5 February 2018

Inferior, by Angela Saini

The subtitle of this useful and righteous book is How Science Got Women Wrong—and the New Research That’s Rewriting the Story. It’s a scientific examination of a slew of ideas about women, busting culturally-entrenched myths left and right with that most radical of substances: data. The book is intended, I would guess, as a comprehensive review of what science currently has to say about females, motivated to support of the feminist ideal of equality between the sexes. It is organized chronologically around a woman’s life, from her time in the womb until menopause. Saini is plainly angry by persistent inequality between the sexes, and in parts of the book her writing sometimes comes off as fiery and insistent. I think this is fine, as it’s motivated by injustice (she should be angry. We all should be!), but it stands in contrast with other stretches of prose that are more reportorial, measured, and apparently curiosity-driven. I’m not sure which flavor I prefer – I think the latter is more likely to stand the test of time (as a distillation of what science has to say about a given feminist related topic), but the angry tone gels more readily with the current national zeitgeist: women fighting back against oppression and abuse. All told, I think it’s a practical compilation of relevant studies and interviews, and it has been released at a fitting moment in history.

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2 February 2018

Friday fold: 3D model from the Portsoy Shear Zone

Today’s Friday fold comes to us from the team at eRocK, a neat repository of structurally interesting 3D models. Their website describes the project this way:

eRocK is a virtual geology project led by Adam Cawood and Clare Bond at The University of Aberdeen. This project aims to provide open-source geological data and visualizations for fellow researchers, educational institutions and the general public. Our models are currently embedded into our own site via the free online viewer Sketchfab.

Though they have many lovely fold models, I picked this one because (1) it’s new, and (2) it has nice differential weathering of the sedimentary layers, resulting in a pleasing texture to the outcrop and the model derived therefrom. Enjoy spinning it around!

Adam describes this outcrop like this:

These thinly bedded, greenish grey and cream units of the Boyne Limestone Formation (Argyll Group) were deposited in a shallow marine setting and later folded during the Caledonian Orogeny (390-490 Mya). The Caledonian Orogeny deformed and metamorphosed large tracts of Europe, America and North Africa; this small outcrop (c. 100cm x 25cm x 25cm) near Portsoy, NE Scotland, records this deformation at a macro scale. Complex fold patterns are recorded in these thin interbeds of calc-silicate rocks, metalimestones and calcareous semipelites of Neoproterozoic age (541-1000 Mya). The dominant folding pattern here is associated with a third phase of Caledonian deformation (D3) which overprints an earlier D1 phase, resulting in fold interference patterns which can be seen on some surfaces. Lat: 57° 40′ 56″N, Long: 2° 38′ 37″W

Happy Friday, all!

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26 January 2018

Friday fold: eastern Andes

This image graces the cover of the new report, Challenges and opportunities for research in tectonics: Understanding deformation and the processes that link Earth systems, from geologic time to human time. A community vision document submitted to the U.S. National Science Foundation:

Make it bigger by clicking it

The photo is of a

landscape in the Eastern Cordillera of the Andes, southern Peru, showing folded Permian carbonates cut by a normal fault (dipping to the left). The snow-covered peaks (left background) were carried over rocks in the foreground by a reverse fault during Cenozoic shortening and construction of the Andes.

The photo is by N.D. Perez. There are a lot of other great images in the report. Check it out! All figures are available for community use in presentations and teaching with attribution (the Figure Credits are outlined in the report’s back matter).

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23 January 2018

A kid and his slicks

My family and I took a hike this past weekend in the George Washington National Forest. We hiked up the hill from our house and explored along the trail system that runs along the crest of Massanutten Mountain, and then exited through Veach Gap. Along the way, my five-year-old son made lots of little discoveries.

Here, he examines some interesting smooth lines on the face of a block of Massanutten Formation quartz arenite (quartz sandstone):

These lines are smooth to the touch, and all parallel to one another:

They are slickensides, little polished grooves that develop on a fault surface when one block of rock grinds against its neighbor. So this side of this cobble is a scrap of a fault surface!

There’s still a tiny piece of the opposite side of the fault attached to this block, right underneath my son’s fingertip. You can see the slicks emerging from beneath that little wedge:

In our region, most of the rock units are pretty susceptible to weathering and erosion, and the most typical lithology to be found is this indurated Massanutten quartz arenite. Occasionally it yields neat features like cross beds or pebbles, but mostly it’s massive. Honestly, it’s not all that sexy. But when it is improved with the addition of a bit of structure, it can hold my attention (and the attention of a five-year-old boy!) for a moment or two.

The age of the sand’s deposition is Silurian, somewhere between 440 and 417 (±10) million years ago. But the age of these slickensides must post-date that: It is, after all, impossible to fault something that doesn’t yet exist. Furthermore, the slickensides must also post-date lithification (turning the sand into sandstone). While unlithified sand can be faulted, it won’t leave slickensides behind as a signature. So I suspect, based on the age of other deformation in the Valley & Ridge province, that these slicks are late Pennsylvanian in age: that’s the time of the Alleghanian Orogeny, an ancient mountain-building event that accompanied the assembly of Pangaea. At this time, this part of the Appalachian system got seriously stressed out. It was compressed from the east/southeast, causing the stratified rocks to crumple and fold. In places, the stresses were too grade for the ductile folding to accommodate, and there were faults that ruptured through the rock, grinding one piece into a new position relative to its neighbor.

