One of the most closely watched volcanoes in the United States could someday produce a catastrophe with echoes of the tsunami-like flash flood and landslide that tore through Nepal.
Mount Rainier in Washington state is an active, ice-laden stratovolcano that towers above the Seattle-Tacoma region, where more than 3.3 million people live in its shadow. Its glacier-covered slopes make it especially dangerous, with the potential to send violent surges of mud, rock and debris racing downhill with little notice.
More than 60,000 people are in Mount Rainier’s lahar hazard zone. These fast-moving flows of water, mud, boulders and debris can move like wet concrete, flattening communities and infrastructure in as little as 15 minutes — and they do not require a volcanic eruption to begin.
Researchers have long cautioned that a landslide, intense rainfall, rapid glacier melt or even a modest earthquake could weaken part of Mount Rainier and trigger a deadly rush through nearby river valleys.
That threat is why the US Geological Survey (USGS) ranks Mount Rainier among its highest-priority volcanoes for potential danger, even though the mountain has not had a major eruption in more than 1,000 years.
The disaster that struck Nepal on Wednesday, killing at least 95 people and leaving hundreds more missing, offered a stark example of the kind of sudden destruction scientists fear could one day unfold in the Pacific Northwest.
Authorities believe the Nepal event may have been set off by an avalanche or glacier collapse, sending an immense slab of ice roughly 2,000 feet wide plunging thousands of feet into the Lhende Khola river valley near the Nepal-Tibet border.
As the ice crashed down, it mixed with water, rock and debris, forming a sudden wall of muddy floodwater that surged into the Bhote Koshi River and caused widespread devastation across Nepal’s Rasuwa district.
Scientists are warning that three Washington towns could be devastated within minutes if a massive volcanic mudflow suddenly roars down Mount Rainier during an eruption
The events in Nepal on Wednesday, which have left at least 95 people dead and hundreds missing, provided a grim warning of the potential destruction which experts fear could take place in the Pacific Northwest at any time
USGS has previously said: ‘The volcano is not “due” for an eruption and we do not see any signs of a potential eruption at this time.’
However, the agency also noted that a devastating lahar could come without warning, citing the Electron Mudflow of 1500AD that was caused by a landslide on the volcano’s west flank.
Scientists have found no signs of a volcanic eruption taking place.
USGS set up a lahar detection and warning system on Mount Rainier in 1998, which uses sensors buried in the ground and tripwires along key river valleys that sense the vibrations of an approaching lahar and automatically alert emergency centers.
The system was later upgraded between 2015 and 2021 with 14 new modern stations to transmit data in real time, cover additional river drainage areas, and use better technology such as seismometers and cameras to spot lahars earlier.
Still, the resulting devastation from a lahar down Mount Rainier could come too fast for residents to react in time.
Studies of the west flank have warned that this area is still vulnerable to a ‘future large-scale collapse’ which would send mudslides down multiple river paths.
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This mudflow could hit communities such as Orting, then continue toward Sumner and Puyallup. It could also travel south toward the town of Ashford and areas near Alder Lake.
A village on Indonesia’s Java Island was inundated by a lahar after the Semeru volcano erupted in 2022
Computer models from USGS showed the mudflow would reach homes and visitor areas inside Mount Rainier National Park in about five minutes, and reach towns outside the park in as little as 15 to 60 minutes.
The deadliest modern US lahar struck during the 1980 eruption of Mount St Helens, when the volcano’s collapsing north flank and scorching pyroclastic flows rapidly melted glacial ice.
The resulting torrents of mud and debris surged more than 60 miles through the Toutle and Cowlitz river valleys, destroying over 200 homes, 195 miles of roads and 27 bridges.
The danger of lahars in Washington has become so alarming that emergency officials now conduct massive evacuation drills designed to prepare residents for a disaster many experts believe is inevitable.
More than 45,000 students and staff from over 20 schools participated in one of the world’s largest lahar evacuation exercises on April 23, practicing evacuations to higher ground while emergency officials tested warning systems.
‘It is necessary to be aware of the natural warning signs of an approaching lahar – ground rumbling accompanied by a roaring sound like a jet or locomotive,’ USGS warned in a statement.
This huge stratovolcano looms over cities such as Seattle, Tacoma, and Yakima in Washington, as well as Portland, Oregon
The 1980 eruption of Washington’s Mount Saint Helens also produced a dangerous lahar that destroyed more than 200 homes, over 185 miles of roads and contributed to the total death toll of 57 people
The most critical piece of advice officials give is to move to higher ground as soon as a siren sounds or the signs of a lahar are felt.
This could mean abandoning cars and running on foot in areas where roads and highways become blocked with traffic.
At least 54 Americans are among the hundreds missing after devastating flash floods swept through Nepal after the landslide.
A total of 579 people have been reported missing, according to figures from the Nepali police.
Surveillance cameras from the scene of the disaster captured the moment when waves taller than the local buildings swept through the streets, decimating the structures and washing away crowds of people who were caught outdoors.
