what was the largest tsunami ever recorded
The largest tsunami ever recorded was the 1958 Lituya Bay megatsunami in Alaska, which produced a run-up height of about 1,720 feet (around 524 meters) above sea level.
What happened at Lituya Bay in 1958?
On July 9, 1958, a powerful earthquake (about magnitude 7.8) struck near Lituya Bay along the Fairweather Fault in southeastern Alaska. The shaking triggered a massive rockfall—tens of millions of tons of rock—into the narrow fjord-like inlet called Gilbert Inlet at the head of the bay. That sudden collapse displaced an enormous volume of water almost instantaneously, creating what is known as a megatsunami.
The wave blasted up the opposite slope of the bay, stripping trees, soil, and vegetation up to a measured height of about 1,720 feet (524 meters) above sea level, leaving a stark “trim line” that is still used as evidence of the event. Eyewitness accounts describe the wave traveling down the length of Lituya Bay and out toward the Gulf of Alaska, with boats being lifted high above the trees yet some survivors managing to ride it out.
Why this counts as “largest ever recorded”
Scientists measure tsunami size in several ways, but for the Lituya Bay event, the critical number is the run-up height —how high the water reached above sea level on land. The 1,720‑foot run-up in Lituya Bay is the highest reliably documented tsunami run-up in modern history, far exceeding typical large oceanic tsunamis, which are usually tens of feet high at the coast rather than hundreds or more.
It’s important to note that this was a very localized, confined event, not a basin-wide tsunami crossing an ocean like the 2004 Indian Ocean tsunami or the 2011 Japan tsunami. Those more famous tsunamis were far deadlier and more widespread but did not reach anywhere near the extreme height of the Lituya Bay megatsunami.
Deadliest vs. tallest tsunamis
When people ask “what was the largest tsunami ever recorded,” they sometimes mean different things:
- Tallest wave (run-up height):
- 1958 Lituya Bay, Alaska – about 1,720 feet (524 m) run-up, caused by earthquake-triggered rockfall in a fjord.
- Deadliest tsunami (most lives lost):
- 2004 Indian Ocean tsunami – wave heights around 30–100 feet in many places, but more than 200,000 people killed across multiple countries.
- Most destructive in modern infrastructure terms:
- 2011 Tohoku (Japan) tsunami – run-up commonly tens of feet, with some localized higher values, but catastrophic damage to towns, ports, and the Fukushima Daiichi nuclear plant.
Here is a quick comparison as HTML, since you asked for structured info:
| Event | Year & Location | Approx. Max Height / Run-up | Key Cause | Main Impact |
|---|---|---|---|---|
| 1958 Lituya Bay megatsunami | 1958, Lituya Bay, Alaska | [7]~1,720 ft (524 m) run-up – tallest recorded | [5][7]Earthquake-triggered rockfall into a narrow fjord | [3][7]Localized; massive tree stripping, few people affected | [5][7]
| 2004 Indian Ocean tsunami | 2004, Indian Ocean basin | [8][1]Typically tens of feet, up to around 100 ft in some locations | [1][8]Huge undersea megathrust earthquake | [8]Deadliest tsunami in modern history, 200,000+ deaths | [10][1][8]
| 2011 Tohoku (Japan) tsunami | 2011, northeastern Japan | [6][1]Commonly tens of feet, with some higher local run- up | [6][1]Magnitude 9.1 subduction-zone earthquake | [6]Extreme coastal destruction, major nuclear accident | [10][6]
Why the Lituya Bay wave was so extreme
The extraordinary height in Lituya Bay came from a combination of geography and the type of trigger. The bay is a steep, narrow fjord, so when an enormous rock mass plunged almost directly into the water, it pushed a huge pulse of water into a confined space, forcing it upward rather than allowing it to spread out. Studies of the event show that both the rockfall and the air dragged along with it contributed to the displacement, amplifying the wave and creating the extreme run-up observed on the surrounding slopes.
Quick TL;DR
- The largest tsunami ever recorded by height is the 1958 Lituya Bay megatsunami in Alaska, with a run-up of about 1,720 feet (524 m).
- It was caused by a massive rockfall triggered by an earthquake into a narrow fjord, making it an extremely tall but very localized event.
- The deadliest tsunamis, like the 2004 Indian Ocean and 2011 Japan events, were much lower in height but spread across huge regions and caused immense loss of life.
Information gathered from public forums or data available on the internet and portrayed here.
