Geomorphological Development Caused by Landslides in the Northern Area of Mt. Shiroumadake, the Hida Mountains, Japan

This paper describes the Holocene development of landslides in the northern area of Mt. Shiroumadake in the Hida Mountains of central Japan. Late Quaternary landforms caused by glaciers or landslides are common in the study area, where previous studies have provided basic information on glacial landforms with only few details on landslides. This study classifies landslide topography into three types : I, II, and III, based on air photo interpretation and field investigation, to reveal morphological characteristics. Type I comprises up-hill facing scarps or linear depressions without a deforming landslide body. However both type II and type III have a visible landslide body. Only type III features frontal debris accumulation. Type I is distributed almost throught the study area. Type II and type III are distributed on slopes underlain mainly by serpentinite and stratified rocks comprising of shale, sandstone, felsic tuff, and tuff breccia. Gravitational rock creep and resulting rock deformation seem to be important in the formation of type I and type II. Type I landslide seems to be transformed into type II landslide with rock deformation on the slopes in the order :(1) gravitational creep,(2) deformation with a discontinuous slip surface, and(3) slide with a continuous slip surface. Radiocarbon dating and tephrostratigraphical evidence reveal that landslide activities began in the early Holocene epoch, and have continued until the present.