This study classified Japanese mountains based on mountain ordering using 1 : 500000 topographic maps, and examined the relationships of relief, relative relief and perimeter fractal dimension for the classified mountains. Mountain order was defined in terms of closed contour lines on the topographic map. A set of closed, concentric contour lines defines a first-order mountain. Higher-order mountains can be defined as a set of closed contour lines that contain lower-order mountains and that have only one closed contour line for each elevation. Relief, relative relief and fractal dimension were measured for ordered mountains using personal computer, and were defined as follows : relief E = H/A1/2, where H and A are the height and area of each ordered mountain, respectively; relative relief R= ∑ hi/H, where hi is the height of the enclosed, lower-order mountains, and represents the degree of vertical roughness of the ordered mountain; fractal dimension was measured for perimeter contour line by the pixel dilation method, and represents the degree of horizontal roughness of the ordered mountain. Japanese mountains were classified into 74 third order mountains and 11 fourth order mountains. The area of a third order mountain varies from 50 to 4712 km2, and that of a fourth order mountain is 2498 to 15563 km2. A significant relationship was found among relief E, relative relief R, and fractal dimension D for the ordered mountains (r=0.91, n=85), and can be defined by the expression :
LogE=-aD-bLogR-c
This relationship shows that Japanese mountains have the following morphological characteristics : a high relief mountain has low vertical and horizontal roughness, and a low relief mountain has high vertical and horizontal roughness. These characteristics suggest that slope angle of Japanese mountains converges within a certain range.
