Working rocks

Last week I made another visit to Knowland Park in preparation for my two upcoming Wild Oakland walks on September 20 (tickets still available) and October 4 (no tickets needed). I’m holding off on posting about the park’s geology until after these events, but it’s hard to wait.

Meanwhile, here’s something different. Oakland has plenty of excellent native rocks, but the days are long past when Oaklanders could shop for Oakland stone at an Oakland quarry. Today newer places must make do with more anonymous stones from distant sources. They do their jobs with stolid competence and the occasional dash of flair.

This roadside lot on Cameron Drive uses guard rocks to discourage parking and keep runaway vehicles from breaking the wall. They’re picturesque, but kind of brusque.


Sobrante Park Elementary School has this splendid green boulder by its front entrance. It’s not serpentinite but, most likely, a beautifully chloritized basalt from the Franciscan Complex. The two neighboring boulders are sandstone. I think their job is keep runaway vehicles from the building, although neither Topanga Drive nor El Paseo Drive is a high-speed thoroughfare.


And down by Lake Merritt, the latest Measure DD improvement, the Sailboat House Shoreline Project, has made the shoreline more wildlife-friendly. The marsh vegetation will have to wait for the rainy season, but the infrastructure is in place.


These boulders are undistinguished sandstone, but they’re laid with care. I predict that the gulls will be cracking mussels on them, if they aren’t already. The rocks will also allow people to step into the marsh without kicking up the reeds and mud. And they’ll keep runaway vehicles out of the lake. Hmm, there seems to be a common thread here.

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