Escape to Kings Canyon, part 3: glaciers were here

This post is part 3 of a series. Click here to read the first post. To see the gallery, click here.

GREENER THAN EMERALD POOLS

Roaring River Falls is a supercharged waterfall which flows out of yet another hanging valley before running a rocky, choppy race to the Kings River. We reached it after breakfast on our first morning at Cedar Grove. It was a short drive from our campground, a walkable distance really. This cascade is loud and fast, making a sound like continuous thunder, even louder than Grizzly Falls the day before. Sundari made no move to swim in the frigid green pool beneath the falls. I think she might have if nobody had been around.

When I learned there was second pool above this one, I was reminded of the Emerald Pools at Zion. Like that stream, Roaring River drops over one edge, then another, before joining a larger channel. But this pool was far more emerald than any water I’d seen at Zion, and the rocks surrounding it were far less red than Zion’s Navajo Sandstone. The Roaring River gorge is made of granitic rock, part of a small pluton called the North Mountain Unit. It's igneous rock, cooled magma, not the same as the metasedimentary rock we’d passed through on our way into the canyon. This granite was much more like what I’d expected to see when I imagined visiting the Sierras. Now that we were down in the canyon, evidence like hanging valleys showed that glaciers had been a driving force in shaping the terrain.

The huge glacier which once occupied Kings Canyon extended from the mountain peaks down to Cedar Grove, roughly the point where, thousands of years later, we would park our RV. Glaciation here was not as thick or extensive as it was at Yosemite, which may be why the canyon walls are not as polished and smooth as Yosemite’s famed cliffs. But Kings Canyon does still show the same characteristic U-shape of a glacial valley, with steep vertical sides and a wide floor. Thinking of this, I wondered: how and why does a glacier change a valley’s shape?

GLACIAL SCULPTING TECHNIQUE

My post-trip research revealed that glaciers carve valleys by means of a process called “plucking.” This process begins when the ice at the bottom of a glacier melts from the friction of the glacier’s slow movement over the bedrock. Melted ice gets into the joints of the bedrock, leading to frost wedging, the term for when melting and freezing of water in the joints of rocks causes the bedrock cracks to expand. The term frost wedging sounded familiar to me. I realized it was because this same type of physical erosion accounts for the creation of the hoodoos at Bryce Canyon. At Bryce, the frost wedging is due to frozen rainwater, not melting and re-freezing of glacial ice. 

Frost wedging makes pieces of rock come out of the expanded cracks, and these get carried along within the glacier when it moves. Large chunks of the valley bedrock get pulled out this way, changing the shape of the valley over time. The glacier finds less frictional resistance in a deep valley with straighter, more vertical sides than in a V-shaped valley with sloping sides. When the valley has been plucked into a U-shape, it’s easier for the glacier to keep moving forward.

Glaciers leave many reminders of their presence after they’re gone. In addition to the U-shapes and the hanging valleys, they also create moraines, piles of debris formed by the glacier as it moves. One such moraine, left behind when a glacier retreated, is thought to have dammed the Kings River here and formed a lake. That lake accumulated sediment on its floor over many years. When it finally broke through its dam, the disappearing lake left behind what you see in the photo below: Zumwalt Meadow, just a short ways down the road from Roaring River Falls, a magical place to be on a late morning in May.

COMPRESSED UNDER THE WEIGHT OF MORE SNOW

When I stood at the edge of the meadow, I tried to imagine it as a lake, full of water from the Kings River. Then I tried to picture it filled with a solid mass of ice. Despite my geology studies before this trip, I knew very little about glaciers. I had more questions. When did glaciers appear here? How long did they last? Were these the same glaciers that took over the continent? And how does glacial ice form out of snow, if the snow never gets warm enough to melt into water and then freeze?

I learned later that multiple episodes of glaciation occurred worldwide during the Pleistocene, which began around 2.6 million years ago and ended around 10,000 years ago. In the Sierras, glaciation happened at the same time as the Great Ice Age, which began around 110,000 years ago, but the glaciers here were not physically connected to the enormous ice sheets that covered the continent further north and east of the Rockies. They developed on their own, from snow that fell into the valleys between high peaks. This snow got so deep that glaciers were able to form from its compacted mass.

Snowflakes compressed under the weight of more snow become spherical - a type of snow called firn -  and form tiny necks that join them to other snowflakes. The joining necks of firn snow get bigger and bigger because water vapor from the firn balls adds to their mass. Eventually the snow becomes a solid mass of ice, without ever having melted into liquid water. It’s a unique, extremely dense kind of ice with huge crystals. I was fascinated to learn that a glacier is considered a type of monomineralic rock, made only of the mineral known as crystalline H2O.

There was no crystalline H2O to be seen when we visited Zumwalt Meadow. The day was warm, a perfect temperature for wearing short sleeves. Our trail began with a suspension bridge over the Kings River and led us into a forest where bright noon light filtered through the leaves of black oak and incense cedar trees. Soon we could see the meadow through an opening in the trees. Above us rose two peaks: the 8,500 foot Grand Sentinel on the south end, and the 8,717 foot North Dome across the valley from us. North Dome was shaped by glaciers, thus the relative smoothness of this rock face. The Grand Sentinel was also shaped by glaciers; in this case, glaciation split off part of the rock to make a nearly vertical cliff.

