Archive for the ‘other’ Category

The 40th Street cut

18 February 2009


Apparently there are people besides me wandering my neighborhood and seeing the vanished past. This image comes from the 40th Street Cut blog, the record of an effort to put together an art show inspired by the Piedmont Avenue neighborhood. I have to say these guys know what grabs me.

The Key Route used to cut through the ridge running east of Broadway between Macarthur and CCA (which I’ve called Montgomery ridge, but on an old map it’s called Thermal Hill). This photo shows that cut before the tracks were pulled up and the cut filled in again. If I only had an hour to examine its walls!

The walls of the cut are steep, but there was no bedrock in it—that’s why the cut was made, because the work was easy. The material of the hill is stiff, well-compacted alluvium from a large, ancient fan that has had gulches cut into it by modern streams. Here the ridge was flanked by the two branches of Glen Echo Creek, one running along Broadway from the Claremont golf course and the other coming down from the cemetery grounds. (They join along Richmond Boulevard just north of 30th Street.) There was no danger of landsliding or rockfalls.

Geologists love roadcuts. In this part of Oakland they’re quite rare.

Oh—the 40th Street Cut people are having an opening reception Thursday the 18th, downtown. Details on the blog.


29 December 2008


I’ve kept this photo around for a long time, but I still can’t say exactly why. It reminds me of shots of Montmartre in Paris. It’s looking southeast toward the intersection of Park Boulevard and Chatham Road, which becomes a freeway onramp at this point. The road in the front is a nameless alley that branches off Excelsior Avenue, serving a tiny block of just nine houses.

I guess the shot exemplifies the hidden treasures of Oakland, hundreds of them, visible only to those who go about on foot with their eyes open. Not all of them are about geology. On top of the geologic palimpsest, the land bears another whole layer of human history: streets and lots laid out and partially erased leaving remnants and traces, not all of which can be deciphered. The people who witnessed the changes pass on, and details vanish. It is something like geology, whose story is likened to a newspaper with most of the pages torn out and the rest burned.

The Oakland geologic map

25 December 2008

geologic map

Time to share my geologic map of Oakland, adapted from USGS Miscellaneous Field Studies Map MF-2342. That map covers a much larger area, but I’ve cropped it to Oakland and faded out the neighboring cities. You’ll note the slash of the Hayward fault. Also note how much of the bay shore is fill. Click the photo to access the 2400×2400 version.

I know you’ll enjoy staring at this. To save traffic on my personal site, it would be best for youFeel free to copy the file to your own machine and view it at your leisure.

Happy holidays! By the way, I have a challenging Christmas geo-quiz up on today; answers tomorrow in a separate post, so as not to spoil the experience for latecomers.

Human geomorphology

2 December 2008

hilltop rink

This clandestine bicycle track in the woods overlooking Montclair seems to be abandoned; there are fallen trees lying across it. I’m assuming that it was used by pedal-pumping kids, because dirt bikes would have been heard for miles around.

It represents a huge amount of work. But that’s our specialty: digging up the ground for purposes far beyond our biological needs. Researchers calculate that human activity, from dam-building to mining and beyond, now surpasses every other single geologic agent in moving stuff around.

Leave the stone alone

9 October 2008

temescal park

Oakland is in an unusual situation. Right now, nobody is exploring Oakland geology, yet the city has a great variety of features worth attention and even celebration. I’d like to see that change, which is one reason I began this blog just over a year ago. Right now, Oaklanders are spreading their attention on fresh culture, the creeks, the government, business, the lake and their houses and families and neighborhoods. People are outdoors—I see them almost everywhere I go—but nearly all of them are either construction crews, joggers or bicyclists. They aren’t there just to BE there. (Maybe I’m not either, strictly speaking, but let’s let that go.) Even if they set out to enjoy some of Oakland’s geology, there are no trails and almost no interpretive exhibits. And even if there were trails, I’m not sure I would favor that because development brings degradation. Let me give an example or two.

