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 use the “Deeper Oakland” newsletter to announce events, like walks and talks; sign up here.
-
Subscribe
Subscribed
Already have a WordPress.com account? Log in now.
Oakland Geology 
25 May 2012 at 8:38 pm
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.
Thanks!
Lesley
[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.]
5 August 2012 at 5:27 pm
A friend of mine suggested you’d be the guy to talk to about identifying this http://www.flickr.com/photos/eastbaywilds/7284738780/in/photostream 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]
28 December 2012 at 9:21 am
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.]
12 January 2014 at 1:36 pm
Andrew — Do you know anything about Sheridan Road in upper Rockridge (see http://goo.gl/maps/2vYPJ and http://goo.gl/maps/rY2m7 ) ? 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]
3 February 2014 at 7:25 am
Andrew — With respect to the slide repairs near Sheridan Road, check out the Caltrans project description at the bottom of page 5 here: http://www.dot.ca.gov/hq/transprog/ctcbooks/2012/1012/00_Vote.pdf
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.]
14 July 2014 at 3:48 pm
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!
About the creek, there is no public right of way there; it’s all private. Only the local kids would know for sure.]
19 July 2014 at 9:58 pm
I was astonished to learn, on June 30, that About.com decided to terminate my contract after 17 years of building the geology.about.com 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.
2 December 2015 at 10:00 am
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 (eastbay.nerdnite.com) happens the last Monday of the month at Club 21, a short stroll from the 19th Street BART station. Bring your laser pointer.
19 January 2016 at 11:23 am
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: http://imgur.com/a/JV1wt
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 About.com gallery of chemical weathering.]
17 July 2016 at 9:50 pm
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.
22 July 2016 at 2:58 pm
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
[Johanna, without seeing your crystals, all I can suggest is to find your nearest rock shop and show the owners your best specimen. It’s possible that a landscaping designer might be interested in them, given their size. But I’ve 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, or anywhere the public can enjoy them.
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]
11 December 2017 at 2:47 pm
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: https://www.berkeleypaths.org/s/Andrew-Alden-Fault-Line-Walk-2017-me87.pdf
17 January 2018 at 10:25 am
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 https://www.theatlantic.com/technology/archive/2018/01/the-earthquake-next-door/550532/
1 April 2018 at 6:49 pm
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!
https://www.thoughtco.com/what-is-epeirogeny-1440831
[Thank you. — Andrew]
25 September 2018 at 7:44 am
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]
17 July 2022 at 3:47 pm
I just discovered you today and I’m thrilled. I love rocks and I’m in Oakland.
23 July 2022 at 4:25 pm
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.
[Thanks. Walks are announced exclusively in the “Deeper Oakland” newsletter. — Andrew]
20 February 2023 at 10:31 pm
Hi,
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 McDonell fire trail if you risk it, and there are some monster Leona Volcanic boulders up there.
[Yes, I’ve done that too, but I don’t recommend it for the average reader. — Andrew.]
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.
8 June 2023 at 8:16 pm
Today’s KQED Forum interview was great! I’m going to get your book !!
2 July 2023 at 11:32 am
Hi Andrew – Thank you for this blog, and for your wonderful book (which I am currently reading). I have a question: I understand that the Bekeley Rock Parks expose examples of Northbrae Rhyolite, an extrusive felsic ingious rock. My questions is about Remillard Park. As you likely know, the exposure at that park is quite different than the others in that, rather than being white/grey, solid in texture with a feeling of flow, the Remillard rock is yellow/orange, more porous, though still very hard, with more diverse in textur, and with no evidence of flow that I recall. Do you know anything and/or is there anything written about the difference between the rock at Remillard and that exposed at the other parks?