Archive for April, 2009

Rock failure

27 April 2009

quarry failure

The Rockridge Shopping Center quarry is in pretty good shape . . . for a Bay area quarry. Most of the rocks in the Coast Ranges are battered and shattered to various degrees, what with being ripped apart and shaken and squeezed into hills by the activity along the San Andreas fault system. Most of this former quarry is holding up well. But the whole length of the rock face has a chainlink fence in front, with piles of rubble trapped behind it. This spot is near a zone of dark, serpentinite-looking rock that has been failing more than the sandstone and lava around it. If these stout timbers can’t deal with it, I doubt the fence will help much when the rest of the slope starts to give.

Rock naturally deteriorates when you strip the soil off it. Actually the soil is made of deteriorated rock itself. Solid rock may be overrated.

Views: Mountain View Valley

24 April 2009

monte vista

San Francisco is famous for its steep streets, but Oakland has as many vertigo-inducing neighborhoods, and not just up in Montclair and the high hills. The big alluvial fan that underlies north and central Oakland has a fairly gentle slope, but where the local streams cut into it some real gorges are the result. Dimond Canyon is the most dramatic, but Pleasant Valley and Trestle Glen are contenders too. The northernmost of these is occupied by Glen Echo Creek, which runs from left to right across this view up Monte Vista Avenue. As far as I know, the valley doesn’t have a name. But Mountain View Cemetery sits at its upper end, and this street is also named “mountain view,” so that’s what I’ll call it.

Foundations

16 April 2009

sidewalk slump

Walking past the Oakland Museum of California on the 10th Street side on my way to the Coliseum yesterday, I saw that the extensive work going on now doesn’t seem to include fixing the sidewalk. There probably is no structural threat to the building; this most likely represents compaction. Try as we may, we can’t always make ground as good as nature alone does. She has the advantage of “world enough, and time.” Foundation work is expensive to do right, but even more so to do poorly.

Geology on BART

8 April 2009

bart geology

One of my pleasures is to find a BART car with clean windows and a reason to ride, because short of having a private car and driver or my own airplane it’s the best way to savor Oakland’s topography. And with the accumulation of walks taken and drives made, I see and recognize more and more detail in that familiar view. In Walden Thoreau wrote, quoting Cowper: “With respect to landscapes, — ‘I am monarch of all I survey, / My right there is none to dispute.’ I have frequently seen a poet withdraw, having enjoyed the most valuable part of a farm, while the crusty farmer supposed that he had got a few wild apples only.”

The emphasis Thoreau placed on the word survey implies both looking over in a synoptic sense and traversing on foot with scopes and stakes. On BART I do the first while recollecting the second.


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