megatsunami

A megatsunami is an unusually large wave, significantly exceeding the height of a typical tsunami. These massive waves are thought to be caused by catastrophic events such as large landslides into or under bodies of water, volcanic flank collapses, or asteroid impacts. Unlike seismic tsunamis, which are generated by earthquakes and spread outward in all directions, megatsunamis are often localized, originating from the event that triggered them.

The most well-documented example of a megatsunami occurred on July 9, 1958, at Lituya Bay in Alaska. A magnitude 7.8 earthquake triggered a massive rockslide of approximately 30 million cubic meters into the bay. This landslide displaced an enormous volume of water, creating a wave that surged up the opposite mountainside to an astonishing height of 1720 feet (524 meters). This exceptional inundation was recorded on the slopes as a distinct debris line.

While the Lituya Bay event is a clear terrestrial example, the term megatsunami is also sometimes applied to hypothetical, even larger waves that could be generated by extraterrestrial impacts. Such an event would have devastating global consequences, far beyond those of a typical tsunami. The scientific understanding of megatsunamis is less extensive than that of seismic tsunamis due to their rarity and the extreme nature of their causes.