Tree well immersion (SIS) and deep powder snow suffocation survival¶

A tree well (or Snow Immersion Suffocation / SIS hazard) is a hidden, unconsolidated void of loose snow, low-hanging branches, and air surrounding the trunk of a conifer tree after heavy snowfall. When a skier or snowboarder catches an edge near an evergreen tree and tumbles headfirst into this hidden pit, the surrounding curtain of dry powder snow collapses inward like quicksand while their skis or snowboard wedge into the branches above, trapping them upside down in total darkness. According to the Northwest Avalanche Center (NWAC) and the National Ski Areas Association (NSAA) in the United States and Canada, non-avalanche Snow Immersion Suffocation accounts for roughly 20 to 25 percent of all in-bounds winter sports fatalities during deep powder seasons, and in survival experiments, 90 percent of volunteers placed into a tree well could not rescue themselves without a partner standing right outside the tree.

This guide walks skiers, snowboarders, snowshoers, and backcountry riders through what to do in the first 5 seconds if you fall into a tree well or deep powder pocket, why thrashing causes immediate snow compaction and suffocation, how partners must tunnel in horizontally from the downhill side rather than stepping on top of the hole, and how to prevent tree well traps on powder days.

Fai ʻeni he taimí ni .¶

1. If you are falling toward a tree well: let go of your poles and grab the tree trunk or branches immediately. Never keep your hands inside ski pole wrist straps when riding near trees. As you fall, reach out with both hands to hug the solid wooden tree trunk or thick upper branches to stop your head and chest from dropping inverted into the void below.
2. If you land upside down in snow: DO NOT thrash, kick, or wiggle your legs. In loose, unconsolidated powder snow, struggling acts exactly like a mechanical cement vibrator: every kick knocks hundreds of kilograms of snow off the boughs above and packs it tighter around your chest and face, sinking you deeper. Freeze your legs immediately.
3. Create a breathing air pocket in front of your mouth and nose first. Before the snow settles, cross one forearm or cup your hands in front of your face to push a small 10- to 15-centimeter (4- to 6-inch) hollow space around your mouth and nose, and tuck your chin or pull your neck gaiter/collar up to keep loose powder from falling into your airway when you inhale.
4. Stay calm, breathe slowly, and blow your whistle (if near your mouth). Panic hyperventilation rapidly consumes your small oxygen pocket and melts snow around your face with warm breath, which refreezes into an airtight ice glaze ("ice mask"). If you can reach the tree trunk with one hand, hold onto it so you do not slide deeper, and wait for your partner.
5. If you are the partner outside: NEVER step on the rim of the hole or pull the victim straight up by their boots/skis. Stepping onto the top edge of the tree well collapses a ton of snow directly onto your friend's head, and yanking upward on wedged skis or a snowboard only drives their head deeper into the pit.
6. Call Ski Patrol or emergency services immediately and dig horizontally from the side or downhill toward their head. Shout for nearby riders to help, call the resort Ski Patrol emergency number (or call your local emergency number: 911 in the United States and Canada, 112 across the European Union, 999 in the United Kingdom; see our ngaahi fika fakavavevave directory), locate the victim's head beneath the boots, and tunnel inward from the side/downhill to clear an airway around their face before unclipping their bindings.

Immediate survival and partner rescue decision flow¶

Whether you are the rider falling into a tree well or the partner who just saw your friend vanish under the boughs, follow this sequence immediately.

flowchart TD
    A["Rider Falls Near Conifer Tree or Deep Powder Pocket"] --> B{"Which Role Are You In Right Now?"}
    B -->|"I Am the Rider Falling Into the Tree Well"| C["Drop Ski Poles Immediately and Grab Tree Trunk or Heavy Branches"]
    C --> D["Stop All Leg Thrashing and Kicking to Prevent Snow Funnel Collapse"]
    D --> E["Cup Hands or Forearm Over Mouth & Nose to Carve a Breathing Pocket"]
    E --> F["Hold Onto Trunk if Reachable, Breathe Slowly, and Wait for Partner Excavation"]
    B -->|"I Am the Partner Outside Who Saw Rider Disappear"| G["Keep Strict Visual Fix on Exact Tree (Mark With Upright Skis or Pole Outside Rim)"]
    G --> H["Call Resort Ski Patrol Emergency Number / 911 / 112 and Yell for Nearby Riders"]
    H --> I["DO NOT Step on Top Lip of Hole and DO NOT Pull Up on Victim's Skis or Snowboard"]
    I --> J["Probe Gently With Hand Along Trunk to Locate Victim's Head and Chest Depth"]
    J --> K["Tunnel Inward Horizontally From the Downhill Side Directly to Victim's Face"]
    K --> L["Clear Snow From Mouth and Nose First, Then Release Bindings and Extract"]

