Announcements/Q & A

A general thread for questions and topics unrelated to any particular post. I delete and condense old comments every now and then.

23 Responses to “Announcements/Q & A”

  1. Lesley Says:

    Hi Andrew. I’ve enjoyed your blog for a while. Now I’m looking for a home to buy and find myself wondering if YOU would buy (or even rent) in Sheffield Village? It’s one of the areas our budget has led us to, but it scares me. And then I wonder if living ON the fault is so much worse than living, say, across the freeway from the fault.

    [Lesley, I’m not a practicing geologist and it would be illegal for me to advise you. I can only tell you that I live less than 2 kilometers from the fault, love where I am, and am not a homeowner. I can also tell you that I adore Sheffield Village. Every homesite has its own unique geologic setting, even within a single development.

    When the big one hits Oakland, we will all be in the same place.]

  2. Andrew Says:

    The City of Fremont will show you around its segment of the Hayward fault in 90-minute walks on three Saturdays this summer. The first walk is next week. See more here.

    While I’m at it, I will be leading a two-hour walk for the Oakland Heritage Alliance on August 18 around the landscape (and rock specimens) of Middle Harbor Park. And on September 8 I’ll lead a walk around the Hayward fault and other attractions of Montclair for Oakland Urban Paths. Mark your calendars now.

  3. Asa Dotzler Says:

    A friend of mine suggested you’d be the guy to talk to about identifying this If you’ve got a minute and you could help out, I’m sure that Pete (Oakland native plant guy) would appreciate it and I’d love to learn the answer.

    [The concentric brown bands inside massive sandstone are common in coastal California. I understand that they mark the passage of petroleum from source beds below on their way toward the surface or an underground trap. They are spectacularly exposed along the Santa Cruz beach cliffs among other places. –Andrew]

  4. Andrew Says:

    Next week—Saturday the 18th—I’ll be leading a walk for the Oakland Heritage Alliance down at Middle Harbor Park, 10 am to noon. The topic is the wonderful recycled landscape there, regarded as both an artistic and geotechnical achievement.

    More details at

  5. Michael Greene Says:

    Hi Andrew,

    There may be a Cretaceous/Tertiary contact exposure near the San Leandro Reservoir. Do you know anything about it?

    -Michael Greene

    [Michael, the contact is mapped as a thrust fault, with the Cretaceous rocks pushed over the younger ones. Moreover, the Cretaceous rocks are of Campanian age while the Tertiary rocks are Miocene, so there’s an age gap of about 50 million years there.

    The nearest true K-T (Maastrichtian–Danian) contact I know of is down in the Panoche Hills.]

  6. Andrew Says:

    On Saturday 31 August I will be leading a walk along the Hayward fault at the foot of Claremont Canyon for the Claremont Canyon Conservancy. There’s no announcement on the website. We start at 10 a.m. at the top of Dwight Way, at Fernwald Road, and will finish before noon.

  7. Neal Parish (@NAParish) Says:

    Andrew — Do you know anything about Sheridan Road in upper Rockridge (see and ) ? The road appears to have slid away at some point, but the right of way still exists. I’m suggesting that the trail over the ROW be included in an Oakland Urban Paths walk at some point, and it would be nice to say something about the slide.

    — Neal

  8. Andrew Says:

    It’s an obvious landslide scar, and the slide later threatened the freeway, which is why there’s been all that repair work going on along the old railroad grade. I don’t know how old the slide is, though. The street maps show a continuous street in 1967, which is suggestive if not definitive.

    See video of the slide and the work being done to mitigate it: part 1 part 2

  9. Neal Parish (@NAParish) Says:

    Thanks Andrew — although the slide repair now underway is a bit away from the area where the road itself is missing. A few months ago, I walked along the old Sac Northern ROW between Florence and the Broadway Terrace onramp right through the construction project (the fence on the south side had been knocked down) — but wasn’t able to make it all the way to Broadway Terrace because we belatedly discovered there was a security guard in a car parked at the north end.

    On a completely unrelated note — where is this house: ?

    [It’s in easternmost Oakmore. Quite visible in Google Maps.]

  10. Debby Goldsberry Says:

    Hi, I really like your blog!! Trying to learn some amateur geology to make the most of my near daily trips to the East Bay Regional Parks. I was curious about a rock formation in Redwood Regional Park, above the West Ridge Trail, between the Skyline Gate and Waterloo Staging area. It is a big formation on the upside of the trail. Do you know anything about it? Also, I found a cool looking rock, and wondered if it was a fossil. Not sure how to post the photo here. Thanks!! Any info is appreciated!

