14,410-foot Mount Rainier with 25 major glaciers looms over millions in Washington. Scientists fear what would happen if one suddenly collapses like in Nepal

A catastrophic glacier collapse in Nepal has killed more than 350 people and left more than 1,000 missing, raising fresh questions about the dangers posed by unstable glaciers and rapidly moving mountain debris. Now, thousands of miles away, scientists have long warned that another heavily glaciated mountain could unleash a devastating disaster of its own — Mount Rainier in Washington state.

The 14,410-foot volcano towers over the Seattle-Tacoma metropolitan area, home to more than 3.3 million people. While there is no evidence that Mount Rainier is about to erupt, the mountain's enormous glacier cover and unstable volcanic slopes make it one of the most dangerous volcanoes in the United States.

Why Mount Rainier is so dangerous

Mount Rainier is covered by 25 major glaciers containing more than five times as much snow and ice as all the other Cascade volcanoes combined, according to the U.S. Geological Survey. That enormous store of ice creates the potential for catastrophic lahars — fast-moving mixtures of water, mud, rocks and volcanic debris that can behave like flowing concrete.


And crucially, such a disaster does not necessarily require a volcanic eruption.


USGS scientists say the most recent large lahar at Rainier, the Electron Mudflow around 1500 AD, showed no evidence of being associated with an eruption. Instead, it was caused by a large landslide on the volcano's western flank. Scientists have also identified areas of the mountain that could be vulnerable to another large collapse.

That is what makes the Nepal disaster such a striking warning sign. In Nepal, scientists investigating the August 26 catastrophe believe a massive collapse of ice and rock may have temporarily blocked a river, creating a natural dam before the blockage failed and unleashed a devastating torrent downstream. The resulting floods swept through communities along the Bhote Koshi River and destroyed bridges, roads and other infrastructure.

A wall of mud and debris could race downhill

At Rainier, a major lahar could move rapidly through river valleys leading away from the volcano. USGS modelling indicates that a large lahar could reach residential areas inside Mount Rainier National Park in about five minutes and communities outside the park in roughly 15 to 60 minutes, leaving little time for people to react.


The danger extends well beyond the mountain itself. Past lahars have travelled tens of miles, and areas once covered by those flows are now densely populated and contain highways, bridges, pipelines and other critical infrastructure.

Communities in the Puyallup River valley are particularly exposed. A major lahar descending from Rainier could follow existing river channels toward populated areas, potentially turning roads and waterways into conduits for a huge wave of mud, boulders and water.

The scale of Rainier's ice makes the scenario particularly alarming. USGS notes that even melting only a small portion of the volcano's glacier ice could produce enough water to generate enormous lahars.

Mount St. Helens showed how quickly the landscape can change

Washington has already experienced the destructive power of volcanic debris flows.

As per a report of the Daily Mail, when Mount St. Helens erupted in 1980, enormous quantities of volcanic material and melted snow combined with water to produce destructive mudflows and debris flows that travelled far downstream. The eruption killed 57 people and destroyed homes, roads, bridges and other infrastructure across the region.

Rainier presents a different but potentially severe hazard because of its huge glacier system and the densely populated valleys surrounding it.

The U.S. Geological Survey describes lahars as Mount Rainier's greatest hazard to people near the volcano. They can originate from either volcanic activity or landslides, meaning residents cannot assume that an eruption warning would always precede a major debris flow.

Could Nepal's disaster happen at Mount Rainier?

Not in exactly the same way.

The Nepal disaster appears to have involved a sudden glacier collapse, debris movement and temporary river blockage. Rainier's hazard is primarily associated with lahars and large landslides involving the volcano's glaciers, volcanic rock and water.

But the underlying danger is similar: a relatively sudden collapse high in the mountains can transform into a devastating flood of water, ice, mud and rock far downstream.

And in Washington, that potential disaster sits above one of the most heavily populated regions in the Pacific Northwest.

That is why Mount Rainier is closely monitored. USGS and emergency-management agencies operate lahar detection and warning systems designed to provide communities with as much warning as possible.

For residents, the message from scientists is not that Rainier is about to explode. It is that the mountain represents a permanent natural hazard — one capable of producing a disaster with little warning.

The deadly glacier collapse in Nepal has offered a grim reminder of just how much destructive power can be stored in the ice and rock of a mountain. At Mount Rainier, scientists know that the ingredients for a similar large-scale debris disaster already exist.