Megatsunami

A megatsunami is an extremely large wave produced by a sudden, massive displacement of material into a body of water, distinct from an ordinary tsunami generated by undersea tectonic movement, which typically tops out around 30 meters. Landslides, meteorite impacts and volcanic collapses can each trigger a megatsunami by displacing water so abruptly that it is thrown upward hundreds of meters, especially in confined bays where the energy cannot easily dissipate. The best documented example struck Lituya Bay, Alaska, in 1958, when an earthquake triggered landslide dropped about 80 million metric tons of rock into the bay and produced a wave with a run up height of 524.6 meters, the highest wave ever recorded and the case that established megatsunamis as a genuine, distinct phenomenon.