At 10:15 p.m. on July 9, 1958, the Great Alaska Earthquake shook the hell out of the Gilbert Inlet. It occurred when the Fairweather fault slipped, triggering an earthquake that measured 7.8 to 8.3 on the Richter scale. That set off a chain of events that led to the largest megatsunami ever recorded: the Lituya Bay megatsunami.
The earthquake was of the strike-slip variety, in which two slabs move horizontally beside each other along a vertical fault line. When it hit, it shook loose some 30-million cubic yards of rock from a cliff that dropped into a narrow inlet (Lituya Bay). It wasn’t a short drop into the bay, either. All that debris fell from as high as 3,000 feet before landing, displacing an enormous amount of h20, which was shoved forcefully through the narrow strip of water towards the entrance of Gilbert Inlet. By the time it reached it, the megatsunami’s devastation reached 1,720 feet in height. Over a thousand feet of ice was sheared from the Lituya Glacier. Trees were ripped out by the roots, soil washed away down to the bedrock, and anything and everything that stood in the way was demolished in the blink of an eye.