On August 15, 2014, Will Richardson-Little and I started hiking toward the Grand Sentinel at 7:20 a.m. from the Moraine Lake parking lot. Our objective was to climb the normal route on the south face (4 pitches, 5.9). We had a standard rack, double ropes, and helmets.

We reached Sentinel Pass about two hours later and started our descent toward the Sentinel. Following the guidebook description, we scrambled along the scree slopes on the left side of the valley (the same side as the Sentinel). The rock was loose and unsettled. A rock the size of a tennis ball fell past me, and I should have taken this as a sign. It had rained lightly the day before, and weather forecasts called for a 30 to 50 percent chance of rain during the day. No rainfall occurred, however.

It took about 30 to 45 minutes to cross the scree slope to reach the Sentinel. After we’d completed the first pitch, between 10 a.m. and 11 a.m., we heard the sound of falling rock. A significant rock slide, lasting five minutes, occurred on the scree slopes we had just crossed, not half an hour earlier. The rock slide was 50 to 100 meters wide. Large boulders, the size of milk crates or possibly larger, were hurtling down with alarming force. The thunder, cracks, and rumbles of the slide could be heard across the valley. After the rock slide, my partner and I realized that we were very lucky. If we had been caught in that area, with nowhere to take cover, we both surely would have been killed.

Analysis

The slide was likely due to warming temperatures in the late morning and melting snowpack high on Pinnacle Mountain. The melting snow, loose rock, and wet conditions likely caused a large boulder or boulders to be released from the snow. The subsequent fall of these large rocks initiated a full rock slide. Scattered rockfall continued throughout the day, and gave us an unsettling and constant reminder of how fortunate we were.

We completed the standard route on the Grand Sentinel (an excellent climb) and descended directly downhill from the Sentinel and across the valley to return by the hiker's trail. Our alternative route was on the opposite side of the scree slopes, adding about 15 minutes to the descent.

This near miss taught us a good lesson about being aware of objective hazards near and far. When the day’s objective is a rock climb, it can be easy to get short-sighted and forget there are other, bigger hazards all around. In the alpine environment, it’s smart to get a very early start, even for a short rock climb. (Source: Eric Chow.)