I’m Andrew Alden. As a writer, I’ve covered 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. As of 2018 I post every other Monday.

I care a lot about my photos. Clicking on them will show them at their best. Starting around 2021 I’ve been posting images at 1000 or 1200 pixels. I’m slowly upgrading the images in older posts, most of which are 450 or 600 pixels.

You can write to me at geology at andrew-alden dot com, and mind the hyphen. You can make a PayPal donation to support my work here — info on this page.

Site news and random discussions can be found on the Announcements/Q&A page.

For 17 years I wrote about everything in geology for About.com, until they cut my contract. Now they’re ThoughtCo.com. I joined Twitter as “aboutgeology” in February 2009. From 2011 to mid-2016 I wrote regularly for KQED, first in Quest Science blogs, writing about geology of the greater Bay area, then as a KQED Science Contributor.

My book, tentative title Deep Oakland: Geology of a City, is coming out in 2023; see updates here.

8 Responses to “About”

  1. 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?

  2. 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.

  3. 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.

  4. Michael Layefsky Says:


    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.

  5. 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

  6. 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.

  7. 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.

  8. Andrew Says:

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

Comments are closed.