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Show SNOW AVALANCHES: THEIR CAUSE AND METHODS OF CONTROL Observations on Avalanches The first pioneers in Chibin had to cope with snow avalanches. These were so unfamiliar to the people from low country that such slides on railroad tracks were long thought to be simply heaps of windblown snow. This error was due to the relatively low relief ( aspect) of the surrounding mountains giving rise to doubts regarding the possibility of avalanches associated in the popular mind with high mountains, and to the fact that windstorms are a constant feature of the Chibin winters. The natives of this country, the Saams, have known of them from time immemorial, and snow avalanches figure largely in their legends and traditions. Our experimental station began observations of avalanches in 1933. For the first winter, only those avalanches occurring in the region of the Nefelin branch line were inspected. Beginning with the winter of 1934- 35, systematic inspection rounds were begun, to Mount Aykuayventchorr, including its southern ramifications, to the west end of Mount Ukspor, to the southern ramifications of Mount Kukisvumchorr, and along the slopes of Mount Vudyavrchorr to a point 15 km up the Belaya River ( Enemanisk), among other places. Some small avalanches were possibly missed this winter. Beginning with the winter of 1935- 36, all avalanches in settled districts were promptly reported to the station, and thus only a few isolated slides could have gone unrecorded. Periodic inspections of avalanches in the area of Hackmann Pass were also carried out from the Kolsk base of the USSR Academy of Science near Lake Little Vudyavr at Mount Apatit. Observations were made of the avalanche terminus pile, the lay of the avalanche, and the break- away site only where weather and relief conditions permitted access. The volume of snow in the terminus mound and the density, formation, structure and consistency of the component snow were measured as part of the examination. Since only the largest and most destructive avalanches have been written up, the opinion has prevailed that small avalanches are not dangerous. However, 500 m3 of snow going over the right of way can overturn a locomotive and car with 50- ton load ( avalanche of April 24, 1934, on Mount Ukspor). An avalanche of not even 200 m^ volume, slipping no more than 20 m, is dangerous for a skier. To understand the physical nature of an avalanche, more than volume must be taken into account. The properties characteristic of a certain type of avalanche may be seen more often and more clearly in small slides. Because of the specific climatic conditions in Chibin, certain types of avalanche do not attain great size and may even go unnoticed. Such slides are still of interest because their particular properties furnish abundant information on the various causes of avalanches, the nature of avalanche movement, the shape of the terminal mound, and other specifics. The possibility is not excluded here of the type of avalanche represented by small slides creating great damage under the right weather conditions, in Chibin and other similar mountainous districts. We refer here to avalanches of dry snow fallen during still weather. The experimental station inspected all avalanches. All those 200 m and over in volume were measured, which meant that nearly as many more went unmeasured. In the areas regularly inspected about 80 sites were plotted where avalanches - 31- |