How a tree well forms and why conifers look safe from above¶

Many skiers and snowboarders assume that if there is 2 meters (6.5 feet) of fresh snow on the open ski run, the snow stays flat right up to the trunk of every pine, fir, spruce, or hemlock tree. In reality, low-hanging evergreen branches act like a giant umbrella:

1. The branch umbrella: As meters of snow fall over the winter, the wide, downward-sloping lower branches of fir, spruce, hemlock, and cedar trees catch the falling snow and prevent it from reaching the ground around the base of the trunk.
2. The hidden 2-to-3-meter (6-to-10-foot) void: Directly beneath the bottom branches sits a deep, conical pit of air, tangled dead branches, and loose, uncompacted feathers of dry snow extending all the way down to the bare forest dirt or rocks, even when the surrounding snowpack is 3 meters (10 feet) deep.
3. The visual illusion: From 5 meters (16 feet) uphill, the snow-covered outer tips of the tree branches blend smoothly into the smooth powder slope. A rider carving a turn too close to the outer branch skirt ("skirting the tree") breaks through the thin crust of branch tips and drops straight into the hidden vertical shaft headfirst.

Ko e polokalama moʻui fakasitepu kapau te ke tō ki ha vaitupu ʻakau¶

Kapau ʻoku mole hoʻo mapuleʻí pe maʻu ha tafaʻaki pea ongoʻi ʻokú ke pitching headfirst ʻi lalo ʻi he ngaahi vaʻa ʻo ha ʻakau conifer, ko hoʻo ngaahi ngāue ʻi he ʻuluaki 3 ki he 5 sekoni kimuʻa pea toki tō ʻa e sinoú ʻokú ne fakapapauʻi hoʻo moʻuí.

Sitepu 1: Tau ke nofo hangatonu pe puke ho'o 'asi 'i he 'akau .¶

• 'Oua 'aupito na'a ke tui ha ngaahi ha'i ski pole 'i he ngaahi 'akau: Kapau 'oku loop ho nima 'i loto 'i he ngaahi ha'i pou 'i he taimi 'oku ke tō ai ki ha vaitupu 'akau, 'oku puke 'e he ngaahi pou 'a e ngaahi va'a pea fakapipiki ho ongo nima ki mui 'i 'olunga 'i ho 'ulu ke 'oua na'a ke lava 'o a'u ki ho fofonga ke fakama'a 'a e sinou. Ka skiing glades pe off-piste efuefu, puke ma'u pe ho'o ngaahi pou puke ta'e 'ai ho nima 'i he ngaahi fo'i 'uhiki'i nima.
• Uma ki he fu'u 'akau pe ngaahi va'a matolu 'i loto: 'I ho'o crash 'i he ngaahi va'a 'i tu'a, lunge 'aki ho ongo nima ki he fu'u 'akau fefeka pe ngaahi va'a matolu 'i loto pea takai'i ho ongo nima pe va'e 'iate kinautolu 'o hange ha koala kaka. Neongo kapau ʻe tō hifo hoʻo ngaahi sikí ʻi lalo ʻiate koe, ko hono tauhi ho ʻulú mo ho umá ke tautau ʻi ha vaʻa ʻi ʻolunga ʻi he luó ʻokú ne fakahaofi hoʻo moʻuí.
• Feinga ke ke takai ki ho tu'a pe tafa'aki (tuck and roll): Kapau 'oku ke pitching 'i 'olunga 'i ho'o ngaahi handlebars 'i he efuefu loloto 'oku fakaava mama'o mei ha 'akau, tuck ho 'aofinima pea takai ki ho tafa'aki pe tu'a koe'uhi ke tuhu ho fofonga ki he langi kae 'ikai ke tanu 'a e fofonga-ki lalo.

