Cerro San Lorenzo part 2 - advanced base camp

So far the weather in Patagonia had been perfect and we were thus anxious to get going. The day after our arrival at Puesto Muñoz the weather continued to be perfect and we thus packed our tent and climbing gear and walked up to the end of the Rio Oro valley to set up an advanced base camp (ABC).

Carlos crossing the rocky river bed on the approach to the Rio Oro valley. The left side of the moraine front is seen above his head.











The first obstacle was a hill made by the moraine front which was easy to cross via an old path marked with cairns. We stayed right of the Rio Oro all the way to the end of the valley in which way we avoided to cross the river by foot.

View of the Rio Oro valley from the top of the moraine hill. Summit of Cerro San Lorenzo is seen in the background.












Except from a couple of big slab boulders we had to pass, the terrain was easy to navigate and we eventually were able to walk from Puesto Muñoz to ABC in just 2.5 hours.

We found a perfect spot for the tent - an amazingly flat square surrounded by millions of rocks. How is that even possible!?

Carlos at the ABC at the end of the Rio Oro valley and at the base of the mountain. Cerro San Lorenzo is seen in the background.











The ABC was located next to a hot spring which according to the Sar family is the only one in Patagonia! It was really nice to wash our feet in the warm water after walking in our hot 8000 meter mountain boots! After our first night in the ABC we learned that the ground under the tent was also hot which provided a heated floor! What a luxury!

Carlos enjoying the hot springs. Amazingly, the water had two different temperatures: the green and red side was ~40 °C and ~80 °C, respectively!

















We spent a while spotting potential routes and found two unclimbed routes being of particular interest: a snow ramp/couloir going up the North-East face (shown in green below) and a snow couloir with a steep ice section going up the Northern East face (shown in red below):

Potential new routes on the North-East (green) and Northern East (red) faces of Cerro San Lorenzo.









Albeit the North-East face route looked great it looked very difficult a the top where we would have to connect to the East ridge somehow. In the end we thus decided to aim for the Northern East face route, which also looked great as it had a narrow & steep (AI5?) ice section.

On a later trip to the ABC we explored how to get onto the glacier from the ABC. It was quite clear that the glacier had receded a lot in recent years as the front was now quite high up compared to our map - and it had even created a new lake in the valley! Basically we were left with two options:

Option 1: continue up the valley to polished slabs (seen behind Carlos), which would take us to the East ridge / North-East face via a heavily broken glacier.









Option 2: go around the lake on the right (North) side and walk up the valley seen in the middle of the picture. At the end of the valley it looked as if we could climb up a ravine towards the right to reach a col high up on the glacier. Due to steep rock going directly into the lake it was not possible to go around the lake on the left (South) side.


None of the options were perfect as the slabs were exposed to ice fall and the North side of the lake was exposed to rock fall. Luckily, the cold temperature seemed to keep the ice and rock fall to a minimum, but neither place would probably be fun to cross in the summer!

Due to lots of crevasses and the lack of snow on the low part of the glacier it seemed very difficult to pass, so in the end we decided to try Option 2 as it looked as it would take us high up on the mountain before we had to get on the glacier - hopefully we would find easier terrain up there.....

Carlos looking up at the ravine at the end of the valley behind the lake.













After dumping our stuff at the ABC we walked back to Puesto Muñoz and started to make plans for our ascent of the mountain. We were totally excited by the easy approach to the foot of the mountain, the new route potential and the great weather. Unfortunately, the latter changed the next morning, which left us with warm (i.e. around freezing point) and unstable weather for the following +2 weeks......

The mountain engulfed in clouds. After a cold and stable start, we got +2 weeks of warm and unstable weather which locked us in Puesto Muñoz.











Read the next part of the story: Cerro San Lorenzo part 3 - life at Puesto Muñoz.

Read previous post: Cerro San Lorenzo part 1 - getting there.

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