Tsunami

Since the terrible tsunami in 2001 which caused widespread destruction, and the Japanese tsunami in 2011, people are learning more about the terrible power of our planet.

What are Tsunamis?

Many people incorrectly call tsunamis "tidal waves," but the cause of tsunamis have nothing to do with tides. The preferred term is "tsunami," which means "harbor wave" in Japanese, indicating that this shallow water wave affects coastal communities and low-lying areas. These waves are massive, sometimes reaching up to 100 feet or more, and can travel at speeds up to 600 miles per hour. One tsunami in Alaska in 1958 was more than 1700 feet tall.

One of the deadly characteristics of tsunamis is as it approaches land it grows bigger. This is due to the energy being transferred from deep water to shallow water. The energy causes the wave to slow down and grow, thus pulling water upwards as it travels towards the land. In many cases, the water pulled up causes the ocean bed to be exposed, thus luring people onto the beach in amazement. This is very dangerous, because the next step is the tsunami wave, itself.

What Causes Tsunamis

Any great disturbance in the ocean, such as the Japanese 8.9 earthquake, landslide or even an asteroid impact may cause a tsunami. Anything that displaces a large amount of water and transfers energy to create shock ripples may cause the tsunami. The size of the tsunami depends on the amount of water displacement by the ocean floor. In other words, the bigger the landslide, the bigger the shift in the earth or the bigger the asteroid, the bigger the tsunami. Other things such as land features can act as deadly funnels for the tsunami, causing it to grow bigger as the space it has to move shrinks dramatically, forcing it to move upward. Channels, isthmuses and other constricted areas are deadly traps as the tsunami will grow to unbelievable heights.

What to Do During a Tsunami

If you are under a tsunami watch, or if there is a tsunami warning, go to higher ground immediately as far from the coast as possible. Depending on where the tsunami occurred and its speed, you may not have enough time to gather things together and get out. Stay away from the coastline. The higher the ground, the more safe it is. Getting 100 feet or more above the coast is preferable. Tsunamis can travel far inland, so going inland isn't necessarily safe.

Do not go back after the first tsunami. Tsunamis often come in a series of waves and it may take hours for them to subside. What's more, if the event that caused the tsunami is an earthquake, there are likely to be aftershocks that may cause further tsunamis.

If a watch is issued, keep tuned to the NOAA radio or keep an eye on the Pacific Tsunami Warning Center, or the West Coast and Alaska Tsunami Warning Center. Contact the American Red Cross, local authorities or other reliable sources for up-to-date information concerning the tsunami.

Reference

The Physics of Tsunamis

Tsunami

American Red Cross

Pacific Tsunami Warning Center

West Coast and Alaska Tsunami Warning Center