Sitepu 2: Ta'ofi 'a e kicking kotoa pe pea fa'u ho'o feitu'u ke manava ai .¶

Kapau kuo ke 'osi inverted 'i loto 'i he vaitupu 'akau pea 'oku cascading 'a e sinou 'o takatakai 'iate koe:

1. Freeze ho va'e he taimi pe ko ia: 'Oku kaila 'a e instinct fakaetangata kotoa pe ke ke teke ho va'e pea feinga ke ke luelue 'o 'alu hake. Teke'i kakato 'a e ue'i ko ia. Koe'uhi ko ho'o skis pe snowboard 'oku 150 ki he 185 senitimita (fute 'e 5 ki he 6) hono loloa pea loka'i 'i loto 'i he ngaahi va'a fefeka 'i 'olunga 'iate koe, 'oku 'ikai lava 'e he teke ho va'e 'o hiki koe ki 'olunga, 'oku ne lulululu pe 'a e 'akau 'o e 'akau pea 'oku ne pack hifo 'a e laui teau 'o e ribcaround yournow tigegrams.
2. Loka'i ha nima 'i ho fofonga ("Ko e Boxer Guard"): 'Omi leva 'a e nima 'e taha pe fakatou'osi ki ho fofonga. Tafiʻi ha ava ʻoku ʻi ai ha ava ʻi ho ngutú mo ho ihú, pea puke ho nima muʻá pe ongo nima kuo ʻosi ʻi ha ngaahi senitimita siʻi ʻi muʻa ʻi ho ngutú koeʻuhí ke tuʻu ʻa e sinou ʻoku nofoʻí ʻi ho nimá kae ʻikai ke lomiʻi palakū ki ho loungutú mo e ava ʻo e ihú.
3. Anu'i ha sinou 'i ho ngutu kimu'a pea ke toki huhu: Kapau na'e hu mai 'a e sinou ki ho ngutu lolotonga 'a e tumble, 'anuhi ia pe tafi'i ia 'aki ha tuhu 'oku 'i ai hono to'ukupu kimu'a pea ke to'o ha 'ea loloto ke 'oua na'a ke aspirate 'a e efuefu ki ho'o windpipe.
4. Fakalahi ho fatafatá ʻi he taimi ʻoku nofo ai ʻa e sinoú: Manava loloto pea kiʻi puke ho ongo tuliki ki tuʻa ʻi he ʻuluaki sekoni ʻe 10 lolotonga ia ʻoku nofo ʻa e sinou vetevete ʻo takatakai ʻi ho sinó; ʻoku tuku ʻe he meʻá ni ha ava fakalahi mahuʻinga ʻoku senitimita ʻe 2 (ʻinisi ʻe 1) ʻo takatakai ʻi ho ʻuhikiʻi huí koeʻuhí ke ke kei lava ʻo mānava ki loto mo tuʻa ʻi he taimi pē ʻoku tuʻu ai ʻa e ngaʻunu ʻa e sinoú.

Sitepu 3: Te ke lava nai ʻo fakaʻauha koe kapau ʻokú ke tokotaha pē ʻaupito?¶

‘I he ngaahi sivi faka‘ilonga ‘i he mala‘é na‘e fakahoko ‘e he tokotaha fakatotolo ‘i he ngaahi vaitupu ‘akaú ko Paul Baugher (Northwest Avalanche Center), ko e peseti ‘e 90 ‘o e kau sivi na‘e tuku ki he ngaahi vaitupu ‘akau mo‘oní na‘e ‘ikai lava ke nau mavahe ‘iate kinautolu pē. Ki he peseti ʻe 10 naʻa nau lava ʻo fakahaofi kinautolu, pe kapau naʻá ke maumauʻi ʻa e tuʻutuʻuni #1 ʻo e skiing efuefu pea heka tokotaha pē ki he ʻuluʻakaú, ko e founga pē ʻeni ʻoku ʻaonga:

