How do people die in avalanches?

1 in 4 from trauma

3 in 4 from asphyxiation

Learning about avalanches the hard way

• People invariably over estimate their skills in estimating avy risk
• Overconfidence would explain why about 90% of avalanche deaths are men and only 10% are women.
• Positive reinforcement plays a role in overconfidence. We go out again and again and still no avalanches
• Any given avalanche slope is stable 95% of the time

Someone with avalanche education may only be three times safe over a 10 year period than somebody who takes basic precautions and does not have any education or experience. Why:

1. Avalanche fatalities are rare
2. snow is stable most of the time, mistakes provide a poor feedback on accidents

The pros travel a well trodden path of proper training, mentorship, checklists, rituals, step by step decision making and group meetings

Many recreationalist operate without any overall system. In a nerve racking chaos, essentially rolling the dice in avalanche path after avalanche path

Chapter 1 Avalanche Basics

Slab – a cohesive plate of snow that slides as a unit on the snow underneath it. Picture a magazine sliding off an inclined table.

What makes a weak layer?

Nearly any type or snow can make a weak layer but they tend to be…

1. faceted snow – very weak, sparkly, angular snow that can form within the snowpack due to high temp gradiant
2. Surface Hoar aka frost
3. Low density or poorly bonded layers in new snow such as stellar crystals or plates (think snowflake on a sweater) or graupel (pellet like snow that looks like foam balls)

Dry Slab avalanches

• account for 95% of avalanche deaths in North America
• Dry slab avalanches on a persistent weak layer (which account for 67% of fatalities in USA and 63% in Canada can lie dormant in the snowpack fordays or weeks
• To make a slab avalanche slide you need a slope steeper than 30 degrees, a slab a week layer and trigger.

Cornice Fall Avalanches

• Cornices have a nasty habit of breaking further back than expected
• When cresting the summit or a ridge people are drawn to the edge to see the view. Resist this urge unless you know you’re on solid ground. it’s oftentimes a cornice.

Avalanche risk results from a combination of these three factors:

1. Hazard (In this case avalanches) – Hazard has two components – probability and consequences.

• Probability means the likelihood an event will occur.
• consequence means what will happen if it does.

2. Exposure: People or property effected by the hazard.

• To reduce exposure, edjust your terrain choice based on the conditions
• safety patrol will close terrain on a resort if it’s too dangerous.

1. Vulnerability: If an avalanche occurs and people are trapped in it. What is the likelihood the avalanche results in an injury or death?

Backcountry travelers minimize vulnerability in these three ways:

1. terrain choices – choose low consequence terrain
2. practicing low risk rituals – planning an escape route, getting out of the way at the bottom, etc.
3. Using avalanche safety great and regularly practicing avalanche rescue techniques.

Chapter 2 How Avalanches Work

In typical avalanches, the weak lager is the important one. Failure and fracture occur with the weak layer, not the slab.

Thick stout slabs are more difficult to fracture and they form better bonds to the crown, flanks and staunchwall than thin flimsy slabs. They are also more difficult to trigger on small avalanche paths.

Soft slabs with little strength can slide on nearly any slope, even small slopes and slopes with anchors. For avalanches the pull of gravity usually exceeds the force of friction on 30 degree slopes.

Anchors such as trees and rocks can hold slabs into place but depends on these factors:

1. stiffness of the slab
2. Number of anchors
3. Effectiveness of the anchors
4. Size and weight of the slab

How do avalanches fracture?

1. Crack initiation – broken bonds or cracks within the weak layer
2. Crack growth – more bonds break and the crack grows in size
3. Crazy propagation – crack becomes too long to support overlying load and all hell brakes loose.

The good news is hard slabs are far more difficult to trigger, but if you do trigger a hard slab it will lead to a much more deadly avalanche.

• soft slabs often break directly underfoot. Hard slabs typically break above so you get caught in the ride.

Trigger points have “sweet spots” where the bonds are weaker than on other parts of the slopes. Typically around bushes or rocks or in shallower areas.

