This river 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.

photos by cmontes and lperez