4483′ Gully 1 GOS

February 21, 2021 at 2:00 PM
Name: Al Mandell| Acadia Mt Guides
Location: Gully 1 GOS 110 degrees, 120 degrees, 100 degrees

2 pits were dug along with numerous hand shears ranging in elevation from 4200 – 4650′ within Gully 1. A protected, non skier compacted (aspect 120 degrees) spot demonstrated reactivity on the Feb 2/3 14% SWE crust layer: ECTP14(40 cm down), fracture was a sudden collapse, Q2. Of interest the 15 – 17 cm soft slab overlying the Feb 16/17 crust was not reactive in this location. This is the layer that released in the reported avalanche in the “south snow fields”. Pit 1’s location was on the skiers right side of the gully in a zone that would be rarely skied. Hand shears were moderate at this location with the overlying soft slab very soft and of light cohesivity (extremely low density more like a storm slab vs a wind slab at this location–ie the slab was not able to really be held or picked up) and a Q2 shear quality, but not propagating in any way.

Moving aspects and locations into the main gully (110 degrees, 4483′, slope angle 35 degrees) demonstrated no instability: ECTX. A shovel shear was performed on this column, breaking cleanly on the Feb 2/3 crust and required EXEPTIONAL force to release it). The 15 cm soft slab was not reactive in this location nor in numerous other locations throughout gully 1. This not only confirms the spatial variability discussed in the 2/22 forecast: South snow fields reactive to skier triggering, gully 1 below 4750 not reactive to both informal and formal snowpack tests, as well as not reactive to skier traffic, but demonstrates slight shifts in location (ie similar but not IDENTICAL) can demonstrate stability vs instability. From 4600′ down this line is currently not experiencing any reactivity in zones actively skied. Gully sides where skiers do not recreate demonstrated reactivity, but are not representative to the actual ski line.