So we’re looking here at a miniature Appalachian geologic history: first deposition of sediment, and then later deformation of the resulting sedimentary rock. And also, I suppose we might add in the effects of differential weathering, breaking down the limestones and shales and whatnot, and leaving the tough quartz arenite poking out proud of the landscape to make mountain ridges. In this single cobble, we can extract information that sketches a rough outline of the entire mountain range’s history.

Lagniappe: later in our hike, we passed the celebrated anticlines of Veach Gap, evidence of a more ductile form of Alleghanian deformation:

Thanks for joining us on this little jaunt. I hope you found it as slick as we did!

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19 January 2018

Friday fold: crumpled quartz vein from VGFC

Remember the Virginia Geological Field Conference from back in October?

Well here’s a folded quartz vein we observed along a small shear zone in the Blue Ridge basement complex. There are two views of it, from approximately perpendicular points of view:

These rocks are Mesoproterozoic, but the vein would obviously be younger than that, and the deformation is likely Alleghanian in age (late Paleozoic).

Annotated copies of the photos:

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18 January 2018

Surviving AI, by Calum Chase

I know what you’re thinking: another book about AI, Callan? Really?

Yes, really. I don’t know what compelled me – but perhaps that the author’s name was so similar to my own spurred me onward. Surviving AI is Calum Chase’s summary of the current state of affairs with AI risk management (specifically, of course, relative to artificial superintelligence). It’s a well balanced book in that it plainly states where there is agreement and disagreement by experts in the field of artificial intelligence. It’s concisely and clearly written (in contrast to the jargon-dense prose Nick Bostrom deploys in Superintelligence) and would serve adequately as an introduction to the topic without any histrionics or undue fretting. It’s a sober book. That said, I don’t think I gleaned too much new from reading it: this isn’t my first time reading a primer on AI. I’d send neophytes instead to James Barrat’s Our Final Invention as the best place to dip into the topic for the first time. They cover much of the same territory, but while Chase’s book is leaner due to a more spare writing style and less indulgence in personal anecdotes, it lacks some of the vitality and passion that made Barrat’s book so powerful. I guess the one thing I’d say I got from this book was Chase’s clear articulation of the tremendous uncertainty about almost every aspect of this subject. That uncertainty shouldn’t stop us: it should motivate us to learn more.

Both authors emphasize the same conclusion though: We really need to be talking about artificial superintelligence as a society, as a species, so we’re sure we’re doing all we can to be prepared for it when it arrives. And for us to talk about it, we all need to get up to speed on the topic. So: please pick one of these introductory books up and start reading!

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17 January 2018

Winter ichnology puzzle

Here’s a puzzler to warm up your chilly brain this Wednesday morning:

Click to enlarge

Figure out the story told by this set of imprints in the snow. The branch of science called ichnology studies the traces organisms leave behind. There’s a neat little story here. If you’ve got a guess, then you can check your answer by watching the video that this screenshot came from. It was posted on Facebook by the town of Cobourg, Ontario, which caught it on a security camera. It’s pretty cool to watch the whole thing unfold. Enjoy!

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13 January 2018

Year Zero, by Rob Reid

I was so impressed with After On that I went out an got the only other novel by Rob Reid, Year Zero. The plot set up is something rather ludicrous, but the novel works in spite of the silly premise. Here’s the idea: There are a lot of alien civilizations out there, and they are really advanced. Banded together into a Refined League, they have mastered almost all forms of art, but they are really deficient when it comes to music. They discover Earth’s music and it becomes an ecstatic addiction. They listen and listen, copying music files and lip-synching performances, and loving it. But then, 30 years in to the sonic orgy, somealien realizes they haven’t paid a cent for it, and are subject to legal penalties according to Earth’s copyright laws. Following legal precedent such as when a college student who shares 30 files has been slapped with a $675,000 fine, the aliens owe the citizens of Earth the entire wealth of the universe. So now some of them want to destroy the Earth to get out of the debt. And in steps our hero. Goofy, right? But it’s worth reading, because Reid is a really skilled writer with a terrific imagination. It’s super fun. And as an added bonus, the novel has at least one character in common with After On, as well as the social media app Phluttr, which was central to the subsequent novel. I like it when authors or auteurs manage to construct multiple independent stories that fit into the same fictional universe with elements like that, akin to Quentin Tarantino’s Red Apple cigarettes or the 1% overlapping novels The Golden Ocean and The Unknown Shore by Patrick O’Brian. Overall, I’d say that After On was a stronger book than Year Zero, but I enjoyed the alien music law fest too. It’s a nice escapist novel.

