A general equation of vertical deformations of the longitudinal profile of a river channel is proposed. It describes the change in time of the altitudes of alluvial river bed due to the change in the flow’s transport capacity along the length of the flow; abrasion and erosion of bedrock of the river bottom; the effect of sediment supply from slopes, and the general change in heights in the river basin due to tectonic movements. These processes and effects are described by empirical mathematical functions that depend on time, longitudinal coordinate, hydraulic characteristics of the flow and conditions in the catchment area and on the territory. The components of the general equation and of the mathematical expressions of individual processes are considered and the main combinations of erosion, stability and accumulation conditions in the river channel are obtained.

The purpose of the study was to establish the relationship between the types of morphodynamic river channel and tectonic and neotectonic structures of different sizes and orders. The typification of the channel and its elementary forms was carried out in accordance with the classification scheme of Moscow State University. Google Earth Pro and Yandex Maps resources were used in the process of deciphering satellite materials and obtaining quantitative information (relief height, length of a river section). Geologic data was analyzed using the materials from the tectonic zoning of the Perm region, maps of neotectonic block structures and geodynamically active zones and seismicity. It has been established that the set of morphological varieties of meanders and braided channels in the structure of morphodynamic types in the upstream, midstream and downstream of the Kolva River differs from each other. Thirteen sections with varying channel types were identified on the Kolva River. The morphometric characteristics of the elements of the channel and the bottom of the river valley were used as identification criteria. These are the size of meanders, the length of straight sections of the channel, the width of the floodplain, and others. The presence or absence of a connection between the development of morphodynamic river channel types and morphological varieties of meanders and braided channels with the geostructural plan of the study area is considered by identifying the spatial correspondence of the locations of morphodynamic sections of the channel and geological structures of different scales and different hierarchical levels. In zones of changing neotectonic activity between adjacent areas, a change in the leading varieties of meanders and/or braided channels was recorded. Areas of a relatively straight channel are replaced by a meandering channel within the forward folds of the Urals. Varieties of meanders are represented mainly by active forms (segmental, forced). In the Pre-Ural trough, the reaction of channel processes to changes in the activity of neotectonic and modern movements was most pronounced within areas in which neotectonic structures are complicated by structures of a lower order.

Beaded channels, which are alternating lake-like extensions (beads) and narrow runs between them, are widespread on small rivers in the steppe zone, but there are different points of view regarding their genesis. To establish the origin of beaded channels, a detailed topographic survey was conducted in two key sites of the valleys, sediments in sections and boreholes were studied, and different versions of the origin of the channel extensions were analyzed. The most ancient rear part of the wide valley bottoms is occupied by the first terrace – a leveled surface with relict cryogenic microrelief and long beaded oxbows, covered by loess-like deposits. The high-level floodplain forms a belt of river meandering at the level of the big meanders, it differs slightly from the terrace in height, but beaded oxbow lakes, ridges and small depressions are clearly visible on it. The middle-level floodplain was formed during the period of decreased discharge. Its fragments are located within the belt of displacement of second-order meanders. The low-level floodplain formed as a result of overgrowing of the former bottom of the wide channel. The floodplain of all levels and the modern channel are underlain by dense silt and loams with a total thickness of more than 6 m, similar in composition to the deposits of the first terrace. The channel lag facies formed by bedload sediments is not distinguished in the deposits. The beaded structure of the channels is maintained due to the absence of bedload sediments in the modern channel. Beaded-shaped oxbow lakes on the high-level floodplain and terrace may have a cryogenic origin, since permafrost existed during the formation of these surfaces, and the fine-grained texture of the underlying sediments is favorable for ground ice aggregation. However, they acquired a bead-shaped form after the channel was abandoned. The possible cryogenic origin of beaded extensions of the modern channel requires a more detailed study of the age and structure of the enclosing sediments. The formation of deep extensions of the modern channel is not associated with silting of the riffles, since the thickness of the agrogenic silt does not exceed 1 m.

