Archive for the ‘other’ Category

Northbrae rhyolite

27 December 2010

Berkeley is full of interesting rocks, many of them preserved in pocket parks. The most prominent of these is Indian Rock.

indian rock

Click the photo for a 1000-pixel version. Some 100 years ago this tough rhyolite, a volcanic rock very high in silica, was mapped as part of the same rock body as the one in Leona Quarry and farther down along the hills. But a master’s student at Cal State Hayward gave it a good look in the 1990s and determined that the Northbrae rhyolite, as this occurrence was named, is quite a different rock. (In fact the Leona rhyolite isn’t considered a rhyolite any more, but rather a high-silica welded tuff/volcaniclastic sequence.) Whereas the first mappers thought that both rocks were Pliocene, which is quite young (about 5 million years), the Leona was later shown to be Jurassic (about 150 m.y.). The Northbrae is not that old, but neither is it as young as Pliocene. It’s just a little older than the Moraga Formation basalt and the volcanic rocks of Sibley volcano, about 11 million years, making it Miocene. It came out in that same episode of eruptions, which today sits to the north around Clear Lake and The Geysers.

And it’s still definitely rhyolite. Rhyolite is the stiff, slow-moving lava that makes up little volcanoes like the young dome inside Mount St. Helens, or the rugged knobs of the Inyo Domes, over the Sierra in the Mammoth Lakes area, or farther south in the Coso Range. It makes great rock for climbers—strong, imperishable, full of handholds and rarely giving way under a person’s weight.

The rhyolite of Berkeley is well worth a visit. Just go at a time when the climbers aren’t busy; the rock parks swarm with them in nice weather. I don’t think Oakland has any of this rock, but it might.


22 September 2010

A few places in Oakland feature these sandstone blocks. Two I can think of immediately are on Lakeshore Avenue, including this one.

sandstone blocks

I always wonder whether the stones were salvaged from somewhere else, like Andy Goldsworthy’s wonderful “Stone River” on the Stanford campus. They have tool marks on them, and I don’t know much about stonecarving tools, but I’ll bet they haven’t changed in centuries. These stones echo the most ancient practices of civilization, in which building stones were recycled again and again without regard to the structures they previously gave life to. The stones were precious in bulk rather than as individuals, the way that gold bullion is precious.

These stones always remind me, every time I see them, of one of William Randolph Hearst’s greatest follies. He purchased an ancient chapter house, built in Spain by Cistercian monks in 1190, and shipped it to California as disassembled stones. He never got around to putting them back together again, and as I recall the story, they sat in a pile somewhere in Golden Gate Park. (That’s probably an exaggeration, but who knows?) Now those stones were precious in the way that old gold coinage is precious—they embody history. These days we are a sentimental people, and the Spanish stones have a bit of holiness in them, as if the monks’ prayers had saturated them. Scattering them on the ground in a strange land is an affront to their previous owners.

That’s why I loved today’s Tribune column by beer writer Jay Brooks. A California branch of the Cistercians, the Abbey of New Clairvaux north of Chico, has acquired the stones and plans to reassemble the chapter house using the profits from a series of Trappist-style beers to be made by Sierra Nevada Brewing next year. The Trappists are the order of monks that include the Cistercians, and they’re famous for brewing Belgium’s greatest beers. That’s worth a toast.

San Francisco suiseki

1 August 2010

Last month the California Suiseki Society had its 15th annual show in the Lakeside Garden Center. It was a sublime exhibit with an attentive audience.


The best photo I got that afternoon is this stone by Jim Broadhurst. See more of the stones here and here.


There is an older suiseki society across the bay, San Francisco Suiseki Kai. They are such purists that until recently they did not even use English, but their current president, Janet Roth, is an Anglophone. Their 29th annual exhibit is coming up next weekend: August 7 and 8, 10 am to 4 pm, in the Japan Center, at the Union Bank Hospitality Room at 1675 Post Street. The collectors themselves award winners of the exhibit by voting for their favorite stones. Me, I love finding out where the stones come from, then scratching my head in happy confusion at the mixture of thoughts, aesthetic and geologic, that arise as I contemplate them.

Janet Roth couldn’t resist saying in her note to me announcing the show, “Of course, if the legislature outlaws serpentine we will be in a pickle.”

My serpentine letter – Updated

28 July 2010

I’ve just mailed the following letter to Assemblymember Nancy Skinner, who represents Oakland in Sacramento:

“Dear Assemblymember Skinner,

“I write in opposition to Senate Bill 624, which removes serpentine as the state rock and removes the category of state rock itself from the State Code.

“Serpentine, or as geologists know it, serpentinite, is a signature stone of California, found in most parts of the state. The reasons for its widespread distribution here are deep clues to the structure and behavior of the Earth’s crust and underlying mantle. That is to say, serpentine is a protagonist in the story of modern geology. It gives California students of Earth science at all levels, from primary grades through postgraduate studies, a handle for learning concepts as well as practicalities.

