Archive for the ‘other’ Category

Local global science

16 December 2014

cider2014

I don’t spend all my time out among Oakland’s rocks. I also take advantage of the Bay area’s opportunities to learn about Earth science. Every year, for instance, I attend the Fall Meeting of the American Geophysical Union, held without fail in San Francisco since 1968. I started in the mid-1980s, and it’s where I’m spending this week. Last year I also started attending the annual sessions of the Cooperative Institute for Dynamic Earth Research, or CIDER, held at Berkeley on the UC campus. It’s a geology geek’s gathering that marked its tenth anniversary last Sunday. UC professor and seismologist Barbara Romanowicz, on the left, is the prime mover; unfortunately I didn’t catch the names of the other two people. CIDER uses an NSF grant to bring together senior researchers and “junior” scientists—grad students and postdocs—who pick a few meaty deep-earth topics and set up a summer workshop to attack them. Last year’s puzzles involved the chemistry of the Earth’s mantle and the nature of the core. This coming year it will be the relation of the solid Earth to climate change, a conversation long overdue among specialists.

Anyway, that meeting was last Sunday and they let me be a fly on the wall. It’s one more thing that makes Oakland the navel of the world.

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.

Claremont-in-Sunol

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.

calaverascobble

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.

calaverascut

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.

calaveraspectens

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.

calaverasdigger

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


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