Callan Bentley Friday it was geese. Today, it’s a Clark’s nutcracker: The Clark’s nutcracker is a beefy alpine corvid (perching birds related to crows) of the American west. It’s a great bird in my mind, because if you’re looking at one, it means you’re up in the high country. It means you’re out where the good stuff … Read more
Another guest Friday fold – this one supplied by Ander Sundell of the College of Western Idaho, and his student Katie Ursenbach, who took the shot and gave permission for me to re-post it here. You’re looking at cuspate-lobate folds due to primary sedimentary settling. the Snake River Canyon in southwestern Idaho. A pile of … Read more
A couple of visitors above the entrance to my building on campus today: They’re honking greetings to all the students showing up for 8am exams…
Today, for your viewing pleasure, I offer you: A series of big honkin’ gas pockets in a 615 ka basaltic lava flow in the Owens Valley of California. This same lava flow has been featured here before, since it imparted a lovely contact metamorphism to the alluvial fan over which it erupted. These things are … Read more
To recap the week so far here on Mountain Beltway: On Monday we looked at some sweet vertical boudinage along the plane of tectonic cleavage (not to mention those folds in a (formerly) horizontal granite dike, now bearing vertical axial planes), and then on Tuesday we looked at a horizontal cut through that same outcrop, … Read more
Have you ever seen Archean pillow basalts? How about Archean pillow basalts that have grown much taller through vertical extrusion along a ductile shear zone? Come to the southern Superior Craton to see more!
Callan shares images of extraordinary boudinage outcrops in strained Archean meta-basalts on the Quetico-Wabigoon subprovince boundary within the southern Superior Craton. Ogle these gorgeous structures in awe and wonder.
This week, I took 20 minutes out of my day to have a conversation with a group of students… …in Canada. As you can see, our conversation was not in person, but mediated by the Internet’s video conferencing technology service called Skype. A free Skype account and a video camera allows free, easy video conversations … Read more
The Friday fold is a contribution from the Massachusetts Geological Survey. It shows a migmatite with lovely structure. An upcoming (free) field trip to this location will be part of the 2012 Structural Geology and Tectonics Forum: an event readers may be interested in attending
Another shot from my pre-GSA structural geology field trip to the Superior Craton last fall, up in southern Ontario, Canada. The image shows slickenlines coated with brownish fault gouge and oxide staining, cutting through a high-potassium granite (see fresh surface at upper left). The slickenlines are little gouged grooves where asperities (bumps) on the block … Read more
I took my structural geology students to that fine outcrop of the Swift Run Formation in eastern Shenandoah National Park on Friday. There, we saw lovely primary structures with tectonic fabric overprinting (as I have showcased here previously). Consider this graded bed with subsequent (vertical) cleavage: And here’s the hinge of a nice passive fold, … Read more
Last Saturday, before the rains moved in…
Once again, we roll around to another Earth Day. I find myself in a more-contemplative-than-normal mood this year, and I’d like to take this opportunity to share a bit about what I’ve been thinking. This is a post about the personal side of geoscience – taking data, and its logical implications, and smashing it into … Read more
I got this note via email last week. Hi Callan, First of all, congratulations to your blog. It is just great. I would like to contribute to your “Friday fold” section. A few words about myself. I am born in Austria and did my BSc and MSc at the Montanuniversitaet Leoben. In September 2011 I started … Read more
Lily and I went out to look at houses last weekend, and I couldn’t help but take some photos of cool rocks I saw along the route. See if you can identify / name / interpret all four: And here’s a bonus: Can anyone tell me what kind of bird built this diminutive nest?
I collected this sample the weekend before last on the Blue Ridge Thrust Fault field trip led by Alan Pitts. It’s a chunk of the Antietam Formation quartz sandstone, a Cambrian beach deposit. The face we photographed measures 15 cm by 12 cm. link It definitely looks best in full screen mode, so please feel … Read more
Last Thursday, my colleague Jim Buecheler and I took two students (Robin Rohrback and Alan Pitts) down to Charlottesville, Virginia, for a meeting at the state geological survey. The Department of Geology and Mineral Resources sponsors an annual one-day symposium on Virginia geology that I’ve participated in two or three times before. Last year I … Read more
I did things a little differently in my latest field class, the Regional Field Geology of Eastern California. Instead of having a post-trip project (like I’ve traditionally done with my Montana/Wyoming Regional Field Geology course), I had the students complete a take-home test. I’ve just finished grading those tests, and was pleased to see the … Read more
Rob Simmon of NASA’s Earth Observatory is the source for today’s Friday folds. Last week, he tweeted this image to me: That’s a excellent example of the outcrop pattern of a more or less horizontal outcrop of folded rock. To the north is a synform (notice that where streams have eroded it, the bull’s-eye pattern … Read more