About

I’m Andrew Alden. As a writer, I cover the Earth sciences for the whole planet and its neighbors. But my city of Oakland is full of interest too, and since I tramp around it a lot I reserved this spot to think locally. I’m also “aboutgeology” on Twitter. And in 2011 I started a regular gig at KQED Quest Science blogs, writing about geology of the greater Bay area. You can write to me at geology at andrew-alden dotcom, and mind the hyphen.

For site news and discussions, please use the Announcements/Q&A page.

18 Responses to “About”

  1. len raphael Says:

    where would i find info on typical temescal oakland water levels over the last 50 years?

    am considering drilling a low flow well for gardening purposes.

    -len raphael

  2. Andrew Says:

    Len, I don’t have a quick answer beyond talking to local well drillers. The city doesn’t have any records that are easy to locate.

  3. Andrew Says:

    I’ve acquired a Twitter account; the name is aboutgeology.

  4. Andrew Says:

    I’ve moved the Oakland Geologic Map onto this site for everyone’s handy reference. Enjoy it, explore it, and don’t republish it.

  5. Gregory B Says:

    Thanks greatly for the map! Nice site for browsing – you have a great eye for detail. But of course, I’m in a section not shown on the map key [KJf; Lincoln Heights, home of the Mormon Temple]. I guess this means Cretaceous-Jurassic, Franciscan assemblage but not of the “melange”. Under our thin topsoil is an orange sedimentary layer, hard digging and crap for gardening but too soft to be called rock. What is this, and how worried should I be about the fault under the house across the street?

  6. Andrew Says:

    Yeah, I missed a few items when I made the key. KJf is “undivided Franciscan,” too mixed up to map in fine detail. Your subsoil might be a patch of alluvium, but it may also be fault gouge, the finely ground rock that occupies many fault zones.

    You should be worried about your house’s earthquake resistance, of course. I can’t say anything more specific, (1) not knowing your location, (2) not having inspected the area and (3) not being a licensed geologist of any kind. I hope you are consulting the USGS’s resources like this and this.

  7. len raphael Says:

    where would i look to find approx depths of various layers in temescal at a particular address. eg. how far south and west does the type of rock found at the old quarry at the Safeway continue.

  8. Andrew Says:

    Len, you would have to look at well logs in your area as well as the geologic map. I’m responding to your email too.

  9. len raphael Says:

    From my discussions with County well person, there have been no licensed wells dug below Broadway in North Oakland other than shallow test wells for pollution measurements. Not sure when licensing started.

    There were some deep wells at the cemetery which might have overdrawn and run dry. Not sure what the golf course does for water.

    There are no local well drillers. They’re all from the valley or north. The one i spoke with has drilled in the Oakland hills and Alameda, but never in the flats.

    Oakland History Room librarian staff were very helpful:

    > Groundwater study and water supply history of the East Bay Plain,
    > Alameda and Contra Costa counties, CA / for the Friends of the San
    > Francisco Estuary ; by S. Figuers and online at:
    > http://www.swrcb.ca.gov/rwqcb2/groundwaterstudy.shtml
    > Steven Lavoie, Librarian II
    > Oakland History Room”

  10. David Bolaños Says:

    Oakland relief map shows what appears to be either a mudslide or volcanic flow along Fruitvale. Feature especially pronounced below MacArthur. Which is it?
    I find your blog fascinating, and sorry I missed your March 17 talk at Dimond library. When will you be making another public appearance?

  11. Andrew Says:

    Perhaps you’re noticing the McKillop slump.

    I don’t know when my next public appearance will be, aside from this blog. . .

  12. Andrew Says:

    I’ve been frantically busy and now I’m out of town, so I’m late acknowledging the East Bay Express, which named Oakland Geology in its 2010 Best of the East Bay list as Best Blog About East Bay Rocks. That earns me a coveted ticket to the Best of the East Bay Party, and what better way to party than with a bag of rocks? Actually I’ll probably leave them at home.

  13. Michael Layefsky Says:

    Andrew,

    Kudos on the Best of the East Bay nod.

    I first came across Oakland Geology while researching Leona Quarry after taking some kite aerial photos of it.

    I have also taken aerial photos of other subjects that you’ve covered in the blog, such as View Middle Harbor Shoreline Park.

    I’m always looking for new subjects to take aerial photos of. If you can think of other geologic subjects that would look great from above, please shoot me an email: michael [at] greatheights [dot] net.

  14. Andrew Says:

    I should mention that I’ve started a new page, “Announcements/Q & A,” for open-ended discussions.

  15. Bob Graham Says:

    Re. Mount Diablo Views
    Post by Andrew Alden on Jun 02, 2011

    Hi Andrew.
    I’m the Bob Graham you quote: “Bob Graham and Peter Lathrop argue convincingly that it was not Diablo, but the whole Coast Range that Carson meant. That’s too bad; it was a good story.” http://longcamp.com/little_mountain.html
    I just yesterday found the article :-)

    Here a found place of mine that is archaeological–a prehistoric salt manufactory on the S. Fk. of the American River–but also geological.

    How does brine seep (tastes like NaCl) out through fractured granite for thousands of years? http://longcamp.com/salt.html

    Earlier this month I led a group of archaeologists from the Eldorado National Forest, and Sonoma State University, to the site.

    Bob Graham, Sacramento

  16. Andrew Says:

    Bob is referring to an old post of mine over on KQED Quest Science blogs.

    Thanks for the note about the Indian saltworks. There is at least one other one that is much, much larger than the one you describe, with hundreds of evaporation pits. You ask about the source of the salt. It’s probably not from the granite per se, but the older rocks that are draped over the granite. Most of these were laid down in the ocean and retained brines (connate water) from their original formation.

  17. Bob Graham Says:

    Thanks, Andrew,
    Yes; I am aware of the Cosumnes site.
    No one knows how that large site was worked, but the one I found has channels worked into the granite leading from the seeps to the excavated basins.
    It is still working! Earlier this month course salt grains were precipitating from the brine along edges and bottom of the basins.
    Bob

  18. Andrew Says:

    OK, I’m freezing comments on this page now.

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