Observation: Summit

Location: John Mt (Summit Lake)

Route & General Observations

Today we checked out a recent avalanche on the west face of Mount John south of
Summit Lake (see photos). We think this released sometime on Wednesday
(2/22). This was a hard slab (blocky debris Pencil+ hard), natural release,
large relative to path, and could have easily buried or destroyed a car or
small building (HS-N-R4-D3). The top of the crown was near 3000 feet and the
toe of debris reached down to 1600 feet.

We dug a pit on an adjacent slope, left of this avalanche (just north
of the lowest portion of the start zone). Total snow depth was 3.2 meters.
The new powder on top was 10 cm deep and sat on top of 1F wind slab which
transitioned to Pencil hard wind slab down to 130 cm. Below this we found a
layer of old near-surface facets that probably formed during the late January
cold spell. This layer was 1F hardness. We got easy failures (CT3 Q2) just
beneath the newest wind slab (about 15 cm down) and then hard failures (CT21
Q2) on an older wind slab layer about 30 cm down. We could not initiate any
failures on the faceted layer at the bottom of the pit.

Photos & Video
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