DESCRIPTION ABOUT TSUNAMI

A. DESCRIPTION ABOUT TSUNAMI
Tsunami are also known as tidal waves, although they have nothing to do with the
tide, and are sometimes called seismic sea waves. Tsunami are great towering waves of massive destructive power. They are caused by large earth movements and unheavals beneath the oceans. In turn, these are caused by earthquakes, volcanoes (again often beneath the ocean) and underwater landslides which result in a sudden large movement of the water. The size of a tsunami is not always proportional to the size of the earthquake, and some of the most destructive ones have originated from quite small earthquakes. This can occur when a huge amount of ocean sediment on a sloping surface (such as the transition point between two different levels of ocean shelf) is disturbed by the earthquake and a very large undersea landslide occurs, triggering the tsunami.

causes of sea waves usually divided into 3 groups, characterized by depth: • Water • Water• Medium length Although shallow water generated tsunami in deep water (about 4000 m below sea level on average), tsunami waves are considered shallow-water wave . Astsunami waves approach the shallow coastal waters, which remain the same period of time,but the wavelength decreases rapidly, thus causing water to accumulate to form anextraordinary summit, in an effect known as shoaling

Most tsunamis are caused by earthquakes generated in a seduction zone, an area where an oceanic plate is being forced down into the mantle by plate tectonic forces. The friction between the sub ducting plate and the overriding plate is enormous. This friction prevents a slow and steady rate of seduction and instead the two plates become stuck. Subduction Zones are Potential Tsunami Locations


Drawing of tectonic plate boundary before earthquake Overriding plate bulges under strain, causingtectonic uplift.





Plate slips, causingsubsidence and releasing energy into water The energy released produces tsunami waves.

As the stuck plate continues to descend into the mantle the motion causes a slow distortion of the overriding plage. The result is an accumulation of energy very similar to the energy stored in a compressed spring. Energy can accumulate in the overriding plate over a long period of time - decades or even centuries. Accumulated Seismic Energy
Tsunamis occur most frequently in the Pacific Ocean , but are a global phenomenon; they are possible wherever large bodies of water are found, including inland lakes, where they can be caused by landslides. Japan is a nation with the most recorded tsunamis in the world. The earliest recorded disaster being that of the 684 A.D.
Tsunami is one of the earth’s disaster. It was a Japanese word meaning “harbor wave,” used as the scientific term for a class of abnormal sea wave that can cause catastrophic damage when it hits a coastline. Tsunamis can be generated by an undersea earthquake, an undersea landslide, the eruption of an undersea volcano, or by the force of an asteroid crashing into the ocean