Hill slopes in the Kawakami area，Okayama are known to be susceptible to landslide．The slopes consist of the Triassic Nariwa Group，which contains thin coal layers．Dips and strikes of the Nariwa Group change from place to place，and because of this complicated structure，many recent surface landslides overlap on tectonically deformed structures．
Characteristic minor folds of alternating beds of sandstone and mudstone are well recognized on hilly slopes．They are regarded as structures formed by surface sliding．These have following configurational characteristics：they tend to appear in restricted layers，have close folds，and axial planes of folds are almost horizontal．Based on the topographic situation that slopes containing minor folds are deeply eroded，they are regarded as remnants of old structures．Gently dipping bedding planes of minor folds may have influenced recent landsliding on slopes by forming potential sliding planes．