structure

Deducing my first anticline

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When I was done with my sophomore year at William & Mary, I embarked on a time-honored tradition among W&M geology majors: the Geology 310 Colorado Plateau field course. Jess alluded to this same course in her Magma Cum Laude contribution to this month’s Accretionary Wedge geology blog “carnival,” too. My version of Geology 310 … Read more

Friday fold: Siccar Point, Scotland

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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

Building stones of the Haghia Sophia

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The Haghia Sophia (or “Ayasophia”) is an astounding building in old town Istanbul. It is an ancient cathedral turned mosque turned museum. Through all these incarnations, the Hagia Sophia has retained some features and had other ones added on: it is a palimpsest of architecture, symbology, and history. Walking through its soaring main chamber, or … Read more

Champlain thrust fault

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Over the summer, I went up to Vermont to visit my friends the Clearys. Joe Cleary is a college friend and a talented luthier. He and his wife Tree and their children Jasper and Juniper have settled in Burlington, a lively town with a lot of cool stuff going on. Joe took time out one … Read more

Friday fold: granite dikes, Barberton greenstone belt

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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

Fine faulting

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Check it out: In the canyon of the Jefferson River, Montana, you can find yourself some limestone (Mississippian Madison Group, I think of the Lodgepole Formation) that has seen a wee bit of faulting: And here’s an annotated copy… Both of these images are enlargeable by clicking through (twice): Note the quarter for scale: this … Read more

Mount Moran

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The other day, Chris Rowan of Highly Allochthonous posted some pictures (and video!) of the Teton Range in Wyoming, a normal fault-bounded block of rock that has rotated along a north-south axis, with the west side dropping down and the east side rising up relative to the floor of Jackson Hole. This is classic “Basin … Read more

Lessons from a broken bottle

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Whilst hiking at Dolly Sods over the weekend, I found this old artifact: Upper 10 is apparently a “Sprite”-esque lemon-lime soda, discontinued in America but still being marketed abroad. But that wasn’t what got me jazzed, of course. Look more closely… That is a lovely little conchoidal fracture, and it’s so exquisite because it preserves … Read more