“O Courel” Fold

The O Courel Fold is one of the sparse geological protected landscapes in Spain. It’s a beautiful recumbent syncline fold on sandstone and shales, with a very good overview by the road on the other side of a valley.

Original fold image
O Courel fold

Located in eastern Galicia (any Camino de Santiago fans out there?), it is cut through by a small river on the green hills of the O Courel mountain range. For the rock enthusiasts, you’ll want to know the fold alternates strata of sandstone and clay-rich shales. For the tree enthusiasts, the area has some of the coolest looking, Tolkien-like forests you’ll find. Worth the visit!

Map detailing the situation of the fold and the information panel. Click on the image to see it bigger.
Map detailing the situation of the fold and the information panel. Click on the image to see it bigger.

To get there, you have to drive to Quiroga, and there follow the directions to Folgoso, Seoane and the “Miradoiro Xeolóxico“.

Now for the geological part, here’s a quick explanation on what a fold is: Layers of rock, firstly laid out one over another like lassagna, get pushed on the sides and bend together. These folds are usually vertical, as the forces that make them are horizontal (tectonic plate movements).


Above: Two cases of fold formation. Below: Types of fold. Ours is the last one on the right.

Recumbent fold, if we look it up on a dictionary translates to some stuff like “has an essentially horizontal axial plane”. This happens if the forces keep pushing the rocks, as the lassagna-like folded rocks fall on top of each other, ending up with a horizontal axial plane. On the case of the recumbent O Courel fold, the forces came from the collision of two continents: Laurasia (ancient America) and Gondwana (ancient Eurasia), which formed the supercontinent known as Pangaea:

Situation of the Earth on the late Permian (260 My.). Marked with a yellow dot is where O Courel was at the time, and on red the collision border between the two continents.

The folded rocks are now visible thanks to some river action: The water has cut through the layers of rock, like a knife would cut through a cake. The fact that all the collision stuff happened 300 million years ago helps, as the erosion has had time enough to do its job.

That’s where i got the idea for the folding symbol on the background of the site!

Read more on:

I’d love to see more geological landscapes protected and explained; we are on the right track by doing it. Feel free to contact me if you want directions or suggestions for geo-tourism in Galicia, or if you want to tell me how awesome the geological landscapes where you live are. I’ll be happy to answer!

About Programming Geology: The banner


Only having a Logo to identify this blog would be boring, so what better than a cool banner to go with it? You can see it below the title of the page and on a greenish colour surrounding the main frame of the web.

I created the image on Photoshop following this nice tutorial on Design Shack. The motifs I selected for the background are, of course, programming geology-related:

On the programming-computers side, two icons: The braces, used in the code of some programming languages  (C++ comes to mind) who stands for the software; on the other side, the integrated circuit, part of every computer component, symbolizes the hardware working behind the code.

The curly braces and the integrated circuit

On the geology side, three icons: The ammonites, a recognizable fossil, serves as a call out to the palaeontologists; the geological hammer is one of the most precious possessions of a field geologist (I talked about it on a specific post about it); finally, folds represent the structural geology, the study of the ground, and tectonics.

From left to right: The geo-hammer, an ammonites fossil and folds

The folding structure used for the third symbol above is a digitalization of the O Courel syncline in western Galicia, Spain: Layers of rock stacked like lassagna were compressed until they bent like a paper sheet would. This fold was created on the time of the Hercynian orogeny (approximately 350 million years old) and again deformed during the Alpine orogeny (around 70 million years old). So, an initially upside down fold was tumbled to its side, looking as gorgeous as one can see below. You can read more on my post on the O Courel fold.

Original fold image
O Courel fold

There are many beautiful geological landscapes around Galicia, and this is one of them. I’ll be making a post about my trip there in the future, but in the meanwhile, you can read a bit more about it on the Luar na fraga blog (in spanish with well-taken photos).

I hope the symbols are to your liking! I’m open to suggestions on more geology or computers stuff. Send me an e-mail or contact me via any of the social networks using the buttons on the right side of the page. Or leave a comment below.

Mobile apps in the Field

The Field, as in the Internet. The capital letter indicates respect, admiration and so on. So for all of you field geologists, who happen to like mud on your boots and sunburns (who doesn’t!) you may find this post useful.

There are many portable geology apps, both in Android as well as in iPhone. When we go mapping on the field we like to carry loads of instruments: Compass, hammer, measure tape, HCl, sample bags, etc. Using a smartphone has at least alliviated the need to carry a camera for quick observations, but what if it could also improve on our compass and notebook? I read about this kind of apps on other blogs like Androgeoid or Un geólogo en apuros.

Geohammer and mobiles
This feels like the right array of weapons.

So, I went ahead and selected three Android apps and tested them in the field: Rocklogger, Fieldmove Clino and to a lesser extent Theodolite (as it offers less geology-related content). For you Apple fans, try Fieldmove Clino for free via iTunes.

Here is what I think about each of them:

  1. Rocklogger has a harsh interface at first, but it’s great and simple. You can easily log measurements of different types and plot them on a map. Paid version offers stereonet or KML export (for use with your favourite Geographic Information System).
  2. Fieldmove Clino has a cleaner interface, offers logging, plotting on map and even photo geotagging. Its core features are similar, with paid versions supplying stereonet and KML export.
  3. Theodolite acts as a clinometer of sorts. For the ones that do not want too complicated apps: Vertical is 0º so you’ll want to substract 90º to get the dip of your plane. No logging so you’ll have to input the data into a notebook or another app.
A) Rocklogger. B) Fieldmove Clino. C) Theodolite.
A) Rocklogger. B) Fieldmove Clino. C) Theodolite.

Be aware that Rocklogger gives dip direction as north-based azimuth and Fieldmove Clino in its compass mode gives East – West declination, so for the two images above the dip direction is approx. N 220º.

I feel the two first programs are similar, with Rocklogger requiring less clicks and dragging to log, so despite the nicer interface of Fieldmove Clino it would prove better in a long traverse.

Testing them against an old Silva compass yielded very close results, so I like the accuracy of the apps: The dip angle was the same for the three apps and the compass; the dip direction gave the same results for both Rocklogger and Fieldmove Clino and was close enough to what I measured analogically.

Here you can see the aspect of the log record in both apps, which are pretty useful to know at a glance the main directions of your lithology:

The logs: Rocklogger on the left and Fieldmove Clino on the right.
The logs: Rocklogger on the left and Fieldmove Clino on the right.

All in all, I see this kind of application as a very good partner in the field for the mapping geologist. It makes measurements take less time, and more measurements mean the small instrumental error can be mitigated (but always make sure to check with more analogical means, just in case).

Give them a try, you’ll not regret it!