Marriot Basin avalanche

Activity

Skiing

Total in the group?

12

People fully buried?

1

People partly buried with normal breathing?

1

People not injured (caught but not buried)?

0

People injured (caught but not buried)?

0

People involved?

2

Terrain shape at trigger point

Convex

Snow depth at trigger point

Deep

Terrain traps

• No obvious terrain trap

Skier triggered avalanche on the slopes to the NE of the Wendy Thompson hut in sparse trees. See bulletins for details about weather. Significant snowfall in the week prior and that day. Despite this we had not found evidence of storm slab formation on the same slopes the day before or earlier that morning. I do not have temperature data but it was warming during the day and was likely near zero. I believe the initial slab was storm snow but it stepped down to a deeper layer. We did not not return the start zone so I do not have more details about the layers involved. The crown triggered on a convex roll after the skier cut across below it. Crown draw in red in photo. Approx 1.5 m deep. Propagated about 15 m to either side, catching a second skier stopped in the trees. Position of skiers at start of slide in blue. Skiers were carried about 100m, stopping at yellow marks in photo. I would estimate a size 2. One partial and one complete burial. Beacon search quickly located the buried skier. No significant injuries from slide.

There were definitely some human factors involved including familiarity (skied the area in storms before), consistency (no evidence of slabs on previous run, decided at the bottom to do another run and ignored evidence of warming that we saw on the way up), scarcity (lots of powder) and social facilitation (large group).

The following day, with better visibility, we saw several similar sized natural avalanches on the south facing slopes above the lake.