MODERN RELIEF-FORMING PROCESSES IN THE VOLGA DELTA LANDSCAPE (A CASE STUDY OF A GROUP OF KNOLL TRACTS)

Abstract

Modern relief-forming processes, especially exogenous, are always associated with the landscape features of theregion where they are observed. Anthropogenic impact on geosystems of different ranks often contributes to these processes. Emerging landforms often result from the interaction of a number of factors. The article presents the results of studies of negative landforms, mainly in the form of dips, fissures, and trenches, which in recent years began to form in the vicinity of the Baer knolls and their surrounding geosystems, located within the central subregion of the Volga Delta landscape. The paper provides their morphological and morphometric parameters. Both natural prerequisites and anthropogenic factors of the occurrence of these landforms are considered. Natural peculiarities of the studied Volga Delta landscape subregion include the presence of ridges on the horizontal and subhorizontal surface, called Baer knolls in the scientific literature, which contributes to the occurrence of temporary surface runoff. Another factor of natural genesis is the presence in the studied group of tracts of the so-called ‘chocolate’ clays of Khvalynsky age, usually deposited on a complex of granulometrically heterogeneous rocks. To some extent, climatic fluctuations recorded in the study area contributed to the emergence of the landforms. Anthropogenic preconditions include significant changes in natural relief during the economic use of the Volga Delta landscape. As a working hypothesis, another reason for the emergence of the studied landforms is seen in a decrease in the ground water level due to the reduced volume and duration of spring floods in the lower Volga. Based on the obtained results and taking into account the absence of karst substrate in the Volga Delta and a short period of formation, the genetic type of the formed relief is defined as anthropogenic pseudokarst