Archive for the ‘other’ Category

Emeryville

9 October 2014

The little town of Emeryville has almost no geology that passers-by would recognize. On the geologic map it’s displayed as largely artificial land and coastal alluvium.

emeryvillemap

The only people who see these things are builders and the geological professionals who advise them with their foundations.

The point was made from scratch—the original shore was a straight line pretty much where the railroad is now. Out at the end it’s been prettied up into Marina Park, a simulacrum of a wooded meadow. I like it there.

e-ville-point

A seawall, made of typical Franciscan riprap, protects it from the mild surf that manages to get here through the Golden Gate.

marinapark

The park-y part of Marina Park offers great views of Berkeley and points north. This is a good place to test your knowledge of the geography: Can you point out Strawberry Canyon, for instance. The highest point in this picture is Grizzly Peak.

e-ville-sculpture

We aren’t making any more artificial land in the Bay area, thank goodness. For a while there, people were planning to fill the whole Bay in. The nice thing about artificial land is that we can feel free to decorate it, whether formally as here or informally as at the Albany Bulb.

Salt weathering (tafoni)

11 May 2014

San Francisco does a few geological things better than Oakland. Here’s one.

tafoni

Salt air, specifically salt spray, causes this dramatic pitting in sandstone of the breakwater out by the Golden Gate Yacht Club, on the way to the Wave Organ. San Francisco simply gets more of that raw sea wind that splashes seawater onto the rocks. As the brine dries out, salt crystals grow in the pore spaces and gradually pry the mineral grains apart. This process, called cavernous or honeycomb weathering, affects inland sites where the rock itself contains some salt (Mount Diablo and Las Trampas Ridge have good examples), but along the coast it acts much faster and more pervasively. The hollows are often called tafoni, however that term is properly used for large hollows. Little ones are called alveoli.

You might see some of this in Oakland rocks, but only down in the port, if there. I can’t think of a good example. The riprap boulders in our port are mostly hard igneous rocks that are much more impervious to water.

Incident at Fontaine

11 December 2013

I want to say at the outset that I am not a licensed geologist, only a writer with a degree in the field. But when I read in today’s paper about a ruptured gas line in East Oakland that started a fire at the intersection of Golf Links Road and Fontaine Street on Tuesday, this was the first thing that came to mind: the Hayward fault. The intersection in question is just to the right of the word “Viejo.”

fontainefault

Perhaps those of you who accompanied me last year on a tour of the Hayward fault in this area thought the same thing.

The paper reported, “An investigation into what caused the fire was underway Tuesday and could take several days to complete, according to PG&E.” Let’s keep an eye out on what they report.

Piedmont sulfur spring

8 September 2013

A comment to one of my posts talked about the sulfur springs of Bushy Dell Creek, in Piedmont Park. I said I couldn’t detect any and the commenter said where to look. So a few weeks ago I looked and found this small example.

sulfurspring

It’s just a trickle, but it offers a whiff of sulfur gas. More tellingly, it supports gray filaments of sulfur bacteria, seen here in closeup.

sulfurspringclose

These look like pollution, and I guess in our context that’s what they are. But whole microbial ecosystems center on a molecular economy of sulfur, oxygen, carbon and hydrogen. They’re mostly hidden underground near sulfur-bearing minerals, but here and there they get flushed out into the light.

New Lake Merritt

12 July 2013

I think it’s safe to say that everyone in town is thrilled with the improvements to Lake Merritt. After seeing the final configuration today, I’m feeling a deep satisfaction.

newlakemerritt

The new roadway and pedestrian bridge over the lake’s outlet serves vehicular traffic as well as ever, but residents and, most of all, the lake and the land get their due. The lake—actually it’s a tidal marsh—is noticeably healthier now that the tidal flow from the bay is no longer regulated with a dam. The range of the tide is greater now and the water is flushed more thoroughly. We have figured out how to trust nature with our lake. We’ll see in the future how the new lake deals with drought and flood, but I think that the city will not overreact to the occasional inundation as it might have in the past.

newlakemerritt2

The new lake is a triumph for the planners of Measure DD, where the money came from. The funds are still being spent on this and many other projects around Oakland, but I’m starting to wonder what the DD crew could do for an encore. Nature holds us in its hand with the Hayward fault, too. Can we envision better ways to live with it?

The gallery of Oakland geological science

31 May 2013

OMCAserp

The Oakland Museum of California has finished its three-years-plus shutdown of the Natural Science gallery; the new Gallery of California Natural Sciences had its grand opening today. I got a backstage look at it earlier this week and gave it a thumbs-up for KQED Science yesterday. For me the highlight is the gateway section of the gallery, all about Oakland. All except for Oakland (and California) geology. As far as geology goes, the museum’s great serpentinite boulder on the roof, shown here in 2000, is still as good as it gets.

You’ll see in the new gallery how Oakland looked 300 years ago: its forests and grasslands and marshes. But you won’t see how it looked 30,000 years ago, or 3 million, or why those times are still relevant today. You won’t get a clue to the underlying framework that explains this landscape, or the deep history encoded there. You won’t see a hint of the active faults that shaped, and continue to shape, our region, nor will you see how they link us to California—how all of California is united—in a tight tectonic embrace. You won’t learn where and why the first Oaklanders dug for stone and gravel and water, or why they stopped. You’ll be able to add your backyard oak to a biome database that maps the ghostly living traces of our original forest—a marvelous thing!—but not your backyard outcrop or neighborhood roadcut.

All those things would have been simple to weave into the plan. The geologic subtheme would have enriched the whole exhibit and made it more truly a natural sciences gallery. Instead the new gallery is stuck, geologically speaking, back in 1969 when the old gallery was built. I’ll keep doing what I can here to fill the gap.

Oakland ochre

24 May 2013

oaklandochre

Here’s the story behind this photo. I just got back from five days in Fresno at the annual meeting of my regional section of the Geological Society of America, the Cordilleran Section. The first order of business was a field trip to see the Pleistocene fossils of the Fairmead Landfill, near Chowchilla. The guy whose hand this is is Blake Bufford, director of the Fossil Discovery Center just across the road from the site. His job is to follow around the giant scrapers at the landfill when they dig new pits and watch for fossils, so he’s the most important pair of eyes in the entire project. Blake showed our group the latest pit and then accompanied us to the Center for a tour and a reception by the FDC’s owners, the San Joaquin Valley Paleontology Foundation. Some nice Madera County wine, local cheese, “mammoth” meat balls and so on.

Blake and I got to talking, and the topic of Oakland came up. He asked if I knew anything about the traditional ochre diggings he had visited there. I told him about the Holy Names site, but that’s not the one he meant. No, he said, this was another place that was in the process of being wiped out to build a supermarket, where both red and yellow ochre were produced. “Let me show it to you.”

The Center is full of fossils, but it also has a little display cabinet dedicated to the people who once had the area to themselves, the Chowchilla tribe. There was an antique woven reed basket, of course, but everything else was a modern replica made with traditional techniques: arrows with interchangeable arrowheads, various kinds of twine, deerbone trowels and scrapers, a tiny wooden flute, necklaces, a soapstone bowl and trade beads, and balls of red and yellow ochre. Blake made all of it. He unlocked the case and showed me everything in it. He made the ochre balls, the size of a small egg, by grinding the stone to powder, then mixing it with boiled soaproot to hold it together. “We don’t know exactly what they used, but this worked.” There were a couple of raw ochre specimens lying next to them. “I collected this one from Oakland,” he said, and I said, “Please let me photograph that.”


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