The subtitle of this wonderful book is “Watermen, Crabs, and the Chesapeake Bay.” It’s an excellent account of crab ecology in the Chesapeake Bay as it stood in the mid-1970s, and simultaneously a sympathetic portrait of the lives of the locals who capture those crabs for sale to the seafood market. The writing is thoughtful … Read more
It’s Friday, and I have another guest Friday fold to share: This one is from my Denver friend Greg Willis, who tells me it’s from near Arapaho Pass, near where we rain-hiked. Ahhhh, yes – a singularly soggy hike up in the Colorado Rockies. I remember it well, and it looks like Greg had better … Read more
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.
I’ve got a few books to catch up on from my summer reading. The first is Under a Green Sky (2007), by University of Washington geoscientist Peter Ward. I picked this up because it was referenced in another book I’d read recently: Peter Brannen’s The Ends of the World (2017). (I’ve got a review of … Read more
Break out your paddle and sunhat. We’re going kayaking on Lake Moomaw, in search of Friday folds…
In the Landisville Quarry, Lancaster, Pennsylvania, there is a quarry that cuts into Cambrian limestones. (The exact identity of these limestones is apparently a matter of some dispute, but that’s not going to stop us!) I visited the quarry in June on a field trip offered through the NAGT’s Eastern Section annual meeting. We witnessed … Read more
The Friday fold is an outcrop of folded chert from the Franciscan mélange in Mendocino County, California. (It should look familiar to anyone who’s ever visited Marin Headlands near San Francisco.)
This is an interesting book – simultaneously about Enlightenment science, energy flows driving human history, and the boundary-less conception of politics, religion, and science that was embraced by Benjamin Franklin, Thomas Jefferson, and the book’s principal protagonist, Joseph Priestley (and to a lesser, or at least less-well-documented, degree by John Adams). The discussion begins in … Read more
Today we feature a famous recumbent, chevron anticline near Hill City, South Dakota has been featured as a Friday Fold or not, but thought I would give it a go. The rocks are Proterozoic metagreywacke turbidites with 70 complete or partial Bouma sequences. This is believed to be a late (D4) fold in the Black … Read more
Hiking Siyeh Pass in Glacier in Glacier National Park on Tuesday with my Montana State University field course, we spotted a few new folds in the Empire Formation (a transitional unit between Helena Formation and Grinnell Formation). Here is one of the students serving as a sense of scale, with interesting features on either side … Read more
Via Twitter, a Friday fold from Maddy Rushing: #FridayFold, @callanbentley? pic.twitter.com/eaKIuuvFgB — Maddy Rushing (@komaddyite) May 25, 2018 This is in the Alps of Switzerland; I don’t know more about it than that. If you recognize the site or the geology, educate us in the comments!
Religion Explained is an interesting book. It examines the phenomenon of religion in human beings from the perspective of our best understanding (as of 2001) of neurology, psychology, anthropology, and evolution. It takes the modern scientific understanding of how brains evolved, and looks there for the origins of religious thought and its tenacity despite countervailing … Read more
A virtual field trip to the deformed quartzites and metaconglomerates of Chickie’s Rock and Sam Lewis State Park in Lancaster County, Pennsylvania.
Chickie’s Rock is a prominent cliff of Cambrian quartz arenite (sandstone) in Lancaster County, Pennsylvania. I visited it last month with field trippers at the eastern section meeting of the National Association of Geoscience Teachers. One of the aspects of the site is this gentle anticline with axial planar cleavage: The yellow rectangle is my … Read more
Last week, I spent two perfect days camping with family at Usal Beach, in Mendocino County, California. Along the beachside cliffs there, I spotted plenty of lovely turbidites: graywacke and shale and a little bit of conglomerate that had been scraped off the subducted Farrallon Plate to help contribute to the bulk of the Franciscan … Read more
Sonora Pass, California, is a lovely place to examine a volcanic-on-plutonic nonconformity that spans about 80 million years of missing time. Let’s check it out on a photo-rich virtual field trip!
Fifteen years after mapping deformed rocks of the Sierra Crest shear zone system in the high Sierra, a family vacation brings Callan back to the pre-batholith metasedimentary rocks which show a pronounced strain.
Another guest Friday fold (keep ’em coming, folks!) – This time from Eric Pyle of James Madison University: This is a weathered outcrop of the Connemara Marble in western Ireland, about a meter wide. Thanks for sharing, Eric!
My friend Karen Aucker from NAGT’s Eastern Section shared these images (and a video!) of the folds she glimpsed from the cable-car on her way up the Schilthorn in Switzerland. I reckon they will do for our Friday fold: [youtube_agu id=RmxCN8Pte38] Thanks for sharing, Karen! These are great. Happy Friday, all!
Today, in Millersville, Pennsylvania, on the campus on Millersville University, I saw these contorted carbonates. They are of the Cambrian Conestoga Formation, and I saw them on a NAGT Eastern Section field trip led by Lynn Marquez of Millersville University. This deformation is purported to be Taconian, but it looks very much like Alleghanian deformation … Read more