Disconformity in northern Colorado
Have a look at this lovely (almost glowing) example of a disconformity between Coloradan limestone and overlying sandstone.
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Absaroka volcanic breccia
A lovely example of a volcanic breccia (from the Eocene Absaroka Volcanics of southern Montana) is showcased, in two different photographs.
Friday fold: a lovely three-dimensional exposure
The Friday fold series returns to Kootenay National Park in Canada for a look at some folded Cambrian limestones.
Stone tools of the Piney Branch quarry, DC
Archaeology meets geology in this visit to the Piney Branch valley of Rock Creek Park in Washington, D.C. Cretaceous deposits of cobbles of Cambrian quartzite were quarried by Native Americans and modified into tools thanks to the fact that they break with a conchoidal fracture.
Friday fold: flying over the Fort Valley with Michael Collier
Renowned geological aerial photographer Michael Collier gives Callan a lift over the Fort Valley and Massanutten Mountain in his two-seater Cessna.
A coiled nautiloid, namesake of a vintage
Callan and his family visit a Virginia winery that features tasty libations and chunky nautiloid fossils, both products of the same local geology…
Graptolites!
Following a tip from a colleague, Callan finds a rich trove of fossil graptolites in Ordovician shales exposed at Mint Spring, Virginia.
Friday folds: Simple shear and the unfolding of folds
The Friday fold combines a moment of insight on a field trip in the Archean Superior Province and a new paper published this month in the journal GEOLOGY.
Four new GigaPans from an intriguing contact
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?
Squashed pillows
Join Callan for a look at submarine volcanism and later deformation near Ely, Minnesota. Archean tectonics fluffed these pillows up and squashed them down again.
Primary structures in the Lake Vermilion Formation
Callan showcases some extraordinary depositional structures (graded bedding and flame structures) seen in Archean turbidites in the Superior province of northern Minnesota.
Friday fold: “V”
The Friday fold photo was taken this morning on a GigaPanning expedition, and shows a small syncline within turbidite strata of the Martinsburg Formation, Page Valley, Virginia.
Friday fold: Fault propagation fold from Cristo Rey
The Friday fold comes from the Texas – New Mexico – Chihuahua triple point, on the flanks of Cristo Rey mountain.
Friday fold: An odd duck
A USGS colleague shows Callan a bizarre fold outcrop in the Conococheague limestone of the Boyce quadrangle, Virginia.
Unconformity seen in the field yesterday
Callan and two colleagues find a “textbook” unconformity on a field trip in Virginia’s westernmost Blue Ridge.
Friday fold: Martin’s metamorphics
A guest “Friday fold” from South Africa: folded gneisses, flavored with other treats of a geological nature.
Crazy veins
Callan & his students visit an outcrop on the Icefields Parkway in Alberta, showing a variety of white veins cutting dark rock.
Scouting out the geology of Doukénie Winery
On Saturday, Lily and I went out for a date. It was only the second time since Baxter was born that we were able to get away for quality time, just the two of us. We headed up to Doukénie Winery near Hillsboro, Virginia. Here it is on a topographic map: Here’s what it looks … Read more
Passage Creek in flood
After a night of torrential rain, Callan wakes to find his sole (vehicular) route to the outside world under several feet of flood water.
Sand avalanche animated GIF
Some of the dynamics of small-scale mass wasting in granular materials are captured in this animated GIF from sand dunes in Death Valley.