You are browsing the archive for 2011 February.
28 February 2011
Callan assesses the quality of the information design displayed in a graphic accompanying a recent article in Science. See if you agree with his critique! Being conscious of our graphic design is important for good science to be unencumbered by gimmicks, propaganda, and layout that obscures meaning.
Lamprophyre dikes on the Billy Goat Trail (Potomac, Maryland): are they offset because of a fault? Or not? Inquiring minds want to know!
27 February 2011
I took my structural geology students out the Billy Goat Trail (upstream half of the “A” loop, near Potomac, Maryland) last Friday, and had them gather data for a project to assess whether or not Mather Gorge is controlled by a fault. I got this idea from Aaron Martin, the structural geologist at the University of Maryland, and I think it’s a nice project for structure students early on in …
26 February 2011
I first mentioned the Waterfall Formation on this blog in May of 2008, but this was my first time visiting it in situ. Previously, including the May 2008 visit, was memorable time with charismatic boulders of float. The occasion to see this geologic unit in outcrop was the field trip 6 days ago with the George Mason University GeoClub, when we took a hike to Thoroughfare Gap. After looking at …
25 February 2011
Last Sunday morning, two of my former GMU students, Aaron and Alan, led a hike for the GMU Geo-Club to Thoroughfare Gap, a water gap in the Bull Run Mountains of Virginia’s eastern Blue Ridge province. I’ve mentioned the Weverton Formation structures we saw there, and a nice example of a hackle fringe in previous posts. We hiked west down the railroad tracks, and crossed the contact from the Weverton …
24 February 2011
Another serendipitous sighting on last weekend’s field trip to Thoroughfare Gap was this boulder of Weverton Formation, lying in the no-man’s-land between the railroad tracks and Broad Run: As you look at this boulder, I hope you will notice what caught my eye and prompted me to take the photo. There’s a big flat surface (white) at left, but at right, in the gray portion of the rock, you can …
22 February 2011
Callan joins some students from George Mason University on a field trip to the rock exposures at Thoroughfare Gap, Virginia, where meta-sedimentary rocks are exposed in the eastern Blue Ridge province.
21 February 2011
Callan begins a new series on the geology of Mount Washington, New Hampshire with a look at a roadside outcrop of metamorphic rock bearing enigmatic inclusions. Tourmaline-bearing pegmatites are also spotted.
18 February 2011
Here’s your Friday fold, straight from the canyon of the Jefferson River, near Cardwell, Montana. Perspective is to the south. East is on the left; west is on the right. Bigger version This is right next to the outcrops of LaHood Conglomerate that I mentioned earlier this week. My Rockies course co-instructor Pete Berquist and I bring the students here for several reasons, including the conglomerate, nearby Lewis & Clark …
16 February 2011
Remember the LaHood Conglomerate? Here’s a few field photos of my Rockies class visiting it last July: Amphibolite clast: Marble clast: I love how well-rounded these clasts can be — like eggs. When these grains were loose cobbles, tumbling down into the Belt Sea, the Earth was only 3 to 3.5 billion years old. The rivers which carried them downhill flowed past a landscape devoid of plants and animals. Since …