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CROW PASS AVALANCHE FATALITY, NOVEMBER 24, 1997
Prepared by Doug Fesler and Jill Fredston, Alaska Mountain Safety Center, Nov. 26, 1997
SYNOPSIS: On November 24, 1997, ½ mile south of Crow Pass (± 3,000 feet elevation) in the western Chugach Range of Alaska, a 34 year old woman hiking with a friend was caught and killed by a small, self-triggered soft slab avalanche which terminated in a gully. Search attempts by her partner were unsuccessful. She was recovered nearly 24 hrs. later by rescue teams after being found by a trained search dog.
REPORT: On the afternoon of November 24, 1997, Angela Paez, age 34 and Bill English, mid 40s) decided to go skiing in the Crow Creek area near Girdwood. Finding the snow conditions were not ideal, they changed plans and decided to hike. For the first two miles, the route follows an old mining road which traverses several steep scree slopes. At the end of the mining road, the route continues as a foot trail following a series of switchbacks that ascend nearly 450 vertical feet up a steep scree slope to a higher trail (old mining road) which continues to the Pass. The switchbacks are typically blown in with snow by the end of September and are not visible to winter travelers. Because they are generally steep (mid to high 30° s), provide poor anchoring (smooth scree) for the winter snowpack, and terminate in a gorge at the base of the slope, traversing them requires skilled evaluation, careful route selection, and luck.
When Bill and Angela reached the switchbacks, they talked about their route options. One option was to follow a windblown scree rib vertically to the high route, then traverse across along the base of the cliffs above. Another option was to try to follow the existing trail zigzagging back and forth across the slope, but because the trail was buried, this made little sense. The third option was to traverse the scree slope (approximately 600 feet horizontally) with the intent of gaining a wind blown rocky rib that ran vertically along the north side (left side looking upslope). They felt that this last route would give them the least exposure and would be the most direct, but to gain this route they had to first climb upslope about 300 linear feet (to be parallel with the beginning of the rocky rib).
Although some slight indentations held more snow, the snowpack was generally less than 12 inches deep with numerous rocks exposed. Boot penetration was to the ground in most places and walking was easy. The sky was clear with temperatures in the high teens/low twenties, and no wind. Bill reached the safety of the rocky rib at 2:35 p.m. and turned around to watch Angela following in his steps. She was only about 50 feet behind him, when the whole slope broke into blocks around her and started to move. The fracture was no more than 50-75 feet above her and extended another approximately 10-15 feet beyond her (roughly 60 feet wide in all).
She was knocked down immediately and assumed a sitting position with her feet facing down slope. Initially, the debris was shallow and slow moving, but quickly accelerated and gained in volume and size as it descended. Angela made no attempt to fight, jump, or roll to the side. Bill carefully watched Angela as she was carried downslope and observed her disappear beneath the debris just before it spilled over the edge of the gorge. He ran downslope, following the trajectory he had observed, jumping the last 20 vertical feet into the gorge to reach the debris. The debris where Angela disappeared was in the shape of a cone roughly 20 X 25 feet, with a depth of approximately 12 feet on the uphill side and 6 feet on the opposite side. Immediately, he found one of her ski poles and placed it vertically in the snow to mark its location. Using his shovel, he carefully dug a series of three trenches, one row above the other, horizontally across the debris. Each trench was about 2 ½ - 3 feet deep. While digging he periodically stopped and yelled her name into the snow. Twice he thought he heard a faint, muffled yell in response, but he wasn’t able to pinpoint the source, either by listening or digging. After an hour and ten minutes of systematic searching (now 3:45 p.m.), Bill decided he needed help.
Getting out of the gorge was not easy, but with skillful climbing he was able to ascend the cliff. He reached his truck by 4:45 p.m. and drove to the nearest residence, approximately 7 minutes away. Upon contact, the Alaska State Troopers alerted Alyeska Ski Resort, the Girdwood Volunteer Fire Dept., the Alaska Mountain Rescue Group, Dogs Organized for Ground Search, the Nordic Ski Patrol, the U.S. Forest Service, Alaska State Parks, the 210th Air National Guard, and the Rescue Coordination Center at Elemendorf Airforce Base.
