A tree well is a natural snow formation that develops around the base of trees, particularly in snowy, forested environments. This phenomenon creates a concealed void or area of loose, unconsolidated snow, often posing a hazard to those recreating in deep snow conditions.
Physical Characteristics and Development
A tree well appears as a circular depression or void around a tree trunk, often funnel-shaped. The snow within these wells is loose and unconsolidated. This void can vary in depth, with some observed to be as deep as 20 feet in old-growth forests. The formation of a tree well is a natural process influenced by several factors.
Dense tree branches, especially from conifers like fir or pine, shelter the area directly beneath them from snowfall. This prevents snow from accumulating and consolidating around the trunk. Snow landing on branches can also shed away, further contributing to the void. Snow bridging, where a layer of snow forms across the top of the well, can hide its true depth. Tree wells are common in deep snowpack environments with large trees, particularly in regions like the Pacific Northwest of the United States and Canada.
Identifying the Danger Zone
Identifying a tree well requires awareness, as they are often hidden from view. Low-hanging branches and fresh snow can completely conceal the void, making it difficult to spot. Even if a depression is visible, its true depth and the instability of the loose snow inside can be deceptive. Their hidden nature makes them difficult to identify by sight alone.
The primary danger of tree wells is snow immersion suffocation (SIS). If a person falls into a tree well, particularly headfirst, they can become immobilized and trapped in the loose snow. The surrounding unconsolidated snow provides no solid support to climb out, and struggling can cause more snow to collapse around the person, further impeding breathing. Research indicates that a high percentage of individuals temporarily placed in tree wells could not rescue themselves.
Staying Safe Around Tree Wells
The primary method for avoiding tree well accidents is to stay clear of trees in deep snow conditions. Treat all trees as potential threats and give them a wide berth, particularly in ungroomed areas or during heavy snowfall. Always ski or snowboard with a partner and maintain visual contact; this is an important safety measure. If a partner falls into a tree well, they may need immediate assistance, as self-rescue is difficult.
If you fall into a tree well, try to grab branches or the tree trunk to prevent sinking deeper and stay upright. Once immersed, create an air pocket around your face to maintain breathing space and conserve air. Remain calm and resist the urge to thrash, as struggling can cause more snow to pack around you and deepen your immersion. Yelling or using a whistle to attract your partner’s attention helps, and removing ski pole straps allows for freer arm movement. Carrying safety equipment like a whistle, shovel, probe, and a transceiver can also be beneficial in deep snow environments.