31 August 2017
I love the “Geology Underfoot” series published by Mountain Press – the same folks who have published dozens of titles under the “Roadside Geology” theme. “Underfoot” is better than “Roadside,” I think, because it tells the story of discrete places, suggesting ideal places to visit. Each chapter is self-contained and useful without extraneous details, and avoids the redundancy of many roads crossing through near-identical geology. The latest title in the series, by Shawn Willsey, is Geology Underfoot in Southern Idaho. I read it last week, thanks to Mountain Press sending me a review copy.
It’s good: good enough that in spite of not being in southern Idaho, I read it with interest from cover to cover. Willsey does a great job covering the essentials of geology with a minimum of jargon and a high level of enthusiasm. I enjoyed reading about places I’ve been (Redfish Lake, Craters of the Moon), places I’ve been meaning to go to (Hagerman Fossil Beds National Monument), and places I’ve never heard of (Black Magic Canyon). Southern Idaho has a lot to offer the geological traveler, from opal to meterorite impacts to dunes to landslides to fossils to caves to plenty of lava. This is a useful book to show you how to find the best of the best, and put the landscape and outcrops into regional contrast. Recommended!
25 August 2017
Okay, I’ll admit this is a bit of a stretch, but here’s your Friday fold:
The mosaic-covered floor of this long hallway in the Villa Romana di Casale in central Sicily shows profound warping. The middle shadowed area sags downward by at least a meter, maybe more. It’s not a geological material that’s been deformed, but an architectural element instead. Still: the principle of original horizontality applies to floors as well as to sedimentary strata. It’s a fold, of sorts.
This Roman villa was covered by a mudslide, which preserved its many mosaics for future tourists to wonder at. Since I’ve brought you here, we may as well check out some of the mosaic imagery in the place:
Happy Friday! If you ever make it to Sicily, this place is worth seeking out – pretty mind blowing!
18 August 2017
When in Rome, do Friday folds as the Romans do?
Here are some images from my brief, sweltering visit to the Roman Forum(s) this past summer. The whole region is a jumblepile of ancient ruins in a thousand styles. Almost nothing is labeled. It looks like this:
This particular building held up a bit better, and its lovely columns sported some folded marbles:
Close-up shots to show the folding internal to these blocks of carved stone:
These ruins are ancient, but the folds? Even more so!
Folds are where you find them, I guess. Happy Friday!
11 August 2017
This Friday, I’m resurrecting some photos I stumbled across in my digital archive from a field trip I took a decade ago. These images show Eagle Rock, a big, messed up outcrop in Botetourt County (Bot-uh-tot), Virginia (the Valley & Ridge province). The strata exposed here are late Ordovician to early Devonian, and mainly Silurian in their bulk. The James River exposed them when it cut a water gap through the ridge (now Crawford and Rathole Mountains on either side of the gap), and that was enhanced by road construction. The strata are both folded and faulted in a delightfully complicated way. Check it out:
…Zooming in for some close-up details:
There are some additional images of the sedimentology of the site at this blog post by Alton Dooley when he was at the Virginia Museum of Natural History. I should get back down there one of these days with my GigaPan rig and make a proper image of these structures…
9 August 2017
Today, for your edification and amusement, I offer five new 3D models that I’ve assembled over the past few weeks from photo sets collected in the field and then fed into Agisoft Photoscan. Enjoy zooming in and out, spinning and turning them.
Orbicular granite from the Sandia Mountains of New Mexico:
Fault-bend fold in Grinnell Formation quartzite and argillite, Glacier National Park, Montana:
Glaciated bedding-plane outcrop of Mesoproterozoic stromatolites, Helena Formation, Glacier National Park, Montana:
Vesicular ventifact, Blackwaterfoot, Arran, Scotland:
Bedding and foliation in Dalradian metaturbidites, Lochranza, Arran, Scotland:
4 August 2017
While attending the Earth Educators’ Rendezvous in Albuquerque a few weeks ago, I noted these specimens on display in the halls of the Department of Earth and Planetary Sciences at the University of New Mexico:
A trio of big “pocket folds” – the perfect way to close out the workweek.
