The 8 Largest Tsunamis Ever Recorded

Most tsunamis go undetected. They are defined as waves triggered by disturbances like earthquakes, volcanic eruptions, or landslides, and typically only rise a few inches, according to NOAA. However, when the triggering event is powerful enough, the consequences can be catastrophic. The most intense tsunamis travel as fast as jet aircraft across the ocean and can reach heights comparable to skyscrapers. Once they hit land, they can obliterate entire cities in mere minutes.

The tsunamis on this list may not be the deadliest or most destructive, but they certainly excel in one area: sheer size. Below are the tallest megatsunamis ever recorded.

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1. Karrat Fjord, Greenland // 295 Feet

Tsunamis are uncommon in Greenland, yet in 2017, one of the largest waves ever recorded struck the region. A landslide in Karrat Fjord generated a massive 295-foot wave that hit the fishing village of Nuugaatsiaq on June 17. The megatsunami resulted in the loss of four lives and swept 11 buildings into the sea. Experts attribute the event to a warming climate that is destabilizing the glaciers. The surrounding mountains are still unstable, and a potentially larger tsunami triggered by another landslide may threaten Greenland in the future.

2. Ambon Island, Indonesia // 328 Feet

The first megatsunami ever thoroughly documented in Indonesia remains one of the largest in history. On February 17, 1674, an earthquake in the Maluku Islands of the Banda Sea generated a tremendous wave that struck Ambon Island, claiming more than 2,000 lives. The wave surged up the coastal hills on the Hitu Peninsula, with its height estimated to be around 328 feet.

3. Lituya Bay, Alaska // 394 Feet

The megatsunami that struck the T-shaped fjord on Alaska's southeastern edge was most likely triggered by a landslide. Tree ring data suggests it occurred in late 1853 or early 1854, and trimlines (the points in the valley where trees were swept away) show the wave reached a maximum height of 394 feet. Lituya Bay has experienced multiple megatsunamis throughout history, and its steep cliffs combined with its location near the Fairweather fault line make it particularly prone to destructive waves.

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4. Lituya Bay, Alaska // 490 Feet

The second-largest tsunami ever recorded in Lituya Bay struck on October 27, 1936. Eyewitnesses reported three enormous waves crashing in from Crillon Inlet, each one following the other at speeds of about 22 mph. The tallest wave reached an astounding height of 490 feet. Although the exact cause remains uncertain, experts believe an underwater rockslide might have triggered the event.

5. Icy Bay, Alaska // 633 Feet

On October 17, 2015, the isolated fjord of Icy Bay in Alaska was struck by a monumental megatsunami. A landslide generated a 633-foot wave that swept across 8 square miles of forest in Wrangell St.-Elias National Park and Preserve. Fortunately, no humans were in the vicinity to be affected by the disaster. Like Lituya Bay, Icy Bay features steep cliffs shaped by a retreating glacier, which intensified the tsunami's impact.

6. Vajont Dam, Italy // 771 Feet

Unlike most tsunamis on this list, this catastrophe was a result of human actions. The construction of the Vajont dam in northern Italy—the tallest dam of its kind when completed in 1960—disrupted the surrounding environment. Cracks began to appear in the nearby Mount Toc early on, and on October 9, 1963, the entire slope collapsed into the reservoir below. The landslide triggered a massive tsunami that destroyed several villages in the Piave Valley within 15 minutes. More than 2,000 lives were lost in the disaster. Reaching a height of 771 feet, the Vajont dam tsunami is one of the largest and deadliest man-made environmental disasters in history.

7. Mount St. Helens, Washington // 820 Feet

The earthquake that triggered the infamous eruption of Mount St. Helens in Washington on May 18, 1980, also caused a tsunami. When the quake struck, the north face of the volcano collapsed into Spirit Lake. This landslide remains the largest on record, and the resulting 820-foot tsunami is the third-largest ever recorded. The wave hit Mount Margaret’s side before splashing back down into the lake's basin below.

8. Lituya Bay, Alaska // 1720 Feet

On July 9, 1958, Lituya Bay in Alaska was struck by the largest megatsunami ever documented. The event was triggered by a 7.8 magnitude earthquake on the Fairweather fault, which caused 90 million tons of rock to crash into the bay. The resulting wall of water reached nearly 1,720 feet—higher than the Willis Tower in Chicago. Five lives were lost in the disaster, including three people on the shore of Khantaak Island at the entrance to Yakutat Bay and two others on a boat in Lituya Bay.