• Nga'unu pe mo e ngaue 'oku tuai, fakakaukau'i, milimita: 'Oua 'aupito na'a ke jerk pe thrash.
• Tauhi e nima 'e taha ke taula 'i he fu'u 'akau fefeka pe ko ha aka/va'a matolu: Ngaue'aki 'a e fu'u 'akau ko ia ko ho'o rung ladder fefeka pe 'e taha.
• Do NOT try to push against the loose snow wall: Instead of trying to climb up the snow, see if you can slowly reach up along your own leg to pop your ski binding heel piece or unbuckle your snowboard ankle straps, only if your upper body is already wedged securely against the tree trunk so releasing your feet will not cause your body to slide 1 meter (3 feet) deeper down the bottomless shaft.
• Sivi'i pe 'e lava ke ke wriggle lahi ange KI LALO pe SIDEWAYS 'i he 'akau 'oku 'ikai ha me'a 'i ai: 'I he ngaahi 'otu 'oku 'ikai ha me'a 'i ai, 'oku fa'a ma'u 'e he tafa'aki hifo 'o e vaitupu 'o e 'akau ha 'ā manifinifi ange 'o e ngaahi va'a mo e sinou 'i he tafa'aki 'o e 'olunga. Taimi ʻe niʻihi ʻe lava ʻe ha tokotaha heka ʻoku maʻu ʻo toho kinautolu ki he kili ʻataʻatā ʻo e fuʻu ʻakaú pea tekeʻi tafaʻaki ki tuʻa ʻo fou ʻi he siketi hifo ʻi lalo ʻo e ngaahi vaʻá kae ʻikai ke nau ʻalu hake.

Fakahaofi hoa ngaue: founga ke keli ha taha mei ha vaitupu 'akau 'o 'ikai tamate'i kinautolu¶

Over 80 percent of tree well victims die simply because their partners kept skiing all the way down to the bottom of the chairlift, waited 15 minutes at the lift line wondering "Where is Dave?", and then rode the chairlift back up to start looking, by which time 30 minutes had elapsed and the victim had already suffocated.

Ko e taimi 'oku ke heka ai 'i loto 'i he fetu'utaki faka'ata mo e le'o 'o ho hoa pea sio kiate kinautolu 'oku nau tumble ki ha vaitupu 'akau (pe sio ki ha tip ski 'e taha, snowboard base, pe to'ukupu 'oku piki ki tu'a 'i lalo 'i ha 'akau conifer), 'Oku ke ma'u 'i lalo he miniti 'e 15 ke ma'u 'a e 'ea ki honau fofonga.

CRITICAL PARTNER EXCAVATION RULES FOR A TREE WELL:
1. NEVER step onto the top rim of the snow cone around the tree (collapses snow onto the victim's face).
2. NEVER grab the victim's boots, skis, or snowboard and yank upward (drives their head deeper and breaks legs/spine).
3. ALWAYS approach from the DOWNHILL or SIDE of the tree and tunnel INWARD HORIZONTALLY straight to the victim's head.

