Weak layers that continue to produce avalanches for several days or weeks after a storm. Persistent Weak Layers: Certain weak layers tend to stabilize quickly after a storm while other kinds of weak layers take much longer to stabilize. The three most notorious, persistent weak layer include: faceted snow, depth hoar and surface hoar. As you can imagine, persistent weak layers cause most avalanche accidents because the avalanche danger can linger several days after a storm, just waiting for a trigger. The presence of a persistent weak layer, alone, doesn’t necessarily mean danger. But If a buried, persistent weak layer also produces a high quality shear and is also weak on your strength tests, you should definitely avoid avalanche terrain where those conditions exist. 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   This glossary contains excerpts from "STAYING ALIVE IN AVALANCHE TERRAIN", by Bruce Tremper -