Photographs of distinct channels and cross-sections of the valleys of the Kardaila and Kupavna Rivers are available at: https://geomorphology.igras.ru/jour/pages/view/dopmat

The article examines a quantitative assessment of basin erosion and suspended sediment yield in poorly developed catchments within the Lena River basin. The first catchment (15 740 km2) is located in the middle reaches of the Lena River near the city of Yakutsk. The second catchment (1709 km2) is located in the headward portion of the Bolshaya Cherepanikha River basin. The assessment was carried out using the erosion-accumulation model WaTEM/SEDEM, as well as a modified model developed by the State Hydrology Institute (SHI) applied to the forested catchments of the river basin. The amount of soil lost to erosion and suspended sediment yield were obtained for each catchment. The long-term average value of eroded soil within the catchment area near Yakutsk increased from 4.7 (2003–2007) to 4.9 (2015–2019) t/km2 per year most likely due to replacement of tree coverage with meadows in the areas effected by wild fires; and decreased from 7.2 (1985–1990) to 6.4 (2015–2019) t/km2 per year within the Bolshaya Cherepanikha River catchment likely due to expansion of tree coverage, decrease of meadows, and disappearance of cropland. To verify the models, the modeling results were compared with measured suspended sediment yield at gauging station. It was established that the observed value of sediment yield according to data from the Bom gauging station located within Bolshaya Cherepanikha River catchment also decreased during two studied periods from 0.41 to 0.37 t/km2 per year. The decline is explained by a decrease in the intensity of agricultural activity in the catchment, as well as an increase in the area covered by forest and a decrease in meadows. Sediment yield trends within the catchment area near the city of Yakutsk and the Lena River were also compared with each other. Thus, the measured value of suspended sediment yield in Lena at the Tabaga gauging station was characterized by an increasing trend from 8.76 to 10.82 t/km2 per year over the same periods. The results showed a significant contribution of basin erosion to sediment yield in smaller rivers (Bolshaya Cherepanikha River), while in the large rivers, like Lena River still remains very small.

The aim of this research is to determine the changes through time of the quantitative parameters of the thermal cirques along the abrasive coasts within the cryolithozone. The analysis of the processes revealed two opposite trends; a decrease in the number of the thermal cirques along the cryolithozone coastlines due to replacement of the older thermal cirques with new ones, and an increase in their number due to the emergence of new ones within the existent forms. This increase results from their division and the display of the new thermal cirques. Based on the calculated average density and size of the thermal cirques the model predicted that under the homogeneous physical geographical conditions the average density of thermal cirques along the abrasive coasts within the cryolithozone should increase with time, while the average size should decrease. The local physical and geocryological conditions influence the values of the dependence parameters, but their relationship remains the same. An examination of the obtained dependence showed that with time, the density and average size of the thermal cirques tend to reach critical limiting values. At the same time the retreating coastal slope continue to change, new thermal cirques appear, and partial or complete disappearance of the existing ones occurs. Thus, after a significant period of development, the morphology of the abrasive coast may reach a state of dynamic equilibrium. Analysis of six abrasive coasts using repeated satellite imagery showed an increase in density and a decrease in average sizes of the thermal cirque along three of them, and an apparent stability of parameters along the other three coasts, which is in an agreement with the obtained modeling results. The obtained regularities should be used when forecasting the dynamics of the Arctic coasts based on satellite imagery.

Sediment redistribution on the beach and offshore slope are the main processes forming the accumulating marine terraces of Iturup Island. The intensity of these processes is controlled by tectonic and seismic activity associated with Kuril-Kamchatka subduction zone. The long-term changes of the island ground level are due to vertical tectonic movement, while the short-term changes are associated with seismicity. Studies of morpholithodynamic processes in the coastal zone on the island of Iturup were carried out using the methods of paleoseismology, geomorphological analysis, and computer modeling. Based on previously collected data, analysis of topographic maps and satellite imagery, and field measurements on Iturup Island in 2022–2023, digital maps and digital elevation models (DEMs) of the coastal zone of the Kuril Bay were constructed. Four buried scarps were discovered within the beach ridge sediments on the accumulative marine terrace, indicating vertical coseismic subsidence that periodically occurs on the Sea of Okhotsk coast of Iturup. Based on tephra from the Tarumae volcano, the approximate age of the young beach ridges has been established (about 280 years). Applied 3D modeling predicted the flooding of the territory at different sea levels. Coastal profile of equilibrium developed from the DEM using the Dean model indicated that the modern marine terrace is stable. The SBEACH software was used to simulated storm surges and storm frequencies at different sea level scenarios. It was concluded that the erosion of the accumulative marine terrace, where the city of Kurilsk is located is possible either by catastrophic storms of rare recurrence, or after abrupt coseismic subsidence of the coast, which can occur during a strong earthquake in the area of the southern segment of the Kuril-Kamchatka subduction zone.

