The bottom of the trough of Zhom-Bolok River along the entire length (about 70 km) was covered by flow of basaltic lavas about 13 ka BP. At present, extensive debris cones formed by river’s tributaries that mainly composed of debris flows material are developed on top of the lava flow. Eighty cones with a total volume of 210 million m3 were recorded in the valley; the largest of them are located in the middle and lower reaches of the river, where they occupy from 15 to 25% of valley’s bottom surface area. During the last 13 ka the average denudation rate in the catchment areas of the Zhom-Bolok River’ tributaries, draining Kropotkin Ridge, was 0.024 mm per year. Obviously, this rate is only the average minimum, because in some cases, the cones of larger streams are partially washed away by the river. Soil development and forest coverage on the debris cones at present indicate that at present the debris flow activity is low. According to research data in the adjacent territory, the peak of debris flow formation activity occurred at the beginning of the Holocene. Along with the effusion of lavas, the removal of significant volumes of loose material by tributaries influenced the morphology and development of the Zhom-Bolok river valley. In the post-eruptive period, the runoff initially went through lava tubes. It is partially preserved to this day. Cones development caused the filling of lava cavities with loose material, preventing the intralava drain, and promoted the formation of lakes at the bottom of the valley and the displacement of the river channel. The total incision of the river into the lava flow during the post-eruptive stage reached 6–7 m. During floods, an erosive floodplain is actively formed in the valley, including due to erosion of the distal parts of the cones. The results of petrographic and mineralogical analyzes of the Zhom-Bolok river channel alluvium suggest that currently it is mostly dominated by material carried by tributaries with the content of basalt fragments not exceeding 10%.