### motion | descent:

Avalanche
* Many avalanches are small slides of dry powdery snow that move as a formless mass.
* Most avalanches break from steep slopes.
* Most avalanches happen during or shortly after storms
  - soon after a storm
  - involve snow
* Most avalanches occur during or just after a storm
  - soon after periods of prolonged or heavy snowfall
  - in the backcountry, outside of developed ski areas
  - spontaneously during storms under increased load due to snowfall
  - represent danger
* Some avalanches occur during storms.
* also serve as disintegrated material accumulation source.
* are a major, unrecognized, weather-related hazard
  - matter of physics
  - real danger anywhere there are mountains and lots of snow
* are a serious danger for winter sport enthusiasts
  - hazard on certain slopes at Crater Lake
  - abrupt, fast-moving collapses of snow, common on steep slopes in mountains
  - an escalating peril as skiers and snowmobilers push the limits into the back country
* are common in the mountains
  - on the high, steep slopes of the Volcanos during the fall, winter, and spring
  - dangerous
  - deadly
  - extremely dangerous in many areas
  - happening
  - in general a major threat to life and limb in mountainous areas
  - intricate and puzzling phenomena
  - most likely to occur either during or immediately following a significant snowfall
  - natural hazards
  - one of the greatest hazards facing winter travellers in the mountains
  - roller coasters
* are the greatest source of danger for mountain travelers
  - major cause of fatalities
  - mass wasting of the snowpack and are a particular hazard here in Colorado
* begin when an unstable mass of snow breaks away from a mountainside and moves downhill.
* break rocks as they fall down the mountainside.
* can be a hazard during winter months, especially during and just after winter storms
  - problem in some areas during the early spring
  - bury mountain side homes and destroy forests
  - happen wherever there is snow lying on ground of sufficient angle
  - motor
* can occur on long or short slopes
  - short slopes as well as long ones
  - only occur in a standing snowpack
  - pose a hazard both in winter and spring
  - take place on short slopes as well as long ones
* change the pattern of erosion and add sediment.
* commonly strip vegetation from the slope.
* destroy villages.
* do, however, occur occasionally in heavily timbered areas.
* happen on mountains with extreme amounts of slow fall and build-up
  - when big patches of snow slide down the side of a mountain
* have capability
  - extent
  - great extent
* kill people in the mountains every year.
* occur almost daily during the winter season unrecorded.
* occur in any area with significant snowfall and steep slopes
  - high-mountain terrains that receive winter precipitation as snow
  - the same places over and over
* occur most frequently when a new layer of snow falls onto the cement pack
  - often after major snowstorms or extended periods of thaw
  - on open slopes, in gullies, and in stands of open trees
* occur when the snow-pack starts to weaken and allows the buildup of snow to be released
  - soft snow under crust collapses
* often destroy roads, cover automobiles
  - occur on the Mountain City Ranger District, particularly in high, steep country
  - pour down the steep canyon walls during and shortly after snowstorms
* present huge objective danger to skiers and mountaineers.

### motion | descent | avalanche:

Debris avalanche
* are common in forested steeplands
  - fast cascades of rocks and soil
  - unchannelized debris flows that move very rapidly
* can also travel well past the foot of the slope due to their tremendous speed.
* occur all over the world.
* pose hazards that are often overlooked.