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Show B. Sunballs: Balls of wet or damp surface snow which run down a slope when sun action is effective, increasing in size as they descend. Their activity is an accurate measure of sun action; usually start under a cliff or trees or wherever a natural reflector exists; are not in themselves a sign of snow instability but indicate possibility sf sun slides. C. Snowslides and Avalanches: I. II, Types. a. Wild snow; chaotic, formless snow movements occasionally reaching large proportions; take place as result of abnormal quantity of new, very dry snow, laid down at low temperatures, b. Dry: Composed of any or all forms of dry snow; has distinct pattern, generally starting at a point or narrow break-off, becoming wider and deeper in descent, moves rapidly and when of major proportions can develop destructive air blast; comes down during or shortly after a major storm but cycle may be prolonged by cold weather which retards normal settling. c. Slab: Composed of windpacked slabs and may be soft or hard; especially prevalent on lee slopes. Unstable condition may persist for long periods; generally breaks off on a wide front with angular lines of fracture; descends with great power and speed. Typically, the entire slopes moves at once; most dangerous type to skiers. d# Damp: Similar in many outward characteristics to slab avalanches; composed of snow at temperatures hovering close to thawing-freezing; breaks off like slab but almost always under a cliff, at the crest of a slope or where there is a definite convex contour; moves more slowly than slab and starts with a portion of snow moving down blanketwise and dislodging more snow on the way, rather than whole slope moving at once. e. Wet J Caused by rain, sun action, prolonged thawing conditions; moves comparatively slowly but can attain great size and power; produces snov/ boulders and has tendency to run in same path yearly and become channelized. Sun slides are those directly attributable to sun action generally in connection with a reflector. The largest wet avalanches are produced by rain and general thawing conditions which penetrate to greater depth than sun action. Size: a. Small: Distinguished from sloughs by being definite movements with form and pattern; may run considerable distances but are shallow, lack momentum and are not dangerous. b. Medium: Attain fair size and momentum but not enough to overcome obstacles; stop as soon as they reach an easier grade or other obstruction; may be extensive but are shallow; mildly dangerous to life and property. -59- |