Anything natural or built into a slope which stabilizes the snow on the slope, or inhibits snow glide.
Anchors are usually considered to be a good thing. However, shallow snowpack anchors such as stumps, shrubs, and rock outcrops can become weak spots later when they are buried in some cases. Slopes with anchors may be more stable themselves but threatened from above also.
For an example of artificial anchors see the webpage on the ones made by Geobrugge of Switzerland.
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