Chapter 7: Snow Avalanches

avalanche cord

a 10m rope that drags behind a person while skiing, snowboarding, or snowshoeing

slab avalanche

a large-scale avalanche formed when a slab of ice and snow breaks away from the main ice pack

avalanche transceiver

a portable device that emits a radio signal to assist in finding the location of a victim

track

along which the avalanche accelerates and achieves its highest velocity

run-out zone

avalanche slows down and deposits snow

point-release avalanches

begin with failure of a small amount of loose fluffy snow, widens as it moves downslope and commonly happen after a heavy snowfall

hoar

consists of ice crystals that are deposited on and within the snowpack when the air is moist and cold

berms

deflect avalanches away from buildings or parallel to roads

hoar frost

frost made from small ice crystals

30-45 degrees

most large avalanches are released from slopes at what angle?

sluff - small snow slide that does not bury a person; small - avalanche stops on the slope; medium - avalanche runs to the bottom of the slope; large - avalanche runs out over areas significantly less steep that 30 degrees, may reach the valley bottom and run up the lower part of the opposing slope

name the 4 sizes of avalanches and their run out

occurrences of avalanches, stability and strength tests, snowpack observations, weather

name the four types of information avalanches are based on

start zone, track, run-out zone

name the three parts of an avalanche's path

start zone

the area where the snowpack first fails

slope steepness

the most important terrain factor for avalanche formation is?

a buried weak layer and an overlying stronger slab

what do slab avalanches require?

annual mean snow depth

what does AMSD stand for?

wind slab

a body of thick, poorly bonded snow deposited by wind

snow avalanche

a rapid downslope movement of snow and ice, sometimes with the addition of rock, soil, and trees.