20 June 2011
“Boudinage” is my favorite geology word
Posted by Callan Bentley
The current edition of the Accretionary Wedge geology blog carnival (hosted by Evelyn Mervine of Georneys) is built around the theme of favorite geology words.
My favorite geology word is derived from the French boudin, for sausage. It’s “boudinage,” and it’s best said with a heavy French accent and a leering, dirty expression.
I love pronouncing it; it’s a delicious word, like a good boudin itself.
So what is it?
Boudinage is when a rock unit (usually a tabular rock unit like a bed of sedimentary rock or an igneous dike or a mineral vein) gets stretched, and responds to that stress in a brittle/ductile fashion. It breaks into chunks, but those chunks show flow in between them. Like taffy, the strain is concentrated in the boudin “necks,” and the less competent surrounding rock flows into that accomodation space between the individual boudins. Viewed in cross-section, this creates a “sausage link” effect, as can be seen with this vertical example of boudinage (of a granitic dike) in the Lawhorne Mill High Strain Zone of Virginia’s Blue Ridge basement complex:
Here’s another one from the same spot, but further down the outcrop:
Sorry there’s no proper sense of scale in these photos — the outcrop wall was protected by a barricade of briers, ticks, and muck. I’ll go back in the winter sometime to document it properly.
Want more boudinage? Here’s some. Here’s some more.
maybe not ideal, but the plants do fine to provide scale
Scrolling down, and down, and down some more on the photos is possibly the best part of this definition. “What’s a boudinage? It’s when your rock streeeeetches down the whole page…”
🙂 Thanks, Mika!
“My favorite geology word is derived from the French boudin, for sausage.”
Actually, it’s a little more complicated than that, as I found out the hard way. My geo profs always told us that, but one time I was in a drilling camp that had French cooks from Quebec. They asked me what I wanted with my eggs for breakfast, and I replied “boudins”, to which I got only blank stares. The direct French translation for “sausage” is “saucisse”. Apparently “boudin” is some obscure type of sausage, more akin to the British black pudding that comes stuffed in a skin. If you plug “boudin” into Google’s French/English translator, you get “flange” back. If you try “boudinage” you get “socking”(!?). No wonder the cooks were befuddled.
This is almost all exact, although I have to add that you can not only eat “boudin noir” (black boudin), which is indeed a blood sausage similar to British black pudding, and especially delicious served with apples, but also “boudin blanc” (white boudin), made out of meat and other stuff. As far as French sausages go, I for my part cannot help recommending andouillette, which upon first contact is a bit unsettling for foreigners (because of the strong smell and the rough aspect) but very rewarding to those generous enough to go beyond appearances and open their culinary hearts to it. It would be best compared with Scottish haggis.
Bon appétit !
And Spanish “morcilla”!
If you’re ever up SE New England way, drop a line, as there are some really spectacular boudins up this way in some of the terrain-bounding faults, among other spectacular things…
Thanks for the invitation — if you ever see mention here on the blog about me planning a NE trip, then feel free to remind me. I’d love to link up and see some boudins!
No Problem… will do. Of course, I always think taking a 4 day weekend to come up to NEIGC each fall is well-worth the drive. Some of the best exposures in (northern) Appalachian geology with most of the experts… all on the same outcrop. It gets lively. 🙂 http://w3.salemstate.edu/~lhanson/NEIGC/
Boudin is fairly common where I am from. I remember going on a field trip as an undergraduate and having the instructor describe these things with what I thought was some arcane geologic term. When we got back and I read about them, the light bulb went on. “Oh, he meant BOUDINS!” Kinda like the epiphany I had when I realized that OM-i-ger was a Greek letter to some people.
[…] may recall that I kind of like boudinage. So it piqued my interest when our field trip leaders (on the pre-GSA Minneapolis trip to examine […]
its more fun to listen “boudinage” from our teacher of environmental geology.
Thanks so much for the simple explaination. I have to write a lesson plan for grade 7 level explaining boudins and how they are formed. I was a bit lost until reading your post.
Now how about explaining why rocks are stronger in compression than in tension!
[…] The strain displayed by this dark schist is hard to miss. Outcroppings of metamorphic rocks are abundant in the ancient crystalline core of the Santa Fe Range, but few of them exhibit such dramatic stretching as this example. Here’s a close up of a structure known as boudinage: […]
[…] down on the beach, checking out the wall-like sweep of outcrop. Can you find three examples of boudinage? Link GigaPan by Callan […]
Doing a little online poking around I was intrigued by this paper on Non-Newtonian flow dynamics: https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/88/2/312/202097/formation-of-folds-boudinage-and-mullions-in-non?redirectedFrom=fulltext
But sweetest of all is this do it yourself demonstration version which ought to be a hit in any classroom, once you get to the clean up part: with a Milche-Schnitte (which turn out to be what I know as ice cream sandwiches). Instructions are given here with English subtitles.
youtube.com – How to make Boudinage with a Milch-Schnitte (I guess you’ll have to search for this).
You can find Boudin in Cajun cooking.