A slush avalanche occurred on Mt. Fuji on March 25, 2007, causing damage including disruption of the Fuji Skyline and collapse of tourist facilities. Large�]scale slush avalanches sometimes reach as far as downstream areas, causing flood damage. This kind of avalanche, called �gYukishiro" in this area, has been known since ancient times. In 1834, a severe slush avalanche occurred on Mt. Fuji, which was recorded in many historic documents.
Similar slush avalanche could be recurred on the mountain flank in the future. To prevent and mitigate damage, it is important to ascertain the actual conditions that occur during such disaster. Therefore, to investigate the development of the phenomenon, I analyzed historical records depicting the 1834 slush avalanche and also conducted field surveys at the damage sites.
It was found that the 1834 slush avalanche had been triggered by a severe collapse at the head stream area of the Yumisawa River. Diverging into the Kazamatsuri River, the avalanche flowed down to the stream area, engulfing sediment and trees that was flooding over the lava area along the way.

Key words�FMt. Fuji, slush avalanche, Yukishiro, historic documents, old maps