Mount Rainier’s newly-approved lahar detection upgrades will have a quirk: A couple of stations planted right in the likely paths of mudslides.
In other words, researchers will be putting their Mt. Wow and Tahoma Bridge monitoring stations “basically in harm’s way,” U.S. Geological Survey (USGS) volcano seismologist Seth Moran says.
It’s not that they’re eager to lose the stations, Moran said. The idea is inspired by a tabletop exercise he and other scientists did years ago at Mt. Baker.
In their fictional scenario, the researchers realized they could jot down the time when their monitoring stations stopped transmitting due to getting knocked out by lahars, which are volatile slurries of mud, rocks and other debris occasionally belched by volcanos or triggered by landslides.
Every time a station went dark, that gave them a data point. Divide the time in between one station’s demise and the next, over the distance between them, and presto: You’ve just calculated the speed of the lahar.
Now you can project how much time you have before it hits something much more valuable, like human life.
“It’s kind of brute force, but it should work,” Moran said. “I think it’s something people can count on. And for us, it’s an awareness that the goal is not only to detect, but to … be able to provide situational awareness after detection.”
The more day-to-day advantage of placing stations so close to the action is that they can detect smaller, more common debris flows, Moran said, giving scientists more hard data on the frequency of those events. In fact, they’ve already placed stations along the Puyallup River (but outside the park) with the idea in mind.
It’s one of the many ways scientists hope to take advantage of nine new natural disaster detection stations that will be coming soon to the mountain. The National Park Service agreed last week to let the USGS add those lahar detection stations on the southwest side of the mountain.
The project could buy precious time for residents in cities like Ashford, Orting and Puyallup, as well as visitors to the mountain, the next time a mudflow or other hazard roils down the mountain.
The new stations, which the USGS plans to start building this fall, will join Mount Rainier’s interconnected monitoring system, which keeps track of the volcano’s gurgling, shifting and shaking and feeds that data back to scientists.
“We’re obviously pleased with the approval,” Moran said. “It’s going to improve our ability to detect and get word out to people about lahar hazards in general. … (And) once all that work is complete, Mount Rainier is going to have one of the most amazing volcano monitoring networks in the world. … It’s also going to produce some pretty interesting research. As a scientist, I’m excited for the potential.”
The new stations should eliminate several minutes of delay by transmitting data faster and catching lahars earlier because they’ll be placed higher up the mountain than the old detectors.
How much does that add up to? Moran gave a “rough ballpark” estimate of about 10 extra minutes. The speed of a lahar, as well as the time it would take for scientists to notice and warn people about it, will differ greatly based on the size, composition and location of the mudflow.
But as an example, let’s say a large, moderately-quick moving lahar, rushing down the Puyallup or Nisqually rivers, is about 50 minutes away from Orting when it starts. The old system might have detected that lahar roughly 10 minutes after it started, giving residents about 40 minutes of time to flee. Scientists hope the new system could detect that lahar almost as soon as it happens — meaning residents in this hypothetical scenario would have close to 50 minutes to prepare.
Lahars are typically caused by either belching volcanoes, earthquakes, rapid glacial melt or the eventual failure of rocky structures — or a combination of those factors. Like a river of wet concrete, a lahar can flood river valleys and destroy any life or property in its way. Generally, bigger lahars move faster, since they develop more momentum.
When the mudflow subsides, it cools and hardens, eventually building new land. If you’re a subscriber to this paper, there’s a good chance you’re sitting or standing above the Osceola Mudflow right now.
The Enumclaw Plateau was formed by that volcanic lahar about 5,600 years ago. The mudflow sent waves of roiling debris down the White River Valley, reaching all the way to Commencement Bay in Tacoma. It buried about 200 square miles of land and formed the latest geological layer upon which modern-day Enumclaw, Buckley, Bonney Lake, Sumner and Auburn are built.
At 14,410 feet tall, Mount Rainier — originally called Tahoma or Tacoma — has the highest volcanic peak in the U.S. south of Alaska. It has erupted at least as recently as the early 19th century. The US Geological Survey estimates about 80,000 people are at risk in the mountain’s lahar-hazard zones, and Pierce County officials estimate 2.5 million people live in areas areas.
The city of Orting is built on the hardened remains of the Electron Mudflow, which tumbled down the Puyallup River valley from the west flank of Mount Rainier roughly 500 years ago.
“When Orting was going through a big growth phase in the ‘90s, it wasn’t uncommon for people to unearth big tree trunks or stumps that had been carried there by the Electron (mudslide),” Moran said.
The USGS says the west flank of the mountain has the greatest potential for unleashing non-eruption-related landslides, due to its large concentration of weaker, clay-rich rock. That’s why researchers are excited to be able to better track what’s happening in the watersheds of the Puyallup and Nisqually rivers.
“It’s really only the west flank that has weak rock,” Moran said. “That, combined with the steepness, (means) it’s really only the west flank that is subject to a spontaneous landslide-caused lahar.”
Lahars generated by an eruption or other volcanic activity, meanwhile, could strike any of the valleys from the mountain.
Monitoring stations can help buy more time for when the mountain starts feeling feisty. But park officials have to balance their value against their potential averse effects on local wildlife, scientific research or recreation.
The park already had more than a dozen monitoring sites by 2020. Five more were recently approved and constructed, mostly along the south side. In 2019, the USGS asked for a dozen more, but they only got approval for nine of them last week.
The three sites the Park Service turned down — Tolmie Peak, Fremont Lookout and Shriner Peak — aren’t as urgently needed but were intended to provide monitoring for remote areas prone to lahars from volcanic eruptions or unrest, Moran said.
“When Mount Rainier does wake up, all drainages except for the Carbon River have potential for a large lahar to go down them,” Moran said. “These three sites would have been situated to get us ahead of the game … in the event we need to do a rapid installation.”