A 7.8 Mw  strike-slip earthquake in Alaska causes a landslide that produces a megatsunami. The runup from the waves reached 525 m (1,722 ft) on the rim of Lituya Bay; five people were killed.

The 1958 Lituya Bay earthquake occurred on July 9, 1958, at 22:15:58 PST with a moment magnitude of 7.8 to 8.3 and a maximum Mercalli intensity of XI (Extreme). The strike-slip earthquake took place on the Fairweather Fault and triggered a rockslide of 30 million cubic meters and about 90 million tons into the narrow inlet of Lituya Bay, Alaska. The impact was heard 80 kilometers (50 mi) away, and the sudden displacement of water resulted in a megatsunami that washed out trees to a maximum elevation of 524 meters at the entrance of Gilbert Inlet. This is the largest and most significant megatsunami in modern times; it forced a re-evaluation of large-wave events and the recognition of impact events, rockfalls, and landslides as causes of very large waves.

Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides.

A megatsunami is an incredibly large wave created by a substantial and sudden displacement of material into a body of water.

Lituya Bay is a fjord located on the coast of the south-east part of the U.S. state of Alaska. It is 14.5 km (9 mi) long and 3.2 km (2 mi) wide at its widest point. The bay was noted in 1786 by Jean-François de Lapérouse, who named it Port des Français. Twenty-one of his men perished in the tidal current in the bay.