What is a Tsunami? | Aftermath | Our Relief Work | How can I help?

How are Tsunamis formed? Tsunamis are caused by sudden movement of the sea bed, during an earthquake or volcano. The result is a ripple of waves, just as if you dropped a large stone into a pool. Tsunami waves can travel at over 400 miles an hour through deep ocean, but don't usually cause any trouble at that stage to ships or boats. That's because the water is deep and the waves are long. Ships and boats just rise and fall gently - and may have no idea that a Tsunami wave has just passed beneath them. However as the wave approaches land, the water becomes more shallow and all the wave energy is concentrated into a very small area. The Tsunami wave slows down and increases in height. It is unusual for the wave to break: more commonly it just looks like a massive tide of water sweeping into the shore. Tsunamis are often called tidal waves, and pictures often show tsunami waves over 30 metres high breaking over the coastline, although the reality is more that the water level rises rapidly, and later falls just as fast. In the 2004 Tsunami, much of the damage was done by seawater returning to the ocean, and also by a second wave a few minutes after the first. Here is some useful data showing how the speed of a Tsunami wave falls as it approaches land, and how the height rises. You can see the graph more clearly, and print it out, by right-clicking on the image and saving it first. How often do Tsunami waves happen? Tsunamis happen far more often than most people realise. Hawai sees a small tsunami every year and Alaska, Californai, Oregan, Washington, Japan, Indonesia, Malaysia, Philipines, India and other parts of the world can all expect to experience larger or smaller tsunamis in the future. Tsunami earthquakes are those where there is a major shift of the seabed as two tectonic plates slide against each other, releasing forces many times as great as an undersea nuclear bomb.   Top   © 2005, bethanyindia.org