Rescue members responded quickly to a staging area on Crow Creek Road and to the Girdwood Fire Station (most volunteers were at the staging area by 6-6:30 p.m.), but because of the dual staging areas, there was some confusion during the early hours of organization. Initial attempts to reach the site by snowmachine were unsuccessful due to deteriorating weather, poor visibility, drifting snow, and the fear that additional slides could trap rescuers. Two attempts at reaching the site in an Air National Guard Pavehawk helicopter also proved unsuccessful due to 25 knot northerly headwinds and poor visibility from blowing snow. Rather than risk the lives of rescuers, the decision was made to resume the rescue effort in the morning, contingent upon better weather and visibility.
At first light, a team of three helicopter-bombed most of the slopes adjacent to the accident site using an A-Star helicopter and brought down several small slab avalanches. A small team of 13 rescuers and two avalanche dogs flew to the site in several helicopter loads. Angela was found by a trained avalanche dog within 3-4 minutes of reaching the site. Still in the sitting position, her head was buried under 2 ½ feet of debris with no evidence of an air space or ice mask. It took another 15 minutes for four to five people to dig her out. She had no vital signs. She was then sling-loaded from the site to the staging area. All personnel were transported back to the staging area by helicopter by approximately 2:30 p.m. and a debriefing was held.
CONTRIBUTORY FACTORS:
Terrain:
. Slope Angle: The bed surface slope angles varied from a measured low of 32° (where Angela was standing) to an estimated high of 38° -41° (along the upper 15-20 feet of the slab in the starting zone, roughly 50 feet above Angela’s position). The average angle of her trajectory was 32° along most of the track from the starting zone to the brink of the gorge (one short segment measured 35° ). The last 75 feet into the gorge ranged from approximately 45° to 80° (the last 20 feet). The runout angle was unmeasurable due to terrain obstacles and map scale deficiencies, but is estimated to be approximately ± 34° .
. Anchoring/Roughness: The scree slope was uniformly smooth and provided poor anchoring. Because most of the scree material was fist to foot size, large pore spaces (3-5 inches in diameter) were prevalent between the rocks. These pore spaces contributed to the effective transmission of warm vapor from the ground into the snowpack at the snow/ground interface, and thus enhanced the rapid development of faceted crystals immediately above the ground.
. Aspect: The aspect was westerly. The 4-6 foot rocky rib on which Bill was standing ran vertically (W-E) upslope and acted effectively as a snow fence, allowing a slightly deeper (16-20 inches) accumulation of snow from cross-loaded winds along the lee side (i.e., the slope where Angela was standing). This shallow depression became a catchment area for blowing snow (i.e., low density wind slab).
. Shape: The slope was uniformly planar with only slight ribs and depressions evident. The ribs were very shallow, with no slab evident. The most significant shape factor was the gully at the base of the slope. If the same avalanche had occurred on a slope shaped like an alluvial fan, the victim most likely would have been caught in snow that was less that knee deep, and probably could have easily stood up and walked away. However, once the victim became entrained in the moving debris, the gully greatly increased the consequences (i.e., diminished the probability of survival).
Weather:
. Temperature: For several weeks, this area had experienced above average temperatures (generally in the 30s). However, a month or so prior to this period, the temperatures had been in the single digits and teens. During this period, the shallow snowpack became faceted at the ground.
. Precipitation: The day of the accident was clear, but the day before, approximately 6-8" of new snow fell, the first significant accumulation in several weeks. This storm started warm and ended cold (see Snow Structure, below).
. Wind: The snowfall of the previous day was without wind until the last couple of hours, when gusty 25-30 mph winds resulted in shallow soft slab formation in leeward pockets.
