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13 October 2011
Superior Craton trip, stop 1
The first stop on our pre-GSA field trip to the subprovince boundaries of the Superior Craton was a place just north of Virginia, Minnesota, where the Mesabi Iron Ranges are mined (same Proterozoic banded iron formations that were portrayed as the backdrop of the mining activity depicted in the film North Country). The pull-off is locally known (to geologists) as “Confusion Hill,” but marked on the roadside sign as the …
28 September 2011
Roadside wonders of Route 287
Northern Colorado’s route 287 connects Fort Collins, Colorado with Laramie, Wyoming. Along its length, it displays roadcuts into Archean-aged basement complex. Two of these outcrops are featured in this post: one metamorphic (mostly), and a second igneous (mostly), with some intriguing polka-dotted plutons.
29 October 2010
Geology of the Richmond area field trip
On Saturday, after a fruitful 24 hours at the VCCS Science Peer Conference, my colleague Pete Berquist (of Thomas Nelson Community College) and I led a field trip to examine the geology of the Richmond, Virginia, area. We were joined by seven of our VCCS science-teaching colleagues and author Lisa Starr, a speaker at the conference. We started off by driving down to Belle Isle, an island located on the …
13 October 2010
Photos from Virginia Geological Field Conference
For the second year in a row, more exotic travel plans meant that I wasn’t able to attend the superb Virginia Geological Field Conference. I see that they have now posted some photos on the group’s Facebook page, so go check them out to see what we both missed last weekend. Here’s a taste: Sheared meta-conglomerate: Metamorphosed mantle (?) xenoliths:
11 October 2010
Two xenoliths
On my last day in Ankara Turkey (last Friday), I took the afternoon off from the Tectonic Crossroads conference in order to pay the requisite visit to the Museum of Anatolian Civilizations. I say “requisite” because Ankara’s not quite so thrilling a town as Istanbul, but this is the one location that everyone agrees is worth a visit. The previous day at breakfast in our hotel, University of Georgia geology …
22 June 2010
At the edge of the intrusion
Mountain Beltway reader Greg Willis attended my colleague Ken Rasmussen’s Triassic Rift Valley field course last weekend, and sent me this photo of the view inside the Luck Stone diabase quarry in Centreville, Virginia: Here’s an annotated version: Both photos are enlargeable by clicking on them (twice). This quarry chews into rock right along the contact between a mafic igneous intrusion and lake sediments that formed when water pooled in …
21 May 2010
Falls of the James III: river work
In today’s post, I’ll finish up with my geologic discussion of the falls of the James River in Richmond Virginia, south of Belle Isle. Previously, we’ve examined the bedrock at this location (the Petersburg Granite) and a series of fractures – some faults and some extensional joints – that deform that granite. Now we come to the final chapter in this story — the story of the river carving up …
18 May 2010
Falls of the James I: pluton emplacement
Last Friday, NOVA colleague Victor Zabielski and I traveled down to Richmond, Virginia, to meet up with Chuck Bailey of the College of William & Mary, and do a little field work on the rocks exposed by the James River. Our destination was Belle Isle, a whaleback-shaped island where granite has been quarried for dimension stone for many years. The island has also served as a Confederate prison for captured …
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 …
17 February 2010
Dalmatian pluton
Continuing with some photos from eastern California… After checking out the faulted moraine, but before heading up the hill to check out the indurated shear zone (which you can just see in the background of this photo), we stopped to check out this visually-striking outcrop: Look at the glee on the faces of Kurt (green shirt) and Marcos (running; he’s so excited!). We were all pretty jazzed by this polka-dotted …
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.