TENSION OF GEOMORPHOLOGIC CONDITIONS IN THE MARGINAL MOUNTAIN BELTS OF THE PACIFIC RIM

Abstract

The maps of naturally determined geomorphologic tension, scale 1:8 million, for the territory of the Russian Far East and the central fragment of the mountain system of the Andes (between 5°S – 19°S) were compiled. We are using the term “tension” to define predisposition of the territory for the development of catastrophic processes. Tension wasevaluated in nominal scores accordingly to the regional level of generalization. Assessment was based on the analysis of seismicity, amount of precipitation, the depth of the relief dissection and the spectrum of the dominant geomorphologic processes. The value of geomorphologic tension in the Russian Far East region ranges from 3 to 16 conventional points: in the Western Okhotsk Sea coast area it was estimated at 7–10 points, in the Sakhalin – 10–12, in the Eastern Kamchatka – 13–15 and in separate Kuril Islands – 16 points. Thus, the study results confirmed the formerly stated supposition about the increase of nature-defined geomorphologic tension of the NW Pacific Ocean sector from the west to the east. The zone of maximum potential development of catastrophic processes in the SE sector of the Pacific Rim is situated at the western mega slope of the Peruvian Andes between 9°S and 13°30’S and in the band width of 100 km along the Pacific coast. The geomorphologic tension of this area reaches 15–16 points due to natural causes. The tension on the eastern mega slope of the Andes ranges from 9 to 12 points, except for some areas where it increases to 13–14; on the Altiplano it decreases to 6–10 points. An important feature of the study area is the asymmetric distribution of geomorphologic processes, so the geomorphologic tension, which significantly different at the oceanic and the inland (continental) slopes of the mountain chain. Comparison of data obtained for the two segments (NW and SE) of the Pacific Rim allows reaching a conclusion about the general regularities of the distribution of geomorphologic tension in the territory of marginal mountain belts around the Pacific Ocean with more confidence. The areas of potential catastrophic processes are located near the edge of the continent in either case.

Keywords

• geomorphologic tension
• catastrophic processes
• mapping
• marginal mountain belts
• the far east
• andes