Evaluation of Steepness of World Mountains Based on Relief and Slope around Summits Using High-Resolution Digital Elevation Model

Abstract

This study extracted the summits of world mountains located between 60°N and 60°S and evaluated their steepness based on the relief and slope around the summits using approximately 30-m digital elevation models (DEMs). The summit was extracted if the center point of a 1-km radius was the highest in the circle. The relief of the summit was calculated from the difference between the highest point (summit) and the lowest point of the 1-km circle. The average slope of the summit was determined for the 1-km circle from the 30-m grid slope angle raster data derived from the 30-m DEMs.

The summits of the world were classified into types I, II, or III; type I was further classified into types Ia–Id. Extremely steep summits, i.e., types Ia (relief higher than 2,000 m and average slope steeper than 50°) and Ib (relief higher than 1,500 m and average slope steeper than 45°), were mostly located in the Himalayas. Several Ib summits were distributed in the Alps, Tianshan, and Andes ranges. Steep summits, i.e., types Ic (relief higher than 1,000 m and average slope steeper than 40°) and Id (relief higher than 500 m and average slope steeper than 35°), were distributed in the mountains of the Alpine-Himalayan belt, Pacific Rim, and Central Asia and African Rift valleys. The distribution of type I summits indicated the importance of active tectonism in their steepness. High-relief and gentle-slope summits, i.e., type II (relief higher than 500 m and average slope less than 35°), were distributed in the mountains of the passive margins in addition to type I mountains. Low-relief and steep-slope summits, i.e., type III (relief lower than 500 m and average slope steeper than 35°), were mostly located in the tower karst region of southern East Asia, showing the significant specificity of tower karst landforms in this region.