historical analysis of avalanche fatalities in denali

HISTORICAL ANALYSIS OF AVALANCHE FATALITIES IN DENALI NATIONAL PARK

Kevin Wright1,2 and Tucker Chenoweth1,3

1Denali National Park Mountaineering Program, Talkeetna, AK, USA2Chugach National Forest Avalanche Information Center, Girdwood, AK, USA

3Alaska Avalanche School, Anchorage, AK, USA

ABSTRACT: Since the first mountaineering avalanche fatality in Denali National Park (DNP) in 1976, atleast 45 climbers have been killed by avalanches in the mountains surrounding Mt. McKinley. Theavalanche problems are different in many cases than recreationists encounter in smaller and lowerelevation mountains. Specific problems include crevasses, glacier icefall, and exposure to large cliffs inthe runouts. We looked at the historical avalanche related fatalities in DNP to refine our educationmethods and drive future research. This paper includes a statistical look at fatal incidents as well as acase study of a recent fatal avalanche event.

1. INTRODUCTION

Denali National Park and Preserve is a 24,584square kilometer area managed by the NationalPark Service (NPS) originally established in1917. The Park’s main attractions includeabundant wildlife and the majestic views of thehigh mountains of the Alaska Range. Formountaineers, Mt. McKinley (locally known asDenali) is a sought after climbing objective, witha peak of 6,194 meters (20,320 ft.) andrecognition as the tallest mountain in NorthAmerica. Each year approximately 1800climbers travel into the glaciated mountains ofthe Alaska range in DNP, with 2/3 of climbersfocused on Denali. The geology of the regionhas produced monumental granite walls,mountain faces with up to 4200m (14,000 ft.) ofvertical relief, and expansive glaciers up to 58km. (36 miles) in length.

1.1 Alaska Range climateThe climate zone of the Denali region is difficultto classify. Large temperature and precipitationvariation occurs within the Alaska Range bothlaterally and vertically. Annual snowfall can besignificant, winter temperatures are severe, andthe mountains are heavily glaciated. Climatezone maps typically classify this region ascontinental, but large snowfall amounts, highlatitude, and permanent glacial ice can forcedifferent considerations from a typicalcontinental snowpack problem. The summit ofDenali lies only 193 km from the

* Corresponding author address: Kevin WrightPO Box 588, Talkeetna, AK, 99676, USA; tel,907-227-6581 email:alaskabackcountry(at)gmail.com

ocean to the south, easily within reach of violentstorms from the north Pacific. The arctic circle is386 km to the north, making it a high latitudeand cold environment. The high variation inelevation (glaciers within the Park range fromless than 300m above sea level to over 6000m),causes elevational differences in the snowclimate. Low elevations often produce a deeptransitional snowpack (1.5 to 3m), with completemelting during the summer, and continental toarctic temperatures. Mid elevations (1500 to4000m) can have maritime snow totals (3m+)but still see very cold temperatures with only thesouthern aspects melting completely. Highelevations (above 4000m) are relatively dry,receive most snowfall in summer months, andhave below freezing temperatures year round.Extreme cold temperatures are common withtemperatures at 5,700m recorded as low as -73˚C and -30° C in December and July, respectively(International Arctic Research Center 2010).Glacial equilibrium (zone separatingaccumulation and ablation) averages near the1800m elevation. All incidents within this studyoccurred well above treeline (600m) and far fromany significant vegetation.

1.2 National Park Service climbing programThe NPS places a high priority on visitor safety.Denali National Park has a long standingmandatory registration and education programwhich serves to advise climbers of the inherentdangers of climbing Denali and Foraker and helpthem choose appropriate climbing objectivesbased on experience and abilities. A discussionof avalanche hazard is an integral part of theseorientations. A study in 2008 found the risk ofdeath while climbing Denali to be decreasingover the years and the measures imposed bythe NPS have contributed to a safer climbing

Proceedings, 2012 International Snow Science Workshop, Anchorage, Alaska

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experience. (Macintosh 2008) Theconsiderable effort to educate climbers onpotential hazards includes safety guidespublished in eight different languages. Theorientation requirement does not apply toclimbers on peaks outside of Denali or Foraker,although climbing rangers are available year-round to give advice and answer questionsabout climbing in the Park.There is no public avalanche forecast for thisregion of Alaska. The remote location, extremealtitude, lack of remote sensing equipment, andlack of resources make macro scale avalancheforecasting inaccurate and impractical. AlaskaRange climbers must rely exclusively on theirown skills and avalanche assessment resourcesto stay safe in these mountains.

