Numerous dacite blocks more than several meters in diameter are densely distributed at the foot of the northwestern scarplet of Mt. Dotoko in Central Shimane, Japan. The presence of these blocks implies the occurrence of large rock falls from the dacite scarplet in the past. The distinctive distribution and accumulation of the blocks indicates that they were deposited by repeated events of a style of debris avalanche.13;
The dacite rock body lies on clayey and soft lacustrine deposits, and thus any sliding movement tends to occur along the boundary plane between them. Such sliding may have influenced loosening of the rock mass. The presence of small open cracks on the top of the slope indicates that it is still unstable, and hence may fail during strong seismic vibrations in the future.13;