A transect across the northern Andes that students can complete mostly by foot/boat.
Dec 2016: In this transect we were blessed by perfect weather and river levels. A swollen Rio Negro, scary as always, but a really fast and easy boat ride. Vegetation, though, was thick as rains have returned to this part of the globe, so the geology was not as spectacular as last time around, during El Niño year. Rio Claro and Samaná were also big, and the outcrops near Pantanillo were better than last year.
Again, with a very large number of students we crossed by foot and boat a segment of the northern Andean orogen.
Dec 2015: As the now usual corollary to the Structural Geology and Tectonics course, we completed a northern Andes cordilleran transect at ~ 5°N. It is always a spectacular field trip. This time, the El Niño drought, and a few forest fires had cleared the vegetation, making the trip much more spectacular.
A Large Group
Student enrollment was over 80 this year, making this the biggest field trip I’ve ever run, and also the last one this size. Two full buses on the roads, and more than 16 boats on the river were needed to carry all the students. The camp sites looked like refugee camps, and food and logistics were very trying. We had the fortune of having lots of good-spirited TA’s, and of course, Carlos’ and Rafa’s professional logistic services.
This time we started from Nemocón, and the same day drove down to Tobia, where next morning we started our hike along Rio Negro, unseasonably calm because of El Niño drought. What was going to be a 15km geologic hike from Tobia had to be cut short due to the sheer number of people on the field stations. We couldn’t simply evacuate them fast enough. Next day we started from Utica, walking 19 km to Guaduero, this time instead of using stations, we separated the group and worked much better. Thank you Carlos. Tony the dog happily did all this hike. We spent the night in Guaduas and next morning got on to the boats in Dindal, rafting all the way to Los Colorados dam. After a few delays and a broken bone, we went to Rio Claro spending two nights. In the way to Abejorral, we did one stop in beautiful Samaná river, and then did only two days in the axis of the Central Cordillera. Not nearly enough to see it all. We had to simplify with one group down near the Armas river and the other one near Pantanillo.
Dec 2014: In rainy early December we (all 70 of us) arrived in Utica to see the Rio Negro surprisingly low and calm. Nothing like last year’s black, menacing river. This time, however, we decided to do the transect by foot. It took us all day, a few students got lost, dehydrated, but we made it back to Utica the same day. The views of the structure are superior to those we got by rafting. Next day we took the buses and made stops along the new Ruta del Sol highway. The river transect from Córdoba to Los Colorados though, seems to yield better observations. Highway stops are safe, there is a wide shoulder and good visibility. An option in the future would probably be to do one half by foot, and the other by boat.
Next we spend the night at Rio Claro where we did the transect in the morning, skipping the Rio Samaná stop. In the future we should spend two nights in Rio Claro to more clearly see this flank of the Cordillera. We arrived in Pantanillo and spread out in groups, this time with the benefit of the road being open all the way to Rio Armas. One of the groups got lost in the westernmost transect, thankfully, all support systems worked, and the group of very tired and thirsty students finally arrived to camp after 8pm, safe and sound.
Nov 2013: The Rio Negro cuts a spectacular canyon across the western flank of the Eastern Cordillera of Colombia. We hired “Dosis Verde”, a rafting operator to take us down the deep gorges where the Rio Negro boils and turns, cutting and polishing the walls of the canyon. This is probably the best site to see the actual structure of the western flank of the Eastern Cordillera. This November, Rio Negro was seasonally swollen, black and menacing. The B/W photo to the right shows the river in August, when it seems calmer and placid. In reality, its waters are more treacherous when low.
We started rafting west, in the segment between Utica and Guaduero, where the percentage of exposure is almost 100%, with vertical walls in the northern side in excess of 500 m. Several structural levels can be studied along this section. The river then turns right, and follows the axis of the Guaduas syncline to the north, only to turn left again and cut another canyon after the town of Córdoba. This canyon is wider and not as deep, but just as rewarding, with multiple structures beautifully exposed in a very short distance. The transect stops short of reaching the Magdalena river, because the natural flow of Rio Negro was regrettably severed by Los Colorados Dam.
We all spent the first night in Utica, and the second in the town of Córdoba, both places badly battered recently by flash flooding, and still in the process of recovery. Some segments of this transect can also be done by foot along the abandoned railway, a sad reminder of Colombia’s lack of commitment to railroad transport.
Dec 2013: In this leg of the trip we kept the focus of our last two trips, seeking to place our observations in a cross-section. The first day we travelled from Bogotá to Rio Claro, where we looked at beautiful deformation structures along the spectacular Rio Claro Canyon. Rio Claro carved its canyon in pure marble. Along the way, we stopped at the Capira Lookout point, the best place to see the Magdalena Valley, and the frontal faults of the Cordillera Oriental. When we got there, the mist was so thick, we could barely see each other. We got to stretch our legs in this long trip, at least.
After Rio Claro, we stopped at the bridge over the mighty Samaná river, and made a few observations before we continued our journey west. We arrived in Pantanillo (gigapan here) after dark, and having witnessed our very skilled bus driver make turns in really tight corners. We stayed in Pantanillo and travelled every day in all directions to try to understand the structure of the region. We were counting on one road to take us down about 1200m to near the Cauca river. When we got there, we got the bad news: road was closed due to huge landslide (watch the video here). So we walked. A lot. Some days we walked over 16 km to get to the outcrops in the lowlands.
Our hostess in Pantanillo was the wonderful Hermana Catalina, who treated us with much love. We were fortunate to land there. Every night we discussed the day’s observations and how they fit in the tectonic scheme of the orogen.