1.3 Previous researchThere has never been a comprehensive study ofavalanche incidents in Denali National Parkexcept for a section of Jonathan Waterman’sbook “Surviving Denali” from 1983. Many of theincidents within this report have never beenincluded in national statistics compiled by theColorado Avalanche Information Center.

1.4 LimitationsThis paper does not look at non-fatal avalancheincidents. There are many avalanche eventswith injuries in NPS records, but the recordscannot be considered complete due to poorreporting from the public. Typically these wereonly recorded if the National Park Service wasinvolved in a rescue capacity.

Several cases of missing climbers includedwithin this paper are not proven to be avalancherelated, but the investigators of thedisappearances believe avalanche to be themost likely cause of the teams going missing.Several other mysterious disappearances ofclimbers were not included in the study eventhough avalanche may have been the cause ofdeath and disappearance. In these cases weclassified the cause according to theinvestigator’s conclusions. The statisticalconclusions derived from this information can beassumed to have a degree of error because ofthis uncertainty.

This paper looks only at the snow and iceavalanche fatalities within the mountaineeringscope of DNP. There have been at least 4recorded avalanche fatalities in the more easilyaccessed, low elevation peaks inside DNP. One

was a ski tourer, the other 3 were snowmobilers.The scope of this study covers onlymountaineering related avalanche fatalities andomits these other incidents.

Some ambiguity exists on classifying certainfatalities as primarily caused by avalanche. 3incidents included within this study wereoriginally classified by the NPS as death due toclimbing falls. In all of these cases a significantfailure of snow caused the initiation of the fallwhich caused the fatal injuries. It is possiblethat many of the fatalities recorded as climbingfalls were caused by a small snow slab failure.Certain places on Denali, such as the OrientExpress, with many cases of entire teams beingkilled in falls may have had a slab failurecomponent to the fall initiation. In most caseswe have no evidence to confirm or deny thispossibility and these cases were not included inthis paper.

Only basic avalanche information was recordedby investigators prior to 2005. We have fewdetails regarding: avalanche size, weak layer,slab, bed surface, trigger, preceding weatherevents, exact elevations, alpha angles, startzone angle, or other technical information. Evenin modern times it can be impossible to accessthe sites to record these details because ofsafety concerns or logistical challenges.

2. METHODS

The National Park Service holds an exclusivejurisdiction over the land in DNP and is theprimary agency responsible for search andrescue, law enforcement, and deathinvestigations. Denali National Park keepsmountaineering records on file starting in 1903and an electronic database beginning in 1976for all events involving search and rescue or afatality. Case incident records includeexpedition information, search and rescueefforts, medical treatment, witness interviews,media reports, maps of accident sites, andaccident analyses. In some cases photos orvideos are available with the reports.

This paper is based on reviewing records in theNPS database as well as interviews withRangers involved in the rescue efforts. Bothauthors of this paper are current mountaineeringrangers of Denali National Park and personallyworked as rescuers and investigators since2005.


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3. RESULTS

Since the first mountaineering fatality in 1932,164 people have died climbing in DNP. 120(73.1%) were on Denali, and 44 (26.8%) wereon other peaks. Out of these, avalancheaccounted for a total of 45 people killed (27.4%),in 22 separate incidents. 13 climbers in 5avalanche incidents died on Denali, 32 climbersin 17 avalanche incidents died on other peaks.

