In August 2025, a sudden landslide in southeast Alaska’s Tracy Arm fjord caused a tsunami that swept away vegetation up to nearly 1,600 feet above sea level, forever altering the glacial fjord's landscape and highlighting the dynamic power of natural forces.
- 64 million cubic meters of rock slid into Tracy Arm in August 2025
- Tsunami stripped vegetation nearly 1,600 feet above sea level
- Event generated seismic signals worldwide, similar to a magnitude 5.4 quake
What happened
On August 10, 2025, a massive landslide unleashed 64 million cubic meters of rock into the Tracy Arm fjord in southeast Alaska, triggered by the rapid retreat of the South Sawyer Glacier. The enormous volume of material displaced water, generating a powerful tsunami that surged across the fjord. This wave stripped vegetation from valley walls reaching as high as 1,578 feet above sea level, and caused extensive damage to shores and islands along the fjord.
Satellite images taken before and after the event by NASA-USGS Landsat satellites clearly illustrate the dramatic changes. The landslide exposed a large scar on the north side of the fjord, while Sawyer Island and surrounding areas lost much of their forest coverage. The slide also caused part of the glacier’s terminus to break off, creating a slurry of icebergs in the fjord. The event was so energetic it produced seismic waves detected globally, equivalent to a magnitude 5.4 earthquake.
Why it feels good
Though the event caused significant environmental upheaval, no injuries were reported, and it offers an extraordinary scientific window into natural landscape transformation in glacial environments. Researchers combined satellite, airborne, and on-the-ground data alongside eyewitness accounts and computer simulations to understand the tsunami’s impacts and behavior, including a seiche—a long-lasting fjord water oscillation—lasting more than a day after the wave.
This deepening knowledge helps scientists identify indicators of similar hazards in vulnerable areas. Understanding how glacial retreat increases susceptibility to landslides and tsunamis can improve early warning systems and safety practices. The event’s documentation also showcases the important role of space-based Earth observation in monitoring dynamic environmental changes and protecting communities.
What to enjoy or watch next
Follow ongoing monitoring of Tracy Arm and other glacial fjords using NASA's Earth-observing satellites to observe how vegetation recovers and landscapes evolve over time. Future studies will aim to refine predictions of landslide triggers by examining factors like rainfall, glacier retreat speed, and geological stability, enriching our understanding of climate change impacts on mountainous coastal regions.
For those interested in nature’s power and beauty, breathtaking satellite images and detailed reports are regularly published by NASA’s Earth Observatory. These provide inspiring visual stories of Earth’s continuously changing face, inviting the public to explore and appreciate our planet’s resilience and complexity.