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12 January 2018

Friday folds: Hayden Butte (“A Mountain”), Tempe

In keeping with the Arizonarific theme of this week’s posts (thanks to my participation in the 2018 Structural Geology and Tectonics Forum), I thought I would wrap up my ‘geology of the Phoenix area‘ posts with a walk I took on my last day there. This was to what Google Maps calls “Hayden Butte,” but the locals call “A Mountain.” Not “a mountain,” but “the mountain called ‘A‘.” It has a big yellow “A” on its south side. It’s adjacent to the stadium where the ASU Sun Devils play, and on the other side is the vibrant Mill Street corridor, the beating heart of Tempe.

Here’s a view from the north, to emphasize the big-picture geology of the butte:

Most of the peak is made of lava flows with an andesitic composition. But these overlie Neogene sedimentary rocks. Both are interesting.

I began my visit there by summiting the butte. The trail is heavily used, which is great, but severely eroded, which is not so great. The views were nice – though it’s essentially an urban vista.

The rocks were fairly unextraordinary, porphyritic to aphanitic in texture, gray in color. They are apparently 18 million years old. I did spot a couple of small light-colored xenoliths, including this one:

I also spotted an interesting set of deflected fractures, resembling a kink fold:

Annotated copy, with the trace of fractures highlighted in white:

Given that these lavas flowed on Earth’s surface less than 20 million years ago, it seems unlikely that they have been subjected to compressional stresses at the brittle-ductile transition in order to kink. So I suspect this is just a visual match, a coincidence of form which isn’t really a kink band. That said, the fractures exist. Fractures form when stresses exceed the brittle strength of materials, so there could well be an interesting story to be extracted from these rocks.

I made a 3D model of this outcrop, which helps to convey the shape of these “kinked” fractures:

Then I walked clockwise around the butte, and found the sedimentary rocks. These were much finer than the coarse landslide breccias at Papago Park. Instead it was mudrocks and sandstones. One thing that was superlative about the site is some boffo soft sediment deformation: certain beds with high degrees of internal contortion.

The first glimpse was relatively symmetrical and open in its folding:

… But then things got more intense:

This is the signature of a density inversion – a deposition of wet sand on top of squishy mud. The sand then sags downward into the mud as big lobes, and to accomodate this relative motion, the low-viscosity mud squootches upward in flame-like projections.

Any thin sand layers within a larger body of mud get dragged along for the ride, acting as nice strain markers.

I saw one nice example of graded bedding:

More soft sediment deformation:

In spite of the hematite ± calcite on joint faces that transect the folded sandstone layers, I found the form of this fold to be quite exquisite:

Here, I annotated it for you:

…And here are 3D models of two examples of the soft sediment deforomation weathering out of the butte:

I think there’s more to be seen on this mountain, but I wish I’d brought another person with me. I encountered some sketchy characters in some of the gullies draining the peak, and I think it would have been wiser to have a bigger group than just one. I’d caution anyone else thinking of visiting to bring along some friends. Maybe a trash bag for collecting litter would also be a good idea!

Anyhow, this mountain is a real treasure to have so close to campus. I wish I could take my students on a short field trip to a place like this. I guess with this set of photos and 3D models, I can at least give them a taste of it.

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11 January 2018

Landslide breccias in Papago Park

Yesterday I outlined the idea of metamorphic core complexes, as expressed in the South Mountains, south of Phoenix, Arizona. We examined the ductilely-deformed footwall rocks. But a bunch of rock slid off the top, too, breaking into domino-like chunks as it slid along the detachment fault. The local mountain called Camelback is mostly made of granite that originally derived from the South Mountains, but it’s on the other side of Phoenix now. It also features a distinctive unconformity, separating the granite from overlying oxidized Neogene landslide deposits – the “red beds” in the image below:

Today we will journey to Papago Park. It has many more examples of these red beds, which in spite of tilted bedding show horizontally-oriented holes of “mega-tafoni.”

One of these is known locally as “Hole in the Rock.” Here it is, with some people for scale:

Hole in the Rock is basically a small version of Camelback:

The granite here is the tip of a big block of hanging wall rock from the South Mountain detachment. It’s mostly submerged in a sea of modern sediment, but also bears a load of lithified breccia. This is the Neogene-aged Camel’s Head Formation. It’s pretty angular, and pretty poorly sorted:

The clasts comprising this sedimentary breccia imply a nearby source of lots of granite, and also some finely-banded rhyolite:

Therefore, there must have been a mountain nearby in the past to shed these clasts off – some local relief from which landslides and debris flows might issue. The mountain is now absent, either eroded to nothing or else buried under the Phoenix Basin’s sedimentary valley fill.

Zooming in on one of the boulders, you can see (in the lower right) a primary igneous contact between the granite and the rhyolite:

So we can actually say something about the structure of this long-departed mountain range by examining a pile of sedimentary clasts like these. Neat-o!

I should also point out that this red bed breccia weathers out beautifully as a series of small buttes looking south toward Tempe and southwest toward Phoenix:

It’s a neat place to visit, clamber around, and contemplate the annals of the former world.

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