Megatsunami

Mega Tsunamis, actually impact tsunamis are called tsunamis, whose height exceeds 100 meters in coastal areas. In addition, the amplitude of a mega tsunami is higher the closer the shaft is located at the origin. So it may happen that the tsunami wave reached already at sea heights of meters. Since the earthquake, according to current knowledge are not able to produce such waves, only catastrophic events such as the impact of a large meteorite or the collapse of a mountain in the sea can cause such mega- tsunamis. As a possible future trigger the Cumbre Vieja applies, for example on the Canary island of La Palma, where some geologists fear that any further volcanic eruptions one flank of the Cumbre Vieja could slip into the Atlantic.

Apart from such ideas are the following facts:

• In the history of mankind uniquely local mega tsunamis are known.
• The possible causes of a mega tsunami are very rare events.
• Landslides cause tsunamis of very short wavelength can not propagate over thousands of kilometers, without using up their energy. After the landslides in Hawaii (1868 on Mauna Loa and 1975 on Kīlauea ) experienced large local tsunamis, without the American or the Asian coast were threatened.

It is controversial whether caused by a meteorite impact crater Mahuika in the sea off New Zealand for a mega- tsunami in the 15th century out of the question, who is blamed for deposits up to 220 meters above sea level on Stewart Iceland.

An exceptional example of a tsunami that reached a height of 520 meters, has been initiated in the summer of 1958 by a landslide in Lituya Bay ( Alaska).