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27 January 2011
Do the math
A video, “The Dreaded Stairs,” has been getting some circulation lately on Facebook. It shows what happens when a staircase (beside an escalator) gets a makeover which features piano-style keys which make sounds when they are trod upon. Watch the video if you would like; I’m going to focus on the accompanying blurb, which reads: There is a set of stairs, with a moving escalator next to it …. both …
16 November 2010
Extended tomb
This summer, strolling atop the massive travertine terraces of Pamukkale, Turkey, I checked out the necropolis (graveyard) of Hierapolis, an ancient city founded around 200 BCE and abandoned after an earthquake in 1534. One thing that caught my eye there was this tomb, built of travertine blocks.
15 October 2010
Friday fold: wavelength contrast
I scored this photo off the Internet more than five years ago, the first time I taught Structural Geology at George Mason University.
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 …
9 September 2010
Mount Moran
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 and Range” extension, but the great thing about the Tetons is that it is so …
5 March 2010
Is this dike a feeder?
A new paper in the journal Geology examines an interesting question: how can you tell feeder dikes from non-feeder dikes? The answer is, normally you can’t. Normally, there’s no way to tell for sure whether a given dike actually funneled magma to the paleo-surface, or whether it never reached the paleo-surface. The reason for this is that usually, the paleo-surface is gone by the time the dike is exposed at …
18 February 2010
Salamander shear
Whilst discussing how to quantify strain with my GMU structural geology students recently, I hit upon a cool analogy. In order for you to understand the analogy (assuming you’re not a structural geologist), I’ll have to review some background information first. Stick with it, and I promise you a salamander at the end. Structural geologists are interested in how rocks deform. If we have some idea of the original shape …
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.