Polotokala keli hoa sitepu-ki-he-sitepu¶

1. Faka'ilonga'i 'a e 'akau pea ui ki he backup 'i he taimi pe ko ia:
   • To hoʻo ngaahi ski pe ngaahi pou ʻaʻau ʻo hangatonu ʻi he sinou ʻataʻatā ʻi ha mita ʻe 3 (fute ʻe 10) ʻi ʻolunga ʻi he ʻakaú koeʻuhí ke lava ʻe he kau Ski Patrol pe kau heka kehe ʻoku nau fakaofiofi atu ʻo sio ki he ʻakau totonú ʻi he taimi pē ko iá (ʻi ha vaotā matolu ʻo e ʻuluʻakau fir ʻe 500 ʻoku tatau, ʻe lava ke ʻai ʻe hoʻo toʻo ho matá mei he ʻakaú ʻi ha sekoni ʻe hongofulu ke mole ʻa e feituʻú).
   • Kaila le'olahi "TOKONI. SKIER 'I HA 'AKAU LELEI 'I HENI." ke faka'ilonga'i hifo 'a e kau heka 'oku nau paasi atu 'i he lele.
   • Fai ha tokotaha hono ua (pe ngaueaki ho o telefoni fakaongoongo lolotonga ho o hiki) telefoni ki he Laine Fakavavevave Fakahangatonu o e Ski Patrol o e resort (polokalama ia ki ho o telefoni kimu a pea ke heka; oku paaki ia i he mape pepa kotoa pe o e hala mo e taulanga hiki) pe taila ki he 911 / 112 / 999 mo e hingoa totonu o e hala mo e taulanga hiki.
2. Fakatu'uma'u 'a e va'e 'o e victim ke 'oua na'a nau 'alu loloto ange:
   • Kapau te ke lava ʻo sio ki he ngaahi sū, ski, pe snowboard ʻa e tokotaha ʻoku faingataʻaʻiá ʻoku lavelavea ʻi he ngaahi vaʻa ʻi ʻolungá, ʻoua naʻá ke toʻo hake, pea ʻoua naʻá ke kei vete honau ngaahi haʻí kapau ko e ngaahi ski snagged ko iá ʻa e meʻa pē ʻokú ne taʻofi honau sinó mei haʻane toe tō hifo ha mita ʻe taha ki he lalo luó.
   • Ka, kapau ʻoku ʻi ai ha tokotaha fakahaofi hono ua, ʻai ke nau pukepuke māmālie pe lash ʻa e boot/vaʻe ʻo e tokotaha ʻoku faingataʻaʻiá ʻo tuʻu maʻu ʻi hono feituʻú koeʻuhí ke ʻoua naʻa lava ʻe he tokotaha ʻoku faingataʻaʻiá ʻo hē loloto ange lolotonga hoʻo tanuhala ki honau ʻulú.
3. Fakatahataha'i ho'o fo'i avalanche mo e tanuhala ki loto mei he TAFA'AKI 'O E MO'UNGA:
   • Sio ki he tuliki ‘o e va‘e ‘o e tokotaha ‘oku faingata‘a‘iá ke fakafuofua‘i tonu ‘a e feitu‘u ‘oku mālōlō ai honau ‘ulú mo honau fatafatá ‘i he fu‘u ‘akaú (‘oku fa‘a mita ‘e 1 ki he 1.5 / fute ‘e 3 ki he 5 ‘i lalo ‘i honau ngaahi sū).
   • Laka takai holo ki he tafa'aki hifo (pe tafa'aki lalo) 'o e vaitupu 'o e 'akau, nofo kakato mei he ngutu sinou 'i 'olunga.
   • Use a collapsible aluminum avalanche shovel (or your hands/snowboard if you have no shovel) to cut a horizontal doorway straight inward through the lower branches and snow wall at the level of the victim's head, shoveling the snow downhill away from the tree so it cannot slide back in.
4. Clear the airway around the mouth and nose FIRST:
   • The moment your gloved hand touches the victim's helmet, jacket, or shoulder, stop using the metal shovel blade near their head so you do not strike their face.
   • Sweep the snow away from their mouth, nose, and chest with your hands, pull down any snow-packed neck gaiter or scarf, and scoop any snow plug out of their mouth.
   • Check immediately if they are conscious and breathing:
     • If they are conscious and breathing: Keep their airway wide open, reassure them, widen the horizontal trench around their torso so their chest can expand freely, and only then release their ski bindings or snowboard straps above so you can slide them gently out through your side tunnel.
     • Kapau 'oku 'ikai ke nau tali pea 'ikai ke nau manava (pe 'oku nau hanu pe): Extricate kinautolu ki ha tu'unga sila'i 'o e palapala 'i he taimi pe ko ia lolotonga hono malu'i honau kia, fakaava 'a e halanga 'ea, 'oatu 5 'uluaki manava fakahaofi (koe'uhi 'oku fakatupu 'e he 'akau lelei 'a e puke 'o e loto kapau 'oku fakatupu 'e he **hypoxia / paicue compression ʻoku akoʻi koe kapau ʻoku ʻikai ke ke lava ʻo ʻoatu ha ngaahi mānava fakahaofi, kamata hokohoko; CPR nima-pe ‘i he 100 ki he 120 ‘o e ngaahi fakamālohi ‘i he miniti ‘i he taimi pē ko iá) pea hoko atu kae ‘oua kuo a‘u mai ‘a e Ski Patrol mo e ‘osikena mo ha AED.

