Spikes’s Gully Avalanche
12th January 2021
Today’s cold and clear conditions were very different to yesterdays mild, damp and claggy conditions. The low temperatures have consolidated yesterday’s wet and unstable snowpack. The clear weather gave me an opportunity to see what had happened during yesterday’s thaw. There had been cornice collapse and avalanche activity all along the East facing slopes of Aonach Mor (and I suspect in the gullies on Ben Nevis). However, the most impressive was a large cornice triggered slab avalanche in Spike’s Gully. Spikes’s Gully is not really a gully, more an open slope. It often forms a cornice, so cornice collapse is not unusual here. However, I have never before seen a large slab avalanche in this location.
In terms of size the vertical fall length from the cornice to the tip of the debris I would estimate at 250 metres, the width maybe 150 metres, and the length 400 metres. All in all quite a substantial avalanche.
The crown wall of the avalanche. It was triggered by a collapsing cornice on the near side of the larger part of the crown wall. I saw quite a few cornices that had slumped and cracked but had not yet collapsed when the colder conditions froze them in place. Mild conditions and rain often cause cornices to slump and collapse, and yesterday’s thaw was no exception.Â
Looking across from the South. There were three tongues of debris, one flowing into summit gully see at the boundary between the light and shadow, another down the slope directly below the avalanche, and a third much large one out of sight in Spike Gully. Debris from an older avalanche can be seen in the shadow in the foreground.
Looking up at the crown wall from below. The avalanche was triggered by cornice collapse, and then the failure propagated a long way to both the left and right.
Looking down part of the avalanche path. The avalanche left these wave like shapes in the underlying snowpack.
Looking back at the avalanche and to the main debris tongue. From this angle the smaller tongues that can be seen in the second photo are not visible.
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Christian Howell
13th January 2021 8:15 pm
Terrific photos clearly showing the processes at work here and the result of the recent milder spell.