Travels in Cascadia: The Toughest Hike I'll Ever Do...Stawamus Chief in British Columbia

Note that I didn't say the toughest hike YOU will ever do. Every hiking experience is individual, and this one left me...breathless. Stawamus Chief is one of the most popular hikes in the Vancouver-Squamish region of British Columbia, and when we passed through the area last July, I knew I needed to give it a shot.

Stawamus Chief is a granite dome that rises more than 2,000 feet above the east end of Howe Sound, the southernmost fjord on the west coast of North America. The dome actually has three summits, the 1st, 2nd, and 3rd, and the trail climbs to the first summit in a little over a mile. That doesn't sound so bad, does it?

The beginning of the trail is pleasingly flat, rising gently through the Stawamus Chief Campground. The wide flat trail offered no clue about what would follow. I know it sounds dramatic, but from the moment one takes the first step upward as the trail starts the climb in earnest, the trail is relentless and steep.

Some of the steps are on wood stairwells, but the rest of them are large uneven stone blocks that I found challenging. And there are no breaks. Many trails are steep, but most all of them have short breaks were the trail is level for a few steps. Not this one. It never stops climbing.

I climbed higher and higher, and grew more exhausted with each step. The thought was slowly building in my head that I was no longer young, and that some trails were simply too tough for overweight 60-somethings. But then another thought immediately followed: this quite probably was the only chance I would ever have at making the summit. Who could know if I would ever be here again, and with time marching on, my ability to climb would no doubt degrade with age. It was probably the toughest hike I would ever do (in the future sense). I decided I had to do it, and kept going. And going.

Everyone's experience will differ, of course, and some younger and healthier people would not have that much of a problem on this trail. Part of my own worries weren't so much the climb, but the descent. All of those huge steps had to be repeated, but going down, and I worried about the impact on my knees and ankles. But I had already come so far.

Stawamus Chief is a granite dome, and the resemblance to Half Dome in Yosemite Valley is unmistakable. One of the things about Half Dome is that it was never covered with glacial ice. The dome took it's iconic shape from exfoliation of the outer slabs of granite. The corners and edges snapped off as the pressure of burial was released upon exposure to the surface. Glaciers at the base quarried away the fallen rocks.

Stawamus Chief was different: as I approached the summit, a most unusual rock emerged from the trees. It was a boulder perched on a granite platform. It was a classic example of a glacial erratic, a rock left behind as the glaciers that flowed over this surface melted away. Unlike Half Dome, the summit of the Chief had been covered by glacial ice. And not just a little...the ice here was over a mile thick!

In the end, I didn't make the true summit. The young men in our group reported that another twenty minutes and 200 feet of hard climbing remained ahead. I just wasn't up to it. But I did make it to the summit ridge, which provided a stunning view of the eastern end of Howe Sound. From this elevation, the glacial origin of the fjord was obvious. And I was happy to be where I was. Elated, even. And thrilled to be alive (literally!).

The knees and ankles took the expected pounding on the way down, but no lasting damage was done. I would live another day, and take on the next challenge. It could well have been the toughest hike that I would ever do (in the future sense; I've done some really tough hikes over the years), but the neat thing about life is that you never know what comes next. Maybe I won't do this trail again, but there are many other trails and challenges ahead. Again, that sounds dramatic, but finding one's limits is always an exercise in drama.

A Series of Fortunate Events: Climbing a Dome That's Not Exactly a Dome...It's Rock Mutton

There are domes and there are "domes". Yosemite National Park has a lot of domes of one sort or another, and there has always been a bit of confusion about their origin. From various points in Yosemite Valley, one can spy at least four them, famous Half Dome, less famous Sentinel Dome, North Dome, and Basket Dome. Although Yosemite is famous as a work of glacial action, the domes actually are not directly related to glacial erosion. As described in the previous post on Sentinel, these domes rose above the glacial ice. They formed instead because of exfoliation, the tendency of slabs of granitic rock to break off the corners and edges of monolithic chunks of exposed rock. In time they take their rounded shape.

Image from http://villains.wikia.com/wiki/Monstro

In the high alpine parts of Yosemite, the situation is different. Tuolumne Meadows is not a "U"-shaped glacial valley. It has an open aspect, with high mountain ridges separated by wide meadowlands dotted with granite monoliths that rise above the dark forests. The granitic knobs look less like rounded domes, and more like Monstro the Whale breaching at sea, with a gentle slope on one side, and nearly vertical cliffs on the other. Two of the most obvious are Lembert and Pothole Domes. Both rocks are popular hiking destinations, and both provide stunning views of the high country of Yosemite. Pothole Dome was our destination on this trip.

