What caused the massive 1958 Lituya Bay megatsunami?

On July 9, 1958, a powerful earthquake struck the Fairweather Fault in Alaska, triggering a massive rockslide into Lituya Bay. This sudden displacement of roughly 30 million cubic meters of rock generated the largest recorded megatsunami in modern history. The resulting wave washed out trees up to an astonishing elevation of 524 meters at the entrance of Gilbert Inlet.

What we know

• The earthquake occurred on July 9, 1958, along the Fairweather Fault with a moment magnitude estimated between 7.8 and 8.3. [2]
• The earthquake triggered a rockslide of 30 million cubic meters, weighing about 90 million tons, into the narrow inlet of Lituya Bay. [2]
• The sudden water displacement created a megatsunami that washed out trees up to a maximum elevation of 524 meters at Gilbert Inlet. [2]
• Megatsunamis differ from ordinary tsunamis because they are caused by material falling into water rather than underwater tectonic plate movement. [4]

Where to go next

• how it workedHow do megatsunamis form?
• what caused itWhat is the Fairweather Fault?
• a case in pointWhat happened during the 1963 Vajont Dam disaster?
• whereHow does Lituya Bay geography look?
• compared withWhat is the difference between an ordinary tsunami and a megatsunami?
• an unexpected connectionHow do historic dam collapses relate to prehistoric meteor impacts?Both human-induced dam destabilizations and ancient asteroid impacts act as sudden material displacements that create devastating megatsunamis.

Sources

• [1]1958 Lituya Bay earthquake and megatsunami (Wikidata Q10745598) · CC0 1.0
• [2]1958 Lituya Bay earthquake and megatsunami · CC BY-SA 4.0
• [3]Lituya Bay · CC BY-SA 4.0
• [4]Megatsunami · CC BY-SA 4.0
• [5]Lituya Mountain · CC BY-SA 4.0