Fig. 22 October 1998 eruption of Hokkaido-Komagatake viewed from the eastern flank (one of the series photographs taken by Mr. Takashi Kudo, Educational Committee Officer of Sawara Town). Rolling ash cloud cells can be recognized, which may be formed as a slope-descending ash clouds from the earlier fallback, ahead to the later ash fall from the drifting ash cloud. Ishikawa and Hashimoto (1943) described remarkable similar phenomena at the time of 1942 eruption of Mt. Komagatake.