CAIC: Colorado Avalanche Information Center

2015/01/06 - Colorado - Kendall Mountain, Rabbit Ears/Arcade

Published 2015/01/17 by Mark Gober, Susan Hale, Josh Hirshberg, Brian Lazar - Forecasters, CAIC


Avalanche Details

  • Location: Kendall Mountain, Rabbit Ears/Arcade
  • State: Colorado
  • Date: 2015/01/06
  • Time: 3:50 PM
  • Summary Description: One backcountry skier, caught, carried, partially buried, and killed
  • Primary Activity: Backcountry Tourer
  • Primary Travel Mode: Ski
  • Location Setting: Backcountry

Number

  • Caught: 1
  • Partially Buried, Non-Critical: 0
  • Partially Buried, Critical: 1
  • Fully Buried: 0
  • Injured: 0
  • Killed: 1

Avalanche

  • Type: HS
  • Trigger: AS - Skier
  • Trigger (subcode): u - An unintentional release
  • Size - Relative to Path: R2
  • Size - Destructive Force: D2
  • Sliding Surface: O - Within Old Snow

Site

  • Slope Aspect: NW
  • Site Elevation: 11300 ft
  • Slope Angle: 40 °
  • Slope Characteristic: Convex Slope,Gully/Couloir

Avalanche Comments

The avalanche was a hard slab, unintentionally triggered by a skier, small relative to the path and large enough to bury and kill a person, that broke into old snow layers (HS-ASu-R2D2-O). The avalanche released on a slope near treeline (around 11,300 ft) that faced north-northwest. The avalanche released on a 9 cm thick layer of faceted snow grains, 2 mm in size with a Hand Hardness of four fingers. This weak layer was about two feet below the snow surface, and sandwiched between two slabs of snow, each with a Hand Hardness value of pencil. The avalanche was two to four feet deep along the crown face, and about 160 feet wide. The slope angle of the starting zone is around 40 degrees. The avalanche ran 700 vertical feet. The alpha angle for this avalanche event was 32 degrees.

Weather Summary

Several storms during the last two weeks of December 2014 deposited 40.5" of snow and 3.4" of snow water equivalent (SWE) at the Molas Pass study plot (5.3 miles southwest of  the accident site). Snowfall decreased and temperatures increased during the first week of January 2015. Three inches of new snow fell on January 2nd, and then no measurable precipitation between January 3rd and January 6th, the day of the accident.

During the 48 hours prior to the accident, the Kendall Mountain weather station (13,065 ft) recorded steady west to northwest winds in the 10-20 mph range, with gusts close to 30 mph. On January 6th, the day of the accident, wind speeds decreased and temperatures increased to 30° F at the Kendall Mountain weather station. 

 

Snowpack Summary

Snowfall from late October survived on cold northerly aspects near and above treeline and in isolated sheltered gully features. The snow metamorphosed into a basal depth hoar layer 10 to 20 cm thick. Two significant storms in November buried the basal depth hoar. Following the last November storm, southwest winds built stiff wind drifts on leeward slopes. These drifts formed the bed surface for avalanche on Kendall Mountain on January 6th.

December began with over two weeks of dry, mild weather. During this period, the snowpack surface experienced pronounced faceting; both at the surface and deeper in the pack (depending on aspect, elevation and sun exposure). All but the sunny south-facing slopes were left with a surface of weak faceted snow, that was subsequently buried by the next storm on December 13th. This faceted layer would become the weak layer in the Kendall Mountain avalanche.

Smaller storms deposited additional snowfall through December 16th, with a larger storm depositing a foot of snow between December 21st and 23rd. The late December storms were accompanied by strong northerly winds that both stripped and drifted snow throughout the near and above treeline terrain. In some areas this formed a stiff layer of snow over the weak surface facets that developed during the long dry spell. In some areas, these facets were sandwiched between two hard layers of snow (as in the fracture line profile below).

The first week in January started with strong northerly winds, a small amount of new snow, followed by a rapid warm-up on January 5th. This sequence of weather triggered a round of avalanche activity on east through south through west aspects. Though notable, this cycle has little connection to the avalanche accident.

