| Recent Avalanches? | No |
| Collapsing (Whumphing)? | Yes |
| Cracking (Shooting cracks)? | No |
Observation: Girdwood
Location: Gulch Creek
Toured to 3100′ up Gulch Creek. Low visibility all day, and snowing lightly. Got a large collapse and easy propagation in pits at 3100′ on 3mm cupped & chained facets. Highly spatially variable slab thickness observed.
Obvious signs of instability
Observer Comments
Got a large collapse atop a medial moraine feature at ~3100 after taking two steps out of my skis. Dug to investigate, collapse was on 3mm cupped, chained facets on a melt-freeze crust 1-2' below a hard slab.
Weather
Overcast to obscured skies all day. Snowing <1"/hr to 1"/hr, total accumulation ~4" at 3000'. Wind calm to light from the west. Temperatures in the 20's.
Snow surface
2-4" of new snow on various melt-freeze crusts (at 1300' on SW aspect there were two 6" melt-freeze crusts stacked at the surface, above about 2500' there is mostly a 1-2" melt freeze crust that is partially breakable). Below the melt-freeze crust the snow is faceted.
Snowpack
The snowpack is highly spatially variable. Depths ranged from 30-45 cm on a southerly aspect of the moraine to 175 cm at 2000' in the gulch, to 55 cm - 120 cm at 3100' on the medial moraine feature where we got a collapse. The mid-January melt-freeze crusts were found all the way up to 3100'. Sandwiched between the crusts and a hard slab are facets. The slab depth varies from 1-3'.
We dug four pits in two locations:
Pit 1 - 2400', SW aspect, 28*slope, HS= 90cm - Stability tests all failed on a facet layer between two crusts 55cm below the surface on 2mm dry facets. CT16, CT17, CT21, ECTN24, ECTP27 (PC) The bottom 1/2 of pit had several facet layers between deteriorating m/f crusts and basal facets on the ground. See photo diagram.
Pit 2 - 2400', SW aspect, 26* slope, HS=260cm. CT30 down 35cm on facets below an old sun crust. Facets above and below the mid-January melt-freeze crust were present, ~100cm below a hard slab, but were not reactive in tests. See photo diagram.
Pit 3 - 3000', SW, 12*slope, HS=90-110cm - Dug a pit in this location immediately after experience a large collapse. Stability tests all failed on 3mm chained facets on a crust 65cm below the surface. These facets were very loose and falling out of pit wall. Test Results: CTV, CT3, CT7, ECTP3, ECTP12. See video
Pit 4 - 3000', WNW, 20*slope, HS=55-120cm. Close to Pit 3. CT14, ECTP4, PST 40/100 END down 35cm on 3mm chained facets on a crust.
Pit dug at location of large collapse. Easy propagation and CT failures on 3mm chained facets on a crust 65cm below the surface.
Wet loose debris below Super Couloir. Age unknown.
Skies were overcast to obscured the whole day, and it snowed lightly, accumulating 3 or 4" at 3000'. The large collapse was on top of the moraine feature in the background.
Pits at 2400'. Note the dramatic difference in slab depth. These pits were ~30' apart.
Location of pits at 2400'.
Looking back toward Raggedtop and Girdwood.
Small crown in steep rocky terrain near Super Couloir. Age unknown.