140 years ago John Muir published an article in Harpers Magazine entitled “The Living Glaciers of California”. According to Josiah Whitney, the California State Geologist, “A more absurd theory was never advanced than that by which it was sought to ascribe to glaciers the sawing out of these vertical walls and the rounding of the domes.”
While he was not a geologist by training, Muir was a keen observer of landscapes and their patterns. Through many summers wandering in the High Sierra certain clues had caught his attention. He noticed in the high country how many of the rocks were polished to a smooth finish, with fine streak marks in them. How there were places where large boulders had been inexplicably scattered across the surface of meadows. And how up in the very highest parts of the mountains of Yosemite there were large snowfields.
“One of the yellow days of last October, when I was among the mountains of the Merced group, following the footprints of the ancient glaciers that once flowed grandly from their ample fountains, reading what I could of their history as written in moraines and canyons and lakes and carved rocks, I came upon a small stream that was carrying mud I had not before seen.” ~J. Muir His Life and Letters, T. Gifford.
“The Lyell Glacier is about a mile wide and less than a mile long, but presents, nevertheless, all the more characteristic features of large, river-like glaciers-moraines, earth-bands, blue-veins, crevasses etc., while the streams that issue from it are turbid with rock-mud, showing its grinding action on its bed. And it is all the more interesting since it is the highest and most enduring remnant of the great Tuolumne Glacier, whose traces are still distinct fifty miles away, and whose influence on the landscape was so profound. The McClure Glacier, once a tributary of the Lyell, is much smaller. Eighteen years ago I set a series of stakes in it to determine its rate of motion which towards the end of summer, in the middle of the glacier, I found to be a little over an inch in twenty-four hours.” ~J. Muir, The Yosemite, 1912.
If John Muir found the living glaciers of California, what is happening in these same places now?
In July and September of 2012 I returned to the Lyell and Maclure Glaciers with Greg Stock, the Yosemite National Park Geologist and Robert Anderson, a researcher at CU Boulder to find out what they look like 140 years after John Muir first measured them.
By placing PVC pipes into the glacier and measuring them with a laser rangefinder and GPS they have been able to track the downhill movement of these bodies of ice over time. Over five years of study they have found that the Lyell Glacier has stopped moving, and the Maclure glacier is moving at about 22 feet per year, barely enough to sustain it’s status as a glacier. If we take Muir’s measurements of “a little over an inch in twenty-four hours” – which translates to about 33 feet of movement per year. While movement is important, what is particularly startling is the volume of ice lost.
While these days the tools are differential GPS and laser rangefinders instead of plumb lines and Whitebark Pine stakes, the goal remains the same: to better understand our world through empirical measurements. What has changed are the outcomes. In Muir’s time it was a revelation for people to realize that there were significant glaciers hiding high in the Sierra Nevada. Now we are concerned about what the effects of these glaciers disappearing will be. While few people visit the Lyell or Maclure Glaciers in a given year, the water from these glaciers visits the faucets of about 2.4 million people every day through runoff stored in Hetch Hetchy reservoir. As usual, I find myself trying to explain, “Why does this actually matter?” Well, I’ll let Bob Anderson tell you. Oh, and look for Greg disappearing down into the ice cave in the background…
Want to see these places for yourself? Stay tuned for a Yosemite Conservancy trip to these glaciers with Pete Devine, or field trips with us next summer! For more, also check out photographer Kirk Keeler’s series on visiting these glaciers this past summer.