Snowpack:
. Snow Structure: No fracture line was visible the day after the accident due to strong winds the night before. However, an examination of the bed surface and adjacent slopes, which had not slid, strongly indicated the following: The cool temperatures of more than a month ago had created a weak layer of intermediate facets (± 2 inches thick and fist hard) on top of the scree. Subsequent warm temperatures and slight accumulations of new snow settled the upper snowpack creating a poorly bonded shallow crust layer ( ± 2 inches thick and pencil hard) immediately above the facets. Note: this layer did not exist everywhere, but most likely did exist to the lee of the rocky ridge where the depth was slightly greater. Well bonded to this (because temperatures were warm when the next snowfall started), was the new snow of November 23. Moderate winds near the end of the storm created both low density wind slab and additional load. Intermediate facets are notoriously weak in shear, but surprisingly strong in compression. The added load of the new snow, the weight and dynamic energy of two hikers, and the incline of the slope all contributed to an increase in stress. The facets were simply not strong enough to hold the slab in place.
. Other Clues to Instability: The avalanche hazard was moderate at the time of the accident. No evidence of recent avalanche activity could be seen along the route. No collapsing of weak layers or shooting cracks were observed. Although no wind slab was detected by the victim or her partner on the day of the accident, this may have been due to the fact that they a) had been following a well beaten trail (during the initial portion of the hike), and b) had just reached a point in elevation where the wind action was more prevalent. In other words, within a few steps they went from an a area of no wind slab to a small pocket of wind slab. This accident is a good example of how a little avalanche ending in a terrain trap can have deadly consequences.
Human Variables:
. Background: Although available information about Angela is limited, it is known that she had climbed in the Andes, the Cascade Range, and Mt. Rainier . At some point, she apparently taught climbing and had lead less experienced friends on climbs in the Cascades. Prior to the accident, she had been in Alaska for three weeks working as a medical intern and was in her third year of medical school at the University of Washington. During the previous weeks, she had climbed a couple of small peaks in the Chugach Range and appeared to have a passion for the mountains. Previous avalanche training is unknown.
Bill, who works as an attorney, had met Angela only two days earlier, though his sister was a longtime friend of hers. He had been to Crow Pass in the summer, but never in the winter. Bill had hiked and skied in southcentral Alaska and elsewhere for years. Neither person can be described as having a high-risk taking attitude or as being ego-involved with the route, but time was a factor in their route selection decisions as sunset was less than a couple of hours away. Bill had no previous formal avalanche education, but had attended awareness talks over the years and had read avalanche articles on his own.
Bill said that the threat of avalanches never occurred to them. The sun was shining, the trail conditions were good, and the scenery was spectacular. In that sense, they may have been lulled into thinking that everything was alright and lowered their guard. Both missed the subtle changes in the snow conditions as they reached the steeper scree slope, but this would be easy for an inexperienced avalanche person to do. They carried some basic avalanche equipment (i.e., a pair of ski poles which could be used as probes and a shovel), but Bill had never had any formal avalanche rescue training. He showed great courage in leaping into the gorge and carrying out a systematic search by trenching a series of ditches. Had he used the ski pole as a probe, he may have found Angela sooner, but it is unlikely this would have changed the outcome.
CONCLUSIONS: This accident is a classic example of how a small, isolated area of instability posed a disproportionately high hazard because of the unforgiving nature of the terrain.
Report Submitted by: Mike Jenkins Utah Avalanche Forecast Center, Logan
Two snowboarders (man and wife in their mid 20s) were post holing up on a shallow slope of 15-20 degrees below a steep wind loaded gully with the intention of building a jump. The man was ahead of the woman when the slide released above them. They tried to run, but could not, although the man was able to jump on his board to ride as if on a snurfer. He was knocked over and buried to his neck, but able to dig himself out. His wife was totally buried below him and he did not have an exact last seen area. After looking for a brief time he heard her voice and dug down to her with his hands. She was facing down hill in an upright position and her head was 4 feet below the snow surface. She was uninjured after having been buried for only a few minutes.
