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"Megatsunamis were only theorized until July 9, 1958, when, in Lituya Bay, a very narrow fjord of the Alaskan panhandle, a 7.7 magnitude earthquake shook 90 million tons of rock and glacial ice off the mountainside at the head of the bay. It dropped off all at once, almost vertically, and landed as a monolith into the bay’s deep headwaters.
This generated the highest wave ever recorded on Earth, 1,720 feet. That’s 470 feet taller than the tip of the Empire State Building’s antenna. It is, in fact, taller than all but the five tallest skyscrapers on Earth today, and most scientists agree that it had sufficient power to rip these buildings from their foundations.
The wave traveled from the head of the bay out toward the open ocean, and because the bay is so narrow, the wave was funneled up the mountainsides. It snapped all the trees off at 3 to 6 feet above the ground, everywhere up to 1,720 feet high around the bay. Most of these were 6-foot-thick spruce trees.
There were a total of 3 fishing boats in the bay, near the mouth, and the wave sank one, killing the two on board. The other two were lucky to ride this wave up the mountainsides and then slosh with it back into the bay.
One of them was anchored, and the 3-foot-thick iron anchor chain was snapped like thread when the wave lifted the boat. One of the survivors estimated the length of time between the wave’s overtopping of the island in the bay to its arrival at his boat as 2 seconds. If this is true, the wave was traveling 600 mph.
It stripped away all the trees, grass, and soil down to the bedrock, and then dissipated in the open ocean."