by Nathalie Cabrol
It has been taunting us for so many days now and the time has come to pay a visit to the Echaurren Valley. The work with the Lake Lander is proceeding as planned, helped by the presence of two engineers from YSI, Fred and Jim, who spent three days with us. The sonde is calibrated, and we have data. The webcam has been installed on the probe, which means that it is spying back on us in camp, sending us the first image of our domes. The biologists have collected and processed a large number of samples. The project is running as smoothly as possible, therefore I can grant myself a day of pure exploration.
Early Friday morning, I leave with Chris and Gordon (who wants to film us). After donning our Mustang suits, we get into the Zodiac. We are towing Margaritaville – that’s the name of our second boat, which is loaded with equipment. The boat’s name is inherited from the fact that its propeller speed would probably make it appropriate only to stir a Margarita. The lake is calm. Because we can only use an electric engine, the expected time to travel the ~ 4km that separate us from the northwest shore is about 45 minutes. That gives us plenty of time to admire the landscape, including the majestic glacial valley of Echaurren that enters Laguna Negra.
As we are nearing our landing site, we can see underwater caves to the east, and the roar of a cascade becomes more present each moment on the west side. I have the feeling of entering the “Lost World.” This feeling will become even more real as soon as we get to shore. What an amazing landscape. From the boat, we can see cascades flowing over thick moss, cutting the fractured and fragile volcanic rock. There are numerous dikes, caves, and strange erosion patterns. Even stranger though is the apparent lack of glacial erosion marks. The shape of the valley is evidence that the glacier came through here. Yet, its marks have faded away, possibly erased by the abundance of water that flows here, and post-glacial fill.
Our landing is tricky: on one side, there are too many macrophytes for our propeller, and on the other, too many large blocks for comfort. Finally Chris, who is piloting the boat, squeezes the Zodiac in between two blocks and we are on shore. There are large blocks everywhere, but this is not really what captures my attention most. From the satellite image and DEMs, I suspected that the ascent to the upper plateau would be “interesting.” I was right. In front of us, we have a wall about 100 m high, whose slope starts around 42-45 degrees. In the last third of the ascent, it turns into an almost 50-degree overhang. Going up is not so much of an issue. I am used to Andean volcanoes whose slopes are comparable. Here, you forget the notion of slope of equilibrium and you just focus on the goal, the summit. As we go up, we encounter lush cascades of fresh water pouring over thick moss. This is the best water I have drunk in a long time. Flowers of all kinds are arranged in a multi-colored carpet. This is simply amazing.
We make it to the top. The valley floor is typical of glacial valleys. There are still morainic bars left and the valley floor is made of light-toned, very fine material. Finally, as we reach the opposite side of the promontory, I see the first block that clearly shows glacial striations. We have only a short hike to the top of a small hill. From there, we see it: Station Lake. I gave the lake this name when I was still at Ames looking at satellite images and trying to identify potential sites for the deployment of our experiments. The bad news is that it lies about 100 m below us. The excellent news is that it is obviously a lake that is still very much connected with the Echaurren glacier. Its color is milky blue. From the moment I see it, I know that we are going to stay at Laguna Negra for the rest of the project.
Our concern with Laguna Negra was its great transparency. With Station Lake, we now have a complete system for our project: The Echaurren glacier, its downstream part composed of a debris-covered glacier, then a rock glacier, melt water coming from underneath the rock glacier base that channels into the valley. This water ponds into the 200-m large basin that forms Station Lake. The outlet flows downstream into another small basin, and then falls into Laguna Negra in the cascade we saw while arriving on the boat. The mixing between the waters from Station Lake and Laguna Negra is characterized by the same milky blue water over a relatively small area, and this water is rapidly diluted into the larger transparent lake.
We decide to split up. Chris will go to the lake and leave the boxes containing the stream gauge experiment he will deploy on Sunday. Meanwhile, I will make my way to the base of the rock glacier about 30 minutes away and deeper into the Echaurren Valley. I want to collect water. A few days ago, we had a discussion with Ruben who studies the impact of deglaciation in the Alps. He told me that the water from the rock glaciers there is characterized by a high abundance of nickel, regardless of geological formation. Sampling here is therefore very important. If we were to find similar results, we could hypothesize that we are confronted to an issue of possibly global, rather than regional scale. As I move up the slope, the algae and vegetation in and around the stream look healthy, though. This is a contrast with what Ruben was showing on some of his slides. Hopefully, we won’t find any nickel anomaly here.
