1 29 T ra v er sing A v alanc he s ar e a le adin g k iller in mount ain ter r ain S ome t ime s t he c ause s ar e c om ple x and t he t imin g un pr edic t able If y ou ar e w or k in g in an a v alanc he pr one ar e a pr ior t r ainin g and ha v in g acce s s to e xper ienced aide is s t r on g l y ad v ised An a v alanc he be ac on is r equir ed A v alanc hes Kinds of A v alanc hes Dr y Sno w or P o wder Dr y sno w or P o wder a v alanches are common in the wint er af t er st orms par ticularly if windy the y are rare in spring or summer We t S n ow W e t sn o w a v alanches consist of hea vy w e t sunheat ed or rain r o tt ed sno w or w e t ne w sno w The a v alanches star t at a point and gr o w in f or ce and size as the y descend The y are most com mon in spring and summer par ticularly on southf acing slopes Slab Slab a v alanches consist of f airly cohesiv e la y er s of sno w and are poorly bonded t o the sno w beneath U nlik e loose sno w a v alanch es slab a v alanches star t o v er wide areas The whole slab begins sliding at once and with great f or ce Slab a v alanches are the most danger ous a v alanches