The open country of Tuolumne Meadows resulted from a different kind of glaciation. In Yosemite Valley, the glaciers only occupied the valley itself. At Tuolumne, the glaciers covered the entire landscape apart from the highest peaks. The depth of the ice exceeded 2,000 feet (~700 meters). Such glaciers are called icecaps or icefields, and they produce a different set of erosional features. Pothole and Lembert Domes are examples of Rock Mutton.

Oh, excuse my French! The domes are examples of a roche moutonnée. This has been translated variably as greasy mutton wig rocks, fleecy rock, or rock sheep, and none of these is a particularly apt description. The first was related to the sheep grease that was used to hold the hair in place in the old wigs worn by French and English dignitaries. The fleece referred to the "resemblance" of these rocks to the locks of hair in the aforementioned wigs, and the last was said to be a description of the rocks appearing as grazing sheep from distant vistas. I don't quite get it, but c'est la vie.

Whatever you might want to call it, Pothole Dome provides an intimate understanding of what rock is like when subjected to intense glaciation. The gentle slope, which faced the oncoming ice flows, has been smoothed and abraded by rocks, sand, silt embedded in the ice. The passage of the gritty ice has left grooves, striations, and polished surfaces that make climbing the dome a great deal easier than one might expect. Most of the huffing and puffing comes from the high altitude (8,000 feet/~2,700 meters) rather than steepness.

The steeper western side of Pothole Dome was "plucked". Ice formed in cracks and fissures of the granitic rock and was pulled loose by the glacier as it flowed away from the rock. This made for a decidedly asymmetrical dome structure if one wants to call it a dome at all.

An alternate term for these rocks is a stoss and lee structure. "Stoss" comes from a German term for "push" or "thrust", referring to the gentle slope facing the flow of ice (the glacier "pushes" up the slope). The "lee" refers to the trailing steeper plucked side. I tend to prefer this description, although it still isn't all that descriptive. How about a "scour and pluck" structure?

The other unmistakable evidence of the passage of glaciers is the sheer numbers of boulders that lie scattered across the surface of the dome. There aren't many good explanations for how these boulders could have gotten here without invoking the passage of ice (the boulders came from a different kind of granite exposed off to the east). These out of place rocks are called glacial erratics.

There are marvelous examples of glacial polish and striations all over the surface of Pothole Dome. The ice was last here around 12,000 years ago, so the rough surfaces surrounding the polished sections provide an idea of how slowly the granite is weathered in this cold alpine climate. At lower elevations, the rock would weather much faster and the polish would rapidly disappear.

From the top of the dome, one can see some of the terrain that stuck out above the icecap, including the Cathedral Range (below). The peaks are classed as horns when glaciers flowed away from the mountain, plucking away at the flanks, or nunateks when the glaciers flowed around the peaks, scouring away at the higher slopes.

Pothole Dome's name reflects the presence of potholes on the south flank of the dome. These round holes formed when ice melted into the glacier through holes and tubes called moulins. The water flowing under the ice mixed with boulders and gravel in large swirling masses to grind out the holes.

The final glacial feature we noticed while climbing down were the chattermarks, concentric fractures caused when boulders being dragged at the base of the glacier skipped and chipped the surface. Usually the cusps of the crescents point away from the ice flow direction, so I found these a bit mysterious. The crescents open toward the east, presumably the direction the ice came from.

The day was passing and we had a few stops left on the itinerary. They'll be covered next time!

Balancing Boulders and Erratic Rocks!

Sunday's mystery photo produced a pretty good response of hypotheses, both of the scientific sort, but also of the fanciful sort (and sometimes the boundary gets blurred!). The rock in question is known as Globe Rock, and it can be seen along the Sierra Vista Scenic Byway, an 85-mile long loop road in the high forest country between Yosemite and Kings Canyon National Parks. The area is drained by the San Joaquin River. The elevation is about 7,000 feet.
As noted on the geologic map by N. King Huber of the Shuteye Peak quadrangle (USGS Geological Quadrangle GQ-728; get all of the central Sierra Nevada geologic maps here), the rock underlying the Globe is the Mt. Givens granodiorite, a medium to coarse-grained hornblende-biotite granodiorite and granite that is locally porphyritic with tabular K-spar phenocrysts with a U-Pb age of about 90 million years (my casual non-geologists readers are forgiven for not following this, but my students had better understand it; there's a midterm Tuesday on this stuff!). The rock is labeled on the geologic map, near the top and to the left.

