On August 10, 2025, an extraordinary natural event unfolded in Alaska's scenic Tracy Arm fjord—a popular tourist destination. A massive landslide triggered a tsunami that reached heights of 481 meters, making it the second highest tsunami ever recorded. Despite its immense size, nobody was hurt, earning it the label of a near-miss. Let's explore the details through these questions.
1. What exactly caused the Tracy Arm tsunami, and how massive was it?
At 5:26 a.m. local time, a colossal wedge of rock—at least 63.5 million cubic meters in volume—broke free from a mountain above the fjord. It plummeted into deep water at the end of the South Sawyer Glacier. This impact generated an initial wave 100 meters high that tore across the fjord at speeds exceeding 70 meters per second. When it hit the opposite shore, the water surged up steep rocks to a staggering 481 meters above sea level. This runup is second only to the 1958 Lituya Bay tsunami (530 meters).
2. Why was this event considered a near-miss despite being so powerful?
The term near-miss applies because there were no injuries or fatalities. The timing was key—it struck very early in the morning, when few people were active in the area. Tracy Arm is a major tourist zone with cruise ships and kayakers during summer, but at 5:26 a.m., most were still asleep or not yet on the water. If it had occurred a few hours later, the outcome could have been catastrophic. Researchers warn that similar future events might not be so lucky, especially as glaciers recede and slopes become unstable.
3. How does this tsunami compare to other recorded megatsunamis?
According to Aram Fathian, a University of Calgary researcher and co-author of the study, this is the second highest tsunami ever recorded. The record remains the 1958 Lituya Bay tsunami in Alaska, which reached 530 meters. Unlike typical earthquake-generated tsunamis—whose waves usually top out at a few tens of meters—landslide tsunamis like this one are far more violent but localized. Since 1925, scientists have documented 27 landslide tsunamis with runups exceeding 50 meters. This event jumps to the top of that list after Lituya Bay.
4. What makes landslide tsunamis so different from earthquake tsunamis?
Landslide tsunamis are triggered by a sudden mass of rock or earth plunging into a confined body of water, like a narrow fjord. This direct displacement of water, combined with rapid variations in depth, creates extremely high, fast-moving waves. Earthquake tsunamis, in contrast, are generated by seafloor uplift over large areas, producing longer but lower waves. While earthquake tsunamis can cross entire oceans, landslide tsunamis are usually confined to a local area but reach terrifying heights. The Tracy Arm event exemplifies this: a localized wave 481 meters high that dissipated quickly beyond the fjord.
5. How did scientists reconstruct this event in detail?
The reconstruction was published in a recent Science study led by Aram Fathian and colleagues. They used a combination of satellite imagery, seismic data, and field surveys. Before-and-after images revealed the scar on the mountain and the volume of displaced rock. Seismic stations recorded the distinct vibration of the landslide impact. Field teams measured the trim line—the zone where vegetation was stripped away by the wave—to calculate the runup height. Numerical models then simulated the wave propagation, confirming the extreme speeds and heights observed.
6. Could a similar disaster happen in other tourist areas?
Yes, many fjords in Alaska, Norway, Greenland, and other glaciated regions face similar risks. As glaciers melt due to climate change, they expose steep, unstable slopes that can fail catastrophically. Scientists are monitoring known unstable slopes, such as the Barry Arm in Alaska, which could trigger a megatsunami. The Tracy Arm event serves as a wake-up call: remote does not mean safe, especially where tourism is growing. Early warning systems and better mapping of unstable rock faces are critical to protect lives.
7. Why hadn't most people heard about this tsunami until now?
Despite its record-breaking size, the tsunami remained largely unknown outside scientific circles because it caused no damage or casualties. Early morning timing meant no one was in the direct path. News cycles often prioritize disasters with human impact, so this event flew under the radar. The research team hopes that sharing these findings will raise awareness about the potential for future landslide tsunamis in populated or tourist-heavy areas. As the authors note, we may not be so lucky next time.