Lituya Bay & The World’s Largest Recorded Wave
The tsunamis that killed over 200,000 people in Indonesia in 2004 and caused a nuclear meltdown in Japan in 2011 were disasters nearly unfathomable in scale. Tsunamis, from Japanese for “harbor wave,” are caused by the displacement of a large volume of water, usually in oceans and usually caused by earthquakes. In fact, the two sets of waves were, respectively, caused by the third and fourth most powerful earthquakes recorded in the world.
And yet these two tragedies only produced waves between 100 and 130 feet high.
Only 130 feet high, you ask? Wouldn’t a wave with the height of a 13-story building pummeling a seacoast bring apocalyptic levels of destruction? Absolutely. I don’t mean to minimize the power and pain these disasters produced and, naturally, a 130-foot wave would absolutely make me pucker. But these two events have nothing on the Lituya Bay Megatsunami of 1958 when it comes to making tall waves.
Before we delve into the specifics of the Lituya Bay event, some background on the science of tsunamis. As described above, all tsunamis are caused by the displacement of water, but there is a technical difference between an ordinary tsunami and a megatsunami.
Most tsunamis, like those in Indonesia and Japan, are caused by earthquakes raising the ocean floor. Picture a bathtub with an adjustable bottom. Raise the bottom a few inches and the water will be pushed up and out of the tub. This process is what occurs during a typical tsunami at the shoreline.
Megatsunamis are formed from an object hitting a body of water, usually a landslide, but also from something like an asteroid strike. In our bathtub analogy, picture a giant rock thrown into the water. The resulting wave can be much larger than a typical tsunami.
In fact, during a tsunami caused by an earthquake, in the open water, the amplitude of the wave can be extremely small. A boat passing through a tsunami hundreds of miles from the spots eventually effected might barely notice. Only when the wave reaches shallower waters and, ultimately, the land itself does the wave height rear up. Megatsunamis, on the other hand, bring the heat from the start.
In 1958 a major earthquake hit the Fairweather Fault in the Gulf of Alaska. The quake, the strongest in the region in 50 years, was felt as far south as Seattle. As we have discussed, an earthquake itself does not cause a megatsunami. But the temblor did send a giant landslide into the water from the nearby mountain faces. Over 30 million cubic meters of rock fell vertically from heights of up to 3,000 feet. That’s quite a rock to toss into this giant bathtub.
The force of the falling stone was so great that the Lituya Glacier was actually lifted into the air. This nearly unbelievable phenomenon was witnessed by one of three boats in the bay at the time of the event. Scientists believe the raising of the glacier released rock trapped under the ice into the water, causing a dual rockslide.
The result was the highest wave in recorded history. The initial wave cleaned the spot in the cove across from the rockslide to the bedrock at a height of 1,720 feet. That figure is 300 feet higher than the Empire State Building and nearly as tall as the Freedom Tower. Because of the geography of the bay, which is shaped like a T, this first enormous wave crashed into the surrounding rock faces and dissipated quickly. However, the energy created was so great that a wave of over 100 feet traveled the entire 7 miles of the bay to the open sea at speeds of over 100 miles per hour.
Three boats were near the end of the bay when the earthquake hit. One was swallowed by the wave and the occupants were never seen again. Fantastically, the people on board the other two managed to survive.
The boats were carried by the wave over the spit and into the open ocean. Because of the vast scale of the bay, the people on the boats actually watched for minutes as the wave came at them. After it reached them, one of the eyewitnesses recounted looking down on trees from 80 feet above as they were ushered by the water. Thinking about that situation is utterly frightening. The earthquake, the wave, then the dread at seeing it come at you, with absolutely no way to escape, The first-hand accounts are a riveting read.
To this day, evidence of the event remains in the bay. Where the waves scoured vegetation and soil to the bedrock is, in 2020, marked by younger trees than those above them.
Scientists believe at least four other megatsunamis have occurred in Lituya Bay in the past 150 years, which means another one will eventually happen.
The widespread damage of this incident was nowhere near the scale of the Japanse or Indonesian tsunamis. The area is uninhabited and megatsunamis tend to be localized events, instead of largescale disasters. Also, higher waves may have occurred on our planet in the past. And in the future, far bigger events are waiting to happen (we’ll investigate potential calamities in Hawaii and the Canary Islands in future issues). But at the moment, this wave from 1958 is queen.
Further Reading and Exploration
BBC Nature: Mega Tsunami – Evidence of Destruction
NOAA Tsunami Program website – National Oceanic and Atmospheric Administration
Anatomy of a Tsunami – PBS Learning Media
Modeling the 1958 Lituya Bay mega-tsunami, II – The International Journal of the Tsunami Society (includes eyewitness accounts)
The Wave: In Pursuit of the Rogues, Freaks, and Giants of the Ocean – by Susan Casey (e-book version)