A lot of the answers to my challenge on Sunday noted the possibility that this was a glacial erratic sitting on a pedestal. This is the most likely answer based on my cursory examination, although the possibility must be considered that it may also be an unusually weathered exfoliation slab (in other words, the rock formed in place, not transported from elsewhere). There are glacial deposits shown on Huber's map only a mile or so away, and the larger pre-Tahoe glaciers may have covered much of the region. In either case, the pillar would have developed because the large boulder protected the underlying rock from weathering, while the surrounding rock was eroded away. In this setting, the amount of erosion suggests that the boulder has been there for a very long time. The odd spherical shape of the boulder itself would also be an indicator of age; corners and edges tend to be weathered away first.

Glacial erratics are very often composed of a different kind of rock, and the black coloring on the boulder certainly causes the rock to appear to have a different composition, but a close look at the base of the boulder (above) shows the rocks to be actually quite similar, and they are both certainly granitic. The dark color is provided by dark oxides and lichens growing on the surface. Even if the rocks are the same, it quite probably could still be an erratic, as the Mt. Givens granodiorite is widely exposed in the region.

Rocks on pedestals are quite interesting for a number of reasons, not the least of which is their contribution to the scenery. If they can be tied to a particular glacial episode, they can be a clue to the rate of erosion in a region. If they are truly precarious, they provide some data about the likelihood of severe shaking during earthquakes. If they haven't toppled in the thousands of years they have existed in a particular spot, it would suggest a limited degree of ground movement (although I have to wonder...this rock is close to major faults in the eastern Sierra Nevada).

The other rock I photographed this weekend illustrates what probably amounts to a younger pedestal boulder, on the flanks of Sentinel Dome in Yosemite National Park. It is less rounded, and has not developed as high a pedestal. This could be a function of age, although differences in composition and local soil conditions could also be a factor. This site is described as being outside the limits of the Sierra glaciations, so it is either a rockfall 'erratic', or it is part of a slab that formed in place.

Balanced rocks are found in many different circumstances and many different places. One of the commenters provided a link to a balanced boulder in Kansas, and I've included a shot of the famous Balanced Rock at Arches National Park in Utah.

What other balanced rocks do you know about? Got any pictures?

Yosemite as an Open Air Classroom: Olmsted Point

At the height of the ice ages in the high Sierra Nevada, an ice cap 2,000 feet deep covered the Tuolumne Meadows region. A massive 40-mile long glacier flowed down the Tuolumne River gorge, the largest in the Sierra, but tongues of ice crept over some drainage divides and flowed elsewhere. At Tenaya Creek, the glacier made a path into Yosemite Valley. Along the way, the glacial scouring smoothed over domes, ripped up boulders, and tore rocks from the base of cliffs, steepening them, most spectacularly at Half Dome.

One of Yosemite's finest vistas can be had from Olmsted Point, up the Tuolumne Road about eight miles southwest of Tuolumne Meadows. If Yosemite Valley lacks easily accessible features of glaciation, Olmsted Point has an embarrassment of riches. To the north (top photo), Tenaya Lake and Mt. Conness provide a nice example of a glacial tarn (lake) and a horn (a mountain peak "sharpened" by having rock plucked from the base of the cliffs below). The valley containing the lake has a broad U-shaped profile.

To the south, Tenaya Creek plunges deep into the gorge below Clouds Rest and Half Dome. The vast granitic face of Clouds Rest (center of second photo) is scored by dozens of avalanche chutes where masses of snow constantly clear off the rock and prevent trees from gaining root. Farther downstream, Half Dome looms over Yosemite Valley. Glaciers never covered the dome. It took its shape instead from the expansion of the granitic rock as it was exposed by erosion. The expansion took the form of fractures that ran parallel to the surface of the rock (exfoliation), which tends to remove corners and edges. Massive vertical fractures called joints allowed the glaciers below the dome to quarry the rocks from below, forming the stunning vertical face of the dome.

Up close, the evidence of the passage of glaciers is plentiful. Hundreds of large boulders, derived from somewhere upstream, litter the landscape (glacial erratics). The surface of the granitic rock has been scraped and scoured to produce glacial polish, striations, grooves and chatter marks (third photo). If you are more interested in the petrology, the glacial polish reveals incredible details in the granite: flow patterns, dikes, and pegmatite veins are visible everywhere, not to mention huge crystals of feldspar.

Olmsted Point is all about spectacular scenery, but there is much in the way of geological learning opportunities as well. On a field trip, it is not to be missed!