Abstract
As the result of a long-term observation from August 1971 in a small scale landslide area in which many instruments were setted up, it was shown that the soil mass was divided into some small blocks and each block behaved complicatly with each other in usually, and in the case of a large deformation occurred, each block behaved systematically. This fact suggested that, even in a small scale landslide area, the movement mechanism was very complicate.
In this period, as a comparative large deformation occurred in this landslide area from July to August 1973, the causes were investigated. As the result of the investigation, the causes were softening of the soil by long rain between June and July 1973 and increase of load at the upper part of this area. This load was only one percent of the weight of the main movement soil mass. This phenomenon seems to be worth notice as a example that a few variation of weight gives an opportunity for recurrence of laddslide movement in a landslide area which has tended to stability after the landslide movement.
