the waves are larger than cars, and in some cases almost as large as buildings!
  • All About Tsunamis – Find out all about the science behind tsunamis, what scientists are doing to learn more about them, and how we can stay safe during a tsunami.
  • A Tsunami Timeline – Tsunamis have occurred throughout time and all around the world. Learn about how some of the largest ones were caused.
  • Earthquake-Triggered Tsunamis – See how earthquakes occur underwater and how they in turn bring about a tsunami.
  • Being Prepared in Emergencies – There are plenty of tips that can help people to stay prepared and safe before, during and after an emergency, such as a tsunami.
  • A Detailed Guide to Tsunamis – Get all the facts about tsunamis and read about some of the most famous and devastating ones that occurred during the past century.
  • More Tsunami Resources – Find out how disastrous a tsunami can really be by viewing satellite images and reading about the effects of recent tsunamis in Asia.
  • A Tsunami Web Quest – Test your knowledge on tsunamis by exploring various resources online and learning more about these powerful natural disasters.