Serpentine and pebbledash on Broadway

22 October 2017

The intersection of Broadway and 20th Street features strong buildings on all four corners. We all know the I. Magnin building (built 1930) and the Capwell (Sears/Uptown Station) building (built 1929) facing it. Across Broadway, we have the metal-clad urban spaceship of the Kaiser Permanente Division of Research building (built 1982) and finally the dark cube of the Golden West Tower Building (built 1968).

One of the nice things about taking the bus is that while you wait, you can look around like architects and urban planners do, as if the cityscape were a stage set. And so, waiting for the 33, I finally took notice of the building wall that I’ve walked past hundreds of times.

It’s chips of dark serpentine, embedded in cement and polished. People in the building trade must know exactly what this is called, but I can’t crack their code. Here’s a closeup.

So all this time, the Golden West Tower Building has been giving the serpentine-clad I. Magnin building a nod, a salute, a shoutout, a heart-tap. I thought that was cool.

That day the 33 took me to Piedmont, where I recognized the same material in Bufano’s “Bear and Cubs” sculpture in Crocker Park, featured here previously.

The other element in that Broadway streetscape is the sidewalk. You’ve all seen it.

This is what’s called a pebbledash finish. Concrete is laid down, then pebbles are pressed into it. When I look at it I think, “What a lovely Franciscan color scheme,” because the reddish and greenish mixture of metamorphosed argillite and chert is so typical of our coastal Northern California rocks. I also think fondly of the red-and-green gravel of Rodeo Beach.


Earthquake apps and post-quake observations

16 October 2017

Seems like disaster is in the air every October. This year the catastrophe is wildfire in the North Bay, bringing up memories of our own turn in the line of fire this very week in 1991.

Yesterday the local paper published an article by Seung Lee that explicitly linked the October fires of 2017 to the Oakland Earthquake of 20XX, not here yet but sure to come.

Lee pointed to some promising smartphone apps that could save us lots of anguish and maybe even lives. Of course, MyShake came first. It’s an Android app (IOS version pending) that turns your phone into a crude but effective, networked seismograph-plus-earthquake-alarm. I’m watching MyShake closely and will let you know when iPhones can participate.

Lee mentioned several apps to help with communications, offering flexibility in the face of degraded cell service and bringing more superpowers to your smartphone. They include Zello, which turns phones into crude but effective walkie-talkies; FireChat, which enables phones to network without internet or cell service by using peer-to-peer technology; and NextRadio, which turns last-generation phones into FM radios. Needless to say, a portable charger belongs in your purse and go-bag — fully charged.

But I’m also writing to point out some possibilities for us to help science after a large East Bay earthquake, once you’ve taken care of yourself and those nearby. Lots of geologists will show up, doing different things. Some will be inspecting damage as consultants. Some will be there doing science on behalf of state and federal agencies. Professors will come with their students, teaching them real-life lessons in disaster response and collaboration with other scientists. You can give them a hand during the aftermath. And some more things you can do of your own initiative.

If you see ruptures in the ground, collect some data. Measure their offsets, photograph them with date and time stamps, and insert objects for scale like a coin or lens cover or your own hand. Do these things quickly before city crews come in to fix the damage. Document offsets in buildings, too. Repeat these observations as the days go on, because afterslip — continuing fault motion once the shaking is over — is a new and lively topic among earthquake scientists.

Ambitious amateurs can practice the structure-from-motion (SfM) technique, by which a series of photos taken from all sides can be turned into accurate three-dimensional models. This yielded dramatically good images after the 2014 Napa earthquake. If I were a maker type, I’d do this. Any practitioners out there?

Monitor your local streams. As earthquakes rattle the ground, they shake down the material of the hills as surely as you’d shake down a jar of coffee beans. When this happens, groundwater gets pushed aside, and a sudden rush of water fills the streams for a while. The Napa earthquake of 24 August 2014 did this all over the North Bay, which I posted about at the time, and Oakland was affected, too. An Eastmont Hills homeowner whose property has a tiny backyard stream valley, dry most of the year, told me that he saw water rise in it within hours of the Napa quake, and the stream ran high for about two weeks.

The Oakland Earthquake of 20XX will be a Katrina-sized event, much worse than the Loma Prieta quake (another October surprise that happened 28 years ago tomorrow). The more we’re aware, the more we prepare, the less likely that our local Katrina will be our Katrina catastrophe. And let’s hope it picks a different month to strike.

In housekeeping news, I’ve pulled earthquake-related posts into their own category, mostly separate from posts about the Hayward fault.

Post 500

9 October 2017

The experts say the greenhouse gases we’ve put in the atmosphere will affect global climate for the next several centuries. Where will we be 500 years from now, once this pulse of carbon dioxide has been drawn down by the seas and soil? What will the post 500 world look like?

I’m fond of talking about the deep present, the idea that we should run society as if any natural event that’s happened during the last 10,000 years or so, not just recorded history, could happen again tomorrow. But for the greenhouse pulse the deep present is no guide, because the world hasn’t seen its like for millions of years. The greenhouse pulse has shoved us into the Anthropocene age in which, like it or not, humans are a large-scale geological force.

