Scientists Warn Mount Rainier Could Trigger a Deadly Mudflow

Mount Rainier in Washington state, about 87 kilometers southeast of Seattle, is often seen as a scenic landmark, but scientists say it hides one of the most dangerous natural threats in the United States. The volcano’s last eruption was in 1450, yet the greatest danger is not lava. According to Popular Mechanics, the real threat is a lahar, a fast-moving volcanic mudflow made of mud, rocks, water and debris that can surge downhill at more than 160 km/h and rise dozens of meters high.

The hazard is especially alarming because it does not require a major eruption. Heavy rain, sudden snowmelt or even a slight ground shift can trigger it. Geophysicist Andy Lockhart, a former researcher at the Cascade Volcano Observatory, called it “the thing that makes noise at night and freezes your blood.”

Rainier is covered by 25 major glaciers that store enormous amounts of snow and ice, five times more than all the other volcanoes in the region combined. Scientists warn that even modest melting could set off a chain reaction that would flood Pierce County, home to about 150,000 people. A sudden collapse on the mountain’s western side could send a lethal wave toward Orting, Puyallup and Sumner within half an hour, potentially affecting 60,000 people immediately.

Local residents are preparing for that possibility. More than 45,000 students and staff from 20 schools recently took part in a large evacuation drill. Volcanologist Lizet Caballero Garcia of the National Autonomous University of Mexico said the phenomenon is complex, changes as it moves and can grow to unimaginable size. She cited Colombia’s 1985 disaster, when a volcanic mudflow killed more than 23,000 people in minutes. U.S. emergency officials have deployed a network of advanced sensors, but scientists say the uncertainty remains huge. For them, the question is not whether such a disaster will strike again, but when, and who will escape in time.