When Nature Strikes: Tsunamis
A tsunami (pronounced soo-NAH-mee) is a series of waves, generated in a body of water by a disturbance such as an earthquake, landslide, volcanic eruption, or meteorite impact. Tsunamis can devastate coastlines, causing major property damage and loss of life.
A tsunami in the open ocean can have a wavelength of more than 100 km. Tsunami waves travel very quickly--up to 700 kilometers per hour--and although they have huge wavelengths, they are typically less than a meter high while they are traveling through the open ocean. As a tsunami travels into the shallower water near the coast, it changes dramatically. Its height increases and its wavelength decreases as it nears shore, so although a tsunami is often imperceptible at sea, it may grow to be several meters or more in height 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 above the level of the sea. The danger from a tsunami can last for several hours after the arrival of the first wave.
Coasts affected by a tsunami will be severely eroded, and 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. This power was demonstrated recently when in 2011, an earthquake off the coast of Japan generated tsunami waves that reached heights of more than 130 ft as they reached land. The tsunami completely destroyed eight villages and caused severe damage in many others, killed more than 15,000 people, and caused a major nuclear accident as waves damaged a reactor at the Fukushima Daiichi nuclear power plant.
Because of the threat tsunami pose to populations living near the sea, scientists like Anne Trehu and Dan Cox at Oregon State University are now studying ways of making structures like harbors and buildings better able to resist the effects of tsunami waves, as well as ways of identifying the earliest warning signs of a tsunami and alerting people who are at risk so they can seek shelter. Although no one can predict when or where the earthquakes that cause tsunami will occur, this research will hopefully lessen their impact on coastal communities.
"When Nature Strikes" is produced by NBC Learn in partnership with the National Science Foundation.
When Nature Strikes: Tsunami Classroom Activity