These weak spots are invisible. To find them you can use tactics like digging pits. After you gain more experience you will learn which weak layers are continuous and which are more localized.

Wind  is usually the most important weather factor to consider in avalanche conditions. Wind can deposit up to 10x more snow than snow falling from the sky.

Settlement or sintering – the process of fresh snow forming bonds. Snow settles faster at warmer temps and slower at very cold temps.

Temperature –  Temperature is minor factor in the snowpack compared to loading. snow temperature is a lot more important than air temperature.

• it’s important to remain causation on a bluebird day after a big storm. Not because of temperature but because powder fever is roaring and any weak layers have just been loaded.

runout distance depends on: size / mass, slope drop, slope transition gentle transitions produce longer running avalanches) and roughness.

Chapter 3: Terrain

Danger increase with slope steepness (increasing from 30-50 degrees. bullseye is 38-40 degrees)

You can cut your probability of trigger an avalanche in half by choosing a 34 degree slope over a 39 degree slope. And in half again by choosing 31 over 34.

Use an inclinometer to measure slope steepness: best to use an app or sight it with your compass, don’t use the ski pole method. Measure steepest part of the slope.

What is the slope locally connected to? You don’t have to be on a steep slope to trigger it:

• A steep slope above can be triggered nearly as easily be crossing a gentle or flat slope below
• You can trigger flatter slopes below you from a flatter slope or ridge top.

Avalanches most commonly occur on planar or concave slopes.

Measuring runout distance – use vegetation clues (flattened trees or bushes)

Anchors: hold strong slabs in place and break up the continuity of a slab so fractures don’t prop what’s as far.

• The good news is anchors hold slabs in place, the bad news is if it does slide you’re in trouble because they turn into trauma objects.

Key point: terrain consequences are extremely important. What will happen if it slides? Will you encounter obstacles like rocks and trees? Is there a terrain trap like a gully or a steam? Will you go over a Cliff?

Chapter 4: Weather

Wind: Wind slabs are the result of wind-deposited snow, and they are dangerous for several reasons (figure 4-3). As wind blows and bounces eroded snow across the snow surface, the show gets ground into small, dense particles. When those particles come to a rest in the lee of an obstacle- -where the wind slows down-they pack into a heavy, dense layer that can not only overload any buried weak layer but also be stiff enough to communicate fractures within a buried weak layer. When strong wind starts to blow, it can turn nice fluffy powder into a dangerous wind slab within minutes, quickly turning safe conditions into dangerous conditions and taking people by surprise. Wind slabs can form in extremely localized areas, meaning only a few inches may separate safe snow from dangerous snow. People have often been heard to say, “I was just walking along, and suddenly the snow changed. It started cracking under my feet, and then the whole slope let loose.” Bottom line: be suspicious of any steep slope with recent deposits of wind-drifted snow.

Top loading: wind blowing snow across peaks and ridges to the other side of a peak or range

Cross loading: wind blowing across the slope depositing in convex low spots.

How can you tell ridge top wind directions? Look at the clouds near the ridges.

Slope aspect & Sun: fragile weak layers such as facets and surface hoar common develop and linger longer with a snowpack primarily on north through east facing slopes. This, most avalanches occur on north and east facing slopes.

Focus on the weight of the snow that falls during a storm, not just the amount of snow.

Right side up: storm stats of warm laying wet heavy snow which bonds well to old snow and then gets colder dropping lighter and fluffier snow.

Upside down snow: starts off light and fluffy and then heavy. Often described as slabby. You can lunch a like through the slab to the softer snow underneath.

Snow temperature and radiation: snow absorbs almost all of the radiant heat that reaches it and likewise Re-radiates any heat it contains. Because of its radiation ability it can be several degrees warmer than the air above.

During the day the Sun heats the snow, on clear nights it will then release the outgoing heat. If there are clods they will capture the heat. If it’s clear the best will escape and temps will be colder

Key points: Clear skies create the most-common weak layers that cause avalanche accidents persistent weak layers such as faceted snow and surface hoar. Usually, the longer the sky remains clear, the worse the weak layer.

