As the relation between the topography and the movement become distinctly at the developed stage of a block type landslide, the forms of landslides were classified into I, II, M, IV (Sasaki, Araya 2000).
The mode of landslide is usually considered to be translation only in type I, while in the others types it might be accompanied by plane rotation movement.
In this study the process of this plane rotation movement was verified by the data of the field instrumentation at Funaki landslide area, Hyogo prefecture.
After this area was divided into three zones of tension, main sliding and compression deform zone by the ground surveys, the ground surveys and the inclinometer observations at each zone proved the plane rotation. Several cracks in echelon at the right side and toe bulge below these, which showed the features of type can be explained by plane rotation movement.
The factor of plane rotation is thought to be important when evaluating and interpreting landslide instability.