ManuTsunami

Megatsunami

23 08 2007

Megatsunami (often hyphenated as mega-tsunami, also known as iminami or “wave of purification”) is an informal term used mostly by popular media and popular scientific societies to describe a very large tsunami wave beyond the typical size reached by most tsunamis (usually around 10 m).^{[citation needed]} A megatsunami is associated with waves beyond the norm for tsunamis, ranging from over 40 metres (131 feet) to giants over 100 metres (328 ft) tall. Note that the waves are often much higher when they meet land, as the water often floods upwards from the force of impact.

Megatsunamis are caused by a very large impact or landslide into a body of water when the water cannot disperse in all directions. For this reason, they are usually a highly localized effect, either occurring when the origin of a tsunami is extremely close to the shore, or in deep, narrow inlets, lakes or other water passages.

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Categories : Megatsunami

Meteotsunami

23 08 2007

A meteotsunami is a tsunami-like wave phenomenon of meteorological origin. Tsunamis and meteotsunamis propagate in the water in the same way and have the same coastal dynamics. In other words, for an observer on the coast where it strikes the two types would look the same. The difference is in their source only. One definition of a meteotsunami is as an atmospherically generated large amplitude seiche oscillation.

The principal source of these tsunami-like ocean waves are travelling air pressure disturbances, including those associated with atmospheric gravity waves, roll clouds, pressure jumps, frontal passages, and squalls, which normally generate barotropic ocean waves in the open ocean and amplify them near the coast through specific resonance mechanisms. In contrast to ‘ordinary’ impulse-type tsunami sources, a travelling atmospheric disturbance normally interacts with the ocean over a limited period of time (from several minutes to several hours).

These types of waves are common all over the world and are better known by their local names: Rissaga (Spain), Milghuba (Malta), Marrubio (Italy), Abiki (Japan).