Tsunami: A Giant Tidal Wave


Even the word itself sounds like a disaster coming. Tsunamis, also known as tidal waves, are generated by any of a number of events that push a large amount of water out of the way. Although the most common cause of these massive waves are earthquakes, they can also be caused by erupting volcanoes, falling glaciers, or nuclear tests. Nor do they strike fear into the hearts of people worldwide for no reason - the 2004 Indonesian tsunami claimed a total of 230,000 casualties and ranks 6th highest on the list of all time recorded natural disasters. Learning and understanding about tidal waves can help people everywhere to know better how to prepare and, most importantly, to recognize when one is coming.

Tsunami Facts: Did you know that...

  • In spite of the cheesy movies that depict giant waves breaking over houses and buildings, the truth is that they rarely look like normal waves with a giant breaker shape. Instead, it may appear as a continually rising tide, with groups of waves arriving together over several hours.
  • The 2006 movie Poseidon, based on the story of an ocean liner struck by a monster wave, is essentially impossible, because even the largest tidal waves are nearly undetectable on the open ocean.
  • When traveling in open water, tsunamis can reach speeds of up to 500 miles an hour, and with wavelengths that are sometimes as long as 120 miles apart, they can strike thousands of miles away with just as much force as they started out with all the way across the ocean.

The Problem With Tsunami Warnings

Predicting tidal waves has become far more of a public focus in recent years, as the Indonesian and Japanese disasters brought home the potential deadliness of these giant waves. However, determining which of the millions of waves that cross the ocean each day is a potential killer is a much more difficult job than it seems. Physics, specifically wave dynamics, means that over deep water a giant wave will not be more than 3 feet high. Only as it approaches coastal waters, and a process known as "wave shoaling" takes place, does its speed decrease and the wave height increase. This difficulty in detecting tsunamis before they approaches land makes for a frustrating experience for scientists, who can only predict the likelihood of a tidal wave for any given coastal area based on the type of earthquake triggering the wave.

The World's Largest Tsunami

Determining which of the tidal waves in history has been the largest is a tricky proposition. After all, there is historical evidence of tidal waves as far back as 6,000 B.C., and everywhere from the Norwegian Sea to the tidal wave capital of the world: Japan. Not only that, but the question of the largest tsunami also must be considered from what angle: Most casualties? Highest wave crest? The 2004 Indonesian tsunami was the deadliest on record, but the question of the biggest has a far more interesting answer. A landslide in Lituya Bay, Alaska, on July 9, 1958 resulted in a tidal wave that was 1,720 feet high at its peak. We know this because the wave wiped everything below that altitude completely clean - no trees, bushes, or life of any kind at all.

The Danger Of False Tsunami Warnings

As anyone who's heard the story of the boy who cried wolf knows, there is a danger in predicting disaster without results too many times: people stop listening to you. As scientists work to improve prediction methods for massive killer waves and warning systems for coastal areas, there is a certain amount of complacency that sets in when repeated warnings fail to come to pass. The most important step you can take in preparing for a potential monster wave is to decide on a high elevation place to take shelter during a warning. Having a basic emergency preparation kit with water, food, and basic medical supplies to take with you is an additional step that could mean saving the lives of yourself and the people you love.

Signs Of A Tsunami

Although not every tidal wave will have what's called "drawback," or a period of extremely low ocean levels before the crest hits land, many times they do. If you happen to live or be near the ocean and notice that the water is drawing far out to sea and exposing an unusual amount of things on the seabed, take immediate shelter on higher ground. It may very well be the precursor to a tidal wave. The story is told of a young lady who had been learning tsunami facts in her school just before visiting Thailand in 2004. When the ocean began to draw far out to sea, she recognized the signs of what she had been taught, and began warning people. As a result of the little girl's ocean wisdom, many lives were saved.


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