The avalanche was a soft slab, 100 yards wide, with a crown height of 1-4 feet. It ran approximately 120 feet with a maximum debris depth of 5 feet. The slide started near very steep cliffs and the upper section of the gully approached 70 degrees. The majority of the crown face was 45-50 degrees and track averaged 38-45 degrees. The bed surface was a melt freeze crust formed in October, 2 inches above the ground. The weak layer was 6 inches of intermediate facets. Storms of the previous several days had deposited new snow and wind drifted snow 1-4 feet deep.
The couple had called UAFC Logan before their tour and had attended one or more of our seminars. They also observed a large natural slide on the slope above that had released the night before. The passed some young kids on the slopes below and warned them about the avalanche hazard. UAFC Logan rated the hazard as considerable on Friday, Saturday and Sunday. It appears the couple survived because they were near the flank and the slide did run very far. The snow covering the couple was very soft allowing for voice contact and ease of digging. The accident site investigation including photos was conducted by UAFC Logan observer Fredrik Norrsell.
APRIL BOWL, No. 2 AVALANCHE ACCIDENT
Investigated by: Doug Fesler, Alaska Mountain Safety Center, Inc.,
Date of accident: November 9, 1997, ± 3:00PM
Location: April Bowl, north face of Peak 4811, 1 mile south of Hatcher Pass, Talkeetna Mountains, Southcentral Alaska
SYNOPSIS: On Nov. 9, 1997 in the Talkeetna Mountains of Alaska, two snowboarders were caught in a self-triggered soft slab avalanche; one was killed. This is the first avalanche related snowboarder fatality in Alaska.
REPORT: A group of seven experienced snowboarders ascended the ridge along the eastern flank of April Bowl, a cirque measuring roughly 1000 ft. wide by 600 ft. vertical. Winds along the ridgecrest were blowing 45 - 60 mph at the time so visibility and voice communication were hampered. Along the route, two test pits were dug by the victim, Andy, age 25. The first pit was dug along the ridge near the false summit in a wind roll area of deeply deposited snow. His second pit was dug in the crown region about 10 ft. below the corniced ridge on the eastern side of the main face. His snow stability evaluation indicated to him that the snow stability looked "good" and he communicated this information to other members of the group within earshot. A second group of three other boarders arrived at the top about this time.
Andy then descended from his pit onto the 38° open slope below making three jump turns in the progress. At the same time, perhaps unknown to Andy, his friend Pat, age early thirties, jumped off a cornice and dropped into the bowl on the western flank following a line of descent down a generally uniform 31° to 33° slope. Three campers bivouacked beyond the base of the cirque said they observed the two snowboarders and two dogs jump into the bowl at nearly the same time. When the boarders had made approximately three turns, the whole slope ripped out above them (as four large plates) and accelerated rapidly downslope.
As the two were carried downslope, the remaining boarders carefully observed their trajectory. Pat was able to board out of the avalanche to safety beyond the western flank while Andy was carried over a steep convexity and taken temporarily out of sight. Spotted by his friend Colin, Andy reappeared in the runout zone as a black dot still in the standing position apparently trying to ride it out. As the moving debris hit the less steep slopes of the runout zone, the terrain changed from 35° to 4° in less than 75 ft. and the last wave of moving debris suddenly overcapped Andy and buried him.
Colin fixed Andy’s location in his mind and immediately descended via snowboard down the bed surface and the debris to Andy’s approximate position. Pat arrived within moments and both started a visual and beacon search for their friend. A signal was picked up almost immediately and within minutes, the others from above (7 people) and below (3 people) were on-site digging. After 10 to 15 minutes of digging, Andy’s exact location still remained unknown. None of the rescuers were carrying avalanche probes, but Colin pulled the basket from a ski pole and started probing the side walls of the hole. Almost immediately, he struck Andy about 4 ft. beyond the western wall of the pit. Within two minutes, his head was uncovered from below approximately 4 ft. of debris. One of the three campers from below, Erik, was a registered nurse and several of the others had EMT and/or CPR training. Andy appeared unresponsive with no pulse or respirations. As his friends continued to remove the snow from around Andy’s chest and legs, Erik cleared Andy’s airway and checked for a pulse and respirations.