How to prevent tree well and deep snow immersion tragedies¶

Every single tree well fatality is preventable by following five non-negotiable powder-day rules endorsed by the National Ski Areas Association (deepsnowsafety.org) and MountainSafety.info:

• 1. Keep your partner in direct visual sight at all times (Not just "meet at the bottom of the lift"): Riding "with friends" does zero good if you split up at the top of the run and meet at the chairlift ten minutes later. In the trees or on deep powder days, ride in short leapfrog pitches keeping your partner within direct line of sight (or constant voice call-and-response every 15 seconds) until both of you exit the trees.
• 2. Take your hands OUT of ski pole wrist straps before entering any glade or off-piste run: Pole straps turn your ski poles into anchors that pin your arms above your head in a tree well and dislocate thumbs/shoulders on branches. Let your poles go the instant you lose balance.
• 3. Wear a loud pea-less survival whistle clipped right next to your chin: Tape or clip a 120-decibel pea-less plastic whistle (such as a Fox 40) onto your jacket zipper pull or backpack sternum strap just 10 centimeters (4 inches) from your mouth so you can reach it with your teeth even if both arms are pinned against your chest.
• 4. Carry an avalanche transceiver (beacon), collapsible metal shovel, and probe, even IN-BOUNDS on deep powder days: Many skiers leave their avalanche beacon and shovel in the car when skiing inside resort boundaries. On any day with 30+ centimeters (12+ inches) of fresh snow or when skiing resort tree glades, wear an active 3-antenna digital avalanche transceiver (457 kHz) in SEND mode and carry a pack with a metal shovel. A partner with a transceiver and shovel can pinpoint and excavate a completely buried rider under a tree in 3 minutes instead of spending 20 minutes guessing which tree they fell under.
• 5. Give conifer trees a wide berth, never cut turns under the branch drip-line: Stay out in the open white lanes between trees rather than hugging the trunks, control your speed so you can stop before hitting obstacles, and watch out for small 1-meter (3-foot) "baby" evergreen tops sticking out of the snow, that tiny green treetop is actually the crown of a 6-meter (20-foot) tall tree with a giant hidden well underneath the snow surface. For related winter mountain emergencies, read our skiing, snowboarding, and slope accidents, avalanches, and wilderness hypothermia and cold ngaahi fakahinohino.

Ngaahi fehu'i 'oku toutou 'eke .¶

Kuo vakaiʻi ʻa e ngaahi maʻuʻanga fakamatalá¶

• Northwest Avalanche Center (NWAC, United States) & Paul Baugher (Crystal Mountain Ski Patrol Director): Tree Well and Deep Snow Safety (deepsnowsafety.org), Empirical Tree Well Immersion Survival Research and Partner Excavation Protocols.
• National Ski Areas Association (NSAA, United States) and Canada West Ski Areas Association (CWSAA, Canada): Deep Snow Safety and Snow Immersion Suffocation (SIS) Prevention Guidelines.
• International Commission for Alpine Rescue (ICAR / CISA-IKAR, International / Switzerland) and Wilderness Medical Society (WMS, United States): Clinical Practice Guidelines for Prevention and Management of Avalanche and Non-Avalanche Snow Burial Victims.
• Avalanche Canada and Canadian Ski Patrol (Canada): Tree Wells, Deep Powder Immersion, and Asphyxial Burial Resuscitation Standards.
• European Resuscitation Council (ERC, European Union) and American Heart Association (AHA, United States): Special Circumstances of Resuscitation, Accidental Hypothermia and Asphyxial Arrest Ventilation Protocols.

Ngaahi fakahinohino fekau'aki¶

• Ko e ngaahi fakatu‘utāmaki ‘i he sikeí, sinoú, mo e ngaahi hekeheke .
• Ngaahi ʻAvaleni
• Ko e hypothermia mo e momoko 'o e toafa .
• CPR nima-pe