With those words, off we drove on a cool, cloudless Friday morning after Thanksgiving, up into the Berkeley Hills via broad, snake-winding Claremont Avenue. At the top of Claremont, at the intersection called “Four Corners,” we turned left onto Grizzly Peak Boulevard and stopped .08 miles further on at the trailhead for Side Hill Trail on the dizzying steep western slope.
About forty people beat us there. Most of them, I suspect, were rockhounds—amateur geologists—but we were no doubt all of one mind on one issue: Better to expend precious time out in the endless open in relatively cleaner air than to spend Black Friday jostling with the great bargain-desperate mass, unwashed and not, at the mall in search of trinkets whose sparkle would fade the day after the Christmas. Time will always be a greater commodity than money.
This outing was a geology walk hosted by the Claremont Canyon Conservancy down into the same-named canyon. We were tipped off to this event via San Francisco environmental activist Jake Sigg’s newsletter (jakesigg@earthlink.net). Our articulate guide for the two-hour and about-one-mile stroll through the Claremont Canyon was Doris Sloan, a retired UC Berkeley professor of Geology and author of Geology of the San Francisco Bay Region.
Doris had clearly once been a teacher: She was articulate, bursting with knowledge and passion and even demanding in her crusty way: She fired off occasional pop quizzes as our large group struggled to both keep up and not get too far ahead throughout the walk. I shrank with a subtle embarrassed guilt at how little I knew. Should I raise my hand to ask permission to step into the bushes?
There’s more to the Berkeley Hills than you’d think at first glance, especially if you’re seeing them from the Emeryville flats. They are a complex, folded and often rugged terrain of canyons and ravines, lumbering north-to-south, a few miles east of San Francisco Bay; hills hiding hills, canyons concealing ravines, many trails weaving about through surprising nooks and crannies. Dozens of varieties of trees grow here, many more than the native oaks and nonnative eucalyptus that are easily identified. Golden meadows sprawl throughout.
Some of the trails aren’t much wider than a two-by-four. These are my favorites, these are the ones that suddenly sweep a walker out around the ribs of the hills into dizzying panoramas of the East Bay cities below and, the world beyond: San Francisco, the Coast Range rolling south down the San Mateo Peninsula and the Golden Gate. The air was bright and clear enough to see the now oil-stained Farallon Islands, forty miles out in the blue Pacific, clearly visible beyond the Golden Gate Bridge, looking like a sailing ship pushing peacefully south through a calm autumn sea.
My respect for science is vast, though my grasp of it is often shaky, but I can say that there’s tens of millions of years of hidden history in these pretty hills. Only a sliver of of it involves us humans. All of it keeps moving. Once in a great while it moves violently. To geologists worldwide, the Berkeley Hills are a favorite trove of evidence and insight into the ancient, and still profoundly active, forces that have been shaping this little blue home of ours even before homo sapiens sapiens was a twinkle in the God's Big Eye.
For instance, that bay you see in the photo above: Nine to ten million years ago, it was a mountain range that has long since been shifted by volcanic activity far north to the wine country, over fifty miles away. This movement took place at about the average speed that a fingernail grows, with occasional bursts of several feet caused by the infamous Hayward or San Andreas faults. Several feet doesn’t sound like much, until you factor in the shift of all that mass and the release of all that power. And the fact that you might be standing on it.
Around that time, the Golden Gate wasn’t even a gate and it was a long walk to the ocean. The third-highest point in these hills, Round Top, located in the Sibley Volcanic Preserve a few miles south of our location, is an extinct volcano that last saw action millions of years ago and many miles south of its current location. To make it even awesomely stranger, these same tectonic forces have tilted, twisted, folded and finally tipped the now-dormant feature onto its side.
That’s a lot of change for our minds to absorb. And a lot of time. After all, when you look at all that hard, dense rock, it doesn’t seem to be moving a bit, does it?
But it has. And is.
Our walk started at the top, through a field of basalt, a type of shale produced by those volcanic forces mentioned above. Doris Sloan stopped along the way to point out the many features of this material, including dabs of white-streaked red rock that turn out to be the remains of gas bubbles. We stopped at the breaking point between the basalt and an area called the Orinda Formation, where we see several types of rock, indicated by the presences of thousands of stream pebbles. After that, we wound our way to the oldest, most unique ground of all: the Claremont Shale.
Very cool, that Claremont Shale. Bands of white rock, dusted with red, parallel to the ground like layer cake. This shale is not inanimate rock, but something fabulous: a mass of once-living things, known by the delightful word "chert." This formation is made of silica, which are the compressed skeletal remains of sea creatures, millions and million of years old. A couple of hundred feet above the Oakland flats and several miles inland, we were standing on and looking at an old sea bed that continues to rise higher. For this we must thank a process called subduction, which loosely resembles what happens when you try to shove your ultra-thick shag rug under your thin handmade Persian rug.
On the way back up to the top of these hills (which, BTW, are comparatively young), I took a couple of photos (above) of some chevron folds, an especially resistant part of the volcanic layer. Elizabeth remarked on how this brief present-day journey through time past had given her perspective on our place in Life and on Nature’s basic toughness in the face of everything, even our current depredations. Nature always either bounces back or finds her way around. If we fail to take care of what takes care of us, we’re the ones who will be gone. “Nature,” Elizabeth said, “will take care of itself.”
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