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.

I’ve begun a newsletter to announce events, like walks and talks; sign up here. Eventually I’ll retool this page.

30 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. 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]

  3. 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

  4. 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.]

  5. 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.

  6. 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.

    [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 — Andrew]

  7. 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.]

  8. 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

    [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.]

  9. 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.

  10. 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.

  11. Andrew Says:

    On Sunday, June 28, I will be leading a geology walk for Wild Oakland in the Montclair hills. This is a ticketed event for vigorous walkers with an attendance limit. Details here.

  12. Andrew Says:

    I will be delivering a talk at the next Nerd Nite East Bay meeting, on 28 December, tentatively titled “Diversity in Deepest Oakland: Rocks of the Town.” I will make the case that, square mile for square mile, Oakland is the most lithologically diverse city in America. If I can squeeze it in, I hope to ponder several different nerdy thoughts about rocks in general.

    Nerd Nite East Bay ( happens the last Monday of the month at Club 21, a short stroll from the 19th Street BART station. Bring your laser pointer.

  13. Ian Says:

    Hi there,

    Thank you for your wonderful blog and for all the free lessons!
    I have a question about a rock formation I saw yesterday in Redwood Regional Park. Along the creek trail there is a heavily eroded embankment that undercuts several large trees, and exposes the bare rock below. The rocks have a really interesting structure, with lots of round, layered structures. I have browsed back through lots of your posts, but have yet to see anything similar. Could you perhaps comment on this rock, or point me to a post which features a similar formation?

    I uploaded some photos here:

    Thank you!

    [Hello Ian, thanks for reading! What you saw is called spheroidal weathering. I posted about it here once back in 2009. See more about it in my old gallery of chemical weathering.]

  14. Andrew Says:

    I am delivering a talk at the Oakland Museum of California the night of Friday March 18, in connection with the “Unearthed: Found + Made” exhibit, where I will “discuss the paradox of considering stones simultaneously as artworks and as geological specimens.” The strange intersection of natural objects and the categories into which we persist in arranging them has tickled my mind for many years, and I’m looking forward to this improvisational presentation in words and exhibits (including some of my own pet rocks). Details here.

  15. Andrew Says:

    Time to announce two upcoming events in July.

    On Monday 4 July I’ll be accompanying the walk up Sausal Creek, from Dimond Park to the Chabot Observatory. Starts at 8:30 in the morning. Free. Details at

    On Sunday 17 July I will lead a walk for the Oakland Heritage Alliance focusing on the building stones of downtown Oakland. Starts at 1:30 in the parking lot next to the I. Magnin building, across 20th Street from the BART station. Not free. Details at

  16. Andrew Says:

    The newest issue of Bay Nature has a little feature I wrote about the sand grains of Point Reyes. And it’s online too.

    I should note that before a last-minute edit, my piece pinpointed the source of the sand as Kehoe Beach.

  17. Johanna Wheeler Says:

    many years ago we fond on our property in Vermont quartz Crystals.
    the largest is 40lb, 20lb, 5lb and some smaller. my question is
    what can I do with them (other than using them as door stops)
    do they have any marketable use? would you please point me to someone who could help me out.
    thank you very much,

    [Johanna, I have always believed that the best use for objects like these is in a classroom or nature center, where young people can fall in love with them. The second-best use is to place them where the public can enjoy them. Without seeing your crystals, all I can suggest is to find your nearest rock shop and show the owners your best specimen.

    Mineral specimens in museums and rock shops come from small mines all over the world. The odds are that your crystals aren’t valuable, just interesting. — Andrew]

  18. matthew fishman Says:

    Hi, been enjoying this site a lot, it has proved to be very useful in an ongoing project of mine: to incorporate native and local materials in pottery making. Some of the rocks around here make wonderful glazes. However, it is hard to know the proper formulations with regards to durability and food safety without analyses of the materials. I’ve googled without much success; happen to know if any group has that sort of information on record? And I hope my philosophy of utilizing the geology doesn’t conflict with yours of admiring it!

  19. Andrew Says:

    I will be speaking at the upcoming East Bay Nerd Nite, Monday the 27th; watch its Facebook page or website for details. The topic is, “Are Rocks People?”