“The concepts embodied by serpentine are the joy of geologists: tectonic interactions of continents and oceans, chemical transformations of deep-seated rocks, the lubrication of earthquake faults, the rise of mineral-bearing fluids into lodes and bonanzas.

“The practicalities embodied by serpentine are relevant to many classes of citizens: Serpentine ground requires special care on the part of builders. Serpentine soil supports a set of distinctively Californian plant and animal communities. Serpentine minerals include the fibrous chrysotile, used since ancient times for fireproofing applications and mined in California during most of the 20th century. Serpentine bodies are associated with valuable mineral deposits including chromium, jade and gold (California’s state mineral).

“The familiar blue-green, shiny serpentine seen in hundreds of roadcuts is a striking remembrancer of those school lessons. The legislature was wise to make serpentine the face of California’s rocks and landscapes. The legislature was bold to make that designation in 1965, when no other American state had ever chosen a lithologic emblem.

“SB624 undoes that wisdom and unmakes that boldness for unscientific and fear-based reasons. It is unscientific in declaring that serpentine causes cancer when, in fact, only a small fraction of serpentine contains the mineral chrysotile. And only in industrial settings, in which large amounts of the powdered mineral were inhaled for years by WWII-era workers, is that one mineral linked to lung disease. SB624 is a profoundly misinformed bill.

“The result of this bill’s becoming law will be to deaden our children’s education, increase their fear of the outdoors, and open all kinds of benign land uses to mischievous litigation. Please assure me that SB624 will not get your vote.”

We’ll see what happens next week.

UPDATE: Rep. Skinner replied with a generic letter. The bill entered the maelstrom of late-session maneuvers, during which the sponsor deleted everything but a single sentence removing serpentine as the state rock, without the noisome preamble. This would have allowed her to declare victory, but for stealth reasons. In any case, the bill was shunted to the Rules Committee, where it died with the end of the session last week. But now I guess I’ll have to watch for its successor in future years.


7 July 2010

As you explore Oakland, you come upon places where something has been erased and not yet replaced.

oakland hills fire

The Oakland Hills fire of October 1991 left these, the first on Acacia Avenue and the other two on Roble Road.

oakland hills fire

There must be reasons for each of these remaining ruins after almost twenty years. But here they are, some quite public and others in quiet privacy. People pass and pay them no mind. Another few decades and the traces might be gone.

oakland hills fire

I got an odd request last year: Henry K. Lee, author of Presumed Dead, asked me to visit the spot in the Oakland Hills where a notorious murderer put the body of his victim. He wanted to know how a geologist would describe the ground there. It was shale, crumbling and easily dug. The place was shrouded in oak woods, but everyday life was within earshot: lawn equipment whining, bicyclists conversing, dogs. The site—which I will not call a grave—was still being visited. But its traces should be left to vanish.

Oakland geography

8 June 2010

I don’t always poke around Oakland’s innards, its rocks and landforms and geologic history. Most of the time, I actually just enjoy the place.

lake merritt

Geography is what geology, climate, history and culture all add up to. Round Top and the ancient volcano it embodies, the hills and the sea air riding up their flanks are merely the stage for Oakland’s beautiful humanity. It is a magnificent arena, where you can see people from every part of the world in one place.

I seem to have caught up with my long backlog of photos and topics. It’s time to get outside again. What questions about Oakland’s geology are on your minds?

Drains to bay, an Earth Day message

22 April 2010

earth day

Some things are as obvious as gravity: Here’s the drain. There’s the bay. The geologist knows this so well that it never needs to be stated. The earliest thinkers of modern geology, as far back as Nicolas Steno in the 1600s at least, recognized that rocks arise from the everyday process of mud washing downstream to the sea. The signs are obvious in the petrified ripple and current marks, the fossilized sea creatures and the sandstones as clean as the stuff of beaches. “Drains to bay” might as well be written on the geologist’s coat of arms.

The rest of us need occasional reminders. Many of us never gave it a moment’s thought, probably those same Oaklanders who think that bears live in the woods up on Skyline. Earth Day is for them, the ignorant. Ignorant people are not bad people. Indeed, they’re only selectively ignorant, in that they don’t know something I consider important. Surely I’m just as ignorant in terms of what they care about. Anyway, “drains to bay” is a good start and it needs to be pointed out everywhere, even here where it’s obvious on Embarcadero East at the mouth of 14th Street Creek.

Earth Day, too, should always point out the basics. The rest of the year is for learning more and for putting knowledge into daily action—for Earth Life.

“Drains to bay” means that what we throw away doesn’t go away, any more than the ancient ripples and prehistoric creatures are totally lost.


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