It’s no use stalling anymore. Let’s continue my series on the Cascade Mountains of the Pacific Northwest. Check out Part I, an introduction to the Range’s geography & geology. So which mountain should be next? Well, there are many interesting options. There are the little-known “climber’s” peaks of Mount Jefferson and North Sister, Glacier Peak and Mount Stuart. There are the popular recreation meccas of Mounts Baker, Bachelor and Hood. But there is just one mountain I can’t put on hold any longer: the Big Kahuna, the sleeping giant, the Mother of Waters, training ground for Everest, Seattle’s sky-ornament, Tahoma, Mount Rainier.
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Mt. Rainier, at 14,411 feet (4392 meters), is one of America’s most spectacular mountains. It sticks up hugely and dramatically a little more than 50 miles southeast of Seattle, Washington. Rainier’s prominence is enhanced by a total of 26 glaciers with over 35 square miles of ice. In North America, only Alaska and the Canadian Rockies have more dramatic, glaciated mountains. By the way, don’t get confused about Part III and Part 1. It’s just that with this particular mountain, there’s too much to fit into one post. Stay tuned for one or two more posts on Rainier, but we’ll still be on the Cascades Part III until we jump to another mountain.
Mount Rainier was named by Captain Vancouver of England for a friend of his, Rear Admiral Rainier. It’s original name, from a local American Indian tribe the Puyallup is Tahoma (or Tacoma).
A Dangerous Volcano
Rainier is considered one of the world’s most dangerous volcanoes, and there are a few important reasons for this. Like Vesuvius in Italy, Rainier is situated quite close to population centers. That is the most important factor that makes it dangerous. The second most important reason is not, as you’d expect, the volcano’s activity level. Rainier sleeps for long periods. Instead, what makes it potentially deadly is the fact that it is steep and weak. In other words, the same thing that makes it dramatic, sticking up so steeply as it does, also makes it dangerous.
The glaciers, with their incredible erosive power, have done a very good job of steepening the volcano. But how is it weakened? As the mountain sleeps between eruptions, it sits above the magma chamber below and literally stews in its own juices. Rainier is in a wet climate, and the mountain’s bulk draws even more precipitation its way. Because of this, Rainier’s rocks are wet. Add heat and acidic gases from below and you have a corrosive mix. As a result the rocks are altered to clays, greatly weakening Rainier’s steep cone over time. In other words, much of the peak is literally rotten. Add these two things together, the volcano’s steepness and its inherent weakness, and you have a very real and constant hazard on your hands.
The biggest volcanic hazard at Rainier is not from lava flows but from mudflows (aka lahars). If the mountain erupts lava or hot ash, large amounts of ice could melt quickly, causing a catastrophic flow of mud, rocks, trees, bridges, cars, etc. that cascades down river valleys, wiping out everything in its path. But here’s the thing: an eruption is not really necessary to bring destruction to the surrounding populated valleys.
Now imagine a small earthquake, perhaps during an unusually warm summer when much of the ice high on the mountain is melting (can you say global warming?). This could easily trigger a large and very destructive mudflow. Geologists know this has happened in the past. In fact, a good portion of the city of Tacoma (plus some of Seattle) is built on deposits from an enormous Rainier mudflow that buried the area some 5000 years ago.
The Rainier region now has a warning system made up of sirens that are triggered when mudflows higher on the mountain begin. Citizens of towns like Orting and Enumclaw are taught to heed these sirens by escaping to high ground. Mudflows are powerful enough to sweep away large bridges and buildings like a spoiled toddler kicks over his leggos. But all their dirty work is limited to river bottoms, so getting up out of the valley will save your life.