The submarine valleys of the north-western Okhotsk Sea have been describe using the expedition studies, cartographic materials and previously published data. The main factors influencing morphogenesis of the bottom relief include the cold water of Okhotsk Sea, the duration of ice cover, strong tidal currents, and an attenuated wave regime. Complex coastal topography is determined by the geological structure of the study area, seasonal sediments supply by rivers, ice activity, and coastal abrasion. Intensive exogenous processes have formed large morphosculptural forms of complex genesis, including submarine valleys. During the study of the submarine valley in the Penzhinskaya Bay, it was revealed that it has a V-shaped transverse profile. The valleys sides are smooth, with the western sides slightly steeper than the eastern. The width of the valley is 1.5–2 km on the northern tacks, and 0.7–1.0 km on the southern ones. The steepness of the slopes reaches 10–12 degrees. Shelikhov’s trench, which connects Bay of Shelikhov with the Okhotsk Sea, stretches in the meridian direction for almost 300 km and mergers with the TINRO depression. Its width ranges from 30 to 40 km. The northern part of the western side of the TINRO depression is cut by large erosive valleys of the meridional strike. In the southern part a dense network of erosive channels has been developed with an incision depth of up to 100 m and a width of 1–1.5 km. The transverse profiles of the channels have a well pronounced V-shape, which indicates an active flushing regime. The channel network has a dendritic pattern. Regardless the origin of these forms, the main factor controlling their development at the present is intense tidal currents, to clarify the genesis, it is necessary to obtain additional geophysical and hydrological data. The performed studies can be used in predicting the further region’s economic development.

The article presents the results of geomorphological studies of the area of widespread landslide processes in the upper reaches of the Okhodzha River basin (right tributary of the Okum River, Black Sea basin). The characteristics of the geological and geomorphological conditions and factors that contributed to the occurrence of a large landslide in January 2021 are given. It has been established that the main type of landslides within the Bedia site are landslide flows developing along the roof of Eocene and Oligocene (Khadum horizon and Maikop Formation) claystones. The thickness of landslide bodies ranges from to 34–78 m. The slope cover is mainly subject to displacement, including the bodies of previous landslides. It is shown that the main condition determining the development of landslide processes is the position of the Bedia landslide site at the junction of the water-logged carbonate rocks of Cretaceous age exposed along the Southern macroslope of the Greater Caucasus, and denuded foothills composed of the Paleogene clayey rocks. The landslides are triggered by prolonged precipitation and facilitated by the coincidence of the slope and the bedrock dip direction on the left slope of the Okhodzha River valley. Due to the large-scale development of landslide processes accompanied by erosion, an erosion-landslide badland was formed on the left bank of the Okhodzha River. The most unstable areas, not recommended for land-use due to periodic landslide movements, are the slopes of small valleys – left tributaries of the Okhodzha River, as well as their wide bottoms filled with landslide deposits. According to the main features of the geological and geomorphological structure, the studied area is similar to the Novoafonsky, Eshersky and Macharsky landslide areas previously described in scientific literature. Economic development of these territories should include not only constructive measures to protect against landslides (retaining walls, artificial terracing, etc.), but also the installation of drainage systems to reduce the water saturation of slope deposits and the water content at the base of the slope.

Geomorphological survey revealed a network of the recently active faults that control the formation of main features of the modern relief in the central part of the Altai Mountains. A paragenetic analysis of the identified latest faults has been performed. The result of the paragenetic analysis with reconstruction of three stress fields turned out to satisfy the formal reliability criteria. In general, the results of the paragenetic analysis confirm the preliminary conclusion about the formation of the fault network of the Central Altai in three dynamic settings made after the implementation of the first stage. They made it possible to construct schemes of faults active in each of the three reconstructed stress fields. Judging by the results of the analysis, the rock massif of the central part of the Altai Mountains is at the third stage of destruction, when individual faults are connected into a complete fault network with a characteristic structural pattern, and the earth’s crust is broken into a system of blocks contacting along faults. The block subdivision of the Central Altai is formed by a system of faults forming an ensemble of a right-lateral strike-slip dislocation. As the scale of the studies increases, the number of identified faults increases as well. On the regional neotectonics maps of 1:1,000,000 scale only major ridges and depressions are expressed in the relief as boundaries of large blocks. A network of faults outlining blocks within the ridges and depressions is identified on neotectonic maps of 1:50,000 scale. In the central part of the Altai Mountains, the fault network follows the lower-level hierarchical structural patterns and orographic structure of the Greater Altai, e. g., northwestern right-lateral strike-slip faults, sublatitudinal reverse faults, and extension zones with a predominant submeridional extension. Paragenetic analysis resulted in a reliable reconstruction of the kinematic characteristics of the most recent faults of the Central Altai based on their position in the structural ensemble. The obtained schemes and settings of the recent faults can serve as a foundation for further discussion about the nature and mechanisms of crustal destruction in the region using seismological, GPS-geodetic and other materials.

