The Amazing Disappearing (and Very Dangerous) Mountain: Mt. Rainier

Yes, disappearing. In two senses, one rather personal. Mt. Rainier is actually one of the most obvious, most visible mountains on planet Earth. At 14,411 feet (4,392 meters), it towers over western Washington, and in clear weather can be seen from more than a hundred miles away in some directions. In clear weather, that is...

I was in Washington just a week ago, part of my eclipse-related journey, but in four days, I saw not one little bit of the mountain. It was mostly overcast, or I was in one of those spots where the peak simply wasn't visible. The peak had disappeared and it was kind of frustrating!

And then there was our summer field studies trip back in June. We had plans for exploring the Mt. Rainier area then as well, but the heavy snows of last winter had not yet melted much, so we only managed a single stop within Mt. Rainier National Park (near Chinook Pass), with only a single view, and no trails that we could explore (although there was an epic snowball fight). That stop makes up the first two pictures of this post. I had to dig into the photo archives to find some other views of the mountain. The one below is from our 2014 exploration of Canada that included a short stop at Rainier along Sunrise Ridge (below).

Mt. Rainier is the tallest volcano in Cascades Range, and is exceeded in volume only by Mt. Shasta. Because it is by far the tallest mountain in the Pacific Northwest, it is completely covered by the largest mass of glacial ice in the lower 48 states, about a cubic mile (I read somewhere that it contains half of the all the glacial ice in the lower 48, but I can't find the source and would welcome any corrections from those who know such things). Aside from the "normal" threats that volcanoes might present to a given region (lava flows, ash flows, and that sort of thing), the snow makes the mountain far more dangerous. It's not hard to imagine why: any small eruption would melt a vast amount of ice, forming volcanic mudflows called lahars that are capable of flowing for many tens of miles, and threatening many of the cities along the southern part of the Puget Sound. The entire city of Tacoma is built on a mudflow that thundered down the mountain 5,000 years ago. The last major eruption occurred around a thousand years ago, although minor activity was noted several times in the 1800s.

The reason I mentioned "disappearing" in two senses has to do with the effect of the ice on the mountain. The volcano is being dismantled. Glaciers are a major force of erosion, especially when the underlying rock has been weakened by chemical weathering related to the hot acidic fluids that circulate and attack the mountain from below (hot springs exist around the summit where the steam has excavated miles of ice caves). The glaciers have scraped away the rock around the original summit, which has also collapsed in several large debris avalanches. In other words, the mountain once stood as high as 16,000 feet, which would have made it the highest mountain in the lower 48 states by far.

My favorite pictures of Mt. Rainier both involved flights. I was returning from a geology trip in Italy a number of years ago, and our flight path took us right over Rainier, giving me the awesome perspective seen in the picture above.

On a different flight from Seattle, we took off just after sunset and I didn't expect to see anything, but the faint twilight allowed the mountain to glow blue, and I got the rather ethereal other-worldly view seen below. The color is the way the camera recorded it (I didn't play with the contrast or color).

Mt. Rainier is a place I would very much like to get to know better.

Northern Convergence: America's Most Dangerous Volcano, and the End of the Journey

Northern Convergence as a name for this blog series was all about the role of a convergent plate boundary in the production of the scenery of the Pacific Northwest. The compressional forces that developed as the Pacific/Farallon/Juan de Fuca plate was stuffed under the North American continent formed range after range of complexly folded and faulted mountains hundreds of miles inland.

Perhaps the most vivid effect of plate convergence is the formation of a magmatic arc, a chain of inland volcanoes and underlying magma chambers. The oceanic lithosphere carries rock and water deep into the underlying asthenosphere where the rocks are heated, and the water liberated. The water has the effect of lowering the melting point of the mantle rock and plumes of molten magma form, which start moving upwards through the continental crust. Sometimes basaltic or andesitic magmas reach the surface. In other instances, the hot magma melts some of the continental granite, forming dacite or rhyolite.

Mt. Adams from Sunrise Ridge

Volcanism is one of the intense and spectacular geologic processes one could ever hope to witness (or avoid, if you not geologically-minded, or sane). Volcanoes are capable of horrific destruction and disaster, but they also provide rich fertile soils and incredible scenery. We had now been on the road for nearly two weeks, and an important early site for our investigations was to be Mt. Garibaldi and the Black Tusk, two of the northernmost Cascade volcanoes. As I wrote previously, rain and clouds obscured our views that day, and all we ended up seeing were some old lava flows (and, it should be said, some wonderful waterfalls).

Not a volcanic eruption, but instead a wildfire. Couldn't help imagining, though.

As we drove west on our final day, volcanism loomed. We would be passing through Mt. Rainier National Park, and it is hard to think of any mountain in the world that dominates the surrounding landscape the way Rainier does (Kilaminjaro comes to mind, or Mauna Loa in Hawaii, but few others). In stark contrast to our earlier visit at Garibaldi, the skies were crystal clear and sunny.

Mt. Rainier from the west

Rainier rises to an elevation of 14,411 ft (4,392 m), just a bit short of being the highest peak in the lower 48 states, but certainly the highest in the Cascades (only Shasta comes anywhere close at 14,179 feet). Glacial erosion has ripped away hundreds of feet of rock from the summit area, so at one time it was almost surely the tallest mountain in the lower 48 (one more contender though could be the San Francisco Peaks in Arizona, another stratovolcano missing thousands of feet from the summit).

Rainier from the air

For all of its grandeur, Rainier is an incredibly dangerous mountain. It contains roughly half of all the glacial ice to be found in the lower 48 states, around a cubic mile. That much ice and a tendency to have eruptions every few hundred years is a frightening combination. Many people think (perhaps influenced by bad Hollywood movies that involve volcanoes) that lava flows are the greatest hazard from volcanoes. They are not; lava flows would hardly be expected to get off the mountain massif itself. Andesite is just too sticky to flow far before congealing.

Source: Mount Rainier - Living Safely With a Volcano in Your Backyard by Carolyn L. Driedger and William E. Scott, USGS -- from USGS fact sheet 2008-3062

The ice is another matter. A modest eruption of ash or lava could melt a vast amount of ice, mixing with the ash to form a fast-moving mudflow called a lahar. Over the history of the volcano lahars have had the greatest reach, extending as far as the Puget Sound. The cities of Tacoma, Puyallup, Sumner and others are built on lahar deposits from Rainier (see above). Tens of thousands of people along the drainages below Rainier will have a few tens of minutes to evacuate in the event of a major mudflow. For all its beauty, the mountain is a ticking time bomb. It's also probably one of the most carefully monitored mountains on the planet. I don't doubt that the slightest hint of activity will bring a flurry of evacuations.

Rainier from the air in 2007

We spent a few hours on Sunrise Ridge, but our time was limited. We had nearly completed our journey and some of our people needed to catch flights at SeaTac. We headed down the hill towards Puget Sound. We had seen many wonders on the roads that took us across the Olympic Peninsula, the ferry to Vancouver Island, a rainsoaked drive through the Sea to the Sky Highway, explorations of Banff and Yoho National Park, a sojourn among the ghosts of dinosaurs on the High Plains, and a drive home through the Rocky Mountains and the Columbia Plateau. I had gotten to know an extraordinary group of people, and a small corner of a most extraordinary country, Canada.