Crown profile from the skier triggered avalanche on the north-facing wall on the Mini Hall of the Gods Chute

Location Name: 
Angora Peak
Echo Summit Area
Date and time of avalanche (best estimate if unknown): 
Sat, 03/06/2010 - 13:30
Location Map: 
United States
38° 51' 41.3964" N, 120° 4' 36.9084" W

Red Flags: 
Recent avalanche activity
Obvious avalanche path
Terrain Trap

Observation made by: Forecaster
Avalanche Observations
Avalanche Type: 
Trigger type: 
Crown Height: 
2 ft
Weak Layer: 
Old Snow
Avalanche Width: 
Above Treeline
8 307ft.
Bed Surface: 
Old Snow
Avalanche Length: 
1 000ft.
Number of people caught: 
Number of partial burials: 
More detailed information about the avalanche: 

The snowpit images above are crown profiles from the skier triggered avalanche on the north-facing wall of the "Mini Hall of the Gods" couloir. The crown was about 30 ft wide and ranged from 6 inches to 2.5 ft. deep (photos 1 and 2). The weak layer was a thin layer of slightly softer, slightly faceted snow grains at the Feb 19th interface (photo 4). This small crown occurred on a 55 degree, north-facing, wind-loaded, unsupported slope with a shallow snowpack. It was triggered as a skier weighted the slope near some rocks where the snowpack was the most shallow and the slab was the thinnest (skier's left in photos 1 and 2). Once this small slab avalanche hit the main chute it entrained the soft surface snow in the chute and carried it downhill. No deeper failures occurred in the main chute or in the steep terrain below the exits to the chute.The slide continued downhill for 1000 ft and deposited a shallow layer of debris over a large area (see previous observations).

Today, layer bonding tests performed at the crown of the avalanche indicated that fractures can still propagate along the Feb 19th weak layer once it breaks. They also showed that this layer can still be broken in areas where the overlying slab remains thin. Other observation on less steep slopes where the snowpack was deeper indicated mostly stable conditions. A melt freeze crust existed up to 8000ft on the westerly aspects. This crust softened by mid afternoon and left a layer of heavy wet snow.

Photos 1 and 2: The avalanche crown. Note the shallower snowpack, thinner slab, and likely trigger points (rocks and a more unsupported slope) on skier's left.

Photo 3: Facetted snow grains at the base of the snowpack on the skier's left side of the slide. These are not the failure layer.

Photo 4: Small slightly facetted snow grains at the Feb 19th interface. This is the failure layer.

Snowpit or crown profile photo or graph: 
Avalanche Photos: 
Avalanche observation video: 


Weather Observations
Blowing Snow: 
Air temperature: 
Above Freezing
Wind Speed: 
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: 

 Clouds breaking over the crest. Areas of scattered precipitation noted.