Tsunamis (pronounced soo-ná-mees), also known as seismic sea waves (mistakenly called “tidal waves”), are a series of enormous waves created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite. A tsunami can move hundreds of miles per hour in the open ocean and smash into land with waves as high as 100 feet or more.
From the area where the tsunami originates, waves travel outward in all directions. Once the wave approaches the shore, it builds in height. The topography of the coastline and the ocean floor will influence the size of the wave. There may be more than one wave and the succeeding one may be larger than the one before. That is why a small tsunami at one beach can be a giant wave a few miles away.
All tsunamis are potentially dangerous, even though they may not damage every coastline they strike. A tsunami can strike anywhere along most of the U.S. coastline. The most destructive tsunamis have occurred along the coasts of California, Oregon, Washington, Alaska, and Hawaii.
Earthquake-induced movement of the ocean floor most often generates tsunamis. If a major earthquake or landslide occurs close to shore, the first wave in a series could reach the beach in a few minutes, even before a warning is issued. Areas are at greater risk if they are less than 25 feet above sea level and within a mile of the shoreline. Drowning is the most common cause of death associated with a tsunami. Tsunami waves and the receding water are very destructive to structures in the run-up zone. Other hazards include flooding, contamination of drinking water, and fires from gas lines or ruptured tanks.
How can I protect myself from a tsunami?
Take protective measures:
* Know your tsunami terms
* What to do before and during a tsunami
* What to do after a tsunami
* Learn about floods that can result from tsunamis
Know Your Tsunami Terms
Familiarize yourself with these terms to help identify a tsunami hazard:
An earthquake has occurred in the Pacific basin, which might generate a tsunami.
A tsunami was, or may have been generated, which could cause damage; therefore, people in the warned area are strongly advised to evacuate.
A tsunami was or may have been generated, but is at least two hours travel time to the area in Watch status.
What to do Before and During a Tsunami
The following are guidelines for what you should do if a tsunami is likely in your area:
* Turn on your radio to learn if there is a tsunami warning if an earthquake occurs and you are in a coastal area.
* Move inland to higher ground immediately and stay there.
* Stay away from the beach. Never go down to the beach to watch a tsunami come in. If you can see the wave you are too close to escape it.
* CAUTION - If there is noticeable recession in water away from the shoreline this is nature's tsunami warning and it should be heeded. You should move away immediately.