Since our departure from Villa O'Higgins, we had crossed a relatively homogeneous geological environment: an area where the metamorphic rocks have been distorted and transformed and where the analysis of the landscape was difficult. Metamorphic geology is not our specialty and we found it difficult to extract useful information from outcrops, and we had to focus more on the very awfull road rather than on the rocks.
That day, we had to climb the Portezuelo Rio Cañon which separates the region of Lago General Carrera and the region of Cerro Castillo. We climbed without particular difficulties and we started the descent on a comfortable road. Suddenly, at a curve, I jumped on my brakes and stopped in front of a beautiful outcrop. In contrast with the rocks we had seen so far, the rocks exhibited hexagonal columns that are typical of volcanic rocks. It was a volcanic flow, probably andesitic. After a short break, we went on.
Half an hour later, it was lunch-time, and we got our traditional bread-thuna-dulce de leche-coffee lunch. But when I turned my head to get the thermos bottle, I figured out about the nature of the gravels around us. "You saw the gravels?" I asked Caroline. "These are pumice stones." The pumice stones are very porous volcanic rocks, ejected during violent volcanic explosions. Looking around us, we then realized that the floor and the side of the road were covered with a layer of pumice. Even some laying dead trees were covered with a layer of 20 cm of pumice. The region is entirely covered! Where did these pumices come from and what were they doing here?
After lunch, we continued our descent and stopped in front of an extremely interesting outcrop: we could distinguish several layers of pumices, in white on the picture, intercallated within blacks levels. Looking at these latter, we could distinguish black holes, probably the traces of ancient roots: these levels were paleosoils. Each level of pumice corresponded to a volcanic eruption. The presence of palaeosols between each level of pumices shows that the vegetation has had the time to develop between each eruption, i.e. there was a significant time lap between each eruption. The presence of traces of plants is important to date the eruptions. Indeed, it is possible to sample these ancient roots that have grown within a level of pumice and to date them using the 14 carbon. The age thus obtained would give a minimum age of the volcanic eruption that produced the pumices. However, the most superficial pumice layer did not show any trace of colonization: the last eruption was very recent!
Fifteen kilometers later, we followed the valley of the Rio Ibañez and we ended up next to a forest of dead trees. The whole forest was dead, and the atmosphere was gloomy. The black clouds were heavy and contributed to this special atmosphere. What happened in this valley? Thanks to a commemorative plate hanged on a rock, we finally found the answer to all our questions: in 1971 and 1991, the Hudson volcano, some tens of kilometers west, erupted. Everything now became clear: the recent volcanic deposits came from the Hudson volcano, hidden in the clouds. While we hadn’t found any trave of volcanism so far, we are now in the Andean active volcanic arc.
Later that day, we stopped at a small campsite in the farm of Rosa, a small charming woman who offered us fresh eggs, milk and other home-made products. We began a very friendly discussion with her, until the topic turned to the Hudson volcano. The face of Rosa became suddenly changed: "Nunca Mas!" (Never again). Then she described, the fear in the eyes, the circumstances of the eruption. "At midday, the sky was completely dark and the night came. A terrible noise was heard, as if all the surrounding mountains collapsed. The ground was shaking continuously. A layer of more than 30 centimeters of ash and pumice stone fell, killing all animals and burning all plantations. We lost everything .. For 10 years, nothing has grown on the sterile soil. In the recent years only, the grass grew and it is again possible to cultivate a garden. " We were at more than 50 kilometers of the volcano ...
Then she repeated: "I do not want to experience anything as terrible as that in my life." We wish her that she indeed will not. But in our geologists minds, we were affraid of the worst for Rosa and her small farm. We knew that the Hudson volcano will erupt again and destroy the entire region. However, it is impossible to know when this will happen, and we hope to Rosa that it will be as late as possible.
Then she repeated: "I do not want to experience anything as terrible as that in my life." We wish her that she indeed will not. But in our geologists minds, we were affraid of the worst for Rosa and her small farm. We knew that the Hudson volcano will erupt again and destroy the entire region. However, it is impossible to know when this will happen, and we hope to Rosa that it will be as late as possible.