31 July 2017
After reading Passing Strange, I found myself wanting to learn more not only about Clarence King, but also about the other great surveys of the American West – those of Hayden, Powell, and Wheeler. I’ve read Powell’s account of descending the Colorado River, and I’ve been delighted this decade past to explore Hayden’s territory in the northern Rockies (but didn’t know the details of his work). Of Wheeler, I knew next to nothing. So I was glad to find there was a volume dedicated to the history of all four surveys – Richard Bartlett’s Great Surveys of the American West, published in 1962. The book is a useful compilation of each survey, its personnel, personality, adventures, and output. However, it suffers from a serious case of mid-last-century perspective. The author’s perspective is both sexist and racist. For example: early in the book, he likens exploring the west to undressing a beautiful woman. Native Americans were the original inhabitants of this “unexplored” land, and Bartlett paints them with a broad brush, sneering that they were “bloodthirsty” or “dirty, sullen, not to be trusted.” He has a similar attitude towards predatory animals – delighting in the killing of grizzly bears and describes a coyote as “a scraggly, sneaking little yellowish cur with its tail between its legs, a symbol of perpetual guilt.” Not exactly ecologically enlightened! These flaws, casually inserted in many places throughout the narrative, make for distasteful reading. It may be unrealistic of me to expect a book by a white man in the early 1960s to share the relatively egalitarian attitudes of 2017, but despite that, I found myself wincing repeatedly as I read and learned. So: caveat emptor. Coming away from reading it, I feel as though the insight i gained was tainted with a distasteful set of attitudes. This history tastes spoiled.
28 July 2017
Here’s a fun fold – I saw this hiking Siyeh Pass in Glacier National Park earlier this week:
(note the four people for scale in the upper photo – 3/4 of the way up the grassy slope.)
Here’s a closer view, with me for scale:
Happy Friday! I’m leaving Glacier today and beginning the journey home. Happy Trails!
21 July 2017
My friend Ander Sundell at the College of Western Idaho is the source of today’s Friday fold. It’s from somewhere in Sardinia, and I think you’ll find it visually striking:
The rocks here are Silurian phyllites generated from mudstones that were deposited on the floor of the rheic ocean basin. The color and grain size variation do an excellent job highlighting compositional layering. They were deformed during the Variscan Orogen, which the last phase of a composite mountain belt that ultimately formed Pangea. This photo shows an excellent example of axial planar cleavage.
Guest submissions of Friday folds are always welcome. Thanks for contributing, Ander!
18 July 2017
I’ve just finished three weeks of travel in Italy, and I was absolutely delighted to read this terrific book by Walter Alvarez while I was there. Alvarez is famous the world over for being the nucleus of the team that proposed an extraterrestrial meteorite impact as the cause of the end-Cretaceous extinction, prompted to that bold hypothesis by the discovery that the clay seam marking the boundary between the Mesozoic and Cenozoic portions of the Scaglia Rossa limestone near Gubbio (the “K/T boundary”) contained anomalously high levels of iridium. But Alvarez didn’t set out to drive a stake into the heart of uniformitarian doctrine. In his career, he hasn’t focused on mass extinctions or meteorite impacts. Instead, in The Mountains of St. Francis, he tells the story of the less celebrated aspects of his career, working on the geology of Rome, then moving afield to the Apennine Range, the mountainous “backbone” of Italy. It was in attempting to match up the foraminiferid fossil record of the Scaglia Rossa with the record of paleomagnetic reversals (The “Rossa” in Scaglia Rossa means “red,” referring to the color that results from a decent amount of magnetic iron in these strata), an important exercise in bolstering the stratigraphic toolkit, that Alvarez stumbled onto the K/T boundary iridium anomaly. Along the way, over decades of Italian fieldwork with his wife Milly and a host of colleagues, he explores basic geological concepts for the lay reader, ideas very familiar to readers of blogs like this one, but in a new, thoughtful, patient, and creative way (and therefore worth reading for that reason alone). In so doing, he makes The Mountains of St. Francis into a calm, insightful introductory text to geology: with concepts discussed ranging from superposition to to turbidites to thrust faulting to delamination to the Messinian Salinity Crisis. Foundational research in many disparate branches of geology happened in this mountain range, and Alvarez is an appreciative, contemplative guide to exploring it. The title of the book comes from St. Francis of Assisi, whom Alvarez examines in the first chapter, including the first mention of the Scaglia Rossa in describing the lovely pink limestones used to construct the Basilica of St. Francis in Assisi, where the saint is buried.
So the book is simultaneously a memoir of a career’s worth of research, a travel guide to Italy, an layperson’s introduction to geological thinking, and a primer on the geologic history of central Italy. It’s unique in trying to serve all these purposes simultaneously, but I think it works. It was exactly the sort of book I wanted for the sort of trip I was taking.
During my Italian travels, I visited both the K/T boundary at Gubbio and the Basilica of St. Francis in Assisi. My experiences at both places were enriched as a result of having read Alvarez’s book. If you are traveling to central Italy and you are a geologist, this is the book to read. It’s highly recommended in that case. If you have no plans to ever go to the Apennines, I’m not sure it will read quite as smoothly, as there’s lots of local flavor that may seem alien until you come to Italy yourself. With that caveat, I highly recommend it.
The K/T boundary at Gubbio:
The pink Basilica of St. Francis in Assisi:
The Scaglia Rossa exposed in Assisi’s building stones, with my Lonely Planet for scale: