Tall killer wave: The 1958 Lituya Bay mega tsunami

Many find the vastness and blue of the ocean or the sea to be calming and soothing. With its sounds and breeze, the waves do pose with the verisimilitude of being something that conciliates and calms. However, the very waves can be scary and even devastating when they take on the form of a tsunami.

A tsunami is a series of waves caused by earthquakes or undersea volcanic eruptions. Earthquakes, volcanic eruptions and other underwater explosions above or below water all have the potential to generate a tsunami. Tsunamis have been known to surge vertically as high as 100 feet (30 meters). However, the largest Tsunami record in modern times has been more than 17 times higher than that.

The largest and most significant tsunami recorded in modern times was the 1958 mega tsunami that occurred in Lituya Bay, Alaska, according an article in Geology.com. The mega tsunami rose as high as 1,720 feet or 524 meters - taller than the famous skyscraper Empire State Building.

On the night of 9 July, 1958, an earthquake along the Fairweather Fault in the Alaska Panhandle loosened about 40 million cubic yards (30.6 million cubic meters) of rock high above the northeastern shore of Lituya Bay in the US state of Alaska. The mass of rock plunged from an altitude of approximately 3000 feet (914 meters) down into the waters of Gilbert Inlet, the impact force of the rock fall generated a tsunami that crashed against the southwest shoreline of Gilbert Inlet.

Lituya Bay a few weeks after the 1958 tsunami. The areas of destroyed forest along the shorelines are clearly recognizable as the light areas rimming the bay. A fishing boat anchored in the cove at lower left was carried over the spit in the foreground; a boat under way near the entrance was sunk; and a third boat, anchored near the lower right, rode out the wave. Photo by DJ Miller, United States Geological Survey.

The wave then continued down the entire length of Lituya Bay, over La Chaussee Spit and into the Gulf of Alaska. The force of the wave removed all trees and vegetation from elevations as high as 1720 feet (524 meters) above sea level. Millions of trees were uprooted and swept away by the wave. This is the highest runup ever recorded for a tsunami.

The impact of rock hitting the water produced a local tsunami that swept the entire length of the Lituya Bay and over the La Chaussee Spit. This wave stripped all vegetation and soil from along the edges of the bay.

What Caused the Lituya Bay Tsunami?

Most tsunamis are caused by earthquakes on converging tectonic plate boundaries. However, tsunamis can also be caused by landslides, volcanic activity, certain types of weather, and—possibly—near-earth objects such as asteroids or comets colliding with or exploding above the ocean.

Photo looking down the Fairweather Fault Trench at the head of Lituya Bay. The front of Lituya Glacier with lateral and medial moraines is seen terminating in Gilbert Inlet. The cliff where the rockslide originated is on the right side of Gilbert Inlet. The opposite valley wall on the left side of Gilbert Inlet received the full force of the big wave, stripping it of soil and trees. Photo by DJ Miller, United States Geological Survey.

An earthquake on the Fairweather Fault caused about 40 million cubic yards of rock to fall from the east wall of Gilbert Inlet. When such a big chunk of rock fell into Gilbert Inlet, the velocity of the rock and its mass produced a powerful wave that rushed across the inlet.

That wave ran up the west wall of Gilbert Inlet to an elevation of about 1720 feet, the water of Gilbert Inlet has an elevation of sea level.