FATMAP difficulty grade
The Cerro Unión is another undisputed classic of the Arenas Valley.
Starting from the Altomaipo trailhead, follow the summer road until reaching the Valle Arenas proper, and then keep to the left, heading up the Valle del Morado. While skinning up the valley, beware of rockfall and slides from the South Eastern aspects of Cerro Unión.
Once rounding Cerro Union´s Base, one must iniciate the first real ascent, turning left towards the reamains of the once giant Morado Glacier.
Do not stray from the sides of Unión, but at the same time, avoid being in the terrain trap underneath the North eastern aspects, where rockfall and wet slides are prevalent in the springtime. Once one reaches the lake plateau, one will be facing the sheer 400 meter face towards the summit of Unión.
Skinning is possible, but if the exposure is too much, we recommend booting.
At the end of the face, one has not reached the summit of Unión, which is a further 20 vertical meters away, again to the left.
A flag marks the summit. In theory, Cerro Unión holds the best snow on its south eastern aspect, which receives much wind loading.
However, the SE face is not very easy to navigate from the top, and its very easy to find yourseld cliffed out.
Unless you have a clear idea of where you are heading, we recommend sticking to the East and North East faces. The return is via the Valle del Morado, so pick up some speed for some fun surfy turns on the way back to the trailhead.