Marriot Basin avalanche

Avalanche

Run Length

100

Slab Width

30

Trigger Type

skier

Avalanche Size

2

Slab Thickness

150

Trigger Sub Type

accidental

Start Zone Aspect

S, SW

Vegetation Cover

sparseTrees

Start Zone Incline

35

Avalanche Character

stormSlab, deepPersistentSlab

Number Of Avalanches

1

Start Zone Elevation

2000

Avalanche Observation

24to48hrsAgo

Start Zone Elevation Band

tln

Avalanche Occurrence Datetime

2018-01-29T13:00:00

Incident

Group Size

12

Terrain Trap

noTrap

Group Activity

skiing

Number Injured

0

Number Involved

2

Number Caught Only

0

Number Fully Buried

1

Snow Depth Trigger Point

deep

Terrain Shape Trigger Point

convex

Number Partly Buried Able Breathing

1

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.