In early November, Rob Smith and I traveled to Cerro San Lorenzo (3,706m), Patagonia’s second-tallest peak. While the Chaltén massif to the south is about ease of access to amazing climbing, San Lorenzo is about big adventure, with difficult unclimbed walls. [See AAJ 2009 for more information about San Lorenzo.]

On November 10 we hired a pickup from Gobernador Gregores into Perito Moreno National Park and got dropped off at the end of the road. It then took three trips by foot over three days to haul all our gear and food into base camp, an old hut known as Puesto San Lorenzo. During our three-week stay we did not see a single other human, although we did see tons of guanacos and fresh puma tracks nearly every day that we hiked in the lowlands.

Although our camp was quite close to San Lorenzo, we could only see the mountain a handful of days, and on clear days the summit remained cloaked in a lenticular cloud. There were two 15- to 18-hour periods of actual good weather during our trip, neither of which we were able to capitalize on. The vast majority of our time was spent hiking with heavy backpacks and navigating the best access to various objectives. There are no trails in the area, and we waded no fewer than 19 river crossings. There is good bouldering near base camp, but it requires wading through a thigh-deep river to access, and it rained nearly every day.

For me, the most appealing objective in the San Lorenzo massif is a massive rock tower at the far southern end of San Lorenzo’s south ridge. It may be the most difficult unclimbed feature in Patagonia. The east-northeast face of this formation is ca 1,000–1,300m. There are two summits, of which the west is higher. The downside is that the rock is lower quality than in the Chalten area.

November 20 was the first of our two periods of good weather, and we made an attempt on this large tower. From a bivy on the flat glacier below the tower, we gained about 600m of elevation in terrible snow to reach the bergschrund, arriving just as sunlight hit the east aspect. Unfortunately, our chosen line started up a large east-facing gully system and it became clear that it was too hot to climb such a terrain trap. We descended back to our bivy and proceeded to pass the best weather day of our trip by taking naps in the tent. We did, however, watch an enormous number of avalanches that day, easily reassuring us that we’d made the right decision.

The forecast was for significantly worse weather the following day, and we were running low on food, but we decided we ought to try to climb something, as it might be our only chance (and this turned out to be the case). We turned our sights to the sharp spire just below and east of the main tower. It is dwarfed by the larger spire but would look proud in most other surroundings. We left our glacier bivy at 2 a.m. and kicked steps up a roughly 500m approach buttress. We climbed the spire via what can be roughly described as the east ridge—really more of a face than a ridge until the last few pitches. The middle of our route follows an ice gully, which was unfortunately decomposing into slush, so we were forced to climb harder variations on the rock. The last three pitches to the summit were only 5.7–5.9 but also the crux of the route due to poor rock. It was cold, windy, and cloudy the entire day, with Cerro San Lorenzo enveloped in its usual lenticular cloud cap. The summit of the spire was spectacularly sharp, and we tagged it one at a time.

The descent took some time, as we rappelled all but 50m. We finished the rappels shortly after dark, descended the approach buttress, and made it back to our bivy roughly 22 hours after leaving. It seemed slow for the size of the objective, but the poor rock required careful climbing. I estimate the technical portion of our climb was roughly 500m. We climbed 14 pitches on the ascent and made 12 rappels. We named our route Romance Explosion (500m, 5.10 M5 R A0) and the spire Aguja Antipasto.

After two days at base camp, we set our sights on the South African route on the east-northeast ridge of Cerro San Lorenzo. It seems like the classic of the region and perhaps could be considered “the Cassin of Patagonia.” It looks to have almost zero walking terrain, yet minimal technical difficulties. It is big, serious, and takes an aesthetic line straight to the summit.

On November 25, the day before a promising weather window, we hiked from base camp to a very nice bivy on gravel just below the South African route. It was ballistically windy, and we started to think less about climbing and more about the possibility of our tent exploding. We left our bivy at 12:30 p.m. on November 26. Within 30 minutes all the stars disappeared and the wind picked up. We broke trail for about 600 vertical meters from our bivy to the bergschrund, and during that time the wind became more constant and it started to snow, heavily at times. For the second time on our trip we bailed at the bergschrund, and again did not regret it, as San Lorenzo ended up socked in all day.

We owe big thanks to Rolo Garibotti and Seba Perroni, who helped us with logistics and weather forecasts throughout our trip.

– Colin Haley, USA