Three large regions of active gully erosion are known in Europe, those are south-eastern, central and southern ones. The main controlling factors are high degree of the land cultivation, a considerable runoff unevenly distributed, and high erodibility of loess and clayey rocks in the regions. Erosion first appears on arable lands, though many cultivated elevations in various parts of Europe lack gullies. That is mostly due to the fact that length and steepness of slopes there are insufficient for linear erosion to initiate. The gully erosion shows zonal pattern which depends on zonal features of drainage density, runoff irregularities and loess distribution.
Several types of erosional-sedimintation systems with closed cycle of evolution have been identified for the first time, such as «river – lake», «ephemeral stream – fan», which are typical of arid piedmonts. The types are defined and described Principal attention is given to the alluvial - proluvial - lacustrine processes interaction, to the transition from linear to areal erosion, and to a peculiar type of morphogenesis which forms the piedmont alluvial plains of complex - alluvial-proluvial, proluvial-lacustrine, alluvial-lacustrine - genesis.
Cartometric measurements of depth and density of dissection revealed differentiation in the dissection character and intensity between main orographic elements of northern and eastern European Russia. Specific features of the dissection pattern have been linked to geology, elevation, history of development and degree of agricultural cultivation. An erosional hazard has been estimated from the relief's morphometric indices, which is important in particular for regions with insufficient observation data on erosion.
Научные сообщения
Some results are presented of geological and geomorphological field studies in the epicentral zone of the 1991 Racha earthquake on the Great Caucasus southern slope. 5 stages are identified in the karst-seismogenic relief evolution, their morphological characteristics being described. In the authors' opinion, the epicentral zone of the Racha earthquake should be ascribed 7 to 8 surficial shocks intensity. They suggest introducing into seism-geological practice a special type of complex continuous observations that is seismic-geomorphological monitoring. Karst-forming processes in the seismic regions are to be recognized as a special variety - seismo-tectonic karst.
In regions of the Southern Coast of Crimea, Mountain Crimea and foothills which are characterized with seismicity 7 to 8, some landforms and deposits have been found which may be placed into the category of «seismogenic» formations by analogy with other seismic zones. They include rock masses detached by pressure-release fissures, rockfalls and debris screes, as well as gigantic landslides of the Southern Coast. Those formations when properly studied and mapped may help to develop more detailed scheme of the seismic regionalization of Crimea.
A conflict between technogenic factor and environmental characteristics of the Baltic coastal zone in Lithuania in the late 19th - early 20th centuries resulted in irreversible degrading of coastal lithodynamic system and formation of morpholithodynamic anomalies. The dimensions of ecologically endangered zone of coast and offshore slope exceed the area of conflict by an order of magnitude. For half a century the sea floor erosion rate averaged to 1.4*106 cub. m per year over a 40 km stretch. Average rate of the scarp retreat during 1905 to 1990 equaled to 0.8 to 2.5 in per year (or 12 to 38 thous. cub. m per year), the mean height of the scarp is about 3 m over a length of 5 km. During the 1980ies the rate of coast retreat increased from 0.7-1.7 to 3--4 m per year. Investigations into morpholithodynamics should be a priority when studying ecological problems of the sea coasts.
On the basis of data obtained by field geological and geomorphological studies in the Los Canarreos Archipelago the authors discuss some special features and time of formation of banier islands - specific sculptural-depositional wave-built landforms on shelf. Certain differences in the barriers elevation and composition of material permitted to distinguish between relict and present day landforms of hydrogenic and biogenic origin. Neotectonic movements of individual blocks near the shelf's edge have made an impact both on the barrier islands morphology and the recent dynamics of their coasts.
After having reviewed various schemes of regional subdivision of karst in the Permian Pre-Ural region and adjacent Ural Mountains as developed by different researchers, the author introduces a scheme of his own. It is distinguished for several features: it strictly follows the hierarchy of natural factors which controls the karst development, it takes more fully into account the environmental characteristics when delimiting territorial units; it applies morphological and morphometric characteristics of the surficial karst landforms to the regionalization.
Three classes are identified in the karst system changes with time, those are: short-period changes related to the system functioning, middle-period ones (many-years dynamics) and long-period macrocycles. The first class manifests itself by variability of rivers' mineralization through short intervals (seasons, phases of hydrological regime), the second class - by many-years fluctuations of liquid discharge, the third class - by different karst generations dated to the Pleistocene and Holocene.
Seasonal deformations of the shallows in the Chulym channel within the segment under study depend on the regime of movement of sandy and sandy-gravel ridges, the height of the ridges – 0.2 to 0.4 m - controls amplitudes of the shallows' crest fluctuations. Ridges of that order exist under velocities (averaged over the stream cross-section) from 0.4 m/s (the 1st threshold velocity) to 0.6 m/s (the 2nd threshold velocity).
The shallows are subdivided into three groups on the basis of average flow velocity (at different discharges) as related to the 2nd threshold velocity; the groups differ in the character of seasonal deformations of the channel.
In the course of long-term studies of small water reservoirs principal features of their coasts development have been established as well as dominant types of coasts. Essentials of the small reservoir - surrounding area interrelation are formulated as well as basic principles of the prognosis of their evolution.
Дискуссии
Оро-гидрографический парадокс осевой зоны Кавказа и некоторых орогенов шовного типа
Taking into consideration mechanisms of the glacial relief formation (as they are known at present) the classification of such a relief based on its genesis distinguishes two principal categories: glacial destructional relief and glacial constructional one. The former includes sub-categories of glacio-erosional and glacio-extrusive relief; to the latter belong sub-categories of glacio-erosional, glacio-protrusive, glaciodynamic texturogenic, and glaciotectonic and glaciokarst relief. Along with the listed categories many element-landforms and form assemblages of complex (mixed) origin are widespread in the areas glaciated at present or in the past; such are marginal glacial formations of constructional-glaciotectonic type.
Хроника
Основанная на базе системного подхода математическая ориентация, опираясь на глубокие теоретические обобщения, прочно вошла в ткань содержательного геоморфологического знания, сформировано особое направление со своими специфическими задачами и целями. Значительный подъем связывается также с развитием компьютерного моделирования. Эти идеи и послужили основой для проведения 23-го Бингхамтонского геоморфологического симпозиума «Геоморфологические системы» (25-27 сентября 1992 г., Университет Майами, США), посвященного 40-летию выхода в свет книги Стралера «Динамические основы геоморфологии» и 30-летию опубликования работ Чорли «Геоморфология и общая теория систем», Леопольда и Лангбейна «Концепция энтропии в эволюции ландшафтов». Тематика симпозиума сфокусировалась на переоценке роли теории систем в геоморфологии и реальной оценке современных достижений в этой области. Оргкомитетом симпозиума (сопредседатели: Дж. Филлипс, Университет Северной Каролины и Б. Ренвик, Университет Майами) были приглашены представители этого направления в геоморфологии из 8 стран: США (24 человека), Англии (2 человека) и по одному представителю из Австралии, Австрии, Венесуэлы, Германии, Канады и России.
Юбилеи
17 марта 1993 г. географическая общественность страны вместе со множеством учеников и коллег за рубежом отметила 70-летие крупного ученого и талантливого педагога профессора МГУ Юрия Гавриловича Симонова. Широчайший диапазон знаний и интересов в области геоморфологии, палеогеографии и физической географии, необъятный географический разворот исследований - от Херсонщины до Дальнего Востока - вот научный почерк Юрия Гавриловича Симонова - одного из ведущих геоморфологов современности.
ISSN 2949-1797 (Online)