At this point, two from the group were sent to alert authorities of the situation and to obtain additional help for transport (typically a 15 minute run). Once notified, Alaska State Park rangers immediately contacted a life support helicopter and the Alaska State Troopers helicopter for assistance. They also responded to the site within minutes. CPR was started by the group members as soon as it was possible to lay Andy flat. An improvised backboard was made from a snowboard and CPR was maintained for approximately 2 hours until the life support helicopter arrived and transported Andy to the nearest hospital 15 miles away. Andy was declared dead on arrival due to cardiac arrest due to traumatic asphyxia. Additionally, some bruises were evident on his body (presumably from impacts with rocks) and one rib was broken (possibly during CPR).
Andy was buried under the snow in a crouched (standing) position with one hand in front of his face and the other extending toward his binding. When uncovered, no ice mask was visible in front of his face and the debris was described as being remarkably light considering the depth of the slab. He was found within 15-20 feet of the toe of the debris and buried under 4 ft. (head) to 7 ft. (snowboard) of snow.
Foot Note: Andy was found only a short distance from where 20 year old Shawn Sande died in an avalanche on November 2, 1994. In that event, it appeared that Shawn triggered the slope from the bottom while ascending alone up the face. Over the years, many others have been caught by avalanches in April Bowl and some have been injured. In all known cases, the avalanches were triggered by the victims.
CONTRIBUTORY FACTORS:
Terrain:
. Slope Angle: Bed surface angles in the starting zone ranged from a low of 28° to a high of 45° with most ranging in the high 30s° and low 40s° . These prime-time angles added significant stress to the boundary regions of the slab. The average angle of Andy’s trajectory prior to reaching the transition zone was 35° for approximately 500 vertical feet. Pat’s trajectory averaged 31° . The runout angle, not to be confused with the bed surface angle, but a measurement of the average angle from the fracture line to the outer edge of the debris, was 30° . This was not a very efficient avalanche; long running avalanches in the Talkeetna Mountains, by comparison, typically range between 17° to 23° .
. Slope Aspect, Sun: April Bowl is predominantly northerly in aspect and remains shadowed until late spring. Because of the absence of sun and warmth, weaker faceted layers often form earlier on this aspect and remain longer during the winter season, all other factors being equal. Wind: The bowl is primarily leeward and usually cross and top loaded with deeper deposits of wind-transported snow. Cornices typically form along the eastern ridge and the summit crest; wind slabs are common in the upper bowl after storms. Because of the shock load cornices place on the slopes below when they collapse due to storms, wind events, warming, or human activity, there is probably a greater frequency of avalanching on this slope than adjoining slopes. This slope had not avalanched yet this winter.
. Slope Configuration: Shape/Roughness/Anchoring: April Bowl is open and slightly undulating, with numerous subtle concavities and convexities interspersed with 2-3 ft. rock outcrops (i.e., stress concentration points). Anchoring is generally poor, consisting of alpine tundra, scree, and isolated rocks. Three turns down from Andy’s last pit, the slope increased in steepness from 38° to 45° at a convexity. Most likely, this area of high tensile stress was a trigger spot consisting of shallower, and thus, weaker snow. The convexity also provided little compressive support for the deeper slab above.
Snowpack:
. Snow Structure: An early season shallow snowpack with cold temperatures had created a weak layer of faceted snow near the ground. Because of the northern aspect, this layer did not receive any benefit of warming from the sun to enhance settlement or melting. Subsequently the facets were capped over by three or more additional layers of finer rounded grains (i.e., wind slab). In appearance, the snowpack was shallow and instability easily detectable to an experienced evaluator. A fracture profile conduced two days after the event indicated a pencil hard wind slab of variable depth (1 inch to 7 ft. with an average of depth of 4 ft.). The slab was composed of three distinct layers caused by three storm events, sitting on top of a four-finger hard layer of intermediate facets 2 inches thick. When the slope avalanched, Andy’s second pit was clearly visible as part of the crown face above where he was caught. At its base was the same weak layer of faceted snow with 4 ft. of wind slab on top.