Loading (added weight) on top of those weak layers makes them dangerous. Loading is caused by the weight of new snow, especially wind-deposited snow.

Radiation balance controls snow surface temperature even more than air temperature.

Because of this relationship, most wintertime avalanches occur on north- through east-facing slopes. Learn how radiation balance works and pay close attention to it.

Chapter 7: Hazard

Reading the avalanche forecast: the avalanche rating scale is on a five level danger rating scale

1. Level 1, green, low (like crossing a 2 lane road)
2. Level 2, yellow, moderate (4 line road)
3. Level 3, Orange, Considerable (8 lane highway)
4. Level 4, Red, High (16 lanes)
5. Level 5, Black, Extreme (32 lanes)

Most avalanche deaths occur in the considerable danger zone

Avalanche problem types:

• Loose dry: aka dry skiffs. Loose new snow avalanches that occur on steeper slopes.
  • Slope cuts can well, travel diagonally to the fall line to avoid being caught
• Loose wet: similar to lose dry but occur when the surface snow becomes wet and losses strength
  • You don’t want to get caught in these, they are heavier and pack a bigger punch than loose dry
• Wet Slab: percolating water from melting snow or rain decreases strength of buried weak lager.
  • Avoid being underneath terrain when these are active.
• Storm Slab: involve only new snow. Common weak layer interfaces include old snow surfaces or relatively weak layers in the snowpack.
  • Dig down with hand or shovel to see how the snow behaves. Jump on a rear slope to see how it responds. Typically settles in a few hours or days
• Wind slabs: Wind slabs are almost always present in the mountains, especially along ridges sis sential to learn to recognize and avoid them. Wind slabs form when wind erodes mai the upwind side of an obstacle, like a ridge, and deposits snow on the downwindit find them especially near ridges, but they are also often cross-loaded onto the sidstif lies, and complex wind deposits can form from complex wind patterns.
  • Experienced folks can use test slopes and slope cuts to test the slope.
• Persistent Slab: These slabs are on a persistent weak layer buried by one or two storms or by wind deposited snow which persistently produces a balanced after storms.
  • Produce most avalanches. Only way to manage is by avoiding on low angle terrain. Most of the time they’re triggered from a shallower area in the snowpack.

What Kind of Avalanche Dragon Are You Dealing With?

1. Is it dry snow of wet snow? These are two radically different beasts- dilfteras caused, forecast, behaved, and triggered.
2. What are the types of weak layers? Persistent weak layers (facets and surface hoard New snow? Wet snow? Weak interfaces? Each has its own characteristics,
3. What kind of slab? How thick? How stiff? Is it uniform or does it vary in thickness?
4. What is its temperature?
5. How slippery and continuous is the bed surface? Slick and continuous bed surfaces produce avalanches more easily than rough or discontinuous bed surfaces.
6. What is the distribution pattern? Almost all instabilities vary dramatically by aspect, elevation, steepness, and terrain type. What’s the pattern?
7. How many dragons are here? Remember that there can be more than one kind of avalanche problem in the same location, for instance, persistent weak layerslowerin the snowpack with wind slabs on the surface. It’s also common to have diferentare-lanche problems in different terrain, for example, wet avalanches at low dealiar persistent slabs on shady slopes, and wind slabs up along the ridges.

Important Questions

1. What kind of avalanche dragon are you dealing with? Rapid changes do not always cause avalanching. Stable snow can withstand a lot of abuse before it gets cranky.
2. Unstable snow can withstand only a small amount. Persistent weak layers produce avalanches for a long time.
3. How much change and how fast? Snow does not like rapid change. A meter (three feet) of dense new snow is a whole lot different than a meter (three feet) of fluff. And a meter (three feet) of new snow added over three weeks is a whole different story than a meter (three feet) added over three hours from wind drifting.
4. Time since changes occurred? Wind loading a week ago pales in comparison with wind loading an hour ago. Has the snowpack had enough time to adjust to changes?
5. What is the distribution pattern? Aspect? Elevation? Terrain type? Avalanche danger is almost never the same on all slopes. There’s always a pattern.

