Archive for January, 2009

Sibley to Siesta

29 January 2009

siesta valley

I showed a view looking down from the head of Siesta Valley last June. Here’s another view, taken from the north end of Sibley Volcanic Reserve in May 2005. Click it for a 1000×750 version.

One of the many things I love about the Bay area hills is the way the vegetation so sensitively reflects the sun, soil and moisture—the terroir, if you will—of every locality. Here stands of oaks mark the rhythmic declivities where a little more shade and a little more water give them a foothold.

I hope you are all taking advantage of the fine weather to tramp these hills; alas, making a living has kept me indoors and off this blog lately.

Huckleberry slickenside

19 January 2009

slickenside

Up in Huckleberry Botanic Reserve my eye was caught by a stone in the path—a clast of Claremont chert, to be exact—bearing this fine example of a slickenside. Slickensides are the polished, striated surfaces on a rock that result from rubbing together, usually by movement along a fault or, in this case, by internal deformation when the rock was being squeezed and uplifted into the Oakland Hills. Little ones are more common than you might think, but ones the size and quality of the one in San Francisco’s Corona Heights are exceedingly rare. I shot this one because there aren’t a lot in the Claremont chert. Usually deformation is accommodated in the shaly beds between the cherty layers, so there’s little chance to get a good rubbing going. The bluish color is reflected skylight, not the chert itself.

Scars

9 January 2009

eucalyptus scars

The hills south of Hiller Highlands, just across route 24, were swept bare by the 1991 fire. Anything that was there besides eucalyptus has been unable to compete, and now it’s a fire-prone monoculture. That suits eucalyptus fine—keeps down those riffraff oaks and madrone, thank you.

The hillside forest was partially cut down maybe ten years ago, then again just a couple years ago. Each wave of attack remains obvious on the landscape. Eucalyptus is like the hundred-headed Hydra in the Odyssey: every head you cut off grows two new ones in replacement. Hercules defeated the Hydra with his sword in one hand and a torch in the other, cauterizing the wound after each head he struck off.

We can only reclaim these slopes by poisoning the stumps, herbicide-haters be damned. For a successful example, see the new slopes along Skyline Boulevard between Broadway Terrace and Elverton Drive, a wedge of land belonging to the Sibley park that has been reclaimed from just this state, exposing some excellent outcrops.


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