Trigger Point:
When weather events (wind, snow, rain or sun) 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 tickle 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.
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