Dave Anderson, Steve Herlighy, and Jamie Selda (USA) and Nacho Grez (Chile) spent 27 days in the Avellano Valley, 80 miles south of the town of Coyhaique. Their main objective was a striking unclimbed granite wall, the Avellano Tower. The expedition was self-supported. Starting on March 13, 2004 the team began ferrying 1,000 lbs. of food and gear toward the Avellano Towers; they eventually hiked a total of 398 miles in and out of the mountains. Base camp was established near treeline at the base of the 4,000' Avellano Massif. The weather was unstable, even for Patagonia. The expedition experienced rain or snow at least part of every day they were in the mountains.

The climbers took advantage of the few hours of good weather they did receive. On March 20 the rain stopped for 14 hours. Climbing in two rope teams, the group ascended steep snow and rock to gain the north col of the Avellano Massif, then traversed across the west face. On the south ridge the two teams combined and reached the summit of the Avellano Tower just after sunset. They spent the night rappelling and downclimbing, reaching base camp as the next storm moved into the valley. They named the route the Conquistador Ridge (IV 5.10 AI3).

After nine more days of rain and snow, the clouds lifted for 23 hours, allowing Anderson and Selda to attempt a direct line up the 2,500' northeast prow of the tower. The climbers navigated through a cracked-up hanging glacier to reach the base of the route. Unfortunately, the storms had encased the cracks with snow and ice, slowing their progress. After climbing 1,000' (5.10 A2), the pair was forced to retreat, as a new front blew in. The temperatures plummeted, and the rain turned to snow, forcing the climbers to pack up their base camp and hike out before the approaching winter made them permanent residents of the mountains.

The Avellano Valley offers a wide variety of objectives: snow walk-ups, low fifth-class ridge traverses, free-climbing on fine-grained granite, alpine snow and ice, and steep big walls. The mountains in this area are not subject to the extreme winds of other areas in Patagonia, but the valley does receive abundant precipitation

The expedition received generous support from the Mugs Stump Award, The National Outdoor Leadership School, and the Mazamas.

Dave Anderson, AAC