The picture above shows how the shape of a tsunami wave changes as it moves into shallower water.
Click on image for full size
What Is a Tsunami?
A tsunami (pronounced tsoo-NAH-mee) is a series of waves, made in an ocean or other body of water by an earthquake, landslide, volcanic eruption, or meteorite impact. Tsunamis can cause huge destruction when they hit coastlines. Some people call tsunamis “tidal waves”, but these large waves really have little to do with tides, so the term “tidal wave” does not really suit them.
Tsunami waves are different from the waves you can usually find rolling into the coast of a lake or ocean. Those waves are made by wind offshore and are quite small compared with tsunami waves. A tsunami wave in the open ocean can be more than 100 km across. That’s roughly the length of 1000 American football fields! Tsunami waves are huge and can travel very quickly, at about 700 km/hr, but they are only about one meter high in the open ocean.
As a tsunami wave travels into the shallower water near the coast, it slows and grows in height. Even though a tsunami may be barely visible at sea, it may grow to be many meters high near the coast and have a tremendous amount of energy. When it finally reaches the coast, a tsunami may appear as a rapidly rising or falling tide or a series of waves with a maximum height of up to 30 meters.
A few minutes before a tsunami wave hits, the water near shore may move away, exposing the ocean floor. Often the first wave may not be the largest, and additional waves may arrive at the coast every 10 to 60 minutes. They move much faster than a person can run. The danger from a tsunami can last for several hours after the arrival of the first wave. Unlike other waves, tsunami waves typically do not curl and break.
Coasts affected by a tsunami will be severely eroded. A tsunami can cause flooding hundreds of meters inland. The water moves with such force that it is capable of crushing homes and other buildings.
Shop Windows to the Universe Science Store!
Our online store
includes issues of NESTA's quarterly journal, The Earth Scientist
, full of classroom activities on different topics in Earth and space science, as well as books
on science education!
You might also be interested in:
The expression “on solid ground” is often used to describe something as stable. Usually the solid ground underfoot seems very stable. But sometimes it is not. "The ground seemed to twist under us like...more
Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky. They are sometimes called "shooting stars" or "falling stars", though they are not stars...more
1. Tsunamis that strike coastal locations in the Pacific Ocean Basin are almost always caused by earthquakes. These earthquakes might occur far away or near where you live. 2. Some tsunamis can be very...more
Earthquakes occur regularly in Sumatra, Indonesia because it is located near the boundary of two of Earth's tectonic plates. These earthquakes occur at 'subduction zones,' which are areas where one tectonic...more
Some scientific problems and processes are so complex that you need SUPERCOMPUTING power to tackle them! Just what is a supercomputer? A supercomputer is a computer that is among the largest, fastest or...more
This picture of the Earth surface was taken from high above the planet in the International Space Station. In this view from above, we can see that there are lots of different things that cover the Earth....more
Like the other creatures of the desert, birds come up with interesting ways to survive in the harsh climate. The sandgrouse has special feathers that soak up water. It can then carry the water to its...more