Mount Rainier looks like the sort of mountain that belongs on a postcard.
Standing more than 14,000 feet tall in Washington state, it’s one of the most recognisable landmarks in the Pacific Northwest.
Behind the picture perfect views, however, scientists have long regarded it as the most dangerous volcano in the whole of the United States.
That’s not because experts have spotted signs that it’s about to erupt and turn parts of Washington state into Pompeii 2.0. Perhaps more worryingly, the most imminent danger might not involve an eruption at all.
It’s all down to what could happen if part of the mountain suddenly and unexpectedly decided to give way.
The biggest threat really isn’t lava. Instead, researchers are far more concerned about what they call ‘lahars’ — effectively a type of dirty avalanche consisting of fast-moving torrents of mud, rock and water that can barrel down the volcano’s slopes with a truly devastating force.
According to Popular Mechanics, these flows can travel at speeds of more than 100mph, grow to absolutely enormous sizes and continue on for up to dozens of miles.
Anything unfortunate enough to be in the way tends not to have a particularly good day.
What makes Rainier stand out is the sheer amount of frozen water that’s sitting on top of it.
The volcano’s 25 major glaciers contain more snow and ice than all the other Cascade volcanoes put together.
That means that even a relatively small disturbance could potentially send huge quantities of ice, water, mud and debris downhill. And fast. Crucially, a volcanic eruption isn’t required for that to happen.
Heavy rainfall, rapid melting of snow or even something seemingly unrelated to the mountain like a dam failure can trigger what’s known as a ‘no-notice’ lahar.
Former Cascades Volcano Observatory geophysicist Andy Lockhart summed up the threat rather eerily, calling them ‘the things that goes bump in the night’ before adding: ‘It creeps me out.’
Thanks, Andy. That’s not particularly reassuring.
The concern is seriously heightened by the number of people living in areas that could be affected by such a thing happening.
Potential lahar routes extend into parts of Pierce County, where around 150,000 people live.
Towns including Orting, Puyallup and Sumner sit among the communities considered most at risk. Experts estimate that a major lahar could reach them in around half an hour, potentially affecting some 60,000 residents.
History shows just how destructive these kinds of events can really be. Back in November 1985, activity at Colombia’s Nevado del Ruiz volcano unleashed a deadly torrent of mud, water and volcanic debris that overwhelmed the town of Armero.
Tragically, more than 23,000 people were killed. And most within just a matter of mere minutes. The disaster remains one of the deadliest volcanic catastrophes of modern times and a stark demonstration of what these lahars are capable of.
Scientists aren’t suggesting that a similar event is about to happen at Rainier. Even so, the possibility of a fast-moving mudslide has led authorities to spend years preparing for a worst-case scenario.
Monitoring equipment has been installed right across the Cascade mountain range in order to detect seismic activity and any signs that a lahar may well be developing.
Information is relayed to emergency responders, helping them react as quickly as possible if an alert is triggered.
Preparation doesn’t stop with technology, though. In 2024, more than 45,000 students and staff from over 20 schools west of Mount Rainier took part in one of the world’s largest ever lahar evacuation drills.
The exercise reinforced a key lesson that emergency planners have repeated for years. When a lahar is approaching and time is running short, getting out on foot and heading for higher ground remains one of the most effective ways to escape danger.