One other thing that I noticed during my visit last weekend to the Virginia Museum of Natural History in Martinsville, Virginia, was this fold. As soon as I saw it, I squealed “Oooh! That’s going to be the Friday fold!” It says something about the crowd I was traveling with that everyone (a) knew what … Read more
Whilst searching the coastline of the U.K. for Where On Google Earth? #226, I found these lovely folds exposed in wave-cut platforms on the east coast of Scotland. I missed the actual location of the Google Earth screenshot (It was in Wales, and Anne Jefferson found it), but I’m happy enough to have found some sweet folds exposed in map view.
The Friday fold this week is the sinuous shape of the Belcher Islands, Canada.
Lately, this blog has been focusing a lot on a subduction zone complex in Turkey, the Tavşanlı Zone. Much of the geologic appeal of that complex is its profusion of high-pressure, low-temperature metamorphic rocks, those in the blueschist metamorphic facies. From the last location visited on the Tavşanlı Zone field trip, I collected this fine … Read more
A week ago today, I went out on the Billy Goat Trail (near Potomac, Maryland) with a group of students: five from George Mason University’s GeoClub, and two that are current Physical Geology Honors students with me at Northern Virginia Community College. One of my students, Robin, observed this lovely fold, and called my attention … Read more
Highly contorted laminations in a blueschist-grade marble, Sivrihisar massif, Turkey.
Today’s Friday fold comes to us courtesy of Gary Fleming, botanist extraordinaire and brother of Tony Fleming, geological Jack of All Trades. Together, the Fleming brothers led a field trip for the Geological Society of Washington. While I was on that field trip, the topic of polyphase deformation came up, which led a couple of … Read more
I scored this photo off the Internet more than five years ago, the first time I taught Structural Geology at George Mason University.
Check out this video I found online whilst uploading last week’s Friday fold: This video was produced and published on YouTube by Markus Beckers, Michael Ketterman, Dennis Laux and Janos Urai. It’s a nice demonstration of how multiple layers of material of different properties and different thicknesses can yield up different flavors of folds. In … Read more
As with last week, I’m going to show you someone else’s fold today. This one should have strong resonance with most geologists, because it’s a fold in the tilted (and contorted) older strata exposed below the famous unconformity at Siccar Point, Scotland: I found this image on the British Geological Survey’s online repository of images, … Read more
Folded & boudinaged granite dikes in tonalitic gneiss, Barberton granite-greenstone belt, South Africa. From Passchier, CW, Myers, JS, and Kroner, A., (1990). FIELD GEOLOGY OF HIGH GRADE GNEISS TERRANES. Very crudely annotated: This is a sweet example of how you can get different structures developing in different orientations relative to the principal stress directions. In … Read more
Fourth edition of the “Friday fold;” second one via video. Happy Friday!
This fold is located on Highway 287, north of Wolf Creek, Montana. Annotated version: As with last week’s Friday Fold, this fold owes its existence to (a) deposition of sandstone and shale in the Western Interior Seaway, and (b) deformation under a giant thrust sheet during the thin-skinned compressional tectonics of the Sevier Orogeny. In … Read more
Happy Friday, everyone!
Photo by Lily Edmon.