Flight over Boulder Glacier Debris Flow

The May 25th debris flow left a dark streak the length of the Boulder Glacier. View looking west. Click to enlarge

by Dave Tucker, MBVRC

Thanks to Bellingham pilot Maureen Briggs for flying me around Mount Baker today in her Beachcraft Bonanza. The goal was to get photos of the debris flow that descended Boulder Glacier May  25th.

The release zone just below the summit of Sherman Peak. The ice wall is around 100 feet high. Click to enlarge.

The debris flow left a you-can’t-possibly-miss-it streak of mud and rocky debris the full length of the glacier. The debris flow began as a snow and ice avalanche at 10,000′ on the north flank of Sherman Peak, the high point on the south rim of Baker’s active Sherman Crater. The avalanche scoured the complete thickness of the snow pack and into the underlying loose rock debris. It transformed into a debris flow and slid down the glacier as a slurry of snow, ice, water and rock fragments for 3.75 km (2.25 mi) to the glacier terminus at about 4800 feet.

As the ice and snow component in the flow

The plugged east breach of Sherman Crater. A large fumarole has melted a hole in the crater glacier at top right. Click to enlarge

continue to melt, the rock portion becomes more prominent.  The east breach of Sherman Crater remains plugged with large ice blocks from the avalanche.  This is NOT a lahar, as it was not spawned by volcanic activity, and initiated in snow and ice rather than in volcanic deposits.

The receding terminus of the Boulder Glacier, mantled by remnants of multiple debris flows accumulated over the years.

The 2016 debris flow was featured in a front page article in the Bellingham Herald June 13, 2016. attracted lots of attention Debris flows initiate every few years in the same place and run down the Boulder Glacier. Go here to read a report on this website about these hazardous events.