Mount Tamalpais, in Marin County, gave rise to mountain biking, starting in the seventies with a close fraternity of obsessive amateurs. Today the sport is an industry that benefits many thousands of people, some of whom—just a relative few—are poor citizens that blaze unsupervised trails and abuse existing ones where they are prohibited. The rocks of north Berkeley, most notably Indian Rock, spawned a lively school of rock climbing starting with the David Brower crowd in the 1930s, and today Berkeley’s public crags are so overrun with exercisers of all ages that visiting for any other purpose is difficult.

All this is just to say that if the geologizers of Oakland are ever to increase in number and sophistication, we have to build in righteous field manners, responsible enthusiasm, at the foundation. For the Oakland amateur, the city’s landscape is as good as a wilderness, and my own practice is evolving toward the wilderness ethic of the Sierra Club: take only pictures, leave only footprints. For some time to come, Oakland geologizing will be, not exactly underground, but unsupervised. And because “to live outside the law you must be honest,” I want to set a personal example of self-restraint.

And so one of my watchwords as I traipse about our streets and slopes is “leave the stone alone.” We aren’t real geologists, with a job to do that requires us to sample and hammer and drill the outcrops. We’re just out there to enjoy and learn, and I believe we should treat Oakland, for the most part, like a park. Everything I show you here in this blog is something I’ve left behind unblemished, so that you can enjoy it just as much.

Suiseki and gongshi—in Oakland?

4 August 2008


Sunday I visited the Garden Center in Lakeside Park, including the bonsai garden, an attraction not to be missed. This large gongshi stone ushers you toward the entrance. The photo is from 2005 (click full size), because at the moment the stone has a wire around its waist holding up a small tree. It reminded me too much of a leashed animal, and I hope they remove it soon. Gongshi stones generally come from China, where the art form arose many centuries ago. This one is a white, deformed crystalline limestone that weathered and eroded into its arresting shape. Inside the bonsai garden there are several interesting California stones in various places. They are not quite suiseki, merely decorative rocks. This is a suiseki:

suiseki by lance plaza

It was collected in California and mounted in its wooden daiza by Lance Plaza for the 2006 suiseki show, in the Garden Center. I’ve enjoyed several of these annual events, but for some reason missed this year’s. Had I gone to San Francisco instead, that very afternoon I could have seen the annual show of the San Francisco suiseki society. But Oakland has a goodly share of suiseki artists, including the bloggers Mas Nakajima and Janet Roth.

These art forms are a braintwister for geologists. We tend to dwell on what the stone says rather than what it is—or is that the other way around?

The labyrinths of Sibley

11 July 2008

sibley maze

Doing urban geology in a place like Oakland adds a new question to the mental checklist that cannot be bypassed: “Is this truly a natural feature?” A boulder may be imported. A terrace may be an old railroad bed. Sibley Volcanic Reserve is a former quarry, therefore it’s safe to assume that this huge pit is not natural and that the labyrinth, one of several in the park, is of even later vintage. But park staff and other visitors have told me that some people insist, against all persuasion, that the labyrinths were made by cosmic visitors.

There is something about human beings, isn’t there? I used to trouble myself over our ability to believe nonsense, but now I realize that banging my head against that wall just hurts my head, and the wall likes it. The fact is, the general run of people love to be amazed. The trouble is, they aren’t particular about what amazes them.

Don’t get me wrong about labyrinths—they are good to experience, they do things to your head, they help pull you out of tedium. That’s cool. I think that crediting them to space aliens is a failure of imagination and a poor reflection on human ingenuity. What amazes me about labyrinths is that we invented them.

But what amazes me more satisfyingly is that people could examine this ground and figure out that it used to be the insides of a small basaltic volcano, now tilted onto its side. It takes imagination first, then the perseverance to test your imagination against the rocks again and again until every question you can think of has been met with a reasonable answer. I haven’t done that at Sibley, but having been to geology school I know how to do it if I set my mind to it. The people who did do that amaze me. They used directed imagination and rigorous skepticism instead of listening for voices and watching for signs, unhuman as that is.


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