Abstract
Debris movement is supposed to depend on the form of the base rock surface. And so, four landslides in which base rock surfaces are well investigated, are picked up. The form of the base rock surface is devided into two; type I and type II in schmatic solid figures.
Considering on the relation between the form and debris movement, it is deduced that the mass in motion and its moving direction correspond to their concaved form.
In order to analize phenomenon of the mass movement from 50 to 100 years more accurately, it is important to know the form of the base rock surface.
