Captain’s Log – Entry #7: Seeking Rock Glaciers

Nathalie Cabrol (r ) and Chris Haberle, during an earlier visit, make their way up the steep slopes above the northwest shore of Laguna Negra. Credit: XenoQuest Media

by Nathalie Cabrol

I was expecting to spend today packing. We are leaving Laguna Negra tomorrow. However, Robert (Jeff Moersch’s student) wants to go document rock glaciers from up close. This is the subject of his work with thermal imaging. He also wants to plan his next step for future investigations. I have to admit that I am tired and not really looking forward to ascending again the now-named “Devil’s Slide” ramp that separates the northwest shore from the perched Echaurren Valley. However, Robert does not have any experience in mountaineering and it would be unwise for him to find himself alone on that type of slope. So, last night, we organized a party of three to reach the foot of the rock glaciers we see on the satellite imagery. Interestingly, the thermal imagery from where we are on the south shore does not seem to show any substantial difference between the rest of the landscape and where we are expecting to see the rock glaciers. We will know more once we are there tomorrow…

We have an early breakfast at 7:00 am to take advantage of good conditions on the lake. Starting around 11:00 am, winds kick in and substantial waves form. The Zodiac is still a small, albeit excellent boat. Cristian will be our pilot today since Chris is leaving for Santiago with Liam, Sandy, and Gordon. Tonight, we will be only 9 at camp, which is a far cry from the 24 we started with.

The lake is quiet as we start our journey around 8:15 am. In addition to Cristian and Robert, Carlos – our doctor – is coming with us. He is a highly experienced mountaineer in the Andes. He will be additional support for Robert if need be, and also some assurance for our climbing party of three. Cristian stays on shore. He has a bad ankle.

Devil’s Slide…It did not get any better since the other day, but maybe I did! Despite the fatigue, it seems that going up on that slope wakes me up. I feel actually pretty good, steadily going up on the central dry gully, using blocks as stairs to gain ground. I am ahead of the guys by maybe 20 meters. I brought an empty Nalgene bottle that I fill with delight on the cascading waters about two-third of the way up.

Robert is doing an excellent job on his very first ascent. Carlos is not too far away from him and both advance with good assurance. Now comes the wall (well, let’s say the even-steeper-part-of-the-same-wall segment of that slope). I find my way in the wet ground, where my feet sink, giving me a bit more footing than on the slippery rocks.

Finally on top. It takes another 5 minutes for Robert and Carlos to join me. I give a high five to Robert who has a big smile pasted on his face. These are the kind of things that allow one to look back and have a sense of achievement. He will remember his first ascent, at least for the next 2-3 hours. I am very sure that this memory will be soon erased by the descent that is waiting for us on the way back. I do not mention it too much for now but he is a clever guy, and I am sure he already has a good sense of what’s in store for him from the effort he needed to put in to get up here.

Station Lake, a potential biological treasure-chest waiting to be opened. Credit: Nathalie Cabrol

The Echaurren Valley is as welcoming as last time. We stop near a small stream for a 10-minute break after our ascent. What is not to enjoy here? The banks of the little stream are covered in low, yellow and white flowers, whose smell fills the air. We have made good time, and that means that we will have time to reach at least the foot of the rock glaciers. We are on the move again. Geology lessons for Robert as we pass by striated rocks. I stop on the small promontory to show Station Lake to Robert and Carlos. It lies 100 m below us. While we are watching the stream cascading in and out of the lake, I am thinking about Edmond’s stream gauge that is now logging water speed and discharge. We leave.

The walk in the valley is comfortable. We have to climb a couple of low ridges, left behind by Echaurren when the ice descended that low. Reaching the top of the second ridge, we need to make a decision. According to the satellite imagery, we have two rock glaciers about 30 minutes away from us, one to the right, and one to the left. We head for the left one, which means gaining some elevation to avoid traversing a sea of large blocks. That still requires some effort. Walking in moraine material is not exactly the best way to make fast progress but for now we have no choice. The almost three weeks of heavy duty work and diving are starting to catch up with me, and Carlos and Robert need a break too. Time to stop for another breather, and for a good sip of that clear mountain water and whatever is on my food list. I am glad to see it is cheese.

