Why Washington's Mount Rainier Still Makes Volcanologists Worry

It's been a 1,000 years since there was a significant volcanic eruption from Mount Rainier, CNN reminds readers. It's a full 60 miles from Tacoma, Washington - and 90 miles from Seattle. Yet "more than Hawaii's bubbling lava fields or Yellowstone's sprawling supervolcano, it's Mount Rainier that has many U.S. volcanologists worried." "Mount Rainier keeps me up at night because it poses such a great threat to the surrounding communities, said Jess Phoenix, a volcanologist and ambassador for the Union of Concerned Scientists, on an episode of CNN's series "Violent Earth With Liv Schreiber."The sleeping giant's destructive potential lies not with fiery flows of lava, which, in the event of an eruption, would be unlikely to extend more than a few miles beyond the boundary of Mount Rainier National Park in the Pacific Northwest. And the majority of volcanic ash would likely dissipate downwind to the east away from population centers, according to the US Geological Survey. Instead, many scientists fear the prospect of a lahar - a swiftly moving slurry of water and volcanic rock originating from ice or snow rapidly melted by an eruption that picks up debris as it flows through valleys and drainage channels. "The thing that makes Mount Rainier tough is that it is so tall, and it's covered with ice and snow, and so if there is any kind of eruptive activity, hot stuff ... will melt the cold stuff and a lot of water will start coming down," said Seth Moran, a research seismologist at USGS Cascades Volcano Observatory in Vancouver, Washington. "And there are tens, if not hundreds of thousands of people who live in areas that potentially could be impacted by a large lahar, and it could happen quite quickly." The deadliest lahar in recent memory was in November 1985 when Colombia's Nevado del Ruiz volcano erupted. Just a couple hours after the eruption started, a river of mud, rocks, lava and icy water swept over the town of Armero, killing over 23,000 people in a matter of minutes... Bradley Pitcher, a volcanologist and lecturer in Earth and environmental sciences at Columbia University, said in an episode of CNN's "Violent Earth"... said that Mount Rainier has about eight times the amount of glaciers and snow as Nevado del Ruiz had when it erupted. "There's the potential to have a much more catastrophic mudflow...." Lahars typically occur during volcanic eruptions but also can be caused by landslides and earthquakes. Geologists have found evidence that at least 11 large lahars from Mount Rainier have reached into the surrounding area, known as the Puget Lowlands, in the past 6,000 years, Moran said. Two major U.S. cities - Tacoma and South Seattle - "are built on 100-foot-thick (30.5-meter) ancient mudflows from eruptions of Mount Rainier," the volcanologist said on CNN's "Violent Earth" series. CNN's article adds that the US Geological Survey already set up a lahar detection system at Mount Rainier in 1998, "which since 2017 has been upgraded and expanded. About 20 sites on the volcano's slopes and the two paths identified as most at risk of a lahar now feature broadband seismometers that transmit real-time data and other sensors including trip wires, infrasound sensors, web cameras and GPS receivers."

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