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21 May 2023

Earthquake Storms, by John Dvorak

I’ve come to the end of my run of reading John Dvorak’s geology books. This is the fourth one for me to consume, but it was apparently the first he wrote. The topic is earthquakes, specifically those that occur along the San Andreas Fault in California. I’ve read a fair bit, it feels like, about the San Andreas: Carl-Henry Geschwind’s history, Susan Hough’s books, and just yesterday I started Andrew …

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26 March 2023

Bird update March 2023

Click to enlarge I’m still birding voraciously. I’m up to 89 species in my county for the year. So that means I added a dozen since last month. A few of those are freshly-arrived migrants from southerly climes, and some are just me putting in the time to go rack up waterfowl at nearby lakes. I’ve maintained my high county ranking, which has oscillated between #4 and #2 this month. …

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17 March 2023

Friday fold: Pinto Gneiss, varnished and un-

Last week, I was lucky enough to visit Pushawalla Canyon in the Indio Hills region of southern California. There, my colleague Kim Blisniuk (San Jose State University) led our students through an exercise mapping alluvial deposits as a way of constraining offsets along the Mission Canyon strand of the San Andreas Fault. I noted that much of the alluvium was sourced to the northeast, to the Little San Bernardino Mountains. …

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10 March 2023

Friday fold: Painted Canyon

Greetings from southern California! I’m running a spring break field course in the Mojave and Colorado desert. Here’s a pretty amazing fold pair in Palm Springs Formation, butted up against (darker) Mecca Formation along a fault. This is in Painted Canyon, in the Mecca Hills, a transpressional pop-up between the Painted Canyon Fault and the San Andreas Fault. Happy Friday!

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29 May 2022

Accretionary wedge turbidites from the Lost Coast

The Lost Coast of northern California shows geological evidence of deep sea turbidity current sedimentation, tectonic accretion during Mesozoic subduction, and then isostatic uplift interacting with shoreline erosion. Check out a few photographs taken by Callan’s wife on a recent backpacking trip through the region.

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18 September 2020

Friday fan: Death Valley, California

Working up some new images for my free, online Historical Geology textbook, I annotated a photograph I took in March of this alluvial fan in southern Death Valley. The development of desert varnish on older parts of the fan shows their age visually in a quick and easy way of determining fan deposit sequence: I’ve been making a lot of these animated annotations as a way of conserving space in …

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27 March 2020

Friday fauxld: a false syncline in Titus Canyon

What day is it again? Hard to keep track in the days of raging coronavirus infections, but it is in fact Friday, which means that if you want a dose of the halcyon pre-COVID-19 days, you can enjoy this example of a false fold from Death Valley National Park’s Titus Canyon.

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20 March 2020

Friday fold: more folds from lower Titus Canyon

We are living in surreal times. It hardly seems possible, but a week ago this evening, I drove down the Las Vegas strip with my students, ogling at the glitz and spectacle and crowds. Now, a mere 7 days later, Vegas has been shuttered, and it’s been shuttered for days. We traveled freely through California and now a week later, everyone in the state is ordered to stay home. What …

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13 March 2020

Friday fold: Bizarro folding in Titus Canyon

Hi everyone, and greetings from eastern California’s Death Valley, where I’m leading a field geology course over our spring break. I found an excellent Friday fold for you: That’s the Cambrian-aged Bonanza King Formation, a package of limestones, as exposed in lower Titus Canyon, Death Valley National Park. Here’s the thing: the lower part of that outcrop is Upper Bonanza King Formation, while the upper part of the cliff is …

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14 February 2020

Friday fold: Miocene slump in Anza-Borrego

Today’s Friday Fold comes from Edith Carolina Rojas, the dynamic geology professor at The College of The Desert in Palm Desert, California. She’s an awesome person, and also the sense of scale in this amazing image: Edith shares that this gorgeous structure is an anticline is located in Split Mountain Gorge in Fish Creek Canyon. It’s a gigantic gravity-slide fold due to soft sediment deformation in the Latrania Formation. Wow …

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