We looked at Denali separately from the otherpeaks because 95% of Denali climbers use theWest Buttress route, which did not have a fatalavalanche incident until 2012. We can assumethat Denali’s trade route has less avalanche riskthan other popular climbs in the region.10.83% of climbers killed on Denali, and 6.4% offatal incidents were from avalanche.72.72% of climbers killed on other peaks, and70.83% of fatal incidents were from avalanche.

Mt. Mckinley climbing fatalities – through 2012120 total climbing fatalities (Figure 1)13 avalanche fatalities10.83% avalanche

78 total fatal climbing incidents5 fatal avalanche incidents6.4% avalanche

Figure 1


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All Other DNP peaks fatalities – through 201244 total climbing fatalities (Figure 2)32 avalanche fatalities72.72% avalanche

24 total fatal climbing incidents17 fatal avalanche incidents70.83% avalanche

Figure 2

4. DISCUSSION

4.1 Multiple fatalities per incidentA significant aspect of avalanches in DNP ismultiple people getting killed in most fatalincidents. We found the average number killedper fatal incident to be 2.04 people, compared to anational average (excluding Alaska) of 1.25 people(CAIC database). A couple of reasons cause thisunusually high number. Roped climbing accountsfor the majority of the multiple fatality incidents. Ofthe 19 incidents in which the mechanism is known,14 (74%) were roped together at the time of theincident. Climbing roped together with one ormore partners is the accepted way to mitigateother mountaineering hazards including crevassedanger and protecting against falls in steep terrain.Unfortunately, climbing roped has distinctdisadvantages in avalanche terrain. First, the ropecreates a bond between partners. Second, itforces close proximity to teammates. Both ofthese make it almost impossible to limit exposureof avalanche danger to one person at a time.Even if climbers were able to climb safely withouta rope, the size of the avalanche paths can makeit impractical to expose only one person at a time,and many alpine routes force long durations ofexposure to avalanche hazard from above.

4.2 Terrain Exposure

Exposure to serious terrain traps was a commonscenario in many of the incidents. The enormousconsequences encountered in the Alaska Rangeare probably one of the most underestimatedaspects of climbing there. The result of gettingknocked off a stance, even in non-technicalclimbing terrain with cliff exposure or other terraintraps below has proven to be fatal in manyinstances.

In at least 9 of the incidents we examined, victimswere killed by trauma in extended falls after theavalanche. Many popular alpine routes in theAlaska range travel through hanging snow fieldswith the bottom edge terminating over steep clifffaces. The consequences of even very smallavalanches in such terrain are inevitably fatal.Evaluating snow conditions while on these routescan be extremely challenging, and retreat may notbe possible. A couple circumstances haverecurred in these cases: 1. Wet avalanchesduring the heat of the day in lower elevation zones(below 10,000 ft.) (avalanches on Frances 2011,Werewolf 2010), 2. The topout where poorlybonded wind slab may be present only close to thecrest of a ridge. In one incident a survivorsuspected that “the avalanche came from anisolated pocket of wind-deposited snow... The 5inches that fell over the 48 hours before theaccident had given us little cause for concern.”(Coombs 1992) The team likely triggered a thinwindslab on steep terrain as they got close to theridge on the upper snowfield. (avalanche onForaker 1992)

In another incident, investigators found tracksleading into a small storm slab crown just beforethe ridge crest and the victims were locatedthousands of feet lower beneath a cliff face.(avalanche on Barrill, 2007) Using climbingprotection in the form of ice screws, pickets, orrock protection may have prevented some of thesetragedies. Climbing roped but without protection iscommon practice with experienced and confidentteams in this kind of moderate but highconsequence terrain. However, in numerouscases in the Alaska Range, this practice ofclimbing roped together without protection hasresulted in a fatal outcome.

4.3 Ski descentsSki descents of the high peaks have becomeincreasingly popular in recent years. Many skierscoming to the Alaska range for the first time don’trealize that snow coverage on the upper mountainis very poor until mid summer. Skiers arriving in


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April or early May to attempt to ski above 4000meters will usually find a firm, wind scouredsurface or ice. Seasonal snowfall at this elevationincreases by late May through the rest of thesummer. Skiers find that the lack of snow makessteeper slopes very unforgiving in the event of afall, but slab avalanche concerns may be less. Asthe summer progresses, the hazards associatedwith falls are traded for better skiing, but at theexpense of increased slab avalanche danger.