The Anthropocene world will be an ad hoc world. Post 500, the sea will be tens of meters higher than today, but once we have the means to regulate the climate I suspect we’ll keep the sea where it is, for stability’s sake. I don’t see us bringing the glaciers back unless there’s an existential need.

Some aspects of the future are sure things. I am sure we’ll still be scrambling to deal with the damages we’ve done to the natural world we inherited: the ruined aquifers, the risen seas, the climate out of equilibrium, the ecosystems lost or knocked askew by extinctions and invasives, the metal ores depleted, the billions of holes we’ve made in the ground.

It’s harder to imagine the state of human society post 500. Look back 500 years to 1517 — the Portuguese empire was pushing into the Spice Islands and the Magellan expedition, the first to circle the globe, was still being organized in Spain. Modern science was many generations ahead.

It makes me uneasy to say this, but unless the human population can be reduced to Earth’s carrying capacity, perhaps one-tenth its present total, we’ll need to engineer fully artificial living arrangements that don’t affect the rest of creation. If you like, call that a zoo for humans. If you like, call it the terrestrial version of a Moon base. It will have to be so good we’ll want to live that way. We’re already getting there.

We will need to minimize our wasteful, precarious agricultural system based on pesticides, fertilizer and soil. To save the world’s plants and animals from widespread extinction we will need to stop encroaching upon their environment — not just stop, but withdraw.

Surely the post 500 world will differ wildly from ours. But the seeds of that world are sprouting today. In the past 500 years we have mastered matter, and in the next 500 I anticipate that we’ll master biology and recycling. We will no longer use fossil fuels, and we’ll do much less mining on Earth than today, if any. We’ll undam most of the rivers and heal the coral reefs.

Why do I bring up all this in a blog on the geology of Oakland? Because we’re building the post 500 world now. Look at the 50 years just past, and imagine that degree of change and progress over the 50 years to come — even as sea-level rise starts to really kick in. The next 50 years is the first one-tenth of the next 500 years, and the most important part. Progress will require knowledge of the Earth and the confidence to apply it. Thus Earth scientists will be central as we make our way.

And Oakland will endure; it’s too important not to. Mass transit will gain ground as population density increases. As the sea rises, we’ll raise our harbor and airport and rail lines, even if they end up on plateaus. We’ll restore the salmon run up San Leandro Creek, and our building stock will improve as we go through repeated earthquakes, rebuilding higher each time.

Those are sure things, and they can be done right if we insist. What matters is our culture. What we do today, and how we do it, will make all the difference on our way to post 500, the year 2517.

(Yes, this is my 500th post.)

Twenty Oakland rock types in a 30-mile drive

2 October 2017

As far as I can tell, Oakland has more rock types within its boundaries than any other city in America. When I added them up for a talk I gave at East Bay Nerd Nite, I counted more than 25, from limestone to blueschist. This 30-mile road trip will take you to most of them, with the Hayward fault as a bonus. It starts above the UC Berkeley campus and runs south the length of the high hills, then goes back north through Montclair and Piedmont to end at Mountain View Cemetery.

That’s 1200 pixels wide if you click on it, but don’t worry, I’ll show it in pieces below for more detail. In fact, let’s go to part 1 right now. It goes from Grizzly Peak through Joaquin Miller Park on Grizzly Peak and Skyline Boulevards.

The numbered segments correspond to the formations on the geologic map, as follows:

  1. Moraga Formation (basalt, andesite, tuff)
  2. Orinda Formation (conglomerate)
  3. Claremont Shale (chert, shale, dolomite limestone)
  4. Sobrante Formation (mudstone, shale)
  5. Unnamed mudstone/sandstone
  6. Redwood Canyon Formation (sandstone, siltstone)
  7. Shephard Creek Formation (sandstone, mudstone, siltstone, shale)
  8. Oakland Conglomerate* (conglomerate, sandstone)
  9. Joaquin Miller Formation (sandstone, shale)

Then there’s part 2, from Joaquin Miller Park to the edge of Montclair on Skyline, Grass Valley Road, Golf Links Road, Keller Avenue, Campus Drive and Redwood Road.

  1. Serpentine (serpentinite, blueschist)
  2. Oakland Conglomerate* (conglomerate, sandstone)
  3. Knoxville Formation (conglomerate, shale)
  4. Leona volcanics (metatuff, metabasalt)

Part 3 takes the freeway to Montclair Village, where you won’t see any rocks, then goes down Moraga Road to Piedmont’s Dracena Park and over to Mountain View Cemetery, where rocks are abundant.

  1. No rocks to be seen, but do stop on Medau Place and spot the offset curbs where the Hayward fault crosses it
  2. Franciscan melange (argillite, metachert, greenstone)
  3. Franciscan sandstone (sandstone, siltstone)
  4. Franciscan melange

The cemetery’s melange has many bodies of hard rock (knockers) that stand above the ground. They have their own blog category. Search this site, or check the category list on the right, for posts I’ve written about these rock units.

*The cobbles embedded in the Oakland Conglomerate offer more rock types, including granite, quartzite, gneiss and schist. That’s how I get up to 20.