Technique for interpretation of archive and recent satellite images to study the slope processes dynamics in the Geyzernaya river valley (Kamchatka)

Based on the database of spatial thematic data sources for the Geysernaya River valley (Kamchatka), the work was carried out to identify the areas of the greatest activation of modern exogenous processes and the manifestation of endogenous processes over the maximum possible time interval (more than 50 years). Space images of high spatial resolution (0.5–3 m), received from Key-Hole-4 (1964), GeoEye (2009), Pleiades-1A/1B (2013, 2016), WorldView-2 (2017) satellites, results of field survey and UAV imagery in 2021, literature and archive materials were used as sources. The developed interpretation technique included both sequential interpretation of preliminary geometrically coordinated multi-temporal images and their digital processing: brightness quantization, calculation of vegetation index NDVI, formation of color multi-temporal composite, which allowed to separate vegetation-covered and bare slope areas by formal features and increased the overall reliability of interpretation. Calculations based on the interpretation results determined that the proportion of the total valley area affected by modern slope processes was 10.5 % in 1964, 14.8 % in 2009, and 13 % in 2017. In the process of images interpretation, it was established that slope processes dominated on the left bank of the Geyser River, where more than 75 % of the area of all outcrops (or 10.2 % of the total studied area of the valley) was concentrated, which is apparently caused by confinement of this valley side to the caldera limiting circular fault, which preserves its activity, and also by the presence of the area of modern uplift there. On the right bank of the river, large areas are occupied by ancient large gravitational shifts, possibly associated with collapsing edges of extrusive massifs. Landslides-slides and erosion in the groundwater outlets are predominant among the modern processes here. The right bank accounts for less than 25 % of the area of all outcrops (or 3.3 % of the total study area).