4.4 CrevassesAt least 5 of the 22 incidents we examined had acomponent of crevasse fall adding to the lethalityof the incident. In 2 recent cases the victims werecarried for only short distances before beingpushed into a crevasse and buried deeply. Noneof these victims were recovered despite searchefforts and a high degree of certainty as to theirlocation. The glacial crevasse hazard proves tobe one of the most deadly terrain traps, pushingthe victims into a vertical fall before burying themdeeply by subsequent debris. The consequencesof crevasse hazard combined with avalancheslopes should be considered nearly as dangerousas a precipitous cliff face. Large open crevassesbelow avalanche slopes will collect some of thedebris, and likely any people who are caught withit. Picture 1 shows the 2012 fatal avalanche andcrevasse in which the 4 victims were caught andburied.

Picture 1: Motorcycle Hill avalanche 2012

Open crevasses cutting across a steep snow fieldmay also make the slope more likely to slide dueto a lack of compressive strength that is typicallyprovided by the adjoining lower snowpack (Smith2005).

4.5 IcefallIcefall accounted for 3 of the incidents, and islikely the culprit for the missing climbers in 1980,1981, and 1987. The dangers and patterns oficefall avalanches are poorly understood,especially by climbers who spend limited timearound large glaciers. A belief that higher daytimetemperatures can destabilize hanging seracs is

prevalent among climbers, but some researchsuggests that nighttime cooling can actually causethe highest frequency of icefall. (Pinchak 1968)The standard practice in the Alaska Range is tolimit exposure under these dangerous featuresregardless of the time of day or ambienttemperature. On steep routes sun exposure willcause increased rockfall and weakened cornices.The larger scale hanging glaciers with significantmass will fail when the underlying glacial stressbecomes too great. Temperature changes likelyplay a minor role compared to the glacial forces.Many potential routes are widely considered to bedeath traps because the overhead icefall hazardcannot be avoided. The northeast basin of Mt.Foraker is a good example of a route with highobjective hazard, and the death of 3 Japaneseclimbers in 1976 is a good reminder of thatassessment. The northeast fork of the Kahiltnaglacier has earned the name “the valley of death”for its reputation of icefall hazard and missingclimbers in 1980 and 1987.

It is common to hear of alpinists who observed aspecific route for an extended period of time tolearn the icefall frequency and patterns beforesetting foot on the climb. When informed climberschoose to travel underneath icefalls it is with anacceptance of the risk and a hope that the oddsremain in their favor. There is still no escapingthe reality that such decisions rely on a gamble,which sometimes ends tragically.

Minimizing exposure to icefall avalanches requiresthat campsites (where climbers will spend a greatdeal of time) must be chosen well away fromicefalls and snow slopes above. The incident inthe Root Canal in 2011 is a poignant reminder ofthis requirement. Measuring alpha angles may bea quick and effective way of staying beyondtheoretical runouts, and using defensive terrainfeatures to divert debris flows is a proven effectivestrategy even when in close proximity toavalanche areas. No research into a standardalpha angle in the Alaska range has yet beendone, and conservative decisions when estimatingrunouts and choosing campsites should beemphasized.

5. CASE STUDY

On April 28, 2011 at approximately 0120 hours anice avalanche released off the West face of theBear’s Tooth and struck two guided climbingparties camped below on the Root Canal glacier.All five climbers were struck by the avalanche, two


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were partly buried while three remained on thesurface. One of the two buried victims was foundto be unconscious with shallow respirations.Shortly after the avalanche, the unconsciousvictim succumbed to traumatic injuries. The victimwas evacuated at 0600 and Ranger medicsconfirmed he was deceased. A site investigationwas completed on 05/06/11.

