basalt

Spheroidal weathering in Columbia River basalt

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I’m in Idaho for the Rocky Mountain section meeting of the Geological Society of America. Yesterday, I was delighted to tour around in eastern Washington’s Channeled Scablands with my colleague Bill Richards (North Idaho College). I took a lot of photos, but here are two to start – lovely examples of “onion skin” style weathering … Read more

Paleoproterozoic dikes in Archean granite, Laramie Range, Wyoming

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At Morton Pass, where highway 34 crosses the crest of the Laramie Range, you can see a nice set of (younger) mafic dikes cutting (older) granite/gneiss basement complex. The pink stuff is Archean; the black stuff is Paleoproterozoic; around 2 billion years old. Click to enlarge I got to check out this outcrop on Tuesday … Read more

Native copper from the Catoctin Formation

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Another new insight from last week’s visit to the Outdoor Lab was that they have several fine examples of native copper found in float of the Catoctin Formation on their property. Here are a few examples: Classic examples – a bit of malachite in there too, it looks like. I wasn’t totally shocked when I … Read more

Four new GigaPans from an intriguing contact

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Callan and his colleague Jay Kaufman (University of Maryland) go to extraordinary lengths to document an intriguing block of rock in northern Virginia’s Blue Ridge province. Great images and a lot of fun result – but what do these rocks tell us?

Fossil Falls fun

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A few shots from Fossil Falls, in the southern Owens Valley, California… This is the now-dry river bed of the Owens River. There’s abundant evidence of water-induced erosion (potholes, polishing, etc.), but nary a drop of water to be seen – Though this particular portion of the Owens River drainage dried up in the Pleistocene, … Read more

Dikes crossing dikes

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A pretty cool outcrop I saw on my pre-GSA structural geology field trip to the Superior Craton: Can you see what caught my eye here? It’s a nice series of cross-cutting relationships. A series of sedimentary rocks were sheared out and metamorphosed, transforming into schists with internal boudins, and then they were cross-cut by first … Read more

Those could be pillows

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More pillow-like structures, seen in the Catoctin Formation, on the west side of the Blue Ridge Parkway about ten miles south of Interstate 64. Mini Sharpie for scale – what do you think? They don’t seem to be as strongly fracture-controlled as the Stony Man area “pillows.” But dang, they sure are small… Read the … Read more

Vesicle-rich layering in Catoctin Formation

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I saw this boulder lining a garden this past weekend down in Nellysford, Virginia, in the scenic valley of the Rockfish River draining the eastern slope of the Blue Ridge. It’s a piece of the Neoproterozoic-aged Catoctin Formation, a series of lava flows and associated rocks that erupted on the breakup of the early supercontinent … Read more

Compton Peak: superb columnar jointing

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After my talk Wednesday night to the Potomac Appalachian Trail Club, I got an email from PATC member Tom Johnson, with an extraordinary photo attached. It shows an exceptional outcrop of the Neoproterozoic Catoctin Formation, exposed atop Compton Peak in northern Shenandoah National Park, Virginia. The outcrop features enormous, well-preserved cooling columns from these ancient … Read more

Block Mountain basalt flow

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This year, for the first time ever, I took students to map at Block Mountain, a classic field camp mapping site near Dillon, Montana. Here’s a quick look (enlarge it by a gazillion-fold by clicking through) of some columnar jointing in the Eocene Block Mountain basalt flow, a paleo-drainage turned mountain through the miracle of … Read more

GoSF4: Kirby Cove

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Part 4 of the ongoing series examining the geology of the San Francisco area. In today’s post, Callan visits Kirby Cove in the Marin Headlands, where intensely deformed chert can be found on one end of the cove, pillow basalts on the other, and an “artificial dune” in the middle.