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Show The slab plus dry snow cycle justified these precautions. Rustler Face avalanched into the ski area. Stonecrusher avalanched into Corkscrew. was The Stonecrusher slide occurring at 11:15 the only one observed in motion due to poor visibility. Slides of all sizes occurred throughout the area, large ones in the Flagstaff Bowl and Baldy cirque. The storm faded out during the day and recommenced during the night. Some concern was felt for the safety of the highway on the morning of the 9th, Superior being the only critical area which had not thoroughly cleaned itself out. Observation was possible by 11:00 a.m. and a demolition charge exploded near the highway failed to dislodge any slides. The highway was, therefore, opened at noon. Restrictions on the skiing area were precautionary. No important hazard was expected and none developed. The few people in the area had all the skiing they could handle in the safe area. Rustler Face was blasted on the 10th without releasing any significant quantity of snow. It is seldom that the avalanche forecaster has such clear-cut situations to deal with. The chart of this storm reveals some interesting details. Why did 7 inches of snow on the 6th produce a dry slide cycle and 10 inches on the 9th produce none? The chart shows that the 7 inches fell with abnormal rapidity and was comparatively heavy. The 10 inches fell at a much slower rate, was lighter, settled more rapidly, and was of a different type. Wind action has been below average for both November and December. This is indicated principally by the lack of cornice formation. The east shoulder of Baldy is bare. The cornices along the comb of Superior are very small for the time of the year. Wind has also been unusually variable in direction. THE ALTA SNOW STUDIES ANNEX E. ALTA EXPLOSIVES OPERATIONS (Taken from the 19^7-^8 Annual Report) III. Controlled Avalanches During the previous season (19^6-^7) I suggested to Wasatch Forest officials that wo should make some experiments in controlled release of avalanches with explosives. The Swiss have long used this method of eliminating the avalanche hazard in certain critical areas. At Alta the policy of skiing down unstable snow has been in force for some time in locations where this can be done with reasonable safety to the operator. The method is entirely satisfactory but limited in its scope. Through explosives, it appeared likely that we could control or at least mitigate the hazard on larger slopes such as Rustler Face. For two reasons we did not consider using mortars or light artillery, the Swiss practice. In the first place, the weapons were not available. In the second place, there was the possibility of dud projectiles turning up on the highway or in the ski area. -69- |
