If you're lucky, you've never seen a tsunami in person, but you know that this type of massive wave can cause enormous damage. They can be measured, too, which easily leads to the question: What was the largest tsunami ever recorded?
Below, we'll take a look at the massive tsunami that occurred in Lituya Bay, Alaska, which is recognized as the largest recorded tsunami in history. Beyond that, we'll also look at the runners up, as well as the science of these giant waves.
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A tsunami is a giant wave (more accurately, a series of giant waves) that is caused by the rapid displacement of water. Usually, this is due to some kind of sudden geological event, such as an earthquake or volcanic eruption.
Tsunamis can also be caused by landslides or the calving of glaciers — anything that displaces a large enough amount of water to generate a wave that has a far longer wavelength than normal ocean waves. The word comes from Japanese and translates literally to "harbor wave."
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Despite what you might've seen at the cinema, not all tsunamis appear as enormous, cresting waves that crash on land. Often, they can take the appearance of a rapidly rising tide, which is why they are sometimes called "tidal waves."
Technically, this is incorrect, since the tides are caused by the gravitational pull of the moon. Tsunamis don't need the moon's gravity to form; instead, they are caused by displaced water. The term "tidal waves," while misleading, is still frequently used.
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The Lituya Bay tsunami occurred on July 9, 1958, when an earthquake struck the Alaskan panhandle along the Fairweather fault line. This 7.8-magnitude earthquake shook loose a huge chunk of rock above Lituya Bay, Alaska, causing nearly 40 million cubic yards (30.6 million cubic meters) of the mountainside to crash into the water.
In the way that throwing a rock into the water will cause a splash — and the bigger the rock, the bigger the splash — the displacement of water caused by this landslide generated a wave that strains imagination.
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The wave rose 1,720 feet (535 meters) above sea level, altering the landscape around the entirety of the icy bay. For reference, had the Empire State Building been rising out of the bay, the wave would've cleared it.
Luckily, there weren't many people in or around the bay at that time, and only three boats were hit by the world's largest recorded tsunami. This led to just two fatalities, which is still tragic, yet far less devastating than other tsunamis that have hit densely populated areas.
Technically, the Lituya Bay tsunami was a mega-tsunami. This term is used to describe events like the one that occurred in Lituya Bay, where the displaced water is caused by material (usually, rock or ice) that falls into the water. Landslides are a common cause.
Why would that make a difference? It seems that when such a collapse occurs, the waves created are even higher than large waves caused from undersea displacement. This could be due to the suddenness of the water displacement.
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While destructive tsunamis are relatively rare, such events have occurred throughout history, and it was only in the modern era that precise measurement became possible. Here's a list of the runners up to the Lituya Bay tsunami, in terms of height of the wave.
Many people are aware of the Mount St. Helens volcanic eruption, which occurred on May 18, 1980. This eruption also created a tsunami — another mega-tsunami, in fact — when the north flank of the mountain collapsed, creating a landslide that then generated a huge wave.
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The wave reached 853 feet (260 meters) high and caused widespread devastation.
On October 9, 1963, a landslide occurred above the Vajont Dam in Italy, generating a 820-foot (250-meter) wave. This mega-tsunami is notable for being partly human-induced, as the dam created a body of water that was deep enough for a tsunami to be generated.
This mega-tsunami also occurred in Alaska, and was also caused by a massive landslide. On October 17, 2015, a huge volume of rock went crashing into the Taan Fiord, which is a finger of Icy Bay.
The resulting wave had an initial height of approximately 330 feet (101 meters), and had a run up of 633 feet (193 meters). The run up height refers to the elevation of where the wave reached in the surrounding landscape.
There's something about Lituya Bay, Alaska. Before the enormous, record setting tsunami of 1958, there was another tsunami in the same bay. This occurred on October 27, 1936, and the cause isn't precisely known (an undersea landslide is a likely candidate), but it did create a massive wave: a run up height of 490 feet (150 meters), and an estimated wave height of between 100 and 200 feet (30 and 76 meters).
In Greenland, on June 17, 2007, a landslide caused by melting glacial ice led to a 328-foot (100-meter) giant wave that surged down the fjord and caused wreckage over 62 miles (100 km) away.
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So far, we've been rating the tsunamis on the size of the waves generated, but a taller wave doesn't necessarily mean a more destructive wave. In 2004, an earthquake struck with an epicenter near Sumatra, Indonesia. This led to the most destructive tsunami in history, dubbed the Indian Ocean tsunami.
When the first wave hit the surrounding shorelines, it caused massive destruction in the surrounding 14 countries, from the east coast of India to the west coast of Myanmar. More large waves followed, and the final death toll reached nearly 230,000 people.
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Although some of the waves were as high as 100 feet (30 meters), most of the destruction and loss of life was due to the densely populated coastal areas.
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