22 December 2016

Dikes at Bunnahabhain

Yesterday I blogged the stromatolites to be seen in northeastern Islay, south along the shore from the distillery at Bunnahabhain.

The sharp-eyed among you may have noticed that in this GigaPan, there’s more going on than merely Neoproterozoic carbonates:
Link 1.46 Gpx GigaPan by Callan Bentley

There’s also a prominent dolerite dike, weathering out recessively. A photo, centered on the GigaPanned dike:


This is but one of several to be seen along this lovely stretch of shore. Check out this lovely example:


…Swiveling around, and looking along strike of this same greenish dike:


One more:


According to Webster, et al.’s 2015 A Guide to the Geology of Islay, the Bunnahabhain dikes may be related to lavas seen elsewhere on Islay, at Glas Eilean. if so, they are Pemian in age, about 285 Ma.

Comments/Trackbacks (0)>>

21 December 2016

Stromatolites of Bunnahabhain

Remember the diamictite I featured here a few weeks ago, from Islay? It was the one that might be a Snowball Earth diamictite. Well, if you follow Snowball Earth science at all, you’ll doubtless be aware that the glaciogenic sediments are characteristically overlain by “cap” carbonates. There’s a stratigraphic successor to the Port Askaig Tillite, too – it’s called the Bonahaven Dolomite.

Unlike what you might expect for a cap carbonate, however, it doesn’t have crystal fans or giant wave ripples or “tube-stone” (a.k.a. “plumb-bob”) stromatolites – all of which are interpreted as evidence of rapid sedimentation or hyperwarm climate from a carbon-heavy atmosphere in the aftermath of the Snowball. Instead, the Bonahaven Dolomite looks a lot like other Proterozoic carbonates that I’ve known and loved.

One thing that makes it worth visiting regardless is its profusion of lovely stromatolites. Let’s examine a few today, all spotted along the shore southeast of the Bunnahabhain Distillery, conveniently enough:












And of course, I’d be remiss if I didn’t offer two outcrop GigaPans of these lovely microbial mats:

Link 1.46 Gpx GigaPan by Callan Bentley

Link 0.81 Gpx GigaPan by Callan Bentley

Comments/Trackbacks (0)>>

16 December 2016

Friday fauxld: The sculptures of José Manuel Castro López

Thanks to my friend Keri Brill, I was alerted to some cool sculpture earlier this morning: the work of José Manuel Castro López. It shows rocks that are sculpted to look as if they were folded, blending the textures of rubber or fabric with the appearance of cobbles and outcrops.

One example:

fauxldArt by José Manuel Castro López

…Now that’s some improbable rheology!

Here’s a post on Twisted Sifter that showcases some of his sculpture.

Happy Friday!

Comments/Trackbacks (0)>>

13 December 2016

The Gene, by Siddhartha Mukherjee

gene Over the weekend, I finished an excellent popular summary of genetics, The Gene: An Intimate History, by Siddhartha Mukherjee. It’s an excellent, thoughtful, current tome, that covers everything from Mendel to Darwin to Lysenko to Rosalind Franklin to CRISPR, written in a personal, accessible way. He begins and ends with a trip to India, examining the genetic roots of madness in his own family. There is a constant attention to the greater significance of the scientific insights — what they mean for society and individuals. It feels grounded and clear-headed as a result, and it’s never boring.

One thing I got from the book was a better appreciation for what eugenics was and is. Mukherjee tells some harrowing tales about the heyday of what he calls “negative” eugenics, the enforced sterilization that stains the early half of the last century in America – its motivations, adherents, and techniques. But the point then was to remove genetic information from the gene pool, hence the descriptor “negative,” quite independent of its negative impacts on human rights. He points out that we are now probably at the cusp of an era of “positive” eugenics, where we can add genetic information to our genomes, edit faulty alleles (changing our genomes), and even do this in a way that results in a permanent alteration of the human genetic line. It’s a different sort of thing from what “eugenics” usually implies, but it too is fraught with ethical concerns. Rather than depriving some sector of the populace of their human rights, the issues now have to do with access to therapy, unintended consequences, and the irrevocable step of finally taking the tiller to steer our own genetic destiny into what may eventually be a distinct species. Those concerns are always present in Mukherjee’s narrative, and he reminds us of them just often enough to keep them prominent in our reading experience, too.

The writing is probably the most extraordinary, exemplary thing about the book: it’s the sort of science writing we should all aspire to. It’s not a coincidence that Mukherjee’s previous book, The Emperor of All Maladies (a book about cancer) won the 2011 Pulitzer Prize. In a thousand small ways, Mukherjee demonstrates concepts with lucid prose and delightful flourishes. For instance, consider this quote, a minor example but one that is fresh in my mind from the final chapter:

Much of our knowledge of our genes and their function is inferred from similar-looking genes in yeast, worms, flies, and mice. As David Botstein writes, “Very few human genes have been studied directly.” Part of the task of the new genomics is to close the gap between mice and men — to determine how human genes function in the context of the human organism.