We are now close to the foot of the promontory we wanted to reach and have time. The rock glacier should be somewhere near, in theory. We sit on rocks. Instinctively, I look down to evaluate the rock diversity that surrounds us. This is when I realize that something is different. On our way here, we have observed chalcopyrite, many other iron oxide minerals, mineralization on rocks but that is different. Scattered around us, pretty much everywhere my eyes can see on that basin are varve deposits. Yes, varves! Sedimentary layers. We found the sedimentary remains of an ancient lake…

The story unraveling in the book of stone carved in those deposits is telling. The lower (older) layers are on average substantially thicker, whereas the upper (more recent) layers are much thinner with still regularly spaced thicker layers. The discharge of whatever stream that entered that lake seem to have changed drastically over time, losing its ability to transport larger grains. The recent larger layers could be related to exceptional years but their regular spacing has me thinking that we are dealing with a cycle. It could be El Niño for instance, but this is pure speculation just looking at the sedimentary rocks. The only thing I can say is that apparently the competency of the water regularly got a bit higher than average. This is well in agreement with what is known of the climate history of the area. The varves also suggest that this lake must have been closely (spatially) connected to the Echaurren glacier.

While Carlos and Robert are looking at a large dead insect in a hole in a block of lava, I am scouting around. We should be on top of that rock glacier but all I can see are rocks and dust. No sign of interstitial ice, no indication that anything is here, no water. If anything was there, it is gone. The satellite image we looked at must have been a couple of years old at most. That confirms my finding on the other side a few days before. I still take Carlos and Robert there. On that side, though, streams are abundant, which  shows that there is flow below the rocks. We will have to climb higher to find the origin of those streams but that will be for next year’s field campaign. As I predicted, Robert didn’t fail to notice how hard the ascent of Devil’s Slide was and, wisely, wants to keep some energy for the descent. Thus, we start our way back. I choose to follow the stream cascading down to Station Lake as our guide to the central valley. When I see the moraine ridge, we head west and climb a 500-m wide pile of blocks. I cannot help looking down than forward. Minerals glitter in the sun. I find two very nice specimens that I pocket. Robert is laughing. We have known each other for only a few days and he tells me the same thing my grandma told me when I was a kid, or close to. He says: “My only photos of you are with your rocks”. My grandma was always saying that I was always either looking up at the stars or down at the rocks but never in front of me. Well, guess what? You were so right, grandma…

It is time to focus again. My right knee is bothering me. I suppose I cannot blame it too much. I dislocated it 15 years ago and Devil’s Slide was bound to revive that memory. I am taking a head start because I am planning to be slow on the way down. I am also opening the way. The secret is to block any dark ideas that can come up in one’s mind about being on a 50 or so degree incline, on slippery rocks, and with a temperamental knee. I know, that’s sounds like a lot, but in fact, it produces the right effect. I am taking my time and, although extremely difficult, this descent seems less overwhelming than last time. One step at a time. I regularly look up, higher in the slope. Carlos and Robert are making steady progress. I reach the beach and Cristian about 15 minutes before them. Robert has been stellar and when he finally gets to the shore I tell him that he is now officially a field geologist. He laughs again but I have to admit that this descent would be scary for any experienced mountaineer. He did extremely well.

We don the Mustang suits once again and we are on our way off the northwest cove with the Zodiac. As expected, the waves are now splashing around us and will until we pass the promontory. Something up there has caught a ray of sun, which gets my attention. This is our meteorological station. I can only think about what its wind gauge is showing right now…After the promontory, the lake is quieter but not calm. The journey back is a bit rough but eventless in the end, fortunately.

As the hours pass, we are getting closer to wrapping up our first field campaign. Our first encounter with the lakes and the glacier have led to more questions than answers, and this was to be expected. The glacier is retreating and the rock glaciers as well. This is worrisome. On the other hand, there is definitely an abundance of life in Laguna Negra. We still do not know about Station Lake. Does abundance translate into biodiversity? That is one of the key questions. The other one is how these organisms are adapting to a habitat that is changing so quickly. Hopefully the coming two years will bring some answers.


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