Picture 2: Bear Tooth 2011

Ice avalanches (serac falls) result from tensilefailure within the ice due to ice flow creep withinthe ice mass and/or glide at the bed surface. It isinherently difficult to predict the timing of this typeof failure. Unlike snow avalanches there is verylittle correlation to time of day, aspect, elevation orweather. This leaves few tools available to thepractitioner for use in the field. Avoidance andlimiting the time of exposure continue to be thebest practice.

The runout distance for an avalanche is thefarthest point to which debris can reach. Currentlythe best methods for determining runout distanceare “(1) long-term observations of avalanchedeposits; (2) observations of damage tovegetation, ground or structures; or (3) searchesof the historical record as preserved innewspapers, old aerial photos, or other writtenmaterial” (McClung and Schaerer, 2006).Unfortunately very few of these are available forthe mountains of the Alaska Range so we must

use other methods.

A field method used by practitioners to estimatemaximum runout distance for snow avalanches isto measure the alpha angle of a given slope.Alpha angle values range anywhere from 15-50degrees (McClung and Schaerer, 2006). Thesevalues are compiled from statistical analysis of“the historical record of avalanche runout in agiven mountain range” (McClung and Schaerer,2006). Because alpha angle values are specificto, mountain range, avalanche path, snow density,snow climate and terrain configuration they varygreatly from location to location. The use of alphaangle values derived from statistics for snowavalanches are not necessarily representationalfor ice avalanches. The alpha angle from the campplacement was approximately 27 degrees. To bebeyond a 15 degree alpha angle (safe) it would bedifficult to camp anywhere in the “Root Canal”.More important than using an alpha angle forrunout avoidance is the ability to read terrain anduse defensive features within the terrain.

Defensive features deflect, stop or dissipate theflow of ice and snow. Terrain configurations thatare most suitable as defensive features are: arapid gain in elevation such as a knob or ridge,large crevasse features that can swallow debris,and extremely long shallow angled or flat runouts.The debris from this event traveled 1,920 feet outfrom the point of impact on an average slopeangle of 6 degrees. This is a substantial distanceon a shallow slope angle, yet the avalancheretained enough energy to hit the camp withimpressive force. A subtle depression channeledthe majority of the debris (estimated at up to 4 feetdeep) and deposited it directly through the area ofthe campsite.

In addition to this small depression, anothersignificant terrain feature that contributed to thisevent is the nearly vertical avalanche path. Thevertical fall of approximately 743ft allowed for analmost free-fall environment for the ice to travel,increasing the speed at which it fell. This appearsto have created an explosive type of impact thatbroke the ice into small pieces allowing them totravel greater distances, also resulting in asubstantial air blast that traveled in front of thedebris. The air blast hit with such force that itejected all five climbers from their tents. It sentthem ahead of the debris, accounting for theirposition mostly on top or only shallowly buried inthe debris.


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The return frequency of this icefall is unknown.We have very little information in the AlaskaRange to estimate icefall frequency. The onlygood historical information on this particular icefallis: the fatal event in 2011, a Google Earth imagefrom 2006, and a photo from 1977 that showssimilar avalanche debris.

5.1 Decision makingAn additional component to this fatality was theguides’ decision to place their camps in thislocation. Historically, camps on the Root Canalglacier have been used on both sides, up anddown the entire air strip. The approximatecampsite location where the accident occurred is apopular area often used by many climbers eachyear for its view of the entire “Ham and Eggs”climbing route and proximity to airplane access.Interviews indicate that there were previouscampsites from this season in this location andnone in other locations. Choosing safe campinglocations in this area is difficult due to the largescale of terrain and multiple potential hazards(rock fall, snow avalanches, weather, and seracfall) that threaten the basin. At times you maytrade one for the other, making decisions difficulteven for experienced guides.