I love that – each sentence leads incrementally to the next; a clear explanation of a fundamental flaw in our understanding of our own genetics, and then there’s a subtle shout out to Steinbeck slipped in. No big deal made of it, it’s just elegant and leaves a brief tickle in the literary part of the reader’s brain. This book is full of pleasurable reading experiences like that.

If it’s been a while since you’ve thought about your DNA and how a tiny string of four nucleobases makes you who you are, then set aside some reading time over your winter break and indulge in The Gene.

Comments/Trackbacks (0)>>

12 December 2016

Fossils as strain markers: the boudinaged belemnites of the Swiss Alps

Don’t you hate it when plate tectonics ruins a perfectly good fossil? This is a sketch of a belemnite from the Swiss Alps:


The thing has been broken into segments, with calcite filling the gaps between the segments. What a bummer! Now we’re going to have a much harder time reconstructing the life habits of the organism that left this fossil behind… It was a squid-like thing, with an internal skeleton made of calcite, roughly shaped like a bullet. That’s the “hard part” that fossilized and is so hopelessly shattered in the example shown above:


… But wait! Perhaps there’s a silver lining to this fractured fossil. Let’s take another look:


Structural geologist Albert Heim realized that this is a terrific resource for quantifying the change in the rock’s shape. We can use the original fossil material coupled with the new vein material to get a sense of how deformed the rock containing them is.

You can measure the length of the individual dark colored fossil segments, and you can measure the overall length of the final post-boudinaged fossil, and you can compare them.

Original length, lo (black belemnite pieces only) = 82 mm

Final length, lf (black segments + white vein material in between them) = 185 mm

Now we can calculate elongation (e) and stretch (S).

e = (lf-lo) / lo = (185-82) / 82

e = 1.3

S = 2.3

So the sample was lengthened by +130% at least, resulting in a final fossil-adjacent portion of the rock that was 230% as long as it originally was. *

I bring all this up because I recently came into possession of three samples of deformed belemnites from this same site (or a similar one). My colleague Declan De Paor is retiring, and he turned over much of his structural geology rock collection to me. I’ve made GIGAmacro images of the specimens, for the sake of sharing them with you here.


Link 0.73 Gpx GIGAmacro by Callan Bentley

Link 1.24 Gpx GIGAmacro by Callan Bentley

Link 0.44 Gpx GIGAmacro by Callan Bentley

* Declan points out in a post-post email that this technique is flawed. See the details in the first comment below.

Comments/Trackbacks (1)>>

9 December 2016

Friday fold: Machir Bay I

Today’s Friday fold is one of those lovely gems that weather out in three dimensions. I spent a few quality moments with it this summer on the north side of Machir Bay, Islay, Scotland.


Lovely! Give it a little twist to the right, and it looks like this:


The fold overprints foliation or bedding in lightly metamorphosed metasedimentary rock of the Colonsay Group (Neoproterozoic).

Happy Friday!

Comments/Trackbacks (0)>>

8 December 2016

Silent samples, holey samples

Here’s a riddle for you: what gets bigger, the more you take away from it?

Answer: a hole!

Here are two geological samples that show holes. In both cases, I’m not totally sure why, and I’m hoping readers can clue me in.


First, consider this piece of ferruginous sandstone from the redbeds of the Devonian Hampshire Formation in the Valley & Ridge province of West Virginia:

Link 3.91 Gpx GIGAmacro by Callan Bentley

By volume, it’s about 30% holes – these spherical to ellipsoidal regions are weathered out “rotten” regions, where the sand is weakly lithified and crumbly. It can easily be scraped out with a fingernail or pencil. I have seen this several times in sandstones along Corridor H in West Virginia, and I’d guess that there’s some mineral concretions that grew out from some initial nucleus in these zones, and the mineral comprising those concretions is unstable at surface conditions, causing it to weather out. But I don’t know the specifics of what’s going on. Enlighten me?

Next up is a specimen of Virginia’s state fossil, the lovely Chesapecten jeffersonius, collected from the Sunken Meadow member of the Yorktown Formation in Williamsburg, Virginia (the Coastal Plain province). [This GIGAmacro is a featured image in a poster at the AGU fall meeting next week.]

Link 2.01 Gpx GIGAmacro by Callan Bentley

What interests me about this specimen is not the scallop itself, but the dozens and dozens of small holes that perforate the shell. The holes are both larger and more concentrated toward the base of the shell. They get more sparse and tinier as you work your way toward the “lip” of the shell. These are doubtless traces of some organism, but which organism, and why do they show these patterns of size and distribution? Someone, please tell me…

Clearly, I don’t have a handle on the hole story.

