Archive for the ‘other’ Category

Claremont chert, and other Oakland rocks, in Sunol

16 November 2014

The other day I took a field trip to see the construction site of the new dam for the Calaveras Reservoir. (The old dam is being replaced because it’s not strong enough to endure a big earthquake on the Calaveras fault, which runs essentially right through it.) It was a cool time, with fossils and big construction vehicles and engineers and grout. As the dam people were orienting us that morning, they passed around specimens of the major rock types in the area, and here was a fine chunk of chert from the Claremont Formation.


The stuff in our Oakland hills is white, because its carbon content was been leached out. This deep specimen retains the organic remains of ancient plankton that make the Claremont, like its larger sibling the Monterey Formation, source rocks for petroleum. (I showed you an exposure of similar stuff down at Alum Rock Park a while back.)

What the heck, I’m not planning to publish these anywhere else: here’s a cobble from a conglomerate down there that’s been stretched and fractured by activity on the Calaveras fault. It was exactly like the examples in our own Oakland Conglomerate.


I think this one was from the Berryessa Formation (which is also found up at Alum Rock). Considering the looseness of the definitions of these formations, I feel safe in correlating them, although Crittenden defined the Berryessa as lying above the Oakland. Anyway, the phenomenon is the same.

One major feature of the construction project is an enormous cut made into the hill on the west side of the dam site. Basically, they discovered an active landslide there and decided to excavate the whole damn thing. We got to wander out along this exposure and hunt for fossils in the Temblor Formation, or at least rocks mapped as the Temblor.


There were a fair number of big ol’ scallop shells to be found, usually in pieces. Also some coaly bits of fossil wood. This is a rare exposure of an actual bedding plane, as marked by a pavement of scallop shells in what looks like their growth position.


We also learned a lot about the recent project that rebuilt part of the Hetch Hetchy Aqueduct that runs through here. Once the work was done, this tunnel-digging machine became surplus.


The guy asked us if we wanted to bid on it. I thought it had the makings of a good Burning Man stunt.

Geological issues in the 2014 election

31 October 2014

Nobody asked for my guidance in this fall’s elections. That’s OK—this isn’t guidance, just a few observations from October.

The mayoral candidates in Oakland, almost unanimously, have ignored the two geological elephants in the room. First is the Hayward fault and its chronic threat to this wonderful city. Oakland is the upcoming victim, at some time unforeseen, of a magnitude-7 earthquake that will rip the ground all the way from beyond Sheffield Village to beyond the Claremont Resort. And ten times as many magnitude-6 events, the size of the 24 August Napa earthquake, will arise from the same stretch of the fault in the next century or so. Second is the rising sea level, which within our children’s lifespans will lap onto the waterfront and airport.

But those aren’t really election issues; they’re policy issues. We have staff making plans and pushing them forward an inch at a time, about as fast as the Hayward fault creeps. I’m sure that our next mayor, whoever it is, will support them fully. One of those plans is aimed at our large stock of vulnerable buildings—soft-story apartments. These multifamily dwellings, many of them fine old buildings, house some 20,000 people. In forecasts of the Big One, fully two-thirds of the Oakland residents made homeless will come from this class of structure. The city has mapped them, and when you contemplate the map maybe you’ll start thinking of them the way fire officials think of old-growth eucalyptus stands.


The Oakland Soft Story program has made good progress this year. Mayor Quan and Councilor Kalb got a task force together in April to get an ordinance ready for early 2015 that will concentrate on this low-hanging fruit of civic resilience, and I commend them both. (City Manager Henry Gardner published an excellent memo this month on the status of the program.) Dan Kalb isn’t up for re-election this year; Jean Quan is. Quan also is the only one of the mayoral candidates to mention earthquakes on their websites. She has a lot going for her, from my parochial viewpoint, like her support for the geology sign at Joaquin Miller Park. She took the time to show up at the Loma Prieta 25 policy conference on October 16, where she presented a spirited defense of the city’s earthquake preparedness efforts.

She gets it. I didn’t vote for her, though, because I think at least three other candidates will make better mayors. It’s OK if you disagree about that. But I trust that all of the likely winners will carry on correctly, with goading from Dan Kalb and skilled assistance from our Chief Resilience Officer, Victoria Salinas. Both of them get it, too.

That’s earthquake preparedness. Nobody’s talking about sea-level rise, but a lot of people are thinking about it, and I believe we’ll make the necessary adjustments in a timely way. It happens that the subject is on Salinas’s radar. If you never heard of her before, it’s because the Chief Resilience Officer is a grant-funded position that just started this year. I very much want her to succeed and be supported here after the grant runs out. Again, not an election issue.

On the state side of the election, I have less to say. The big water bond, Proposition 1, will direct some money at the Delta levees, which is an enormous area of vulnerability to earthquakes and sea-level rise. The more money the better, I say.

And in the Secretary of State election, I believe in Alex Padilla. He was off my radar until he sponsored the legislation for the statewide Earthquake Early Warning network last year. And last month at the Third International Earthquake Early Warning Conference, he showed up and seemed quite at home among the scientists and emergency-response people who care deeply about this technology. Turns out he’s a trained mechanical engineer, and as state senator for the district including Caltech, he regularly visited the school to keep up with the science there. It was by chance during one such visit that he got wind of the ShakeAlert early-warning system, and to his credit he took up the issue and carried it over the goal line. I believe that as Secretary of State, he would do the right things for the state’s voting technology. Actually I’m sure Pete Peterson would do a good job too, but I want to reward Padilla for good behavior even if he never deals with earthquake stuff again.

BTW check the Announcements/Q&A page about a walk I’ll be leading on November 8.


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