I meant to write this ages ago, but life got away from me. Better late than never. In may we went on a 10 day island hopping field trip in the Cape Verde Islands, which were created by hot spot volcanism. There is still a mantle plume down there, and it sits under the islands of Fogo & Brava.
Though Island hopping sounds exciting and very holiday-esque, it was a really exhausting trip. We would spent on average 2 days on one Island, travelling to another island every second day, before or after a full day of hiking. Though a beautiful and fascinating field trip, I was so exhausted by the time I got to Lisbon I spent most of my weekend there reading in the botanical gardens.
I became the designated translator on the trip. Since I speak French and some Spanish and the locals spoke a mixture of French, Portuguese and Creole, we managed to communicate in some shape or form on each Island. Which was important when it comes to telling the drivers not to drive off and leave us stranded in the middle of nowhere.
The hiking itself was rarely all that bad but the heat was intense on some days. Hiking, working & thinking in plus 30 degrees with a heavy bag on your back gets exhausting. So, lots of snacks and sneaky lunch naps.
The islands consist of beaches and Volcanos. My kinda place. Those two pimples there are Volcanos. If you had any doubts.
High lights of the trip involved a half day at the beach, where we went swimming in the Atlantic for a few hours, followed by unintentionally hiking a volcano in flip flops. Our professor kept saying ‘we’re just going over there, you don’t need to put your hiking boots on’.
Managed to get to the top, spot a couple of hauyne (enjoy trying to pronounce that) crystals and then back down without breaking anything. I don’t advise hiking a volcano in flip flops. It’s a really stupid idea.
On Santa Antao we saw some really exciting dykes. To those not familiar with certain geological terms, the dykes I am referring to are igneous intrusions. In the first photo you can see how the dykes that feed volcanos from a magma chamber behave. Almost like fingers, that are reaching out along the planes of weakness. When things go well, one (or more) of the feeder channels can reach the surface, resulting in a volcano erupting on the surface.
The edges of these ‘channels’ are solid, and they behave as a conduit for the magma to travel. Like liquid through a straw. You can really see that in the second photo.
Now that dyke is pretty freaking exciting to me. You can see the walls of the dyke in contact with the country rock (surrounding stuff). From what we could see, the magma eventually stopped feeding the dyke, so there was just a cavity. Later pyroclastic eruptions then filled up the cavity in successive layers.
As dykes go. Yowza.
We got to see the famous ‘Darwins Profile’. I forgive you if you haven’t heard of it. I can’t say that I found the profile itself excessively exciting, however I got to see a side of pillow basalts that I had not seen before. The beaches were nice too.
Pillow basalts don’t look like pillows, as the name implies. rather they are tubes. At Darwins profile we got to see the pillows in 3D. Pretty perfect rocks right there.
However, the best part of the whole trip was definitely when we visited the Pico do Fogo on Fogo Island. This was our first view of the Pico.
All that broken up land you see if lava. At this point we were standing within a Caldera which had formed about 10,000 years ago. Then over the last 250 years that pico formed in the middle. Within the Caldera, there was a town called Portello. It was entirely covered in lava over a period of 2 days, during a recent eruption on December 5th & 6th, 2014. The eruption continued from November 2014 until February 2015.
Our driver used to live in Portello. Since I was one of the only ones who understood him, he kept on saying to me how terrible and horrible it was. Repeatedly. Every once in a while he would call my professor over to show him something. He spent most of the time looking at the town with his hand over his mouth, shaking his head. Eventually he pointed down into a valley and said ‘that is my house’.
We couldn’t actually see anything more than the roofs of the houses. The lava covered everything but the tops of the taller buildings.
Over the years I have had people tell me so many times how my degree is boring, merely an ‘arts’ degree, not a science. How on earth could rocks be interesting? Well, in this case, geologists saved lives. A group of geologists had been monitoring the volcano for some years, and before the eruption occurred they managed to warn the entire village and evacuate so that no one was hurt. There are volcanic observatories around the world monitoring volcanos in case they might erupt.
The more we understand about natural hazards, the more deaths caused by them can be prevented. Right now, what we know is a drop in the ocean. There is just so much work to do.
When I heard about the eruption initially I was so excited. I hoped that it was still erupting when I got out there. I had read that a village had been destroyed, but all I could think about was seeing my subject in action. I found it difficult to reconcile my excitement of the eruption with what I saw in that village. I love what I do, and when I see my subject in action I get so excited. It’s a puzzle I need to figure out. In the face of that destroyed village, my excitement felt almost crass. At the same time, when I got into the field work for the day I cannot say that my excitement was in any way diminished. So, I hope that the work I will do in the future might contribute to our understanding of igneous activity. The more we understand, the more deaths can be prevented.
The 2014/15 eruption occurred on the flank of the volcano, as a parasitic vent. My partner and I hiked the volcano trying to access a fissure that formed in the 1995 eruption. In the lower photo, you can see a small scar on the far left. That was the furthest we got. It was too dangerous to go any further towards the craters.
If you look closely you can see two craters, both with yellow colouring the rims. That yellow is native sulphur. We found some bombs covered in native sulphur around th 1995 vent and now I have a bunch of rocks covered in sulphur stored away at home. The dark brown/black stuff on the bottom of the vents is fresh lava flow, which covered an older lava flow from 1995 (the brown colour).
What I found unbearably awesome was the fact that the lava was still hot. it was deposited a few months before we got there, but it was too hot to sit on at times. the heat itself moved in waves. When eating our lunch, we were happily sitting on the lava when all of a sudden it got so hot I yelped and jumped up.
Not only was their a lot of heat, the craters themselves were still degassing. That was why we couldn’t approach any closer. Those gases were toxic, and we would have suffocated had we gone too close to the craters.
I learnt a lot on this trip. Getting to see such young lava alongside older eruptions taught me a lot. I’m pretty excited about it still. I think it made me better at what I do.