Sonora Pass: Susie and I were taking in the fall colors along the Sonora Pass (CA108) when we drove by a one of those national park-style-signs that said Columns of the Giants.
My first thought was they’re talking about giant trees, which aren’t hard to find in the Stanislaus National Forest. But it turns out it’s about giant columns of basalt.
So we circled back, parked the trusty Honda Element and headed onto the easy trail, which started with a bridge over the Middle Fork of the Stanislaus River.
After a short walk the trail opened up into a rubble-strewn clearing, bounded by straight-edged columns of rock 20 and 30 feet tall. These formations are technically called columnar-jointed basalt and are created when molten lava begins to cool and neatly contracts into these geometric palisades that we see before us.
Given the right circumstances, many times the lava will contract uniformly into these 6-sided hexagons, with corners that form at angles of 120º. The ‘right circumstances’ include the a uniform chemical signature of the molten basalt itself, and a chance to cool slowly from the bottom up.
In the case of this stop, the giant columns began forming some 100,000 years ago as lava pooled into the Stanislaus riverbed and began to cool. The trail we’re walking on now used to be under many, many feet of basaltic lava, but has been cleared away by glaciation and river erosion. While some exposed rock formations along the trail show signs of being smoothed by glaciation, the walls of columns retain their original sharp edges only because what we’re seeing is freshly exposed and hasn’t yet been subjected to the weathering and erosion.
This location also features what is known as a colonnade and entablature structure. The colonnade is the well-defined columns and the entablature is the much less organized basaltic rubble that the columns appear to be supporting.
The entablature above was probably subjected do a different cooling circumstance than the columns it’s resting on, and formed into much smaller, yet still geometric, shapes.
I have to admit, for many years I didn’t know the difference between basalt and bath salts. But the more time I spend along the Eastern Sierra Nevada, one cannot help wanting to know more about the amazing, complex and very active geology of the region. It simply makes the hiking and photography a much richer experience.
The better example of this columnar-jointing basalt is Devil’s Postpile National Monument, a couple of hours away on the eastern Sierra Nevada next to Mammoth Lakes. Created under similar circumstances, Devil’s Postpile site has the option of a hiking trail to the top of the formation where glaciation has smoothed the surface to reveal the wonderful geometry created by the cooling process.
If you can, plan your visit to either location after the summer crowds (and heat) but before the snow arrives. But regardless of the time of year, these sites are a feast for the little bit of ‘rock nurd’ in all of us.
Here’s a link to our Sonora Pass trip for Fall colors where we stumbled on this site.
Photo Factor: I’ll cut right to it; bring a polarizer in your kit to photograph these formations. A combination of flat, reflective dark surfaces and the often very bright California sunlight really makes for a super high-contrast situation. You also will want to bring a longer mm lens to get some detail shots of the columns, otherwise you’ll have to scramble over the talus tailings at the base of the features, and that doesn’t strike me as much fun with any amount of camera gear. I’ll always bring along a flash unit as well, to fill in the shadows on some closer, detail type shots. A bracketed series of tripod mounted RAWS would be ideal, but I managed to pull out some decent shots by flooring the shadows and highlights in post.