It is really a pity that our time is limited. We have to keep an eye on the weather. For the past three days, we had afternoon thunderstorms starting 4:00 pm and winds descending over the lake. We need to leave the northwest shore at 2:00 pm at the latest. I still cannot help it. I look on the ground, which is glittering with minerals reflecting the sun. There is an abundance of hematite, for sure. I have to move up. I reach the base of the rock glacier shortly before 1:00 pm. Water surges underneath the rocks in intricate ways. There are probably many underground channels below those rocks.
A loud rumbling freezes me. By reflex, I look up. This sound is not good news. There is an avalanche higher up. I am well protected where I am, so I wait. I contact Chris by radio. He heard it too. It is “wait and see” for a few seconds. I still have in mind this meter-sized boulder that came at me at day-break on the slope of Shasta 10 years ago in the Californian Cascades. I still can see it turning on its axis several times per second. I had to wait the last second to duck as it was tumbling down erratically on the slope. I have been really scared only a few times in my life, but that was one of them. So, I duck and wait. The sound dissipates. It is safe to continue. I have my samples and I know that I am running late. Chris is already at our meeting point on the promontory. I tell him to descend and prepare the boat. Clouds start to accumulate. The water samples make my backpack heavier, but overall, the way back to the promontory is short enough. Now, I am on the overhang valley, looking down 100 m to the landing where Chris and the boats are waiting. Going up a couple of hours before was not such a big deal despite the slope. Going down is suicidal.
I have to forget about the insane gradient and focus on where to put my feet. My poles have become an impediment so I keep them in one hand. The load in my backpack is pulling me backward. That’s not good news. This descent is simply dangerous, and I know what dangerous slope means. I had plenty of those on the volcanoes. This one is nasty between sheer rocks made slippery by the cascading water, the loose blocks, and the very fine material where rodents have made their burrows. It takes me almost 20 minutes and a few close calls to finally get to the boat. At this point, I am pretty much exhausted. Still, I am there in one piece and this is all that counts. Chris also had some adventures going down, sliding on slippery rocks. I tell him that there is no shame going down on our butt. It is always better than to go head first. On that, we agree.
We don our mustang suits and are back in the Zodiac. I cannot believe the size of the waves this lake can generate. We have a very rough departure from shore and for about 20 minutes, it seems that our little electric engine cannot do much against the wind and the waves, especially with Margaritaville in tow. We are being seriously splashed in the Zodiac. And then, as soon as we pass the promontory, things completely change. The lake is almost a mirror again and the water calms down.
Making our way to our camp landing, we are acquiring bathymetry. For now, our deepest point is close to 290 m. The bathymetric map is coming together. We still have a lot to cover, but for now, most importantly, we have documented the region where Planetary Lake Lander should be deployed. This data will help the engineers decide on a mooring point in an area of scientific significance for the project.
It takes us about an hour to reach “Base Camp Landing,” our landing area near camp. The rest of the crew is waiting for us on the small beach and helps us unload the boat. We have samples and photographs. The reconnaissance of the Echaurren Valley, and the discovery of the glacial sediment load in Station lake has helped us to reach a major decision for the project. We have everything we need in the Laguna Negra region to achieve our science objectives, and will stay here in the coming years. I am also thinking about moving camp from the south shore to the Echaurren valley next year. That will require yet another level of logistics, and most definitely a helicopter.
The mood is upbeat tonight at camp. After dinner, we discuss the plans for the last week at Laguna Negra. That includes the “need list” and the “wish list.” Considering our progress, I am confident that we will be able to complete our wish list as well. After dinner, I meet the engineers in the “Robo Dome.” We line up the science objectives, possible mooring points, and the bathymetry. After weighing the pros and cons of several locations, we come up with the operation site for Planetary Lake Lander and its twin sonde for the next three months. The transfer of PLL from Launch Point to its mooring position should happen tomorrow, and will mark a great achievement for this year’s deployment, as well as a phenomenal achievement on the part of the engineering team.