  20. Andrew Says:

    On November 18, I’ll be leading a walk in Berkeley for the Berkeley Path Wanderers starting and ending in Codornices Park. Details at

  21. Andrew Says:

    The Berkeley Path Wanderers have posted my writeup of the walk I led around north Berkeley on November 18. It’s detailed enough for you to lead yourself around the route and pretend I’m talking to you about it. See it here:

  22. Andrew Says:

    Alexis Madrigal, a writer for The Atlantic, felt the recent magnitude 4.4 earthquake at his home and sought me out last week to talk about earthquake geology and other topics. The resulting article, “When an Earthquake Hits Next Door,” came out yesterday at

  23. dlreader Says:

    I wanted to thank you for your post over on ThoughtCo about Epeirogeny. That is, literally, the only info on the whole web (including a number of Physical Geology books) that has any kind of a discussion of subsidence and what causes it. Zillions of posts on mountain building, and subduction zones, but it was like a conspiracy of silence as to the fact that whole sections of the the main continental plate has experienced dramatic uplift and subsidence. Back in the 1850s to the 1920s the geologists talked about this all the time, but since then… nothing.

    I wish you’d gone into more detail than you did, like on “passive cooling of hot lithosphere” since that is still definitely a mystery to me…but as an overview it was brilliant. It finally gave me a feeling for what was going on, from the point of view of modern geologists, and some additional words to search on!

    [Thank you. — Andrew]

  24. Andrew Says:

    I will be leading a walk for the Oakland Heritage Alliance the afternoon of Sunday 15 July. It will wander over the San Antonio segment of lobe 4 of the Fan between Central Reservoir and San Antonio Park. Details and tickets here.

  25. Stan Roe Says:

    Hello Andrew—I’m a retired geologist looking at the Knoxville formation north of Mt. Diablo. I’m searching for its contact with the Franciscan formation and recently went to the west shore of Lake Chabot to observe the contact you’ve described. Please let me know when you intend to lead a walk in the Lake Chabot area as I have some questions about the exposures.

    Thank you!

    [Hello Stan, thanks for visiting my site (and Oakland).

    I’ve made posts about the Knoxville exposures along Lake Chabot for three exposures: (1) just east of the dam, (2) on the north side of the reservoir, and (3) east of Fairmont Ridge. I only mentioned the contact — actually, the proximity of the contact — in post 3, so I assume that’s what you’re referring to. But I haven’t actually seen the contact anywhere. Of those three sites, the Knoxville is mapped in contact with the Franciscan only at locality 2, and the contact is mapped as a thrust fault.

    Feel free to write me directly (my address is on the About page). — Andrew]

  26. Andrew Alden Says:

    Been a while since I made an Announcement: I’ll be giving a talk to the Friends of Sausal Creek, on 18 September at the Dimond Library, titled “Sausal Creek: The Last Million Years or So.” FB RSVP | event calendar

  27. Andrew Alden Says:

    I’ll be giving a talk to the Rotary Nature Center Friends this Friday, 10 September at 7 p.m., titled “Lake Merritt: A Geologist’s Take.”

    [And the recording of the talk is now up at .]

  28. Robin A. Dubner Says:

    I just discovered you today and I’m thrilled. I love rocks and I’m in Oakland.

  29. Chris Says:

    Hi, Andrew. Are you still doing any walks? I just found your website. So cool. Just finished reading “Hella Oakland” and have been thinking a lot about our town. Can’t wait to read your book.

  30. Christopher den Breejen Says:

    Enjoy your website very much.
    Took the hike to Crusher Quarry you mentioned. Some great rocks at the “end” of the trail there. Gets really steep, but you can actually get through up to Mc Donnel fire trail if you risk it, and there are some monster Leona Volcanic boulders up there.

    Next time you are in Leona Heights, I have seen a couple residences there worth a peek at their yards. One with great “eye candy” in their front garden. On Belfast little past Bermuda. Nice size red Leona Volcanics rocks in the yard there.

    As well as a great mixed huge rock display on Leona street between Mountain and Griffen.

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