On August 10, 2025, a massive natural disaster occurred in Alaska. At 5:26 AM, a large piece of rock broke off from a mountain wall and crashed into Tracy Arm fjord.
This rock wedge had a volume of approximately 64 million cubic meters. When this immense weight hit the water, it created one of the largest waves ever recorded in modern times.
According to the Science Journal written by Dan H. Shugar and his colleagues, the result of this megatsunami reached a maximum runup height of 481 meters (1,578 feet). This is way higher than the iconic Petronas Twin Towers in Malaysia that stand at a height of 451.9 meters.
How Did the Megatsunami Happen?
Most people believe that tsunamis are “only” caused by earthquakes under the ocean. However, when a landslide happens inside a narrow body of water like a fjord, the results are incredibly destructive.
The steep walls of Tracy Arm acted like a funnel, trapping the water and forcing all the kinetic energy into a tight space. Dan H. Shugar stated that the disaster started with a breaking wave that was 100 meters high.This initial wave moved through the fjord at a speed of more than 70 meters per second.
The power of this moving water was immense. As the wave tore through the fjord, it ripped all the trees, soil, and bushes off the rocky walls. This destruction left behind a very clear visual line on the landscape, which scientists call a trimline.
This event also produced a very unusual geological phenomenon. When the landslide displaced the water, it caused the entire fjord to act like a giant bowl. The water began sloshing back and forth continuously, an event that scientists refer to as a landslide-induced seiche.
When the water moved back and forth, it created a steady, rhythmic vibration that traveled directly into the ground. This seiche generated a monochromatic 66-second seismic signal that continued to shake for 36 hours.
The Impact of Climate Change
This landslide was not a random coincidence. The mountain slope had actually stayed intact for thousands of years. It only collapsed because global warming weakened the geological structures holding it together.
The retreat of the South Sawyer Glacier left the slope without any physical support. The local summertime temperatures in the area have increased by 1.1 degrees Celsius since the year 1875. As the glacier melted and pulled backward, the mountain lost its natural rock buttress, which made a major collapse inevitable.
As global temperatures rise, glaciers across the Arctic will continue to thin and melt away. This means that these types of dangerous landslide events will likely become much more common in the future. This is a major concern because these remote Alaskan fjords are popular routes for large tourism cruise ships.
The rapid retreat of glaciers due to climate change has substantially increased the risk of these monster waves in coastal environments. As this place is one of the famous tourist destinations in Alaska, scientists are now trying to use advanced seismic monitoring systems to detect microseismicity, which means the tiny earth tremors that happened 24 hours before this landslide, to give people an early warning next time.
