Geologists Sound Alarm: The Greatest Threat Looming in the Pacific Northwest

Three of my friends and I decided to hike near Mt. Rainier. Mt. Rainier dominates the skyline of the South Seattle/Tacoma region. Rainier, like Mt. St. Helens, was inactive on that sunny, warm Saturday. We didn’t make it to the top but we made it to the treeline and I was able to take some great photos using a 35mm pocket-sized camera that I had lost most of over the years.

I remember standing there admiring the views and discussing how small the mountains could make us feel. We didn’t talk about the fact that this noble peak was a volcano, and what would happen if it erupted. Now, geologists who study volcanic eruptions, or vulcanologists, are looking into what could happen. And it’s not good.

Mount Rainier is a constant source of worry for me because it threatens the communities around it. Tacoma, South Seattle, and other communities are built upon 100-foot thick (30.5-meter-thick) ancient mudflows that resulted from Mount Rainier eruptions,” Jess Phoenix said in an episode of CNN’s “Violent Earth with Liv Schreiber.”

In the Pacific Northwest, the sleeping giant’s destructive power is not in the lava flows that, if an eruption occurs, are unlikely to spread more than a couple of miles outside the Mount Rainier National Park boundary. According to the US Geological Survey, the majority of the volcanic ash will dissipate to the east and away from the population centers.

Many scientists are more concerned about the possibility of a “lahar” — a rapidly moving slurry containing volcanic rock and water that is formed when ice or snow melts quickly by an eruption. It picks up debris while it flows through drainage channels and valleys.

This lahar may very well affect Tacoma (where Ft. Lewis lies) and south Seattle. Both of these towns were built on massive lava flows from previous eruptions.

In the United States, we’ve had a lot of luck when it comes to major geological events. People think of the San Andreas fault and its associated strike/slip faults in California. But there is a more dangerous scenario in the Pacific Northwest. In the Cascadia subduction zone, the Juan de Fuca oceanic plate is slowly being pushed beneath the North American continental plates. There are quakes of Richter scale 9, with tsunamis that span the Pacific Ocean. In the Pacific Northwest, a tsunami and a magnitude 9 earthquake could wipe out large areas of the region. Seattle, Tacoma, and Vancouver are all at risk. Only a few moments to move out of harm’s way.

The entire Pacific rim is geologically active; that’s why it’s often referred to as the Ring of Fire. Even here in the Great Land, we have volcanoes and earthquakes; now and then the normally quiescent Mt. Redoubt will burp out some ash, covering the Kenai Peninsula, normally just enough to be annoying. Mt. Rainier and the Cascadia subduction are all part of that.

Nature is huge. This magnitude of natural disasters can erase hundreds of years’ worth of human effort (and even humans) in an instant. It’s not worth worrying about things that we cannot change, and humans are powerless to change such events. However, it is interesting to reflect on events like these. This gives an interesting perspective.