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18 September 2020
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 …
27 March 2020
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.
20 March 2020
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 …
13 March 2020
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 …
14 February 2020
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 …
7 February 2020
The Friday fold shows disharmonic crumpling in marbles of the Boyden Cave Root Pendant in California’s Sierra Nevada. The GigaPan image displayed is part of the digital legacy of Ron Schott, who passed away a year and a half ago.
13 December 2019
A pre-Fall Meeting field trip to the coast of northern California yields rare sights of garnet-bearing blueschist, plus eclogite, some pillow basalts, birds, waves, wind, and a lot of rain.
10 December 2019
This week marks the launch of a new digital revision of a field guide to the geology of San Francisco, “Streetcar 2 Subduction.” Learn more here!
22 November 2019
Because I’m putting together a field course for spring break 2020 to Death Valley California, I was looking through old Death Valley photos this week, from the last time I went to that special place. It was seven years ago! How time flies… This one is in Mosaic Canyon, and was taken by my student Marcelo Arispe, a talented photographer as well as a talented geologist: By the standards of …
4 October 2019
Hey, let’s go back to Angel Island for today’s Friday fold. We’ve been there once, twice, thrice previously. The rocks in question are metaconglomerates that Jess Ball and I found at first only as float on the beach at Camp Reynolds, like these two examples: …Look at those beautiful elongated pebbles, transected by wee white veins! Where there’s float, there may be outcrop — Sure enough, with a minute or …