Archive for January, 2012

Davie quarry

30 January 2012

Davie Tennis Stadium is a set of courts in a former quarry, administered by Oakland but situated within Piedmont. But what about the stone, you ask.

davie chert

I haven’t checked the whole place out, but the exposures near the entrance display this dark chert or siliceous metashale. The quarry exploited the Novato Quarry terrane of the Franciscan complex, a large pod of which underlies Piedmont and its immediate surroundings. The terrane is mostly sandstone, but some fine-grained rocks occur in it too.

I’ll be leading a walk to this and three other Oakland quarries for the Oakland Urban Paths organization on February 11. Watch the OUP site for details.

Radio Tower Hill

20 January 2012

On Tuesday the skies were so clear I made a point of visiting the hills. Not as clear as Monday, but from the top of Radio Tower Hill this is how the Golden Gate looked. Remember this when the weather is dismal.

golden gate from radio tower hill

Click the photo for a 1000-pixel version. That’s the Farallon Islands on the horizon, perched at the edge of the continental shelf on the Pacific plate. They consist of the same granite found on Point Reyes, Bodega Head, Montara Mountain and points south in the Salinian terrane. The blob just below them is a freighter bound for the Port of Oakland, or perhaps a tanker bound for Point Richmond. Downward in the image is the bridge, Alcatraz Island, Treasure Island and the foot of Ashby Avenue in Berkeley.

Radio Tower Hill doesn’t really have a name. It’s the hill at the intersection of Grizzly Peak Boulevard and Marlborough Terrace. It’s made of Claremont chert.


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