Oakland Geology

focused on, near and under Oakland, California

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Stone speaks

Mar 12, 2010 12:38pm

Mountain View Cemetery is a celebration of stone even if you ignore the knockers scattered about the grounds. Granite and marble are the two traditional rock types used—or I should say, stone types because commercial granite and commercial marble aren’t always what the geologist would call them. Marble and granite combine...

The big rock show

Mar 7, 2010 9:27pm

Sometimes I go out of town. Today I visited the annual show of the Mineral and Gem Society of Castro Valley, held down in Newark this year. For me, coming from the geological side of things, it’s dazzling kind of place. The hall was full of families, because there’s something for...

Wacke

Feb 28, 2010 6:23pm

Wacke is pronounced “wacky.” It’s a name for coarse sandstone that contains a lot of junk: clay, rock fragments and minerals other than quartz. This is a closeup of wacke from the Oakland Conglomerate from Shepherd Canyon (more about that below). The geologist looks at this and envisions a young mountain...

Punk shale

Feb 23, 2010 10:00pm

Up along Skyline Boulevard between Snake and Shepherd Canyon Roads is a long section of crumbling roadcut. The rock there is mapped as brown mudstone that has been questionably assigned to the Sobrante Formation. OK, enough of that. What struck me about it is how weak it is. This exposure...

Redwood Canyon Formation

Feb 18, 2010 6:02pm

I visited the Montclair Railroad Trail yesterday, while the sun was shining, and found it a delightful transect of some important Oakland bedrock, including this. The Redwood Canyon Formation is part of the Great Valley sequence, a thick sequence of sedimentary rocks laid down between 150 and maybe 60 million years...

Middle Harbor Park guards

Feb 12, 2010 8:35pm

Middle Harbor Park is graced with large boulders. They look pretty and are interesting to study at close hand, but they’re actually at work barring entrance to vehicles. None of them come from Oakland, as far as I can tell. The rock in the foreground is a lovely example of cobble...

Creek mouths

Feb 7, 2010 1:39pm

Down at the Martin Luther King Shoreline Regional Park, three creeks debouch into San Leandro Bay. I already talked about San Leandro Creek; the other two are Lion Creek, below (more about it here and here), and Elmhurst Creek, bottom. Maybe with all our recent rain, they carried some sediment down...

Eastern knockers

Jan 31, 2010 8:46pm

Recently I visited some of the knockers in the steep hillside east and south of Mountain View Cemetery. These three are chert of deep-sea origin; the middle photo best shows its typical “ribbon” bedding. This area borders the steep gorge of Moraga Canyon and harbors a number of deer and turkeys,...

Chabot gorge

Jan 24, 2010 7:22pm

As you walk up to Chabot Dam the valley carved by San Leandro Creek opens up below, and it’s quite impressive (click photo for bigger version): At the top, the dam is buttressed against a ridge of the volcanic rock of Leona Quarry. Before the dam was built, there must have...

Old-fashioned water filtration

Jan 16, 2010 5:20pm

On the path up to Chabot Dam, you pass this row of big tanks (click for big version). They were used to filter the water from Lake Chabot reservoir, and they’re still filled with fine sand plus, I suppose, the decades’ worth of slime and crap they kept out of Oaklanders’...