The Megatsunami Of Lituya Bay

Alaska's Lituya Bay had been used for many years as a temporary shelter for boats traveling the eastern Pacific, but no one lives there permanently. In fact, the local Tlingit people told the legend of a monster at the mouth of the bay who shook the ocean to send huge waves. They knew what was going on. The unique geography of the bay amplifies waves to a terrifying extent. Travelers were there when the largest tsunami wave in recorded history blew through Lituya Bay in July of 1958. It reached about a third of a mile up the shore, destroying everything in its way. It started with a magnitude 8 earthquake.

The earth shook for anywhere from one to four minutes—eyewitness reports varied. When the fault finally came to rest, the foamy water of Lituya Bay settled back into something resembling its ordinary lazy waves, and a new quiet blanketed the bay. Despite the cessation of shaking, Orville and Mickey Wagner on the Sunmore—the boat headed for the bay exit—continued their retreat toward the open ocean.
After a minute or so of apparent calm, a crash described as “deafening” rattled the atmosphere. One of the unnamed mountain peaks that stood at the inland end of Lituya Bay had broken off, dropping ninety million tons of rock into the water with the force equivalent to a meteor strike. The resulting impact shook loose other rocks on the slopes, and chunks of adjacent glaciers, and these plunged into the water practically all at once. Millions of cubic yards of displaced water heaved upward and formed a wave traveling outward at about 110 miles per hour (180 km/h).
Within about a minute, the approaching wave became visible to the boats still at anchor, and the occupants looked on in awe as the wide skyscraper of water traversed the length of the bay towards them. When it reached Cenotaph Island another minute or so later, the proportions of the wave became clear. The center of the wave was almost as high as the highest point on the island, 300 feet in the air. On the two opposite shores, the plowing saltwater reached over 1,700 feet (over 500 meters) onto land, twisting even the most massive trees from their roots and scraping the bedrock nearly clean.

Read the story of the Lituya Bay megatsunami, gleaned from eyewitness accounts and the geologic record, at Damn Interesting