Comments/Trackbacks (3) >>

5 December 2016

Cinder cones in Iceland (with lichen)

Lichen covers the slopes of a small cinder cone in southwestern Iceland:


The colonization of the reddish black cinders by the off-green lichens yields a remarkable suite of colors to these volcanic landforms. For instance, here is Grábrókarfell, with its portrait taken from the rim of neighboring Grábrók.


Link 1.28 Gpx GigaPan by Callan Bentley

Here’s another cinder cones on the Snæfellsnes Peninsula:


Link 0.82 Gpx GigaPan by Callan Bentley

Enjoy exploring them embedded GigaPans for insights and details.

Comments/Trackbacks (0)>>

2 December 2016

Friday fold: Dalradian kinks, crenulations, and folded crenulations on Arran

For the Friday fold, let’s travel to the northern edge of the Isle of Arran in southwestern Scotland, where near the town of Lochranza, you can find Dalradian metagraywackes that display a lovely suite of folds. There are kink bands, like this one:


And this one:


And these en echelon kink bands:


And these:


But there’s also a more pervasive structural fabric to be seen: symmetrical crenulations:


And in places these highly crenulated rocks have been folded into a variety of secondary contortions:



There’s much to be seen in and around Lochranza. I’ll return to this site in future blog posts.

In the meantime, happy Friday!

Comments/Trackbacks (0)>>

1 December 2016

Novels by Ernest Cline

armada rp1 In the past couple of months I listened to the audiobook versions of Ernest Cline’s two novels. They are of a common piece, and so I opt to review them in tandem. There is a feeling I have that I am increasingly at odds with the students I teach in terms of cultural references and common interests. On a field trip recently, I made a joke that referenced Indiana Jones and the Temple of Doom, and it fell utterly flat. Probing for why (I have no shame), I learned that NONE of the students on the trip had seen ANY of the Indiana Jones movies. These films were touchstones for my youth and worldview. Only Star Wars has a higher position in the Bentley pantheon. Another angle: I read a lot, and I don’t get the sense that my students do. When I was in high school and college, I read voraciously outside of class, and many of my friends did too. In the calm, organizational moments before a class began, many of my peers would be reading books. Nowadays, it hardly needs saying, the students are paying attention to their smartphones instead. What books could possibly bridge this generational cultural chasm?

My money’s on Ernest Cline.

Ready Player One, his debut, is set in a dystopian future where most people spend most of their time online in a simulated universe called the OASIS. The creator of this ne plus ultra virtual reality dies, and sets up with his will a competition for his accumulated riches that’s based on exploring the OASIS with a thickly-cultivated sense of 1980’s music, movies, TV, and games. I’m not a gamer myself, but I watched a fair amount of TV in my youth, and I’ve been a constant cinematic consumer throughout my life. And I’m familiar with most of the music referenced, though none of it comes close to the Talking Heads for me. Bottom line: there were a veritable gigatonne of 1980’s pop cultural references that were woven into integral plot developments in this novel, and they are so much fun to revisit in the context of a new cut-throat competition for the biggest pot of money on Earth. Poor boy Wade invests his passion in mastering every little detail of Steven Spielberg*, Atari, Rush, and Japanese monsters. When various trials are presented to him, he has the skills to succeed. Along the way, there’s a fairly traditional romance subplot, but call me a sucker for that sort of thing – it’s just like all the movies I watched in the 1980s!

So what else has the guy written? That was the question as I closed out Ready Player One. It turns out, there’s only one other option at this point: Armada. I checked it out from my library, and just finished it yesterday. I think I liked Armada even better. It’s set more or less in the present day, and the plot hinges on the notion that all of the science fiction movies and video games we’ve been enjoying as a culture are in fact intentionally preparatory. More specifically, two massively multiplayer online games, “Terra Firma” and “Armada,” are specifically designed to train Earthlings for a forecast alien invasion (ground combat and space ‘aerial’ combat, respectively). The protagonist, like that of Ready Player One, lacks a father but discovers that before his father died, he had clued in to this massive cultural conspiracy. The protagonist, Zack, is really good at playing “Armada,” and soon discovers that his dad’s nutty old journals were right, and now he too is being folded in to this effort to fend off Earth’s annihilation by hostile aliens. As with RPO, there’s a ton of pop-cultural tie-ins, though this time the connective tissue runs in the other direction. Star Wars, The Day the Earth Stood Still, Independence Day – those were all propaganda to get everyone up to speed. Fun: Carl Sagan got the funding for the original Cosmos by virtue of his involvement in the cover up. Brief cameos by Seth Shostak, Stephen Hawking, and Neil DeGrasse Tyson. Twists and turns in the plot, and another cliched romance sub-thread, and it’s all good. Overall, a rollicking good time.

I should note that both audiobooks I listened to were read by Wil Wheaton, which is perfect, since the Stand By Me / Star Trek: The Next Generation actor is an exemplar and advocate for geek culture across the decades.



* Spielberg is directing the movie adaptation of Ready Player One, which I predict will be awesome. Due date: 1.5 years from now.

Comments/Trackbacks (0)>>