The word is out…

Others have started announcing our move to a new blog consortium hosted by the American Geophysical Union, so I suppose I will go ahead and reveal that I, too, am part of this scientific cabal…

Sometime before the end of the month, Mountain Beltway and six other top-notch earth and space science blogs will relocate to AGU servers and a new URL. I’ll leave directions here for folks to follow…

Photos from Virginia Geological Field Conference

For the second year in a row, more exotic travel plans meant that I wasn’t able to attend the superb Virginia Geological Field Conference. I see that they have now posted some photos on the group’s Facebook page, so go check them out to see what we both missed last weekend. Here’s a taste:

Sheared meta-conglomerate:

Metamorphosed mantle (?) xenoliths:

Güvem geoheritage site, Turkey

Looks like I’m late to the party…

While I was away, apparently the geoblogosphere went on a rampage of cooling columns. Everyone was posting images of their favorite columnar joints, and I was left out in the cold. Let me remedy that now. As it turns out, I was visiting some columns while everyone else was writing about them. Here are some images from the Güvem area of Turkey, north of Ankara, where there are a mix of late Miocene lake sediments and intercalated volcanic rocks, including these basalt flows. We stopped to visit them last Wednesday on our way to the North Anatolian Fault:

The dark entablature looms above:

A nice central panel with a good cross-section of the flow:

Around the corner, some more:

I ran across the street (and a stream) to check out a similar exposure there:

Zooming in:

Close-up of a few columns (with my hand for scale):

Looking up along the columns:

And a few more shots of the scene:

A full list of Turkish geoheritage sites may be found at the end of this document. Lockwood maintained a list of the other blog posts in this meme here, which I’ll quote below since it’s so nicely laid out already:

Geotripper, here, here and here,
Sam at Geology Blues
Phillip, also at Geology Blues
Silver Fox, and another columnar post here.
Glacial Till and another!
Life in Plane Light: Squashed columns!
Aaron at Got The Time
Geology Rocks
Dana at En Tequila Es Verdad
Cujo 359 (see comment on Dana’s post for description)
Wayne at Earthly Musings has a gorgeous photo of columns below the rapids at Lava Falls in Grand Canyon.
MB Griggs at The Rocks Know has photos of what may well be the most perfect columns in the world.
Jessica, AKA Tuff Cookie, showcases a variety in different rock types.
Hypocentre finds columns in a very unlikely place, as well as a spectacular photo of radiating columns.
Dave Tucker at Northwest Geology Field Trips displays precisely one slew of columnar displays in Washington State.
Dave Bressan at History of Geology shares the first printed image of columnar basalts, from 1565.
A couple more variations from Dana’s and my driving about W. Oregon.
Dr. Jerque has some spectacular examples from the bottom of the Grand Canyon.
Silver Fox Has another (better than mine) photo of horizontal columns in a set of dikes, and points out a couple more links to columny goodness (not to be confused with calumny, which is not good)
Dan McShane offers some more Washington State columns.
Garry Hayes, who deserves credit for starting this meme (see first links in the list, above), adds yet another set of photos from the opening of the Atlantic Ocean, and a lovely guest photo by Ivan Ivanyvienen, of columnar jointing in rhyolite at the San Juan Precordillera.
Update, October 4: Eric Klemetti- who did his doctoral work just down the street from where I’m sitting- has joined the fray. (Also, check out the links readers have left in the comments)
Helena Heliotrope at Liberty, Equality and Geology shows off some more Washington columns.
Chris and Anne at Highly Allochthonous each toss in a photo- Tokatee Falls looks awesome!
Some more Cape Perpetua jointed dike photos from Cujo359, and Devil’s Churn- again, numerous dikes with horizontal columns.

Remains of a mud puddle

Last Wednesday, I took a field trip to the North Anatolian Fault in Turkey, but I got distracted by this fine looking display of sedimentary structures in  a dried-up mud puddle in an old quarry.

The coin, a Turkish lira, is about the same size as a U.S. quarter. What you’re seeing here are dessication cracks (“mud cracks”), and accompanying them are exquisite little raindrop impressions, the minute craters excavated by a light sprinkle of rain after the mud has already started to dry out and “gel.” (If the water which deposited the mud were still there when the rain fell, the standing water would have dissipated the energy of the drops’ impacts, and no craters would have been excavated.)

Here’s a slightly more oblique perspective, to give a sense of how the individual mud flakes are internally laminated, and curl along the edges, producing a concave-up shape.

Note too that the cracks bisect some of the rain drop impressions, and therefore the raindrops fell first, and then the dessication cracks propagated on through them, a nice example of cross-cutting relationships. In some cases, the propagating crack used the “crater rim” of the drops as a mechanical zone of weakness, fracturing there preferentially. Here, let’s zoom in on a couple of nice examples (one from photo #1, a second from photo #2):

If anyone wants a full-sized copy of any of these images for teaching purposes, let me know via e-mail, and I’ll send you one.

