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 … Read more
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. … Read more
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 … Read more
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 … Read more
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.
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 … Read more
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.
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 … Read more
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 … Read more
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. … Read more
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.
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.
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!
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 … Read more
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 … Read more
The western edge of O’Shaughnessy Boulevard, near Glen Canyon Park in San Francisco shows beautiful examples of crumpled cherts. Here are a few dozen photos of these glorious outcrops, and instructions on how to visit.
The Friday fold is a guest contribution to “Mountain Beltway” from the manager of the AGU Blogosphere, Larry O’Hanlon. It shows apparent crumpling of a few sedimentary layers at the toe of a soft sediment slump at Calafia State Beach in southern California.
It’s Friday, and I’m grateful that Bret Leslie of the NRC has stepped up with a Friday fold contribution from coastal California: Bret says this outcrop is: from my trip last month to the Sonoma and Mendocino coast. The first is the cliff below the Pt. Arena lighthouse. The marine deposits (now a marine terrace) … Read more
When a dike is subjected to shear, how does it deform? A guest Friday fold from Darrel Cowan of the University of Washington teaches a nice little lesson. Join the field trip in Monarch Canyon of Death Valley National Park…
The Friday fold can be found in a boulder of gray chert layers on Black Sands Beach, at Marin Headlands in California.