The Mountain is Out (To Get You)

What would happen if Mount Rainier erupted?

We prefer to purchase homes that tout views of it; we do a double take when we see it shimmering in the distance on a sunny day; we put its likeness on murals, signs, mugs, and T-shirts; and we spend our weekends hiking its trails.

Still, one could argue our adoration of Mount Rainer has clouded our vision to the danger that it poses.

We all know Mount Rainier to be one of many Cascade Range volcanoes, a towering neighbor of other notable volcanoes: Mount St. Helens, Mount Hood, Mount Jefferson, and Mount Adams to the south, and Mount Baker to the north. While Mount Rainier might not be the most explosive volcano in the chain, it is considered among the most dangerous due to its proximity to populated cities and urban centers.

The flat floor of the Puyallup River Valley — which includes much of Puyallup and Orting — is the site upon which the homes of thousands of families are built. It also is made up of mudslide deposits that surged into the valley from Mount Rainier between 500 to 1,000 years ago.

While many people envision an eruption with lava flow and volcanic ash, these mudslides — also called lahars — are some of the most terrifying and destructive hazards facing the South Sound region if Mount Rainier were to awaken, according to United States Geological Survey hydrologist Carolyn Driedger.

Photo by formulanone via flickr

“You look at the Puyallup River Valley, and in some ways, it’s more suited for daffodils than two-by-fours,” Driedger said, referring to the homes that continue to be constructed in the valley and within former destruction zones.

“It’s truly amazing to go to the Puyallup River Valley and to look at some of the excavations in the ground that are being done, and you see these enormous slopes of old-growth cedar and Douglas fir (that) were buried — they are the testament to the mudflow that came through,” Driedger said. “It’s not just scientists that find them. When I go out and do talks in the community, I hear (about it) from all the old timers. Back in 1963, (they were) working on Highway 410 and dug up thousands of these tree trunks and always wondered where they came from.”

The Puyallup River Valley isn’t the only place where these deposits have been found. More than 27 communities lie downstream from Mount Rainier with evidence of these deposits. In his 2009 article in the Journal of Volcanology and Geothermal Research, research geographer Nate Wood noted, “There are more than 78,000 residents, 59,000 employees, several dependent-population facilities (e.g., child daycare centers, nursing homes), and numerous public venues (e.g., churches, hotels, museums) in (the) Mount Rainier lahar-hazard zone.”

Will lahars bury the valley again? It’s uncertain, but USGS officials believe it’s possible.

In a typical scenario, the volcano’s reawakening would be signaled by precursors that would occur hours, days, weeks, or even months before any significant volcanic event, and include a range of things — a series of earthquakes that would increase in frequency and magnitude, steam plumes at the summit and possibly elsewhere around the mountain, and the volcano’s visual deformation.

As these precursors accelerate, there may be what scientists call a phreatic eruption of steam indicating that magma is heating up the exterior of the volcano. At this point, a few things could happen, according to Driedger.

“No. 1, the volcano could say, ‘OK, I’ve let off my steam; I’m going back to sleep,’” Driedger said. “Or it could continue for a long time, and everyone is just on pins and needles wondering what is going to happen next. It could go on for weeks or months. Another option is that it will continue to progress into an active eruption where there is fresh magma coming to the surface.”

Whatever volcanic events happen (or don’t, as with the first scenario), there will be a lot of snow and ice melt on the volcano. That water will mix with the mountain’s loose volcanic rock and create volcanic mudflows, or lahars.

The size of the mudflow is variable, but the result will likely be the same, as it tends to bulk up many times over, picking up fresh rock, tree debris, and whatever else is in its way as it proceeds down into the surrounding valleys.

It will travel miles before it reaches a wide section of the valley, allowing it to spread out and lose momentum, and the water to dissipate.

How can residents in low-lying areas protect themselves from this natural disaster? An advanced lahar detection system with electronic monitoring at Mount Rainier will be triggered by lahars and the scientists at the USGS Cascade Volcano Observatory in Vancouver, Washington, will be notified. So, too, will residents in those affected areas via numerous sirens scattered around the area, giving them approximately 40 minutes to evacuate the valley floor for higher ground.

To ensure everyone is ready for evacuations, Driedger and her colleagues at USGS work closely with school districts and city emergency managers, such as Kirstin Hofmann from the City of Puyallup. Hofmann is responsible for the city’s preparedness for emergencies like earthquakes, fire, flood, and yes, volcanoes.

Hofmann works with county and state agencies to run drills, give safety talks, designate evacuation routes, and educate the people of Puyallup about the dangers of lahars — this is a job Hofmann said is never done.

“Some people say they went to an emergency preparedness course so they could check off the box and be good for two years,” Hofmann said. “I remind people that they need to talk about it all the time.”

“Just because you are not seeing action at a volcano, just because it is not erupting, just because it is covered with snow and ice, (that) doesn’t mean it isn’t active.”

When practice lahar sirens go off in Puyallup every Monday at noon, Hofmann said she hopes the citizens of Puyallup take the time to think about what that means. “I always remind people that when they hear those, it’s a great reminder to think, ‘If I’m here, where would I go? Do I know the evacuation routes to get to higher ground?’” she said.

Each community that could potentially be impacted by future lahars has bright blue evacuation signs posted along routes to help evacuees know where to go. But Hofmann encourages citizens to visit their cities’ websites, which often have downloadable maps with clear routes out of the valley. Copies of these maps should be kept in emergency kits, backpacks, and glove compartments.

Moreover, Hofmann said there are a number of questions families should ask themselves and then plan accordingly.

“Do you know your evacuation route? Have you walked it? Have you driven it? Have you showed it to family, loved ones, other people in your neighborhood?” Hofmann said. “Do you have supplies in case you have to evacuate and relocate? Is everyone in your family aware of what that is going to look like? If you have anyone in your family with any kind of special needs, have you made accommodations for that? If you have animals — big ones, small ones, fluffy ones, scaly ones — have you made plans for them as well?”

The Washington State Department of Health recommends building disaster kits containing enough food and applicable medicine for several weeks. For those outside of the South Sound area, emergency managers are not as concerned with lahars, but volcanic ash can travel great distances and can be a nuisance at best, or a serious human health problem at worst. Take steps to avoid being outdoors until conditions improve, if possible.

At the very least, USGS’s Driedger said, the main point she wants to get across to people living, working, and playing in the looming shadow of Mount Rainier is to remember that though beautiful, the mountain does present a clear and present danger.

“We want people to recognize that these are active volcanoes, and they are doing what volcanoes always do,” she said. “They are like humans, in a sense. They sleep, they wake up occasionally, sometimes they turn over a little bit, and sometimes they (fully) wake up. Just because you are not seeing action at a volcano, just because it is not erupting, just because it is covered with snow and ice, (that) doesn’t mean it isn’t active.”


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