Chapter 8: Route finding &  low risk travel rituals

1. Go one at a time and leave someone in a safe spot.
   1. If something does go wrong somebody needs to be in a safe spot.
2. Never Cross Above Others – if you trigger an avalanche and someone is below you, your mistake could kill them.
3. Have an escape route planned – slope cut to a safe place.
4. Cross high on the avalanche path – if you do get caught in a slide. Snow below you can’t bury you.
5. Never go first.
6. Start Small and Work Your Way Up – find test slopes that have extremely low consequences.
7. Be obsessed with consequence.
8. Communicate – most accidents can be avoided by communication.
9. Pause at critical decision points –
   1. Pre trip planning the night before
   2. On the way to the trailhead
   3. Transceiver check at the trailhead
   4. Route junctions
   5. When digging a pit
   6. Every time we expose someone to avalanche hazard

Chapter 9: Rescue

Your transceiver requires lots of practice reps so you are familiar with the process in the event of a buried avalanche victim.

Due to stress and chaotic environment real life rescues are much more difficult than practicing on  flat land.

EMERGENCY PLAN of the search.

1. Assess the scene.

2. If possible use snow-sport equipment until you until you reach the finale search. Keep your backpack and gear with you at all times.

3. I am searching with my transceiver: SEARCH mode

I am not searching: transceiver OFF

4. At least one rescuer immediately starts transceiver

SEARCH, while looking and listening at the same time

5. Assemble probe and shovel only when the fine sent is concluded.

6. Transceiver search finished: set all transceiver to SEND

7. Excavate and perform first aid.

Grid Search

Hold the transceiver horizontally and keep it pointed in the same direction throughout the grid search. Start moving across the fall line, watch the distance indicator, and listen closely to the sound issued by the transceiver, as well as the distance numbers. At the location where the distance numbers (or the sound) indicate you are closest turn and walk in a perpendicular line to see if the numbers decrease. If they don’t, turn around and march in the other direction until the distance reaches a minimum again. Then turn 90 degrees and follow yet another perpendicular line across the slope to the lowest distance number, then turn perpendicular and find another close point, and so on, until the smaler and smaller grid brings you to the pinpoint location.

When you get close, it’s important to bend over or even get on your knees and run lie transceiver very slowly over the surface of the snow to make it even more accurate don’t bounce up and down. Keep the transceiver near the snow all the times.

Pinpointing

Finally, when you have narrowed the search to as small an area as you can with your transceiver, quickly assemble your probe and start probing in an ever-expanding spiral until you strike the victim. Leave the probe in place and start digging from the downhill side of the probe.

Check your transceiver in the parking lot

The leader should check everyone’s signal and then set their transceiver to send and and have somebody check theirs.

Probing

When you Locate the strongest signal start probing in an expanding spiral motion

Shoveling

For shallow burials (under 2 feet) dig down along the probe on the downhill side.

For deeper burials, start digging horizontally 1 meter downhill and dig horizontally to the victim.

For deeper burials or burials on very flat debris, start digging about twice the burial depth downhill of the probe. With several diggers, line up a shovel-length apart down the slope. The person closest to the victim should be doing most of the digging, and the others should be lined up below the main digger, passing snow out in the middle.

Don’t lift the snow, but instead slide it sideways, which takes much less effort. It’s important to rotate the diggers every two minutes, the same way bicycle racers take turns in the lead, rotating those digging closest to the victim to the back of the pack to recover. Make the hole bigger than you think you need, which always saves time in the long run. Once you can extricate the victim, you will need a large, flat platform to perform CPR and attend to the victim medical and environmental needs.

strategies for victims:

1. Yell to get your partners attention
2. Try to escape off the slab, try to move off the slab or up the slab. Grabbing a tree can help.
3. Get rid of skis and poles
4. deploy an airbag if you have one
5. Swim
6. As the avalanche slows down, use your arm to create an airpocket around your mouth to avoid asphyxiation

Strategy for witnessing an avalanche

1. make sure it’s safe. You don’t want to put yourself and other in danger trying to make a rescue.
2. Last seen area: Start looking where the victim was last seen.
3. Potentially call for help: If you had no way to identify where the victim might be, you may want to call 911 before beginning the search.

