Abstract
This paper describes geomorphological and geological characteristics of landslide topographies in the Yuya Tertiary Formation, Shunan crystalline schist and Yanai gneiss areas, Yamaguchi Prefecture. They are classified into four geomorphological types of landslides; the simple type and complex type including subdivisions of nested type, parallel type and clustered type. The geomorphological development of landslides types is discussed from the view point of the topographic over-lapping of landslides units. The Tertiary landslides in the Yuya area are predominated in the nested and parallel types with large dimensions (more than 10 hectares). They occur as the simple type landslide controlled by the bedding plane, and develop into the nested type, then into the parallel type with complex inner structure. The landslides in the Shunan crystalline schist and Yanai gneiss areas, on the other hand, are mostly clustered type with smaller dimensions (less than ca. 3 hectares), and have somewhat slope-failure features. Landslide units in these areas are generated in detritus deposits, and gather into a clustered type along the valley.