The study presents the results of sedimentological investigation of the core recovered from from the Pervomayskaya-1 (Pm-1) borehole, which revealed the most complete structure of the upland loess-soil series (LSS) in the central Pre-Caucasus. The borehole reached a depth of 13.8 m. Luminescence dating for two samples from the core yielded ages of 62±3 and 102±7 thousand years, attributing the entire studied sequence to the Upper Neopleistocene. Lithostratigraphic units were identified based on macroscopic core examination and geochemical analyses. The Mezin pedocomplex (13.8–9.1 m, MIS 5) consisting of three paleosols was identified at the base of the section. Above it lies a horizon of Valdai loess (9.1–1.2 m, MIS 4–2) of substantial thickness with weak signs of interstadial pedogenesis in its middle part. The section is capped by a Holocene chernozem (1.2–0.0 m, MIS 1) showing signs of anthropogenic transformation in its upper profile. The LSS structure revealed in the Pm-1 core shows stratigraphic unity with previously dated reference sections and boreholes of the Pre-Caucasus LSS: Beglitsa (Bg), Vorontsovka-4 (V-4), Sladkaya Balka-1 (Sb-1), and Otkaznoye-20 (Ot-20). Moreover, the Pm-1 column fits within the main trend of increasing loess thickness and grain size from west to east across the Pre-Caucasus. For the Pm-1 and Ot-20 columns, consistent variations in magnetic susceptibility and grain size were identified. Using these consistent variations as chronostratigraphic markers allowed for a more detailed depth-age model for Pm-1. Based on this model, estimates of loess accumulation rates for the Late Neopleistocene and Holocene were calculated: maximum rates (15.9–17.5 cm/thousand years) correspond to the interval of 36–16 thousand years ago; elevated rates (11.4–12.5 cm/thousand years) align with the interval of 80–40 thousand years ago; low rates (9.1–10.4 cm/thousand years) were recorded in the interval of 128–81 thousand years ago; minimal rates (6.0–6.6 cm/thousand years) correspond to the interval of 13–5 thousand years ago. The intensity of loess accumulation in Pm-1 shows consistency with the most complete LSSs of Eastern Europe, as well as with the mineral dust concentration in Greenland ice core NGRIP.

The analysis of macroscopic charcoal particles in sediments of different genesis is one of the most common approaches to reconstruct the past fire regimes. The method requires a great deal of time and effort on the part of the researcher. It implies continuous sampling of the sediment core and counting of all charcoal particles with linear dimensions greater than 125 µm in a sample of fixed volume. The purpose of this paper is to present an automatic method that we have developed for the calculation of macroscopic charcoal particles using image analysis. This method is easily reproducible, not technologically demanding, and fast. It allows us to obtain additional palaeoecological information based on the study of geometric characteristics and particle area. A comparison of the results obtained by a standard manual count of the charcoal particles in the test samples and the number of particles determined from the image showed that the method was accurate enough for palaeogeographic reconstructions: Spearman correlation coefficient R = 0.85, R2 = 0.71, MAPE = 31.58% (the mean absolute percentage error), determined particle area comparison revealed R = 0.99, R2 = 0.98, MAPE = 21.45%. The results of macroscopic charcoal analysis of the peat core from Pobochnoye peatland (Buzuluksky Bor National Park, Orenburg region) are presented to demonstrate the capabilities of the developed method. One thousand samples collected from 10 m of peat sediments accumulated over 11.4 ka years were analyzed, and 6,000 images were processed. The results of the analysis include determined charcoal accumulation rates, fire episodes and inter-fire intervals, as well as classification of charcoal particles into grass and wood morphotypes. The variation in charcoal particle size was also estimated for each fire episode, providing additional palaeoecological information about Holocene fires.