The area where a trigger initiates an avalanche.

When weather events (typically wind, snow, or rain) stress the snowpack close to its breaking point, often just a small thump will initiate a fracture and cause the whole slope to shatter like a pane of glass. Since snow varies quite a bit from place to place, sometimes several people can cross the slope before one person finds the “trigger point”.

Often the trigger point is a place where, 1) either the buried weak layer is especially weak, 2) the stress on the weak layer is especially great, or 3) the overlying slab is thinner or softer and a person can more easily affect the buried weak layer, which initiates a fracture. For instance, In continental or intermountain snowpacks with faceted snow as the weak layer, often the trigger point is near shallow, rocky areas on the slope or near a ridge where the slab is thinner. On a recently wind loaded slope, the trigger point is often where a thick layer of wind drifted snow has overloaded a steep part of the slope.