Professionals often rely on experience to helpguide their decision making process. Howeverexperience based decisions are not alwaysflawless. Studies have shown that novices andprofessionals make decisions using “heuristics” ormental shortcuts. These shortcuts allow for quickdecisions during complex tasks and are based onlimited information. Two heuristics thatprofessionals are especially prone to are “socialproof” and “familiarity”. In this case the existingcampsites and historical use of this area may fallinto McCammon’s “social proof” category. “Thesocial proof heuristic is the tendency to believethat a behavior is correct to the extent that otherpeople are engaged in it” (McCammon, 2002).One of the two guides had also been to the areamany times and camped in a similar location onseven previous trips without incident. His decisionmay fall into the “familiarity” category. “Thefamiliarity heuristic is the tendency to believe thatour behavior is correct to the extent that we havedone it before” (McCammon, 2002).

Complex terrain in the Alaska Range demandsattention to detail every step of the way and timingwill always be a part of it. Using all of our tools toavoid and reduce exposure will help to reduce therisk but cannot take away all of the risk. The

decision to camp in this location worked for manypeople for many seasons but did not this time.Based on this tragic event, we can conclude thatthe hazard of camping in this location is greaterthan previously assumed and we cannotrecommend it for future climbers.

6. CONCLUSION

The Alaska Range presents some avalancheproblems that do not exist in non-glaciated andlower elevation mountains. Climbers need to tunetheir senses to the different problems and higherrisks found in these areas. Terrain traps includingcrevasses and cliffs carry high consequences.Icefalls are unpredictable and poorly understood.Besides the obvious hazards associated with bigavalanches, the Alaska Range is an inherentlyhostile environment. Surviving a traumaticavalanche is unlikely, and rescue is even lesslikely. Most climbers fly 45 minutes from thenearest town of Talkeetna to the glaciers of theAlaska Range to start their expeditions. Theremote location makes rescue and recoveryextremely difficult. Out of 45 climbers killed inavalanches only 17 were recovered. Theremaining 28 bodies were lost in the accumulationzone of the glacier. Even in instances where thewhereabouts are known, the benefits of recoveryor a rescue attempt may be outweighed by the riskto rescue teams.

6.1 Future ResearchIcefall alpha angles and avalanche frequency arepoorly understood. The high alpine zone of DNPholds numerous hanging glaciers, in some casesabove common climbing routes. The dishednature of glacial valleys creates a very steeptransition from steep or vertical terrain to relativelyflat ground below. In addition, the chunky andhigh density of icefall may behave differently thanstandard snow slab avalanches. Regressionanalysis of alpha angles on large avalancheevents has not been done, but may shed somelight on icefall behavior in the Alaska Range.

A detailed study including hazard mapping of the14,200 ft. basin on the West Buttress of Denali(advanced basecamp) could help prevent a masscasualty avalanche in the future. The large slopeshanging above the traditional camp zones havecreated avalanches that dusted camp and leftdebris close to tents. The destructive potential ofa 50 or 100 year event is poorly understood in aplace where upwards of 200 climbers can becamping.


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Acknowledgements:Special thanks to Denali National Park, ChugachNational Forest, and Alaska Avalanche School forhelping make this project possible. Also to Paulaand Leighan for giving us time to work in the lastweeks of pregancy.

7. REFERENCES

Coombs C. (1992). Kahiltna Peaks Expedition.

McCammon, Ian. (2002) Evidence of HeuristicTraps in Recreational Avalanche Accidents.Available from Snowpit Technologies,www.snowpit.com

McClung, David, and Peter Schaerer. (2006) TheAvalanche Handbook, 3rd edition. Seattle: TheMountaineers Books.

Mcintosh S., Campbell A., Dow J., Grissom C.,(2008). Mountaineering Fatalities on Denali. HighAltitude Medicine and Biology. Volume 9, number1.

Pinchak A. (1968). Avalanche Activity on theVaughan Lewis Icefall, Alaska. Journal ofGlaciology, Vol. 7, No. 51.

Smith B. (2005). Analysis of the HuntingtonAvalanche Accident 2/15/2005. NPS document.

Waterman J. (1991). Surviving Denali: A Study ofAccidents on Mount McKinley, 1903-1990, AACPress, New York.


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historical analysis of avalanche fatalities in denali

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