| What it is | Loose-snow void around a tree base |
| Danger | Snow immersion suffocation (SIS) |
| Where | Deep snow, in the trees |
| Mitigate | Ski with a partner in sight; avoid tree bases |
A tree well is the void or pocket of loose, deep, unconsolidated snow that forms around the base of a tree, hidden beneath the branches, in deep-snow conditions. A skier or rider who falls into one can become trapped head-down and suffocate — a danger called snow immersion suffocation (SIS). It’s a serious deep-snow and tree-skiing hazard, mitigated by skiing with a partner in sight and avoiding close tree wells.
This is general educational information, not safety training. Always ride trees with a partner in sight.
A non-avalanche killer
A deep-powder hazard while tree skiing or snowboarding in the backcountry — never ride trees alone.
Frequently asked questions
What is a tree well?
A tree well is a hidden pocket of loose, deep snow that forms around the trunk of a tree, where the branches prevent snow from packing down. In deep snow, especially after big storms, these wells can be deep and unstable, and a skier or rider who falls in can become trapped, often head-first.
Why are tree wells dangerous?
Falling into a tree well can leave you inverted and unable to free yourself, with loose snow collapsing around you — leading to snow immersion suffocation (SIS), a leading non-avalanche deep-snow killer. The more you struggle, the more snow can fall in. Many victims can't self-rescue, which is why partners are critical.
How do you stay safe from tree wells?
Ski or ride with a partner and keep each other in sight at all times in tree and deep-snow terrain, so help is immediate if someone falls in. Give tree bases a wide berth, stay on more open lines, carry a whistle and avalanche gear, and if you fall in, try to keep an air pocket and avoid thrashing while signaling for help.
Sources
- Tree well & deep snow safety — Avalanche.org
- Snow immersion suffocation — Wilderness Medical Society