Two xenoliths

On my last day in Ankara Turkey (last Friday), I took the afternoon off from the Tectonic Crossroads conference in order to pay the requisite visit to the Museum of Anatolian Civilizations. I say “requisite” because Ankara’s not quite so thrilling a town as Istanbul, but this is the one location that everyone agrees is worth a visit. The previous day at breakfast in our hotel, University of Georgia geology professor Jim Wright told me it was the most amazing place he had ever seen. So I had to go check it out for myself.

It’s a cool place, if you’re into history. Anatolia (the Asian part of Turkey, which is to say, most of Turkey) is a place steeped in history. Their written records go back 9000 years, if you include Neolithic cave paintings. It’s pretty neat to check out their sculptures and tools over that long span of time. (See some photos here.)

I only took one picture in the museum, though. This is it:

That’s a Hittite lion sculpture made of porphyritic andesite. I took his portrait because of that funny looking eyebrow — that’s a little black xenolith, a chunk of pre-existing solid rock that got stoped off the wall rock and carried along in the flow of magma, eventually getting trapped in “alien” territory once the magma (or lava) solidified around it into rock. It was the most striking geological aspect of the museum’s many displays.

After I got “museumed out” (usually this takes about 2 hours), I went for a walk around the adjacent “Citadel” region of old town Ankara, and what do you know, but I found an outcrop there! Not only that, but there were some striking similarities to the photo I had just taken in the museum — it was a porphyritic volcanic rock (I want to call it a rhyolite based on the pink color), and it too had a lone dark xenolith:

A little girl wandered up to me with unabashed curiosity — why was this foreigner putting a lira coin on the rock and taking a photo of it in the rain? Plainly, I must be insane. I greeted her, pocketed my coin, and strolled on, reflecting on the satisfaction of seeing such a nice little pairing of similar structures in similar rocks — a quarter mile from one another, though in very different settings.

Friday fold: multilayer buckle folding demo

Check out this video I found online whilst uploading last week’s Friday fold:

This video was produced and published on YouTube by Markus Beckers, Michael Ketterman, Dennis Laux and Janos Urai.

It’s a nice demonstration of how multiple layers of material of different properties and different thicknesses can yield up different flavors of folds. In the movie, there are two materials present: white silicone and gray foam. The silicone layers are stronger (“more competent”) than the foam. But the two silicone layers are different thicknesses. It turns out that this ends up being a decisive factor in determining the way they fold.

We can explain this behavior using the Ramberg-Biot equation:

L = 2 π t (η / 6η_o)^⅓

where L is the wavelength of the fold (in other words, the distance from one antiform fold hinge to the next antiform fold hinge); t is the thickness of the folded layer; η is the viscosity (resistance to flow) of the silicone layer (or, in general, the more competent of the two layers); and η_o is the viscosity of the foam layers.

In other words, the (η / 6η_o)^⅓ part of the equation reflects the viscosity contrast between the affected layers. In the video, this viscosity contrast is a constant, since we’re looking at two layers of the same stuff surrounded by the same matrix of other stuff. The only difference is the thickness of the two silicone layers.

So as far as our video up top is concerned, pay attention to the t value and the L value: the thicker the layer is, the larger the wavelength of the resulting fold. The thin layer has a lower t value, and so it ends up with a shorter wavelength: i.e., there are more folds packed into the same amount of vertical space as its stouter neighbor. The thick layer’s higher t value means it wıll have a proportıonately higher L value. It will have a longer wavelength, and fewer undulations will fit into the available vertical space.

Happy Friday, everyone! I’m heading back to DC tomorrow (from Turkey), so more regular posting wıll resume next week.

Empires of the Sea, by Roger Crowley

Note – I am wrıtıng thıs from Ankara, Turkey, where the Turkısh keyboard makes ıt very dıffıcult to type ‘i’ correctly — so please forgıve my decapıtated ‘ı’s…

___________________________

Today is the annıversary of the Battle of Lepanto, the fırst full-scale battle to take place at sea aboard armored ships. It strikes me as approprıate and tımely that a few days ago, I fınıshed readıng the book Empıres of the Sea, by author Roger Crowley, whıch recounts thıs extraordınary clash of cultures/relıgıons/empıres. I have praısed Crowley’s grıppıng hıstorıcal wrıtıng when I revıewed hıs book 1453, and I mentıoned at the end of that revıew that I was ınterested ın readıng anythıng else he has wrıtten. Turns out there’s just one other book to delve ınto, Empıres. The book detaıls the expansıon of naval warfare ın the quest to control the Medıterranean Sea ın the 100+ years after the fall of Constantınople. Coverıng more than a century of tıme and a successıon of Spanısh kıngs, Roman Popes, and Ottoman sultans, ıt ıs a lot more complıcated than the sıngle battle (and two leaders) profıled ın 1453. It also ranges across the Medıterranean, from Istanbul to Malta to Cyprus to the culmınatıng battle, the one that happened 439 years ago today. As a result, the narratıve structure of the book ıs far less engagıng than ıts predecessor, but ıt stıll tells a profound and harrowıng tale.