AMATEUR GEOLOGIST TRIUMPHS IN THE END

For John Muir, founder of the Sierra Club and wilderness preservation hero, the shapes of these giant stone masses, especially near their peaks, was proof that ice had been here. Muir was not a trained geologist, yet he was the first to suggest that both Yosemite and Kings Canyon had been shaped by glaciation, at a time when this theory struck many as farfetched. He fell in love with the Sierras and visited Kings Canyon several times in the 1870s. He figured out that glaciers had shaped the canyons within his first few months of being in the Sierras, in the summer of 1869. He was an amazingly astute observer of nature.

His glaciation theory was disputed at the time by California’s state geologist Josiah Whitney, an otherwise brilliant scientist and contemporary of Muir and the person for whom Mount Whitney, the highest peak in the lower 48 United States, was named. Whitney thought that Yosemite Valley and other Sierra valleys were formed through fault activity. In his scenario, the valley’s sheer walls could only have been formed by the dropping of the valley bottom during some cataclysm of the earth. He was wrong, but he defended this position vehemently, calling Muir an “ignoramus.” Many others mocked him along with Whitney.

When acceptance finally came for his glaciation theory, Muir was credited for his remarkable intuitive interpretation of the signs of glaciation he’d seen at Yosemite, evidence he had carefully observed and recorded during many visits. Though in hindsight the geologists of Muir’s day seem like ignoramuses themselves, it’s not hard to understand why they would have trouble believing that glaciers could be responsible for large-scale physical transformation of the earth. Water in the form of a glacier behaves in strange ways. The processes of glacial sculpting are slow, mysterious ones, difficult to observe. This makes it all the more impressive that Muir was able to deduce them merely from what he saw with his own eyes.

XENOLITHS AND DEEPER GREENS

John Muir called Kings Canyon “a rival to the Yosemite,” and Zumwalt Meadow is where I could most easily see the similarity between the two parks, especially when our trail left the trees and climbed a very gradual slope into a field of enormous granite boulders. This combination of meadow, mountains, rocks and river was a wilder, more sharp-edged version of Yosemite Valley. It felt like a distillation of the essence of the Sierras.

We were tiny people among the debris of giants on this trail. By now I was far behind my companions, able to photograph them looking small next to big rocks. I loved walking through those boulders, pieces of the south side of the valley wall which have fallen off to form a talus slope. This was my chance to examine up close the kind of granite that makes up the canyon cliffs. It was light-colored with dark specks, some of which were quite large. These are xenoliths, pieces of native rock that fell into the granite while it was still in its magma state, sort of like mini roof pendants.

The path dropped out of the talus slope and into the open meadow, and I lingered to feel the heat of the sun. I was sweating now, lifting my camera, exhilarated by the brilliance of the greens and blues and whites. Soon I reached the boardwalk that protected the meadow’s wetter, more vulnerable section. There was more plant variety here than anywhere else we’d been in Kings Canyon. Interpretive signs on the trail told us that the montane meadows of the Sierras contain greater plant species diversity than any other ecosystems in the range. Meadows are of crucial importance to wildlife here. They serve as food sources, as breeding and pre-migration habitats for many birds, and of course as homes for amphibians. They also play a crucial role in the functioning of the watershed, by filtering sediments from rivers and regulating the release of snowmelt. 

THE DELICATE NATURE OF THESE ECOSYSTEMS

This particular meadow is protected, but for many years livestock were allowed to graze in the Sierras during summer months when the Central Valley was parched and dry. Back then, the meadows were thought to have enough green plants for perpetual munching; 19th-century livestock owners didn't understand the delicate nature of these ecosystems, nor would most of them have been likely to care about such things.

John Muir's first visit to the Sierras was in the company of grazing livestock. He was hired to work as a summer shepherd driving sheep into the mountains. He eventually spoke out against these grazing practices and the damage they caused to meadows. Today, the threat comes from California's ongoing drought and the weather extremes brought on by climate change. These events alter the composition of meadow soil in ways that affect its ability to absorb and hold water. Optimistic people talk about meadow restoration, but in many cases the damage done to meadows by drought and overuse is not reversible.

I hope this place will still be green when I come back someday, I thought, knowing that the future of even a protected meadow is uncertain. At the edge of the boardwalk I encountered two fellow visitors, strangers to me, sitting in silence. We looked out at the scene together, all breathing in the same fragrant ferny air, listening to the varied music of the birds. No one spoke, and even though I knew we were probably just too tired for conversation, it felt like I’d wandered into the place of worship of some miniscule secret meadow cult.

One of the strangers held out a bag of candy. I took a handful with a few words of thanks and put them into a pocket in my camera bag. Over the next few days, I ate my candy slowly, one piece at a time, with many hours in between. It became a kind of meditation. The taste of sugar brought back the light through the trees and the silence of those two people I would probably never see again.