論文の公開元へ2019年5 月21日に木曽御嶽山で発生した大規模雪崩の状況と原因に関する考察
概要
A large-scale snow avalanche that occurred on 21st May 2019 on the slope between the Ichinoike and the Ninoike craters at Mt. Kiso Ontake was unprecedented in terms of location and scale. The avalanche flowed into the Yukawa River downstream of the Ninoike crater, where a mudslide also occurred. Field observations of avalanche slopes were conducted, and the sediments transported by the avalanches were analyzed from the geological viewpoint of grain size and mineral composition. Volcanic ash deposits, which derived from the 2014 phreatic eruption, were observed on the snow surface around the area where the avalanche was produced, suggesting the finegrained ash with low water permeability caused the avalanche generation. Simple snow block sliding experiments, investigating snow conditions and the effect of volcanic ash, indicated that not only appropriate weather and snow conditions but the presence of volcanic ash promote sliding. We concluded that the avalanche was possibly promoted by muddy water with volcanic ash in addition to heavy rains and high temperatures.
