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28 October 2010
Accretionary Wedge #28: Deskcrops
In honor of this month’s Accretionary Wedge (geoblog carnival; this month the theme is “deskcrops”), I recorded the following short video, showcasing some samples I have in my office: stromatolite (western Montana), conglomerate (Patagonia), schist (New Hampshire), anorthosite (New York), amygdular meta-basalt (Virginia), amphibolite (California), hematite concretions (eastern Montana), and a stretched-pebble lineated meta-conglomerate (Turkey).
16 October 2010
Where on Google Earth? #215
With a helpful Twitter hint from Ron Schott, I won my second “Where on (Google) Earth?” challenge, the 214th edition of this popular geoblogospheric competition. As a result, I get to host the next one, Where on Google Earth? #215. The aim of the game is to figure out where on Earth this satellite imagery comes from, and then post the coordinates (lat/long, UTM, whatever) and give a brief explanation …
8 October 2010
Friday fold: multilayer buckle folding demo
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 the movie, there are two materials present: white silicone and gray foam. The silicone layers …
30 September 2010
Words’ worth IV
Back on the first incarnation of this blog, I occasionally posted about words that bugged me. A few more have piled up since then, so here we go with the latest consideration of “words’ worth”… First off, let’s consider the use of “outcrops” as a verb. This came up recently on this blog when commenter Tom Skaug pointed out that I was incorrectly using that term. He’s right of course, …
Words' worth IV
Back on the first incarnation of this blog, I occasionally posted about words that bugged me. A few more have piled up since then, so here we go with the latest consideration of “words’ worth”… First off, let’s consider the use of “outcrops” as a verb. This came up recently on this blog when commenter Tom Skaug pointed out that I was incorrectly using that term. He’s right of course, …
27 September 2010
Deducing my first anticline
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 was led by the legendary Gerald Johnson (a.k.a. “Dr J”), a dynamic and enthusiastic educator …
24 September 2010
Friday fold: Siccar Point, Scotland
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, which are available for public use with attribution. I found out about the BGS photo …
21 September 2010
EARTH: the biography, by the BBC
Last week, I watched the BBC/National Geographic series “EARTH: The Biography,” hosted by Iain Stewart. Stewart is a charismatic host, with a thick Scottish accent that cannot disguise his enthusiasm for geology. The five episodes focus on: volcanoes, ice, oceans, atmosphere, and “rare planet.” Overall, I thought the series did an good job covering some of the greatest stories in geology with an emphasis on presenting the latest ideas. Snowball …
20 September 2010
Champlain thrust fault
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 morning to show us a superb example of a thrust fault on the shore of …
17 September 2010
Friday fold: granite dikes, Barberton greenstone belt
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 this particular part of the Barberton Greenstone Belt, compression (orange arrows) operated from the top …
Callan Bentley is Associate Professor of Geology at Piedmont Virginia Community College in Charlottesville, Virginia. He is a Fellow of the Geological Society of America. For his work on this blog, the National Association of Geoscience Teachers recognized him with the James Shea Award. He has also won the Outstanding Faculty Award from the State Council on Higher Education in Virginia, and the Biggs Award for Excellence in Geoscience Teaching from the Geoscience Education Division of the Geological Society of America. In previous years, Callan served as a contributing editor at EARTH magazine, President of the Geological Society of Washington and President the Geo2YC division of NAGT.