What Makes Tsunami so Dangerous?

Tsunami is a japenese word, meaning harbour waves. Tsunami are gaint waves caused by the underwater earth-quakes, landlines or volcanic eruptions. Among these three, mostly earth-quakes cause Tsunamis, as tremors are strong enough to displace the water on the bottom of the occeans, which generates waves all the way from the bottom to the surface of the occean. Tsunami are behaving like tides, that is why they were earlier called tides. But unlike, tides they are not formed by the gravitational forces acted upon by the sun or the moon on the earth. Besides, these are not destructive like Tsunami. So usage of the term tides is discouraged for the Tsunami by the oceanographers. Tsunami originates from the ocean floor where water has displaced due to earth-quakes, volcanic eruptions or landslides. Tsunami looks a normal tide in the deep ocean, as it is able to lift the water only slightly due to its large depth. It’s speed is maximum in areas where the water is deepest. It’s speed decreases as the water gets shallower which is close to the shore. Since it’s total energy remains the same, it transfers the energy in rising the water resulting in very large amplitude (height) of the waves as they reach the shore. This is called wave shoaling. They form like wall of water and moves to the shore devastating everything that comes its way. The first Tsunami wave may not be the largest. Tsunami occurs as a series of waves. As the the first wave reaches the shore, it’s speed reduces considerably. But the waves following it are still in deep waters, hence their speeds are very high. These waves are reaching the shore just as the first wave is about to strike. So many waves are striking the shore instantly resulting in formation of the large wall of water which moves very deep into the inland areas, causing massive destruction.
If the first part of the Tsunami reaching the shore happpens to be the trough. Then water draws back dramatically from the shore exposing parts of the shoreline that are normally under water and leaving many marine creatures stranded. The drawback can be a warning that a Tsunami is approaching the shoreline. But the problem with it is that there is very less time from seconds to few minutes at the most, from the water receding the shoreline and full blown Tsunami hitting the shoreline. There is very less one could do at that time. People unaware of the drawback danger remains around the seashore to see the exposed sea bed which could extend hundrends of metres are at very high risk. One couldn’t differentiate between tide and tsunami in the deep waters. As both look similar waves there. This is where the warning is important and must be followed strictly. If there is earth quake, then there are chances of Tsunami hitting the area. Don’t get fooled by the calmness of the occeans after the earth-quakes. There are warnings already before the Tsunami arrives. One must be take them seriously and move to safer places before it arrives. Around 80% of all Tsunamis occur in Pacific occean around ” the ring of fire”. This area is geologically most active where tectonic shifts make earthquakes and volcanoes very frequent. The Tsunami warning stations round the globe are in constant contact with the seismic stations. They work together to issue the Tsunami warnings to particular areas. As they know which areas got hit by earth-quakes and which areas are likely to get hit by Tsunami due to the earth-quake. The people visiting these areas or living in these areas must always keep an eye on the warnings issued by the weather stations to save themselves from the inevitable.
( The author is a freelancer. Views are his own)
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