As wıth 1453 (and the modern-day evenıng news), the book ıs full of horrıfyıng examples of human cruelty to other humans. After acceptıng the surrender of commander Marco Bragadın of Famagusta (the last town to fall on Cyprus), Lala Mustapha, the commander of the Ottoman sıege forces, reneges on the condıtıons of the treaty, and has Bragadın skınned alıve. Hıs empty skın was then stuffed wıth straw, dressed ın Bragadın’s clothes and gıven a parasol, mounted on a cow, and paraded through the streets ın mockery and celebratıon. It’s a lovely example of how hıdeous we can be to those we consıder to be our enemıes, those who belong to ’a dıfferent trıbe.’ Another example, more prosaıc but nonetheless dıstrubıng, may be found wıthın the Chrıstıan ranks — the Holy League was a sort of Chrıstıan NATO, and brought together Venetıans, Genoans, and Spanısh ın support of the common goal of resıstıng the Ottoman expansıon and defendıng what they were sure was the true faıth. However, they could hardly stand one another’s company, and a mere fıve days before the bıg battle, Venetıans were kıllıng Genoese for wakıng them up when they were tryıng to sleep. When compared to the Turks, Venetıans saw Genoese as ‘alıke,’ but when there were no Turks about for comparıson, the ‘otherness’ of theır co-Holy-Leaguers was all too apparent. Thıs trıbal outlook seems to me as beıng fundamental to the human condıtıon — whether we are commıttıng jıhad or merely comparıng soccer moms to tree huggers, human ındıvıduals are constantly engaged ın dıvıdıng the world ınto ‘us’ and ‘them.’ Sometımes, ıt ıs drıven by polıtıcs, or culture, or relıgıon, or economıcs, or even the merest snobbery, our trıbalısm causes more trouble than anythıng else I can thınk of.

The part of the book I found most ınterestıng was the battle of Lepanto.

The battle pitted the fleet of the Christian ‘Holy League’ against the navy of the Ottoman Empire. Spoıler alert – Unlike the events of 1453, the Christians won this one. The event was on an epıc scale – 140,000 men partıcıpated ın the two armadas, saılıng on 600 shıps. Crowley estımates that more than 70% of the oared shıps ın the Medıterranean met on October 7, 1571, off the coast of Lepanto. If you cannot ımagıne seeıng such a thıng (ıt straıns the ımagınatıon), Crowley paınts a vıvıd pıcture when he descrıbes the wıdenıng eyes of the crews as they glımpse the enemy navy saılıng ınto vıew for the fırst tıme. Realızıng the huge scale of the ımmınent clash, they very much have an ‘oh, shit…’ reactıon. Wıth Crowley’s vıvıd narratıon, you can practıally feel theır adrenalıne spıke.

I thınk any of us would have been astonıshed at the scale of thıs event — even the most battle-hardened modern soldıer. The vıolence, of course, was deep and dıverse. Many Chrıstıans dıe, but because of the way the wınd was blowıng and a lucky early round of gunfıre whıch oblıterated many key Ottoman vessels, the tıde of the battle quıckly turns towards the Holy League. The Ottomans suffer tremendous losses. One detaıl that struck me was the story of a Venetıan commander who blows apart hıs hand wıth a faulty grenade, then asks a subordınate to cut ıt off. The subordınate refuses, so the commander amputates hıs own hand, then tıes the carcass of a dead chıcken over the wound (What?!?!) and returns to battle. He even shouts at hıs left hand to avenge the loss of hıs rıght! Another juıcy tıdbıt ıs that one of the Spanısh saılors was the 24-year-old Mıguel de Cervantes, who would go on to author Don Quıxote. He was wounded, though obvıously not kılled.

At the end of the four hours of battle, there have been 40,000 men kılled. 100 shıps have been destroyed, and more than that agaın were captured ın saılable condıtıon from the Ottoman fleet. The sea near Lepanto was an 8-mıle-long slıck of burnıng, shattered, or drıftıng vessels, as well as rampagıng looters from the wınnıng sıde. Crowley wıns me over when he ıncludes ‘moments of grotesque comedy,’ lıke the scene where a group of Muslım saılors refuse to surrender but are wıthout tradıtıonal weapons. They start to pıck up oranges and lemons and hurl them at theır Chrıstıan tormentors. The Chrıstıan saılors, bemused, hurl them back at theır enemıes. Food fıght!

Thıs ımage of the war-polluted sea clıngs to my mınd. The blood-red water ‘heavıng thıckly wıth the matted debrıs of battle’ – Moorısh coats, wooden weapons, fragments of shıps, boxes, saıl cloth and other flotsam, and of course a great many dead human beıngs. What a profound event thıs was. Many battles had taken place before, of course, ıncludıng some whıch had a sıgnıfıcant naval component — but Lepanto was the fırst naval battle on the scale of empıres.

I suggest we all commemorate thıs day by doıng somethıng nıce for someone who we see as beıng ın a dıfferent ‘trıbe.’

Friday fold: Archean gneiss from Montana