Reader John Christian shared these folds with me via email last week. They are quartz veins in slightly metamorphosed Precambrian igneous rocks found near Sunflower, AZ in the Mazatzal Mountains. The second photo is a close-up shot of the curviest, cleanest batch of folds from the first shot. These are beautiful examples of folds in … Read more
Today, we take a look at the structural geology that reveals the deformation evolution (first ductile, then brittle) of the South Mountains metamorphic core complex, south of Phoenix, Arizona. Expect lots of photos of smeared-out rocks, broken by faults.
Watch the flow of frictional melt in a “fossil earthquake,” frozen in time atop the South Mountains metamorphic core complex in Phoenix, Arizona.
A reader asks: “What is foliation and what makes it so important to the structure of rock?”
Callan answers with a lot of images of beautifully foliated rocks.
This is a block of rock I found in the rock garden at Northern Arizona University a few weeks ago: It’s intensely folded. Not sure what kind of rock it is, but it was quite dense.
In keeping with the Arizonarific theme of this week’s posts (thanks to my participation in the 2018 Structural Geology and Tectonics Forum), I thought I would wrap up my ‘geology of the Phoenix area‘ posts with a walk I took on my last day there. This was to what Google Maps calls “Hayden Butte,” but … Read more
A visit to Papago Park, north of Tempe, Arizona, reveals hanging wall rocks from the South Mountain detachment fault, a long way from South Mountain. Also, feast your eyes on these gorgeous red sedimentary breccias, interpreted to be landslide deposits from the Neogene.
A virtual field trip to the Phoenix Mountains and South Mountains of Arizona, along with participants in the 2018 Structural Geology and Tectonics Forum.
Deep in the Grand Canyon of Arizona, Steve Mirsky found a Friday fold to share with you.
I was in Tucson this past weekend for a book project meeting, and my editor and coauthor and I took a hike on Sunday morning in the Tucson Mountains to Wasson Peak. Not far from the summit, we saw an epidotized tuff, where the fiamme and pumice blobs had undergone reactions to produce pods of … Read more
Reader Mike Pendergrass contributes this Friday’s fold: I found your blog a couple years ago and I share your love of structural geology. I did my Master’s Thesis while at Northern Arizona University in the early 80’s and mapped an area on the Mazatzal Mountains of central Arizona. The Mazatzals in my field area contain … Read more
Happy Friday! Here’s a beautiful folded obsidian sample, replete with conchoidal fractures, on display outside the geology department at Arizona State University in Tempe, where I was last week:
A week ago today, I was in Tempe, Arizona, at Arizona State University, for a workshop on broadening participation (increasing diversity) in the geosciences. One of the neat things about ASU as a setting for this meeting is their enormous meteorite collection. I was particularly taken with the display of material from the extraordinary Chelyabinsk … Read more
A new video book review! Under discussion today are two new books from Mountain Press: Geology Underfoot Along Colorado’s Front Range by Lon Abbott and Terri Cook, and Arizona Rocks! by T. Scott Bryan. Enjoy! [youtube=”http://www.youtube.com/watch?v=n82EJwZ6c_o”]
Lee Allison, State Geologist of Arizona and exemplar of public outreach via blogging, sent me an e-mail yesterday regarding that awesome coastal Greenland shot by Alistair Knock that I featured as the Friday fold. Lee, like many of you, found the image entrancing and intriguing, and as he explored the unannotated version, he made some … Read more
This series of cartoon images ended up on the board yesterday in Historical Geology lab… E = erosion D = deposition Yes, oversimplified: I didn’t include the newest thinking about the subtleties involved in putting together the Brahma and Vishnu Schists and Zoroaster Granite, and I didn’t include mention of faulting (either ancient or more … Read more