Tsunami

What Is a Tsunami?

Tsunamis are often incorrectly referred to as tidal waves, but a tsunami is actually a series of waves that can travel at speeds averaging 450 (and up to 600) miles per hour in the open ocean. In the open ocean, tsunamis would not be felt by ships because the wavelength would be hundreds of miles long, with amplitude of only a few feet. This would also make them unnoticeable from the air. As the waves approach the coast, their speed decreases and their amplitude increases. Unusual wave heights have been known to be over 100 feet high. However, waves that are 10 to 20 feet high can be very destructive and cause many deaths or injuries.

Tsunamis are most often generated by earthquake-induced movement of the ocean floor. Landslides, volcanic eruptions, and even meteorites can also generate a tsunami. If a major earthquake is felt, a tsunami could reach the beach in a few minutes, even before a warning is issued. Areas at greatest risk are less than 25 feet above sea level and within one mile of the shoreline. Most deaths caused by a tsunami are because of drowning.

Two plate systems in the Atlantic Ocean are of concern to officials along the East Coast: one off the coast of Europe and Africa and the other north of the island of Puerto Rico. Both have the potential to cause Tsunamis that could affect our coastline.

Quick Emergency Info
  1. The best protection following a tsunami warning is to evacuate from coastal areas or move to higher ground.
  2. A tsunami is a series of waves. Do not assume that one wave means that the danger is over. The next wave may be larger than the first one. Stay out of the area.
  3. The greatest danger exists in those areas at an elevation of less than 20 feet. Water being pushed inland by the tsunami will bring massive amounts of debris as it pushes inland, including vehicles and small buildings.
When a Tsunami Strikes
  • Listen to a radio or television to get the latest emergency information.
    • Be ready to evacuate if asked to do so. If you hear an official tsunami warning or detect signs of a tsunami, evacuate at once. Climb to higher ground. A tsunami warning is issued when authorities are certain that a tsunami threat exists.
  • 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.
  • Return home only after authorities advise it is safe to do so.
    • A tsunami is a series of waves. Do not assume that one wave means the danger is over. The next wave may be larger than the first one. Stay out of the area.
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