A brief article on the formation of tsunamis and how to prepare for them.

Tsunamis; what are they, and more importantly what causes them? We know from recent events in Asia that Tsunamis are destructive forces of nature that cause massive property damage and life loss. However few people actually know what causes tsunamis and how to be prepared incase one hits.

Tsunami is Japanese for harbor wave. This term has been adopted internationally by the weather services as a term for a series of waves traveling across the ocean with extremely long wavelengths. There can be hundreds of miles between wave crests in the deep ocean. This sounds very similar to a tidal wave however there are several major differences between the two.

Tidal waves are a periodic movement of water that has been proven to be caused by the gravitational attraction of the sun and the moon. Tsunamis, on the other hand, have no connection to gravity or weather. Harbor waves are caused by any disturbance that causes mass amounts of water to be displaced in a single area.

For years the biggest cause of tsunamis has been earthquakes. An undersea quake displaces vast amounts of water in a sudden jolt. Huge shallow waves rush through the ocean at a speed up to 500 miles an hour. Upon reaching a gently sloping coastline the waves slow down and begin to compress up. They can rise from one meter up to twenty meters in a matter of seconds. The waves then crash ashore, causing devastation from the beach to all the low-lying land. This was seen most recently in the wave that hit Sri Lanka.

The devastation of the wave is a direct correlation of the size of the ripple that made it. The most damage will be done the closest to the cause of the wave. Coral reefs help to break the wave up as it nears islands thus making the damage less.

Landslides whether they are above or below the shoreline, can cause tsunamis too. While these are less common now days there have been examples of them in the past.

Volcanoes are a common cause of tsunamis in the Pacific Ring of Fire. This volcanic hotspot suffers from eruptions daily. While most of these eruptions are minor, it would only take an eruption like that of Mount Saint Helen to level several of the Pacific Islands.

An asteroid that makes an impact with enough force into the ocean would be able to start a tsunami too. So far I have pointed out only nature's way of making them, but man can make them too. In World War I there was a bomb that exploded with enough force to start a tsunami that caused massive amounts of damage. It has been theorized that a nuclear explosion could have the same effect but most of the nuclear bomb testing remains classified so this has never been fully tested.

The biggest threat that tsunamis’ present is loss of life to those that are in the low-lying areas when they hit. In 1946, a tsunami with waves of 20 to 32 feet crashed into Hilo, Hawaii, flooding the downtown area and killing 159 people. If you hear a warning on the radio about a possible tsunami heading towards you head for highland immediately. Do not stand on the beach and watch the waves come in. Scientists are able to predict when and where a wave will hit. Remember a narrowing bay will likely increase the wave height, by compressing the energy along the bay sides, as well, as the decreasing depth of the ocean bottom.

As with all natural disasters, FEMA recommends having a survival kit ready. This kit should include the following items: flashlight, portable battery-operated radio, first aid kit, emergency food and water, non-electric can opener, essential medicines, cash and credit cards, sturdy shoes, blankets, and extra batteries. This kit will work for tornadoes, blizzards and hurricanes too. Another recommendation is to know the evacuation routes for the area you live in.

For more information on tsunamis or any other natural disaster seek help from the FEMA or NOAA web pages respectively.