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

Snowpack Anchors

Anchors such as trees, rocks and bushes help to hold the slab in place.


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.


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


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.


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.


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

Additional Terms:
Anchors Hard Slab Avalanche Slide
Aspect High Danger Sluff
Avalanche High Marking Snowpit
Avalanche Path Isothermal Soft Slab Avalanche
Avalanche Transceiver Layer, Snow Stability
Bed Surface Leeward Stability Test
Collapse Loading Starting Zone
Concave Slope Loose Snow Avalanche Stepping Down
Considerable Danger Low Avalanche Hazard Sun Crust
Convex Slope Melt-Freeze Snow Surface Hoar
Cornice Metamorphism, Snow Sympathetic Trigger
Corn Snow Moderate Danger Temperature Gradient
Couloir Persistent Weak Layers Terrain Trap
Cross Loading Point-Release Track
Crown Face Probe Trigger
Danger Ratings Propagation Trigger Point
Deep Slab Avalanche Rain Crust Upside-Down Storm
Density, Snow Remote Trigger Weak Layer
Depth Hoar Rime Weak Interface
Dry Snow Avalanche Runout Zone Wet Snow Avalanche
Extreme Danger Sastrugi Windward
Faceted Snow Settlement Wind Loading
Fracture Ski or Slope Cut Wind Slab
Glide Skinning, Skin Track Whumpf
Graupel Slab