First, the basics: A tsunami is a very large wave that is created when something like an earthquake or volcano eruption causes a sudden change in the ocean water level. These events can happen close to the shore, creating a tsunami that reaches the coast within minutes, or they can happen far away and travel more than 600 miles an hour to beaches on the other side of the ocean.
For far-away earthquakes, the National Oceanic and Atmospheric Administration has created a system of tsunami warnings, watches and alerts that can help warn people along coastlines around the world of an impending tsunami. However, tsunamis are very unpredictable, and when an earthquake happens close to the coast, a tsunami could happen without warning. For these reasons, it’s important that everyone knows the signs of a tsunami:
- Feeling an earthquake while on or near the beach, especially if it is so strong that it knocks people over.
- Seeing the ocean water level suddenly get very low or very high.
- Hearing a loud roaring noise, like an airplane or a train, coming from the ocean.
Tsunamis are not only a concern for people who live near coastlines — anyone who travels to a coastal city for vacation or work should also have a plan. To learn more about tsunami preparedness, check out our Get Ready tsunami fact sheets in English (PDF), y tambien en Español (PDF).
For more tips on preparing for a tsunami, watch this great video from NOAA’s TsunamiReady program: