Scientists are warning that parts of the United States face the risk of devastating natural disasters similar to the recent flash flood in Nepal, where collapsing mountainsides can unleash enormous waves and torrents of mud. These risks are amplified by thawing permafrost and retreating glaciers, which destabilize slopes.
Researchers have identified two primary areas in the U.S. with significant potential for such catastrophic events: Barry Arm in Alaska and Mount Rainier in Washington state. In 2020, Marten Geertsema, an adjunct professor of earth sciences at Simon Fraser University, and 13 other scientists published a warning about Barry Arm in Alaska's Prince William Sound. They noted that an unstable slope there could collapse into the water, triggering a tsunami, and estimated this possibility as 'likely within 20 years.' The thawing of permafrost and receding glaciers are identified as key factors contributing to the instability of mountainsides in the region.
Geertsema explained that in Alaska, retreating glaciers expose more of these unstable mountainsides to deep seawater. When rock slides into these bodies of water, it can generate exceptionally large localized tsunamis. Historical precedents include a 2015 landslide in Taan Fiord, which sent water surging 633 feet up nearby slopes, and a 1958 event in Lituya Bay, where an earthquake-triggered rockslide caused a tsunami that reached 1,720 feet up a ridge, destroying a cabin and killing two people. Another incident at Tracy Arm in August 2025 saw a collapse send water nearly 1,600 feet up an opposite mountainside, stripping vegetation.
Mount Rainier, a heavily glaciated stratovolcano near the Seattle-Tacoma metro area, presents a different but equally dangerous threat: lahars, or volcanic mudflows. These powerful mixtures of water, rock, and debris can form and descend without a volcanic eruption. Over 90,000 people are estimated to live within mapped lahar danger zones. Models suggest a significant lahar could reach populated areas within 15 to 60 minutes of its start. While the U.S. Geological Survey (USGS) has stated the volcano is not showing signs of an impending eruption, a devastating lahar could occur with little to no warning. The Electron Mudflow of 1500 AD, caused by a landslide on the volcano's west flank, serves as an example of such an event. Communities like Orting, Sumner, and Puyallup are identified as being at risk, with potential flows also extending south toward Ashford and Alder Lake. The USGS installed a lahar detection and warning system on Mount Rainier in 1998, which has since been upgraded to improve real-time data transmission and detection capabilities. However, the speed at which these flows can travel raises concerns about the effectiveness of evacuation warnings.
The recent disaster in Nepal, where an enormous chunk of glacier broke away and plunged into a valley, serves as a stark reminder of these hazards. More than 360 people have died and over 1,400 remain missing following that event, illustrating the concept of a 'hazard cascade' where one event triggers a chain of destruction.