Thursday, August 24, 2017

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.

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