Executing a Rescue

1. Your priorities in a rescue are: 1) Yourself 2) Other survivors 3) the victim
2. Is it safe?
   1. When to consider saying no:- multiple avalanche paths &- the victim was buried by a natural avalanche from above &- The weather causing avalanches in the first place will likely cause more avalanches
3. Stop, Think, Plan: If it is safe to go in, then you go to the next step. As Doug Fesler says, “Sometimes the best way to go faster is to go slower.” Strong emotions, poor communication, equipment prob-lems, logistical problems all conspire to make rescues a mess, even among professionals Stop, think, plan.
   • Any witnesses? Do not let them get away. Ask them for information.
   • Figure out which group member has the most avalanche-rescue experience, and appoint that person as the leader.
   • Take a quick inventory of equipment: transceivers, probes, shovels, first-aid kit.
   • Turn transceivers to search and check everyone’s transceivers to make sure, because one transceiver inadvertently left on send can short-circuit the entire rescue. (This mistake occurs in many rescues.)
   • Find out who is good at what. Put your best transceiver people on the job.
   • Remind everyone to communicate with the leader.
   • Remind everyone to keep their equipment with them. Do not litter up the debris, or you will not know which equipment belongs to the victim and which belongs to the rescuers. If anyone needs to jettison any gear, be sure to make an organized pile well off the debris.
4. Transceiver Search
5. Triage: If multiple burials, focus on the shallowest buried victim
6. First Aid

Probing without transceivers.

• Look on the uphill of trees, at the bottom, and at the outside of turns.
• Look for something sticking out of the snow.
• Systematically probe in areas where the victim is most likely buried. Stand in a line across the hill, space your distance palm to palm and probe three times. Left, center and right.

Chapter 10: the human factor

• Accidents are hardly ever about individual practitioners, because their errors are a symptom of systemic problems that everyone may be vulnerable to.

•Do not rely on tighter procedures because humans need the discretion to deal with complex and dynamic circumstances for which pre-specified guidance is badly suited.

Do not get trapped in promises of new technology. Although it may remove a particular error potential, new technology will likely present new complexities and error traps.

• Try to address the kind of systemic trouble that has its source in organizational deci-sions, operational conditions, or technological features.

Human error in avalanche terrain tends to stem from physically easy or mentally easy decisions:

• Physically easy:
  • Not taking the time and energy to climb up or around avalanche hazard
  • Not taking the time to check everyone’s equipment, food, water, time constraints, etc
  • Choosing better snow quality over safer terrain
  • Not taking the time to get out a belay rope, check a map, jump on a test slope, dig a pit, consult a check list, read the avalanche report, etc.
  • Making poor decisions because of hunger, thirst, cold, heat, exhaustion, etc.
  • communication problems because of faulty tech, noise, distance, etc.
• Mentally easy: Cognitive bias and heuristic traps that we can fall into.
  • Familiarity: Successfully riding the same terrain in the past gives you false confidence in the future
  • Acceptance: activities that get us noticed or make people accept us. It’s easier to go along with a crowd into dangerous terrain.
  • Commitment: the desire to reach a goal or an objective makes you overlook avalanche signals.
  • Expert Halo: Blindly following  experts without following your own knowledge or instinct.
  • Social proof: showing off for your friends or other skiers. Seeing other tracks gives them confidence they can ski above their ability.
  • Scarcity: ie powder. The desire to get first tracks or ski before it’s all tracked out may lead to hasty decisions.

Using checklists can help us remember gear and procedures instead of relying on memory. Especially when we have little to no experience.

Encourage a dissenting opinion or Devil’s advocate – “how might I be wrong?”

Ulysses contact: before the day begins make your plan and do not waver. You can give yourself options with parameters but do not allow yourself to change plan.

Helicopter pilots use a green, yellow, red rating at the beginning of the day to mark which slopes they should attempt, use heightened caution, and avoid all together that day.