Last week I bought a copy of Secret Stairs East Bay, by Charles Fleming, and met the author in person at a book event at the Solano Street branch of Pegasus. As I leafed through the book and heard the author, it was clear that while the walks offer lots of insight into Oakland’s history and culture, the geologic stories to be seen on these walks were yet to be told. I thought, Well, I can try that.
Sunday my wife and I took one of the walks, number 34, to Dracena Park (featured here before) in Piedmont. It begins at Chapel of the Chimes on Piedmont Avenue and takes you on a pathway across the valley of upper Glen Echo Creek (which I’ve called Mountain View Valley). Here’s the view back toward the Chapel from the other end.
The stream was culverted long ago, but on the 1897 topo map it’s shown as Hayes Creek. Today it’s Glen Echo Creek. The valley floor is so flat because it was graded and planted to houses. But in my unprofessional opinion, its flood hazard today is as low as anywhere.
Onward! The book directs us to the head of this little gorge, part of Pleasant Valley Creek’s watershed, and thence to the old quarry pit now known as Dracena Park.
You should always suspect humans as a land-shaping agent in Oakland, and indeed Walter Blair, who ran the quarry at this site and a dairy nearby, may have had a flume or a transport line of some sort here. But its original form appears to be intact.
We turn into the park proper, and glorious bedrock appears — Franciscan sandstone, ready-fractured for its purpose.
Go ahead and inspect the stuff; no hammer is needed (and none allowed anyway) when it crumbles so readily. Fracturing and tectonic movements — and surely some seismic work, like a bartender’s cocktail shaker — has rubbed and even polished parts of the stone.
Fleming says that the stone went into the homes of Oakland, but that is not true. This is not dimension stone by any means, but rather the usual quarry of Bay Area stone hunters in general: crushed stone and aggregate for roadbeds, underlayments and concrete mixes.
What was once a noisy scene of dynamite and dust is now a green bowl punctuated by the cries of children.
The walls of the park are pretty well greened over, but watch out anyway: bedrock exposures don’t last forever. Maybe in a marble or granite quarry, where solid rock is sawed away in blocks, but here rockfall is a continuing potential hazard.
These are not decorative boulders emplaced by landscape designers, but fallen rock. And that ivy-covered fence at the left? It’s really a safety measure to keep landslides away from picnickers. Here’s the whole thing.
Dracena Park is a worthy way to remake an old quarry. But if you’re here when an earthquake strikes, get away from the walls. Meanwhile, the rest of walk #34 beckons.
Oakland Geology 
10 August 2011 at 11:48 pm
Related to your first photo…As you know this alley starts on Moraga Avenue and ends at Piedmont Avenue. Did you know that Glen Echo Creek comes above ground about three doors from the alley? Runs behind the gym and then goes under ground again.
[That little stretch of creek is marked on the watershed map, but I’ve never sought it out. Do I need a gym membership?? — Andrew]
10 August 2011 at 7:25 pm
Very cool! I saw your comment on the photo from the event. If you find errors, particularly with directions, but also with facts about what people are seeing, let Charles know. He’s hoping it does well enough for a second printing, and he can correct any errors then. I’ve already found a few very minor ones, some which I noted in my review.