You are browsing the archive for Friday Fold - Mountain Beltway.

18 April 2014

Friday fold: Sideling Hill

Friday fold: Sideling Hill

Here’s what the Sideling Hill road cut looked like last month: It’s a terrific example of a syncline. Usually I show folds in profile view, but here, the view is essentially perpendicular (not parallel) to the axis of the fold: Sideling Hill’s rocks are early Mississippian in age, made of debris shed off the late Devonian Acadian Orogeny, and they were folded during Alleghanian deformation in the Pennsylvanian-Permian.

Read More >>

1 Comment/Trackback >>


11 April 2014

Friday fold: kink from the Billy Goat Trail

Friday fold: kink from the Billy Goat Trail

My student James O’Brien took this image of a kink band along the Billy Goat Trail, downstream of Great Falls in Maryland’s metamorphic Piedmont province. A lovely little structure, don’t you think? Thanks, James! Happy Friday, all.

Read More >>

No Comments/Trackbacks >>


4 April 2014

Friday fold: ‘Ben Folds One’

Friday fold: ‘Ben Folds One’

We have a guest Friday fold today, from reader Ben Mackay-Scollay of the Monash University School of Geosciences in Melbourne: Ben writes: Hey there Professor Bentley, been a fan of your blog for a while and I thought you might be able to use this for your Friday Fold series. It’s an upright fold at Bermagui in New South Wales, where I visited recently as part of my post-grad coursework …

Read More >>

No Comments/Trackbacks >>


28 March 2014

Friday fauxld: the “Not a Box” at Confusion Hill

Friday fauxld: the “Not a Box” at Confusion Hill

It’s Friday… that means it’s time for a fold. Let’s try this outcrop at “Confusion Hill” in the Franklin Mountains of West Texas: See it? Let’s zoom in… From the shadows to the left of the hammer, trace out the dark green layer… it may make you think of a box fold: …but it’s not. This is actually a completely planar sedimentary bed, tilted to more or less vertical, and …

Read More >>

1 Comment/Trackback >>


21 March 2014

Friday fold: a random sample from the campus of UTEP

Friday fold: a random sample from the campus of UTEP

I know nothing about this sample, other than the fact that it was a thrown-away sample found in the rock pile next to the old geology building at the University of Texas at El Paso. Happy Friday!

Read More >>

No Comments/Trackbacks >>


7 March 2014

Friday fold: Obsidian on display at ASU

Friday fold: Obsidian on display at ASU

Happy Friday! Here’s a beautiful folded obsidian sample, replete with conchoidal fractures, on display outside the geology department at Arizona State University in Tempe, where I was last week:

Read More >>

No Comments/Trackbacks >>


28 February 2014

Friday fold: limestones of the Silurian, Corridor H

Friday fold: limestones of the Silurian, Corridor H

For the Friday fold, let’s journey back to the Silurian, as exposed in the limestones of that age that were deformed during Alleghanian mountain-building (Pennsylvanian and Permian), and exposed along Corridor H in eastern West Virginia. Some buckling (cuspate-lobate form) seen in that one… A little pop-up with hinge collapse: And, finally, as a digestif, consider this little morsel: That’s a bite-sized Friday fold. Have a good weekend!

Read More >>

4 Comments/Trackbacks >>


21 February 2014

Friday fold: Shuswap marble, British Columbia

Friday fold: Shuswap marble, British Columbia

Howard Allen, a blog reader from Canada, digitized a bunch of folds for us from his old Kodachrome slides. You’ll be seeing selections from these images over the weeks to come. Get psyched! There are some great folds in this batch. Here’s the first: Howard’s description: 3D folded marble, Shuswap Metamorphic Complex, north of Sicamous, British Columbia. Specimen was bulldozed out of the way for a logging road. Photographed in …

Read More >>

No Comments/Trackbacks >>


14 February 2014

Friday fold: Valentine’s Day at Newberry Caldera’s big obsidian flow

Friday fold: Valentine’s Day at Newberry Caldera’s big obsidian flow

Scott Johnson contributed this special “Valentine’s Day” edition of the Friday fold: a lovely primary igneous structure that evokes a heart: That’s a close-up view (lens cap for scale) that Scott took when he GigaPanned this feature: link … the big obsidian flow at Newberry Crater in Oregon. That’s a really dry lava flow that oozed out of the Earth sometime in the past thousand years or so. It’s even …

Read More >>

1 Comment/Trackback >>


7 February 2014

Friday fold: Hartland Quay, Devon

Friday fold: Hartland Quay, Devon

I ran out of folds last December, I asked for help on Twitter. Laura Hamilton was among the first to respond, with a link to this image: @callanbentley Hartland Quay, Devon UK. Huuuuge chevron folds! pic.twitter.com/7bhRfLib9Y — lau.rah (@hammijam) December 23, 2013 Thanks, Laura, for another great image!

Read More >>

No Comments/Trackbacks >>