. Other Clues to Instability: No collapsing, shooting cracks, hollow-sounding snow, or recent avalanches were observed by the group as they ascended to the base of the cirque via an old mining road. In part, these clues probably were not detectable because much of the route followed a well compacted road and a bare ridge. Also, visibility and audibility was poor due to blowing snow and strong winds. However, four days prior to this event considerable collapsing and shooting cracks were observed along creek banks at lower elevations and small slides were easily detectable. The day before the accident, a natural release to the ground was observed on a similar aspect and elevation ½ mile to the west and one day after the accident, a similar event occurred ¼ mile to the east. Although park rangers and nordic ski patrollers were aware of the instability and attempted to advise the recreational users they encountered, this group was unaware of the lingering instability and had not talked to locals knowledgeable with conditions.
Weather:
. Wind: Strong winds started blowing late Saturday night, with significant snow transport occurring at higher elevations. By around 2:30 PM, when the group reached the crest of April Bowl, the wind had been blowing for 13-15 hours and several feet of new wind slab had been deposited. The added load of the wind-deposited snow, combined with the stress due to slope angle, and the added weight and impact of the snowboarders was more than the snowpack could adjust to in a short time. In fact, for this group, the only major clue to potential instability was the observation of strong winds and evidence of snow redistribution in combination with steep, leeward slopes.
. Temperature: On November 4th through 6th, the temperatures were in the high teens to mid twenties. On November 7th and 8th, the temperatures warmed up to the low thirties. On November 9th, the day of the accident, the temperatures rose to 37° (as recorded at the Independence Mine State Park Visitor Center at 3,200 ft., 2 miles away from the accident site). This may have contributed to accelerated creep and glide in the upper layers of the snowpack, but not in the lower layers which were cooler. This discontinuity in flow/stress rates probably increased the shear stress along the interface of the slab and the bed surface and contributed to a build-up of stored elastic energy within the slab. With shear stress nearly equal to strength, all the slab needed was some additional stress to tip the balance. If no people had ventured onto the slope during that day, more than likely the path would have avalanched naturally later in the day, triggered by a cornice collapse.
. Precipitation: Only a trace of new snow was recorded (Independence Mine State Park Visitor Center) on the day of the accident and none the day before. But for the four days prior to that, 15 inches of new snow fell at relatively cool temperatures. Thus, sufficient low density snow was available for transport on the day of the accident.
Human Factors:
. Ego/Attitude (toward risk taking, goals, etc.): This group was generally comfortable with exposure and accustomed to taking risks. They weren’t considered reckless, just a little loose with their travel procedures (i.e., more than one person on a slope at a time, etc.).
. Skill/Knowledge: Technical travel skills were high; all were proficient skiers and/or boarders and several were certified instructors. Because of their high level of skill, they felt comfortable with exposure and sought terrain that would challenge their skills. The group’s avalanche hazard evaluation skills were considerably less refined than those required for the terrain at hand. It is not unusual to have a dichotomy between the level of traveling ability and avalanche hazard evaluation skills. Many had previous medical training, which though unsuccessful in this incident, could well make the difference between survival or death in another.
. Physical/Mental State: All were strong and in good shape, which may have contributed to an overestimation of abilities.
. Equipment/Resources: All carried avalanche rescue transceivers and knew how to use them, though some members had not practiced searching with their beacons since last season (10 months or more). Because of this they had difficulty fine-tuning the final grid in the beacon search and wasted considerable time digging in the wrong location. No group members were carrying avalanche probes, though some usually did. Having probes for spot probing would have enabled responders to pin point Andy faster, perhaps cutting 10-15 minutes off the search time.
