Callan Bentley 
Another fold seen in the Catoctin Formation, where last week we encountered a very different style of folding — chevrons overprinting Catoctin foliation. Here, we instead have a light colored vein that appears to have been buckled into a semi-ptygmatic form. The trace of the foliation in the Catoctin is discernible, too. Enjoy your Friday!
Okay, a final post (for now, anyhow) sharing some images from last Friday’s field trip to the Billy Goat Trail, in Potomac, Maryland. Yesterday we looked at lamprophyre dikes, but there are other dikes on the Billy Goat Trail, too. Like this granite pegmatite: What’s interesting to me about this is that the joint set … Read more
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!
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 … Read more
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 … Read more
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 … Read more
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 … Read more
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.
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.
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 … Read more
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 … Read more
And now, for the final half of my final day in Capadoccia, Turkey… We continued hiking along up the scenic valley that I mentioned a few days ago, checking out the lovely scene in the lovely weather… The valley floor was reasonably wet and vegetated, but the higher slopes were eroding at a rate too … Read more
A year and a half ago, on my way back to Modesto from Yosemite, I pulled over at the side of the road and found a piece of urbanite full of whoppers. But that curiosity wasn’t what caught my eye and made me pull over in the first place. Instead, what I noticed was this: … Read more
Originally posted in September 2010 as part of this missive on the Champlain Thrust Fault. Happy Valentine’s Day!
I’ve got two more batches of Capadoccia photos for you. Sorry if you feel bored with this continuing series — but I think it was not only my favorite part of Turkey (and geomorphologically interesting) but photogenic too… So on our final day in Capadoccia, Lily and I took a hike up another valley. We … Read more
The Friday fold takes us to some high-grade metamorphic rocks in the Piedmont of northern Virginia.
Mystery mineral from Mount Washington, New Hampshire: radiating needles of something black… I’d venture “tourmaline”… but you tell me.
Here’s an amazing sight that caught me unawares in Capadoccia — some paving stones outside a small “museum” (preserved Byzantine hoodoo church) that were chock full of some AMAZING trace fossils. Sense of scale is provided by a Turkish 1-lira coin, about the same size as a U.S. quarter. Check out the variety, size, and … Read more
I just got an e-mail which screams “scam!” Apologies for having to reach out to you like this, but I made a quick trip to the UK and had my bag stolen from me with my passport and credit cards in it. The embassy has cooperated by issuing a temporary passport, I just have to … Read more