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21 November 2018

Brittle overprinting ductile in the South Mountains metamorphic core complex, Phoenix, Arizona

Today, we take a look at the structural geology that reveals the deformation evolution (first ductile, then brittle) of the South Mountains metamorphic core complex, south of Phoenix, Arizona. Expect lots of photos of smeared-out rocks, broken by faults.

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26 October 2018

Friday folds: Mather Gorge Formation

It’s been a very Billy-Goaty week for me. Three times since Sunday afternoon, I’ve taken people to the Billy Goat Trail’s “A” loop in C&O Canal National Historical Park. On Tuesday and Thursday, it was my NOVA Physical Geology students. On Sunday, though, it was just my son and me. Good news! He helped me discover a new fold by exploring some new rock outcrops and climbing on them. He …

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19 October 2018

Friday fold: the Brooks Range, Alaska

It’s Friday, thank goodness. Today our “Friday fold” feature heads north, way north, to the Brooks Range of Alaska. There we find a trio of mountainsides exposing folds photographed in the 1990s.

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11 October 2018

Q&A, episode 6

A reader asks about Callan’s source of inspiration, a fitting question given the advent of Earth Science Week, which this year has as its theme “The Earth as Inspiration.” Brace yourself for a tantalizing cavalcade of gorgeous images of patterns in rocks!

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28 September 2018

Friday fold: Big Cottonwood Fm., Slate Canyon, Utah

It’s Friday and that means it’s time for a fold. Today we head to Cottonwood Canyon, Utah, with reader Octavia Spencer, for a lovely antiform.

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11 September 2018

Drawing geological structures, by Jörn Kruhl

After blogging about geovisualization, reader James Safranek alerted me to this new book about two of my favorite things: drawing and structural geology! I requested a review copy from the publisher, who kindly provided one. It’s great! This is “a whole book” about drawing and geology and specifically structural geology. As such, it’s not going to be as pertinent to every reader as it was to me. But I found …

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7 September 2018

Friday folds: Continuing contorted Conestoga carbonates

The first Friday of September calls out for a fold. The Burle Business Park in Lancaster, Pennsylvania has an answer – several of them, in fact!

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16 August 2018

A suite of deformational features in Lancaster limestones

In the Landisville Quarry, Lancaster, Pennsylvania, there is a quarry that cuts into Cambrian limestones. (The exact identity of these limestones is apparently a matter of some dispute, but that’s not going to stop us!) I visited the quarry in June on a field trip offered through the NAGT’s Eastern Section annual meeting. We witnessed multiple varieties of deformation there. First off, there was straight-up brittle extension, resulting in bedding-perpendicular …

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15 July 2018

Chickie’s Rock, Pennsylvania

A virtual field trip to the deformed quartzites and metaconglomerates of Chickie’s Rock and Sam Lewis State Park in Lancaster County, Pennsylvania.

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23 June 2018

Deformed conglomerate of Frog Lakes, California

Fifteen years after mapping deformed rocks of the Sierra Crest shear zone system in the high Sierra, a family vacation brings Callan back to the pre-batholith metasedimentary rocks which show a pronounced strain.

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