Ultimately, Andy was found by probing in the side walls of the hole with a 4 ft. ski pole with a basket removed. Once located it took only a couple of minutes to uncover his head, but considerably longer to excavate his whole body. All, or nearly all, members carried shovels, an essential tool for obvious reasons. Responders worked well in a concerted effort to remove the snow from around Andy who was locked onto his board with non-releasable bindings. Having releasable bindings may have helped Andy to break free of his board and stay on top of the moving debris easier; with non-releasable bindings the board certainly acted as an anchor which prevented any possibilty of escape once the snow started piling up around him.
COMMENTARY: The seven group members were all friends who had partied together the night before and had decided to snowboard April Bowl the next day. All were highly skilled snow boarders and most had skied or boarded at April Bowl on previous occasions. Andy had skied April Bowl numerous time during the previous 10 years and twice on the previous two weekends. Most had had no formal avalanche education except exposure to basic awareness talks and rescue principles combined with home-schooling and knowledge picked up from others in the field.
To reach April Bowl, the group had to drive approximately 2 ½ hours from Girdwood to the trailhead and snowshoe for 1 ½ more hours to reach the top. They talked about the potential avalanche hazard being "high" due to the strong winds and blowing snow, but each felt a certain amount of security being equipped with avalanche rescue transceivers and shovels and traveling with close friends. Strong winds notwithstanding, they were committed to achieving their goal: snowboarding together at April Bowl. The roar of the wind on the ridge made communication difficult and probably added to a sense of urgency for getting down.
Andy’s first pit was dug in an area of deep wind deposited snow, one not representative of the slopes below. The second pit was dug in a good location and contained all the critical information required to make a "No Go" decision: a 4 ft. deep fresh wind slab poorly bonded to a 2 inch thick layer of weak faceted snow sitting on a 38° slope being loaded by 45-60 mph winds. But he either didn’t dig this pit deep enough to reach the weak layer (not likely), misinterpreted the data he found, or ignored the data because it conflicted with a preconceived notion based upon previous experience or intended purpose. We’ll never know. In any event, the information was communicated to the group that stability looked "good" and nobody questioned that evaluation. Had several members gathered stability information along the way and discussed the results, a different decision might have been reached.
Placing two people and two dogs on the slope at one time, plus jumping from cornices and doing jump turns on steep slopes significantly increases the chances of human-triggered avalanches by shock loading potentially weak shear zones buried beneath the slab. This is particularly true on steep slopes with variable depth slabs and recent wind-loading where the stresses may be greater. Evaluating the stability, testing that evaluation (by dropping cornices, ski testing, etc.), and then descending one at a time along the flanks of the path and well out beyond the runout zone optimizes group safety while minimizing exposure. Utilizing a low angle slope for a first descent may minimize human impact and give the first traveler a chance to evaluate the slope further. Remember, as slope angle increases, so does the stress along all of the boundary regions of the slab Meanwhile, all eyes should be on the person descending and all observers prepared to act upon a rescue plan.
At a minimum, each backcountry traveler should carry and know how to use: an inclinometer (for measuring slope angles), an avalanche rescue transceiver (compatible with the new international frequency of 457 kHz), an avalanche probe (8 ft. or longer, for pinpointing the exact location of the victim), and a short, strong scoop shovel for rescues and stability tests (a one piece shovel is preferred for a speedy rescue). Other useful gear includes a 100 ft. length of 8mm rope (helpful for belays and cutting cornices for stability tests), a snow saw or length of parachute cord for cutting the back wall of rutschblocks and shovel/ski shear columns, and a notebook and pencil for recording snow, weather, and terrain data.
ADDITIONAL DATA:
Weather Log from Independence Mine State Park Visitor Center
Date Temp. Snow Wind Obsv.
4th 27° 5" 0-5 N poor visibility
5th 28° 3.5" 10-15 S very windy up high
6th 18° 2" 5-10 N drifting
7th 33° 4.5" 0-2 S drifting
8th 32° 0 0-5 N pluming on ridge crests, wind out of SE
9th 37° T 15-30 S very windy
Sources: Most of the information in this report was based upon interviews with Dennis Heikes, Pat Murphy, and Colin Murphy, and upon a field investigation conducted by the author in the company of Colin Murphy, who witnessed the event.
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