Imagine standing on a small fishing boat in a remote Alaskan bay. It's late evening, July 1958. Suddenly, the world starts shaking so hard you can't even stand up. Then, a roar. Not just a loud noise, but a sound like the earth itself is splitting open. You look toward the head of the bay and see something that shouldn't be possible: a wall of water so high it’s literally scrubbing the trees off a mountain peak.
This isn't a scene from a big-budget disaster movie. It actually happened.
When people ask what was the largest tsunami in the world, they’re usually looking for a single number. That number is 1,720 feet. To put that in perspective, that is taller than the Empire State Building. It’s taller than the Willis Tower in Chicago. It’s a height that feels fake, yet the scars on the Alaskan landscape prove it was very, very real.
The Night Lituya Bay Changed Everything
Lituya Bay is a T-shaped fjord on the coast of Southeast Alaska. It’s beautiful, remote, and—as it turns out—incredibly dangerous. On July 9, 1958, a massive 7.8 magnitude earthquake struck along the Fairweather Fault. This wasn't just a little tremor; it was a violent lurch that sent 40 million cubic yards of rock and ice plummeting 3,000 feet straight down into the Gilbert Inlet at the head of the bay.
Think about that for a second. That's enough rock to fill about 8 million dump trucks, all hitting the water at once.
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The result wasn't just a wave; it was a "megatsunami." The sheer force of that rock hitting the confined space of the bay created a splash wave that surged up the opposite slope. Geologists later measured the "trimline"—the literal line where the forest was erased and only bare rock remained. That line was 1,720 feet (524 meters) above sea level.
Basically, the water didn't just flood the coast. It climbed a mountain.
Why This Tsunami Was Different (and Why Size Isn't Everything)
Most of us think of tsunamis as things caused by underwater earthquakes in the deep ocean, like the tragic 2004 Indian Ocean event. Those are "tectonic" tsunamis. They have long wavelengths and can travel across entire oceans, hitting multiple countries.
The Lituya Bay event was a "landslide-generated" tsunami.
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These are different beasts. They are local, concentrated, and ridiculously tall. While the 2004 tsunami had waves that reached maybe 100 feet in some places, it killed over 230,000 people because it hit densely populated areas. In contrast, the largest tsunami in the world in Lituya Bay only killed five people.
Why? Because almost nobody lives there.
The Survivors' Story
Honestly, the most insane part of this story isn't the height of the water—it’s the people who lived through it. There were three boats in the bay that night.
- The Sunmore: This boat was near the entrance. Sadly, it was caught by the wave and disappeared. The couple on board were never found.
- The Badger: Bill and Vivian Swanson were on this boat. The wave actually picked their boat up and carried it over the La Chaussee Spit—a strip of land covered in trees—and dumped them into the open ocean. Bill later said he looked down and saw the tops of the trees below him as they "surfed" the crest. Their boat eventually sank, but they survived in a small skiff.
- The Edrie: Howard Ulrich and his seven-year-old son were anchored further in. Howard saw the mountain fall and the wave coming. He couldn't get the anchor up fast enough, so he let out all the chain and stayed at the wheel. The wave snapped the anchor chain, lofted the boat up, and he basically steered it like a wild horse until things settled down.
Breaking Down the "Megatsunami" Math
Scientists like Dr. Hermann Fritz have spent years trying to model exactly how water behaves when a mountain falls into it. Using scale models, they found that the Lituya Bay wave wasn't a single "surge" like a tide. It was a massive "splash" followed by a gravity wave that raced down the bay at about 100 miles per hour.
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| Tsunami Type | Cause | Max Height (approx) | Primary Danger |
|---|---|---|---|
| Megatsunami | Landslide / Volcanic Collapse | 500+ meters | Localized, extreme vertical run-up |
| Tectonic Tsunami | Subduction Zone Earthquake | 30-50 meters | Ocean-wide reach, massive inland flooding |
| Meteorite Tsunami | Impact | Theoretical (thousands of feet) | Global devastation |
When you look at the "trimline" today via satellite imagery, you can still see the difference in vegetation. The younger, lighter green trees show exactly where the 1958 wave stripped the earth bare. It’s a permanent scar on the face of Alaska.
What Most People Get Wrong About Big Waves
A common misconception is that the "largest" tsunami is always the "deadliest." It’s a weird quirk of geography. A 1,700-foot wave in an empty Alaskan fjord is a scientific marvel; a 30-foot wave in a flat coastal city is a humanitarian catastrophe.
People also assume these waves look like the curling "pipeline" waves surfers love. They don't. A tsunami, especially a megatsunami, looks more like a wall of churning debris—rocks, ice, and thousands of uprooted spruce trees—moving like a liquid bulldozer.
Lessons for the Future
If you're ever visiting the Alaskan coast or similar fjords (like those in Norway or British Columbia), there are actual things you should know. These events aren't as rare as we'd like to think. Lituya Bay had smaller but still massive waves in 1853, 1874, and 1936.
Actionable Insights for Coastal Safety:
- Feel the Earth? Move. If you are near the coast and feel an earthquake that lasts more than 20 seconds or makes it hard to stand, don't wait for a siren. Just get to high ground immediately.
- Watch the Water. If the ocean recedes unusually far, exposing the seafloor, that’s the "trough" of the wave. You have minutes, maybe seconds, to run.
- The First Wave is a Liar. Tsunamis are a series of waves. Often the second or third is the biggest. People die because they go back down to the beach to see the damage after the first wave recedes.
- Vertical Evacuation. If you can’t get inland, go up. At least 100 feet. In the case of Lituya Bay, 1,700 feet would have been necessary, but that’s a geological outlier.
The story of Lituya Bay is a reminder that the earth is a living, moving thing. We live on its surface by permission, and every now and then, it reminds us just how small we really are. To see the impact for yourself, you can actually take flight-seeing tours out of Yakutat, Alaska, to fly over the bay and see the 1958 trimline with your own eyes. It's a humbling sight that no textbook can truly capture.