    [Hard to say, Debby. I haven’t been on that trail, but it goes through Redwood Formation sandstone and a younger unit of sandstone/mudstone. As for a photo, if you’ve posted it anywhere on the web, you can link to it here using the “img” tool.]

  11. Neal Parish (@NAParish) Says:

    Andrew — With respect to the slide repairs near Sheridan Road, check out the Caltrans project description at the bottom of page 5 here:

    One more comment; I recently spoke to the owners of a bunch of lots along the missing section of Sheridan, and they said there was no slide in this location — the road was apparently never built because of the slope. They reviewed City records and hired engineers and others to investigate the site before drawing that conclusion.

    [Neal, thanks for this research. It’s still odd that street maps used to show a street existing there. Next step is reviewing aerial photos, I guess.]

  12. Maureen Kennedy Says:

    Hi, Andrew: I’m Maureen Kennedy, a realtor-broker in Piedmont. Also the daughter-in-law of David Alt (of Roadside Geology fame). I just came across your blog while googling Wildwood Creek–I sold the home at the top at 3 WW Gardens, and now am listing the house at the bottom at 89 Oakmont. I think I checked all options, but don’t see a walk down that creek bed? Thanks, Maureen

  13. Andrew Says:

    Maureen, pleased to hear from someone of your distinguished family! I haven’t ventured much into Piedmont, but that looks like quite a dramatic little gulch. However, there is no public right of way along the creek so I won’t be walking there — or if I do I won’t be talking about it here.

  14. Andrew Says:

    I was astonished to learn, on June 30, that decided to terminate my contract after 17 years of building the site. At the same time, my wife and I had decided to move to a new place in Oakland, and that came down faster than we’d anticipated. So this month has been an unusual one, and until today I’ve done almost nothing fun. But the good part is that I have more time to work on this site.

  15. Lesley Says:

    I’m sorry to hear that, Andrew. Unless you are excited about the change! Still loving your blog. Also I had forgotten about my question at the the top of this page. We ended up buying in Estudillo Estates, so here’s hoping those earthen dams hold up!

  16. brianrhill Says:

    Sorry to hear about You are a relentlessly upbeat and resourceful person. I hope/believe you’ll move on successfully. Maybe guided tours and multimedia applications showcasing your knowledge like Joel Pomerantz has built some business around in San Francisco? Anyway, I’m glad I have found your site and am looking forward to following your posts.

  17. Andrew Says:

    Thanks, Lesley and Brian. I’m stunned more than excited, so I’m trying to do my thinking in the subconscious until some time in August.

  18. Mike Rudmin Says:

    Suggestion: Google “Mish” Mike Shedlock. He spun out his own blog — in his case, a financial blog — and ran his own advertisers. You might consider doing the same. Right now, you have a following, mostly highly local to the west coast. Get your advertisers from there, especially restaurants around the area [people on geotreks get hungry] and bed-and-breakfasts… and I expect you’ll do quite well.

  19. Andrew Says:

    I will be leading a walk along part of the Hayward fault in easternmost Oakland on Saturday November 8, for the Wild Oakland organization. More here.

  20. David Frischer Says:

    Hi Andrew, my name is David Frischer and I am a middle school science teacher in Oakland. I teach at a charter called Lighthouse Community. We are finishing up work that was centered on geology in the East Bay. I stumbled on this site a little late but am curious if you would be willing to speak by email about geology in Oakland and teaching it to 7th and 8th graders. We have done a lot of fieldwork but I would love to try and find some way to bring someone in who has insight and knowledge of Oakland’s geology. Thanks.

  21. RJ Says:

    Hi Andrew,

    I recently encountered your post on about the Mohs hardness of different pennies and have a few comments you might find interesting. I tried a few coins myself on an iceland spar calcite sample and realized the following:

    1. We have to be careful to distinguish between the coin itself and the oxidation of its surface, which may sometimes be harder, or may be scratched off by the calcite (so we think we’re scratching the coin, but really we’re just making a mark into the thin oxide layer). Maybe we should dunk our coins in a cleaning solvent before using them for Mohs tests.

    2. The U.S. mint has “Fun Facts” posted about the composition of coins through time. This page is for the penny:

    The geologically-relevant summary is that before 1837, the penny was pure copper; from 1837-1982 it was variations on copper with some amounts of zinc and/or tin; since 1982, it has been zinc with a copper coating. The very important exception is 1943 pennies which are zinc-coated steel and therefore on their interior, probably much much harder.


  22. Andrew Says:

    Thanks for that!

  23. Andrew Says:

    I’ve just put up a new page with information about making donations to support my work on this site.

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