Anchors
Trees, bushes or rocks protruding though the slab that may help hold it in place.

DISTRIBUTION:
Anchors need to be thick enough to be effective. The more thickly spaced, the more effective. Sparse anchors, especially combined with a soft slab, have very little effect.

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SNOWPACK PENETRATION:
Anchors that don't stick up through the weak-layer have no effect. They need penetrate to well into the slab.


ANCHOR QUALITY:
Spruce and fir trees with branches frozen into the slab are a much more effective anchor than a tree with few low branches such as an aspen or lodgepole pine. Also, snow falling off of trees tend to stabilize the snowpack around trees.

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SLAB TYPE:
Anchors hold hard slabs in place much better than soft slabs--like the difference between cardboard and tissue paper when affixing them to a bulletin board with a thumbtack.


STRESS CONCENTRATION POINTS:
Avalanche fracture lines tend to run from anchor to anchor because they are stress concentration points. In other words, you stand a better chance of staying on the good side of a fracture line by standing above a tree instead of below.


"FLAGGED TREES":
"Flagged trees" -- trees with all the uphill branches stripped off--mean that tree regularly gets hit by avalanches.