Udmurtia: A Combination of Ancient and Current Landforms on the Eastern Part of the Russian Plain

This paper considers ancient and current landforms developed under the influence of specific features of the geological history in the Neogene and the Quaternary and recent exogenic processes. The regional morphostructure is characterized by cuesta-like ridges, stepped landscapes (three surfaces of different ages with different heights), and relict denudation small-hilled terrain called “puga.” It has been proven that the puga deposits are sediments of ancient Late Permian and Triassic rivers, while the puga hills are inversion forms. The relict morphosculpture related to periglacial phenomena in the Pleistocene is widespread. It includes the periglacial alluvium of Pleistocene terraces in river valleys and asymmetric cross-sections of small and medium-sized river valleys filled by slopewash–solifluction loams; in the interfluve areas widespread are aeolian landforms such as sand covers and continental dunes (up to 8–12 m high), as well as relic permafrost forms including polygonal–block and depression microterrain, cryogenic–nival niches, and cirques. The recent exogenic processes and related landforms are also analyzed. Channel processes, gully erosion, wave erosion of the banks of water reservoirs, and landslides are predominant. The gully erosion monitoring data on the period from 1978 to 2023 are reported. Karst and suffusion forms are rare. Gully forms of various genesis are widespread.