Avalanche

The compass direction a slope faces, which governs how much sun and wind it gets. Both shape the snowpack: sun weakens layers through melt-freeze cycles, wind loads leeward slopes with extra snow.

A mass of snow releasing and sliding down a slope, anywhere from a harmless sluff to a slope-wide slab avalanche capable of burying a party.

A collapsible aluminum or carbon pole, assembled and pushed into the snow to pinpoint a buried partner's exact depth and location once an avalanche transceiver has narrowed the search, before anyone starts digging.

A small metal shovel with a detachable handle, carried collapsed and assembled to dig out a buried partner once a probe has pinned their location -- digging through avalanche debris by hand isn't realistic.

A radio device worn by everyone in a party, transmitting a locator signal at all times and switching to search mode to find a buried partner's signal during a companion rescue.

The search, probe, and dig sequence a party performs for a buried partner in the minutes before professional help can arrive, the only realistic rescue option for most backcountry avalanche burials.

A cohesive layer of snow releasing all at once along a fracture line, usually where a weak layer fails underneath a stronger one. The far more dangerous of the two basic avalanche types.

The single biggest factor in avalanche likelihood: most slab avalanches release on slopes between about 30 and 45 degrees, steep enough to build tension but not so steep that snow sloughs off before it can accumulate.

Loose, unconsolidated snow sliding as individual grains rather than a cohesive layer, typically smaller and slower than a slab avalanche but still capable of knocking a climber off their feet on steep terrain.

The full layered structure of accumulated snow on a slope, built up storm by storm over a season. Instability comes from how well, or poorly, those layers are bonded to each other.