Avalanche on Ralston

Location Name: 
Echo Summit Area
Date and time of avalanche (best estimate if unknown): 
Sun, 02/28/2010 - 07:55
Location Map: 
United States
38° 50' 14.766" N, 120° 5' 58.6356" W

Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path
Terrain Trap

Observation made by: Professional Observer
Avalanche Observations
Avalanche Type: 
Trigger type: 
Crown Height: 
2 ft
Weak Layer: 
Avalanche Width: 
Above Treeline
8 600ft.
Bed Surface: 
Old Snow
Avalanche Length: 
1 000ft.
Number of similar avalanches: 
Number of people caught: 
More detailed information about the avalanche: 

On Sat night we camped between Upper Echo Lake and Ralston Lake. During our approach on Sat, we noticed appx 5 large crowns between Becker Peak and Ralston, on the North facing aspects viewed from Echo. Light snow continued through most of the day, with a few clear periods. Temps remained cool except during these brief clear periods. Winds were low to moderate, with a few moderate to strong gusts noted overnight. Winds shifted from SW to NE during the late afternoon.


On Sun morning at 7:55AM we watched from camp as 4 skiers descended from the looker's right ridge of Ralston, towards Ralston Lake. All 4 successfully descended the first pitch and regrouped. The first and second skiers to descend the second pitch chose an appx 30 degree slope with no distinct terrain configuration features, save for the obvious lack of anchoring. The third skier took the same route, but stopped midway to watch the fourth. The fourth skier traversed hard skier's right, above a steeper slope with a convex roll and several exposed rocks. A few turns into the rocks, the slab fractured well below him and to each side, but fortunately only appx 20ft above him. He remained on top of the flowing debris but we lost sight of him due to terrain. When we contacted the skier at the base of the debris, he was pretty excited to be alive, and suffered only a bloody nose and lost goggles.


Photo 1:  The skier who triggered the slide standing right where he exited the debris. Note his tracks just above him. The tracks in the lower right foreground are from after the slide. The debris pile to his left measured just under 3 meters deep. A terrain feature diverted debris, splitting the avalanche into 2 paths and debris piles. This was the smaller of the 2.


Photo 2: Looking down on the deposition from the stauchwall directly under the trigger point. Click the image for the full size to better see the debris on the lake.


Photo 3: The crown varied from 1ft at the trigger point to 4ft here. There was no evidence of a step-down, simply variance in depth of the weak layer.


Photo 4: Graupel on top of the bed surface. This was pretty wide-spread throughout the bed surface we examined. Bed surface was pencil hard and nearly impossible to skin. When we looked at the crown, graupel was present but not obvious - the 2cm weak layer was rounds and graupel, 4F sandwiched between 1F above and pencil below.


Photo 5: Mid-slope debris showing the stratigraphy of post Feb 19th storm layers.


Photo 6: Looking across the debris pile. Depth until probe moved more easily was just under 300cm.


Photo 7: Taken later in day, shows travel routes of all 4 skiers, red X marks the trigger point, skier exited debris out of frame lower right. The two skier's tracks to the immediate right of the debris are from us, after examining the site. The three tracks to the far right are from skiers 1, 2 and 3.


3/1/10 edit to add link to video: http://www.vholdr.com/video/2-28-2010-tahoe-backcountry-1

Thanks for making this public!!!

Avalanche Photos: 
Weather Observations
Air temperature: 
Below Freezing
Air temperature trend: 
Wind Direction: 
Accumulation rate: 
More detailed information about the weather: