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19 December 2010
GoSF1: Introduction and overview
The first in a multi-part series on the geology of San Francisco and the surrounding area.
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).
4 April 2010
Easter egg
Searching through my photo archives this morning for something suitably “Eastery”… something in pastel colors, perhaps? … a petrified lagomorph? … how about an egg, or something egg-shaped? This is as close as I got: This is in the Owens Valley of eastern California, showing a boulder of the Mesozoic Sierra Nevada Batholith bearing a faulted xenolith. I love outcrops like this, with a combination of primary structures (like the …
25 March 2010
Transect debrief 5: sedimentation continues
We just looked at the Chilhowee Group, a package of sediments that records the transition for the North American mid-Atlantic from Iapetan rifting through to passive margin sedimentation associated with the Sauk Sea transgression. Well, if we journey a bit further west, we see the sedimentary stack isn’t done telling its story. The saga continues through another two pulses of mountain building. Consider this “unfolded, unfaulted” east-west cross-section cartoon: Part …
4 March 2010
Triassic rifting in the Capitol
My girlfriend’s mom was in town in January, and we took her down to visit the Capitol Building. The tour had a good bit of history, but definitely missed the opportunity to talk geology. I was particularly struck by the columns in the Hall of Statuary: Close up of one column, with my hand for scale: That’s the Leesburg Conglomerate, a Triassic-aged deposit found in the western part of the …
23 February 2010
Plutonic contacts in eastern Sierras
Last September, at the location of the faulted moraine (eastern Sierra Nevada, California), I took some photos of some of the sexier plutonic contacts exposed in big boulders (erratics) of the glacial till composing the moraine. Check them out. What do you see here?
18 February 2010
"Prehistoric": D.C.
Mark your calendars! Prehistoric: D.C. will profile (part of) the ancient past of Washington, D.C., in an episode to air February 28, 9pm, on the Discovery Channel.
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.