Events Leading to the Avalanche

A group of two (Skiers 1 and 2) set off on a tour with the intent of summiting Kendall Mountain and skiing the Idaho Gulch avalanche path. They started on the Lackawanna road just outside of Silverton, Colorado. They left the road at the edge of Swansea Gulch and crossed the valley. They ascended a short, steep route into the trees on the northwest face of Kendall Mountain. From here, they started up a wind-exposed, rocky ridge towards the summit.

They decided there was not enough time to reach the top. They traversed to the west to the Idaho Gulch avalanche path and engaged in a discussion about skiing it. Neither skier was comfortable entering Idaho Gulch, so they decided to traverse back to the east a short distance to the Rabbit Ears avalanche path. They recognized a steep, wind-loaded terrain feature at the top of the path as a hazard and decided to go around it. They entered the path slightly lower and skier's right in an area they felt would be safer. They regrouped below this steep feature and Skier 1 began her descent. Soon after she entered the path, the slope avalanched, fracturing a short distance above Skier 1.

 

Accident Summary

The avalanche caught Skier 1 and debris quickly swept her up. The slope angle steepened to 42 degrees just below the trigger point. The avalanche accelerated down the steep pitch and Skier 2 lost sight of Skier 1. 

Rescue Summary

As soon as the snow stopped moving, Skier 2 turned his transceiver to 'search' and began searching for Skier 1. Skier 2 continued his search downhill until he saw the distance readings on his transceiver start to go up, indicating he was below Skier 1. He stopped, removed his skis, and started back uphill towards the skiers left side of slope.

Skier 2 saw Skier 1 wrapped around a small tree. Her body was on the surface but her head was partially buried. Skier 2 uncovered it and recognized that Skier 1 had snow in her airway.  Skier 2 cleared the airway and assessed her for any signs of breathing and circulation. Neither were present. Skier 2 called 911 to initiate the Search and Rescue response and then began CPR. Skier 2 continued CPR for over an hour until the first of the rescuers arrived and took over the scene.

Skier 2 placed the 911 call at 3:50. Rescuers including the San Juan County Search and Rescue team, Flight For Life, and employees of Silverton Mountain Ski Area assembled at the Kendall Mountain Recreation Center parking lot at the base of Kendall Peak. The Flight For Life helicopter ferried four rescuers, three of whom were EMT-B, to an area above the accident site. They descended to the accident site with a Sked rescue sled. They arrived and assessed Skier 1, finding a very weak carotid pulse and no respirations. The rescuers took over CPR and prepared the sled and patient for transport off the mountain. The pilot and a CAIC forecaster searched for a possible landing zone below the accident site, but could not find a suitable area. Additional rescuers ascended the avalanche path to meet the descending team. Snowmobiles assisted transport from the base of the mountain to a waiting ambulance. Skier 1 was initially stabilize in the ambulance, then transported by helicopter to Mercy Medical Center in Durango. Despite an involved and well-orchestrated rescue, Skier 1 died from injuries sustained in the avalanche.

 

Comments

This accident is another tragic reminder of how relatively small avalanches can be deadly. In this case the consequences of getting caught in a small avalanche increased because any avalanche would wash the victim through a stand of trees. Backcountry travelers often look at trees as a source of protection. However, once you are caught in an avalanche, trees become a source of harm. Studies of avalanche accidents show that 30% of people injured by trees in an avalanche are killed (McCammon et al. 2008) and that trees are the source of injury in about two thirds of trauma deaths in avalanches (Boyd et al. 2009, Haegeli et al. 2011). One author put it simply, “In our study, trees were identified as the most common objects hit in trauma deaths” (Boyd et al, 2009). This calls into question the belief that backcountry skiing below treeline, or on treed slopes can be the safer choice.

The group recognized the hazard of the steep wind-loaded roll above the avalanche path. They made efforts to reduce the risk, but underestimated both the extent of the slab and the consequences of even a small slide in such a hazardous terrain feature. 

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Snowpits

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Figure 11: Fracture line profile.