Grand Sentinel Near Miss (Rock Slide)

Grand Sentinel: Rock Slide Near Miss

Rock slide area apparent in light grey band on scree slope (mid-August 2014)

August 15, 2014

CAUTION: ROCK SLIDE HAZARD ON SCREE SLOPES APPROACH FROM SENTINEL PASS LATE IN SUMMER SEASON TO GRAND SENTINEL

My climbing partner (35M) and I (29M) started our hike towards the Grand Sentinel at 7:20am from the Morraine Lake parking lot with the objective of climbing the standard 5.9 route.  We had a standard rack, double ropes and helmets.

We reached Sentinel pass about 2 hours from the parking lot and started our descent across the scree slope towards the Sentinel.  Following the guide book, 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 loose rock the size of a tennis ball had fallen past me, and I should have taken this as a sign.  It had rained lightly the day before and weather forecasts called for 30-50% chance of rain during the day, no rain fall occured on the day however.

It took about 30 - 45 minutes to cross the scree slope to reach the sentinel.  After the first pitch, we became aware of the sound of falling rock across the scree we had just passed.  It occurred between 10am and 11am.

A significant rock slide lasting 5 minutes occurred on the scree slopes we had just crossed not half an hour ago.  Rock and debris from high above tumbled down the slope, pushing the scree down as well. Large boulders, sized up to a milk crate (or possibly larger) were hurling 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 we had dodged a bullet. If we were caught in the rock slide area, we would both surely be dead with nowhere to take cover.  The slide occurred in an area roughly 50-100 m wide.

The slide was likely due to warming temperatures in the late morning, and melting snowpack high on Pinnacle mountain. The wet 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 rock fall continued throughout the day, and gave us an unsettling, and constant reminder of how lucky we were (https://www.youtube.com/watch?v=wsPt-YjGnU8)

We completed the standard route on the grand sentinel (an excellent climb), and descended directly downhill of the sentinel into and across the Valley to return by the hiker's trail, on the opposite side of the rock slide scree slopes.  The first two pitches were 5.easy. The 3rd pitch of 5.8 was sustained up the crack and across left of the roof (one piton at roof). The last pitch, although rated 5.9 has one crux move, with the remaining pitch in the mid-5 difficult.  An excellent climb, on stellar rock.  Two pieces of gear were encountered - a stuck X4, and a very questionable dyneema sling half-way up the 5.8 crack. The sling is not to be trusted.

All climbers are advised to take the hiker's trail on the opposite side of the valley from the Grand Sentinel on approach and return, especially late in the summer season.  Early in the season, it is possible that snow conditions are stable and settled high on Pinnacle, but the risk of rockfall / avalanche should be considered.  The hiker's path adds minimal distance to the approach (maybe 15 minutes to get back across the valley).