Dynamics of Slope Processes in the Geysernaya River Valley (Kamchatka) According to the Interpretation Data of Multi-Temporal Space Images

Abstract

The interpretation of high-resolution satellite images (0.5–3 m) of three time slices (1964, 2009, and 2017) allowed us to identify the areas of activation of modern relief-forming processes. The outlines of outcrops were made by visual analysis of multi-temporal images, by brightness quantization, and by calculation of the vegetation index. The results were compared with the thermal survey data and verified in the course of geomorphological field studies and UAV surveys. The methodology for mapping the dynamics of slope processes based on the interpretation of multi-temporal images over a time interval of more than 50 years was tested in two key areas characterized by diverse and different-scale manifestations of exogenous geological processes. Calculations made on the basis of the image interpretation made it possible to determine that the last two large landslide collapses in 2007 and 2014 sharply reduced the area covered by vegetation: from 70 to 7% and from 60 to 4%, respectively. It was established that the ratio of the area with traces of activation of slope processes at the Northern key site has increased in the last 53 years from 20.9 to 30.2%; at the Southern site, from 12 to 30%. An asymmetry in the distribution of slope processes was revealed: all large modern displacements are observed on the left-hand side of the river valley, which, apparently, is due to the confinement of this side of the valley to the active ring fault outlining the Uzon–Geysernaya caldera, as well as the presence of numerous thermal manifestations and the neotectonic uplift area, recorded by interferometry data. At the same time, more ancient large gravitational displacements associated with collapses of the margins of the extrusive massifs occupy large areas on the right-hand side of the valley. The modern slope processes are predominantly demonstrated by small landslides and erosion in ground-water discharge areas. An analysis of the spatiotemporal distribution of sites of modern activation of slope processes has shown that, in addition to well-known triggers (heavy rainfall and earthquakes), a wider range of endogenous processes (gas-hydrothermal activity, uplift of the valley sides, the presence of active fault zones, and excessive rock fracturing) obviously has an impact on the displacement of the stone material on the slopes.