Eloquent Images by Gary Hart
Insight, information, and inspiration for the inquisitive nature photographer
Dome Sweet Dome
Sunset Sentinel, Half Dome, Yosemite Glacier Point
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Poll 100 random people about the feature they most associate with Yosemite, and you’ll probably get a variety of answers. Near the top of the list will be El Capitan and Yosemite Falls. Bridalveil Fall might get some love too. But I’d wager more than half of the votes would go to Half Dome, both for its striking profile, and for the way it towers in prominent magnificence over its granite domain.
The Half Dome story began more than 150 million years ago, with the start of the slow-motion collision between the oceanic Farallon, and continental American, tectonic plates. The Farallon Plate, being heavier, was subducted beneath the westward plowing American Plate. Over the next 100 million or so years, the Farallon Plate was driven deeper, toward the super-hot mantle, where it became hot enough melt and form large pockets of magma. Some of this magma made it to the surface as volcanic eruptions. The magma that didn’t reach the surface slowly cooled and hardened into the granitic batholith (a large, subterranean mass of igneous rock) that forms today’s Sierra Nevada range.
But how did this subterranean granite, still miles beneath Earth’s surface, come to rise to the nearly 3 miles above sea level we see today? I thought you’d never ask.
Deep beneath Earth’s surface, the same inexorable tectonic forces that initiated the subduction process continued (and continues to this day), slowly deforming and pushing upward the crust and underlying granite. The uplifted overlying sedimentary rock was far more easily eroded than the much harder granite and eventually swept away, exposing the Sierra’s signature granite backbone.
Once exposed to wind, rain, and snow on the surface, granite is subject to its own form of erosion. Rather than consisting of a single molecular structure, granitic rock is made up of a variety of minerals in varying percentages (for simplicity, I’ve just lumped all the various granitic rocks into a single “granite” designation). Depending on its composition, some granites are prone to horizontal jointing that causes it to break along parallel planes. Other granites experience exfoliation, breaking away in concentric sheets. The jagged granite of the Sierra Crest near Mt. Whitney is the result of jointing; Yosemite’s rounded granite domes (like Half Dome) are the result of exfoliative sheeting.
The granite that would eventually become Half Dome formed deep beneath Earth’s surface nearly 90 million years ago. Of course at formation it was just a blob of granite that didn’t resemble the Half Dome we know today, but through millions of years of uplift, exfoliation, and exposure to the elements, a rounded granite pedestal began to take shape. But it still wasn’t Half Dome.
Though one look will tell you why it’s called Half Dome, the truth is, that’s a misnomer. A better, albeit less glamorous, name would be Eighty-Percent Dome. That’s because there is no missing half—we still enjoy about 80 percent of this prestigious monolith’s original form.
Another common misconception is that Half Dome was carved by glaciers: it was not. Instead of half of its bulk being carved off by glaciers, Half Dome’s flat northeast face got that way incrementally, as the most exposed of many preexisting parallel cracks filled with water, that froze and expanded each winter. Each freezing cycle expanded the crack a bit more, until eventually the exposed sheet of granite fell away. This exposed another crack, and the freeze/expand cycle continued, until about 20 percent of the rock was lost.
Many people are surprised to learn that no glacier ever reached the top of Half Dome—the largest, the Sherwin Glacier, which receded about one million years ago, still left 800 feet of Half Dome’s summit exposed; subsequent glaciers were much smaller. But while glaciation didn’t carve and polish Half Dome, glaciers did sweep away the granite debris that had fallen from what we now call the face.
It’s fun to travel around Yosemite and photograph the product of all this natural sculpting from as many angles as possible. Since I time my personal trips and Yosemite workshops to avoid summer crowds, my viewing locations are mostly limited to Yosemite Valley. But even from the valley, there are extreme differences: compare the Tunnel View perspective in the west, to the many views from the valley’s east side: Sentinel Bridge, Cook’s Meadow, Ahwahnee Meadow, and (especially) Mirror Lake.
I do get to see Half Dome from Olmsted Point each October, and when a fall color trip happens before Glacier Point closes for the winter. This year’s Yosemite Fall Color and Reflections workshop threaded the needle between a couple of temporary snow closures (it will close for the season with the next major storm) and I managed to get my group up there for sunset one evening.
I love the face-to-face relationship with Half Dome that Glacier Point offers, but I’ve been here enough that I rarely photograph this view anymore. But when the sunset sky started to pink up this evening, I couldn’t resist clicking off a few frames. As you can see, I didn’t really come up with anything terribly unique, but I enjoyed creating a close-up portrait of Half Dome beneath a beautiful sky. In fact, as I took this picture, I thought the composition was so ordinary that I’d probably never process it. But going through my images while trying to view them through the eyes of people much less familiar with Yosemite’s magic, I decided to go ahead and share it.
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The Many Views of Half Dome
Click any image to scroll through the gallery LARGE
Eloquent Images by Gary Hart 
Very informative, Gary. Thanks.