Tsunami

Tsunami are sometimes referred to as tidal waves. In recent years this term has fallen out of favor, especially in the scientific community, because tsunami actually have nothing to do with tides. The once popular term derives from their most common appearance which is that of extraordinarily high tidal bore. Tsunami and tides both produce waves of water that move inland, but in the case of tsunami the inland movement of water is much greater and lasts for a longer period.
Tsunami is a large ocean wave that caused by sudden motion the ocean floor. This sudden motion could be an earthquake, a powerful volcanic eruption or an underwater landslide. The impact of large meteorite could the open ocean at great speeds and build into large deadly waves in the shallow water of a shoreline.
Most tsunami are caused by earthquake generated in subduction zone, area where an oceanic plate is being forced down into the mantle by plate tectonic forces. The friction between the subducting plate and the overriding plate is enormous. This friction prevents slow and steady rate and instead the two plates become stuck.
As the stuck plate continues to descend into the mantle 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 accumulated I the overriding plate over a long period of time decades or even countries.