A tree well is a void or area of loose snow around the trunk of a tree enveloped in deep snow. Also known as "spruce traps", these voids present danger to hikers, snowshoers, skiers, and snowboarders who fall into them.
A tree's branches shelter its trunk from snowfall, allowing a void or area of loose snow to form. Low-hanging branches as on small firs further contribute to forming a tree well, as they efficiently shelter the area surrounding the trunk. Such wells have been observed as deep as 20 feet. They can also occur near rocks and along streams.
Tree wells may be encountered in backcountry, on ungroomed trails, off-piste, and on ungroomed/piste boundaries. The risk of encountering one is greatest during and immediately following a heavy snowstorm.
Victims can get trapped in tree wells and become unable to free themselves. In two experiments conducted in North America 90% of volunteers temporarily placed in tree wells were unable to rescue themselves.
Frequently victims end up in wells head first, complicating recovery efforts. Often they are injured in the process, suffering joint dislocation or concussion. When fatal, this type of incident is termed a Non-Avalanche Related Snow Immersion Death (NARSID).
During a snowshoe hike in Garibaldi Park near Whistler British Columbia Canada, at 2:00 a.m. on April 1, 2014, Christine Newman of Calgary, Alberta Canada went outside the overnight hut for a washroom break and became disoriented in the darkness and fell into a tree well. The next day the group from the hut, who thought Christine had gone back to the parking lot 14 kilometers/8.7 miles away, set off on the trail but spotted her orange backpack along the way. The group of six strangers performed CPR on her for 2 1/2 hours and kept her warm with blankets and hand warmers until search and rescue arrived. When she arrived in hospital , she showed no vital signs and her core temperature was 18 Celsius/64 Fahrenheit; she was hooked up to a machine to warm her blood. As of Sunday, April 6, 2014 she is reported to be conscious and making a good recovery. 
- "Tree well and deep snow safety". NW Avalanche Institute. Retrieved 2007-12-18.
- http://www.torontosun.com/2014/04/06/woman-rescued-after-spending-freezing-night-in-tree-well> Toronto Sun April 6, 2014