Deformations of the continental lithosphere are considered in connection with the World Ocean level fluctuations. Geodynamic crises - such as plates' disruptions or collisions - influence stresses in the lithosphere. The tectonic-eustatic curve is in close correlation with those changes. Sea level drops at the periods of the plates rearrangement during the geodynamic crises correspond to (quick uplift of the land» (W.M. Davis) and are accompanied by progeny. At the same time drainage network down cutting proceeds on global scale. Several independent methods provided evidences for global peneplain (more than 250 m above the sea level on the average in the Late Cretaceous - Paleogene. A notion of the limiting base level is introduced, that is a theoretical sea level towards which the real level tends under condition of total degradation of endogenic and exogenic relief-forming processes. The difference between the real and limiting base level is an important indicator of the state of global relief.
Seamounts are found on all large morphostructures in the Indian Ocean, mostly in the west, along mid-ocean ridges and fault zones. Unlike the Atlantic and Pacific oceans, tectonic and tectonic-volcanic seamounts prevail in the Indian Ocean, they are formed within rift zones as well as in areas of crust-breaking and crust blocks displacements. The volcanic seamounts concentrate principally within deep-sea basins and on longitudinal ridges. Highest seamounts appear as islands and form systems of well-known archipelagoes of the Indian Ocean. The morphology of many seamounts in the Indian Ocean is affected by their tectonic and tectonic-volcanic genesis; seamounts of block type are typical in particular of both periphery and near micro-continents in the Central part of the ocean. Results of geomorphological studies and deep-sea drilling data suggest a possibility of new seamounts to be found.
Дискуссии
Spatial-temporal structure of the relief may be described using conceptual-terminological system based on three initial concepts, those are: spatial organisation, hierarchic sequence and morphological sequence. The unified space-time of the relief is five-dimensional: it involves a time coordinate, three coordinates of the Euclidean space and a coordinate of grouping which describes relations between levels of organisation of the Earth surface relief.
Considerations of the unified space-time of the relief require development of concept of the relief's proper time - the geomorphology must re-discover the relief.
Principles and criteria are considered of morphodynamic unit’s identification in mountain topography. Territorial differentiation is based on mountain basins - the principle suggested by I.I. Khodzko as early as 1864, but neglected by later investigators. A definition of mountain basin is given and its principal characteristics are defined which permit it to be considered as an integral morphodynamic territorial system. A case study of Armenia indicates portability (hierarchy) of mountain basins and their internal differentiation with respect to elevation.
Types of bonds are considered which exist between linear landforms and tectonic zones. Two examples are given of correlation between geologic structure and tope-morphostructural situation. Based on previous experience a conclusion is made that tope-morphostructural maps give an additive reflection of geological effects. As to Kuznetsky Alatau, the most distinct structures in its topofield are those formed during the Mesozoic phase of the tectonic-magmatic activity.
Научные сообщения
Investigations of the bed relief structure revealed principal types of channel landforms which form hierarchic sequence of gravel formations on Lena, Aldan, Kirenga and Dniester rivers. Linear parameters of bed ridges appeared to depend on the river's order. The development of the channel macroforms is shown to result from the bed load transport.
A critical review of existing approaches to landforms typology and interpretation of the Kola Peninsula geomorphology permit to classify the regional relief as plateau type. The latter is considered to be a transition from mountains to plains. The plateau occupies (in its various modifications) most part of the peninsula and changes into typical plain in the extreme south-east.
Channel morphology and dynamics were analyzed in the upper reaches of the Neman River from the source downstreams (within the boundaries of Byelorussia) and revealed regular changes in the channel's principal characteristics depending on the river discharge and position in different geomorphological regions. The channel is divided into segments differing in dominant morphodynamic type, and in kind and intensity of the channel's deformations.
The geomorphic appearance of the Adjinour foreland is determined by rocks lithology and structure and by climate, which control the spatial pattern of exogenic processes and the soil erosion in particular.
High percentage of skeleton is typical of soils in Eastern Mongolia which develop on solid rocks eluvium (such as granites, syenites, siltstones). Colluvial, alluvial and lacustrine deposits of piedmonts and valleys also contain coarse material in large quantities. Mammals' activity accounts for so-called zoogenic weathering: animals bring debris to the surface and also enhance common weathering process. Examples from various regions of Eastern Mongolia show conclusive evidences of the skeleton reduction in soils within the areas of burrowing mammals habitation, Lasiopodomys brands Radde, Marmota sibirica Pall., and Meriones unguiculatus Miln.-Edw. in particular. The process rate depends on the degree of the soil reworking by the animals, that is on- the relative age of the holes. In some regions skeletonless soils may result from the burrowing mammals activity.
Geomorphic features are discussed which are typical of the areas directly influenced by faults, and special features of the topography and relief-forming processes in particular. Each morphological-genetic type of faults is proved to correspond to a certain set of landforms and geomorphic processes. Those characteristics can be applied to mapping the areas dynamically influenced by faults which are both of practical use and theoretical significance.
Наука за рубежом
Новые работы о стоке наносов и эрозии на Земле - Jansson M.B. A global survey of sediment yield // Geografiska Annaler. 1988. V. 70. ser. A. N9 1-2. p. 81-98.
Хроника
В течение 1986-1990 гг. в рамках межвузовской программы по изучению эрозионных и русловых процессов (научный руководитель - проф. Р.С. Чалов) организовывались ежегодные совещания, рассматривавшие самый широкий спектр вопросов, связанных с изучением деятельности постоянных и временных водотоков. На одном из них (Луцк, 1989 г.) было решено, кроме того, проводить рабочие совещания по более узким темам. Первое такое совещание под руководством проф. А.П. Дедкова и проф. Р.С. Чалова состоялось 30-З1 января 1991 г. в Казанском университете и было посвящено рассмотрению причин и механизма пересыхания малых рек и деградации речной сети Европейской части СССР. Заслушано 13 докладов из 8 вузов - участников межвузовской программы «Эрозионно-аккумулятивные процессы и почвоводозащита».
Вопросы геоморфологии аридных областей неоднократно привлекали внимание исследователей главным образом в связи с комплексным анализом природных условий при освоении пустынь. Назрела необходимость и специального рассмотрения этих вопросов ввиду их дискуссионности и большого практического значения геоморфологических работ в пустынях. Именно эти обстоятельства послужили причиной созыва Всесоюзного совещания по проблемам аридной геоморфологии, которое состоялось в г. Ашхабаде с 9 по 13 октября 1990 г. Организаторами совещания выступили Институт пустынь АН ТССР Геоморфологическая комиссия АН СССР и Институт географии АН СССР. В нем приняли участие представители различных научных и производственных организаций, вузов, всего 42 участника от 25 учреждений.
Юбилеи
ISSN 2949-1797 (Online)
