Walls of Water – Tsunami 101

Tsunamis have been in the news over the last several years and cause significant damage to life and property. A tsunami is a set of ocean waves caused by a large disturbance of the sea or sea floor.

Often, an earthquake causes this disturbance but it could also be the result of a massive object, such as a meteor, hitting the sea, or even a large submerged landslide. After the ocean is disrupted, the water and waves move away in all directions at equal speeds of 400 to 500 mph, with wave heights of just a few feet.

Tsunami diagram - Credit: Scholastic.com

Tsunami diagram – Credit: Scholastic.com

Now, this may not seem like much of a threat, but as the water approaches land, the waves slow down and begin to grow, often to heights of 10 to 30 feet! When the waves smack into the shoreline, the force of the water wipes out everything in its path.

Aftermath of the 2011 tsunami in Japan - Credit: Official U.S. Navy Imagery via Flickr

Aftermath of the 2011 tsunami in Japan – Credit: Official U.S. Navy Imagery via Flickr

Here are quick facts from NOAA regarding these monster waves that you should be aware of:

  • Tsunamis that strike coastal location in the Pacific Ocean Basin are most always caused by earthquakes. These earthquakes might occur far away or near where you live.
  • Some tsunamis can be very large. In coastal areas their height can be as great as 30 feet or more (100 feet in extreme cases), and they can move inland several hundred feet.
  • All low lying coastal areas can be struck by tsunamis.
  • A tsunami consists of a series of waves. Often the first wave may not be the largest. The danger from a tsunami can last for several hours after the arrival of the first wave.
  • Tsunamis can move faster than a person can run.
  • Sometimes a tsunami causes the water near shore to recede, exposing the ocean floor. The force of some tsunamis is enormous. Large rocks weighing several tons along with boats and other debris can be moved inland hundreds of feet by the tsunami wave activity. Homes and other buildings are destroyed. All this material and water move with great force and can kill or injure people.
  • Tsunamis can occur at any time, day or night.
  • Tsunamis can travel up rivers and streams that lead to the ocean.

Watch this video on the 2011 tsunami that hit Japan. Warning, may be intense and graphic. Viewer discretion advised:

So, what can you do? NOAA recommends the following:

  • If you are in school and you hear there is a tsunami warning, you should follow the advice of teachers and other school personnel.
  • If you are at home and hear there is a tsunami warning, you should make sure you entire family is aware of the warning. Your family should evacuate your house if you live in a tsunami evacuation. Move in an orderly, calm and safe manner to the evacuation site or to any safe place outside your evacuation zone. Follow the advice of local emergency and law enforcement authorities.
  • If you are at the beach or near the ocean and you feel the earth shake, move immediately to higher ground. DO NOT wait for a tsunami warning to be announced. Stay away from rivers and streams that lead to the ocean as you would stay away from the beach and ocean if there is a tsunami. A regional tsunami from a local earthquake could strike some areas before a tsunami warning could be announced.
  • Tsunamis generated in distant locations will generally give people enough time to move to higher ground. For locally generated tsunamis, where you might feel the ground shake, you may only have a few minutes to move to higher ground.
  • High, multi-story, reinforced concrete hotels are located in many low-lying coastal areas. The upper floors of these hotels can provide a safe place to find refuge should there be a tsunami warning and you cannot move quickly inland to higher ground. Local Civil Defense procedures may, however, not allow this type of evacuation in your area. Homes and small buildings located in low lying coastal areas are not designed to withstand tsunami impacts. Do not stay in these structures should there be a tsunami warning.
  • Offshore reefs and shallow areas may help break the force of tsunami waves, but large and dangerous waves can still be threat to coastal residents in these areas. Staying away from all low-lying coastal areas is the safest advice when there is a tsunami warning.



Stay Safe and Know Before™.

The WeatherBug – Earth Networks Team



This entry was posted in General, Safety.
  • Share and let your friends and family #knowb4:
  • Subscribe via Email

    Enter your email address to subscribe to KnowBefore and receive notifications of new posts by email.

  • @WeatherBug on Twitter

  • Latest Posts

  • WeatherBug Apps

    Know Before — Download WeatherBug today to get Dangerous Thunderstorm Alerts:

  • Archives