The geomorphology is considered to be an independent science which had been developed on the basis of both geology and geography. The initial geomorphological paradigm is a view of the Earth's topography as a result from interaction of endogenous and exogenous forces. The geomorphology studies topographic elements differing in magnitude and genesis: geotectures, morphostructures, rnorphosculptures. An importance is emphasized of elaboration of the plates tectonics geomorphological aspects. A necessity is stated to develop a new strictly geomorphological terminology corresponding the present state of knowledge.
Abyssal hills cover about 140 mln. sq. km of the ocean floor and represent the most widely spread relief of the Earth surface. They have not been observed only on flat abyssal plains and on sloping plains near the continental rise; here they are buried under sediments and can be found by means of seismic-acoustic sounding. In some places (such as rift zones of mid-oceanic ridges, aseismic rises on the ocean floor and transform fault zones) the abyssal hills were reworked later by tectonics. Bathymetrieal charts of some proving grounds reveal relicts of this type of relief. The abyssal hills seem to have been far more widespread at the ocean floor in the past, their formation preceded this of the flat and sloping abyssal plains.
Solid runoff (estimated by annual specific discharge) is considered to be one of most unbiassed way to erosion rate evaluation. After the specific discharge value calculated for largest rivers, all the landscape zones are subdivided into 5 groups differing in the erosion rate. The latter is mainly controlled by degree of cultivation and by liquid runoff. Zonal and azonal factors impact on the erosion rate is discussed.
Two models of erosion processes are developed: natural and natural-anthropogenous; the choice of a model depends on prevalence of channel (fluvial) or areal (sheet and gully wash) erosion.
Discussions
A current trend in geomorphology which was pronounced also during the session to consider endogenous and exogenous relief-forming factors as «equivalent» cannot solve nor dismiss the problem of causal relation between the forces and of their interaction through the geological time. A high degree of differentiation of the geomorphology (clearly seen in the session's papers) is a necessary and natural phenomenon. As causal relations in the topography_geospheres interaction are divided into direct and inverse ones, the author suggests to use this ontological principle of the division as one of logical bases of geomorphological trends classification. Once the principle is systematically used, it reflects satisfactorily the present state of the geomorphology as well as permits to foretell the process in the future.
Attempts to apply the systems theory techniques to geomorphological studies are critically revised. The system approach is but one of ways to the relief's knowledge, it cannot substitute for other traditional branches of theoretical and regional geomorphology, neither can it be a subject of a study. The relief as subject of the geomorphology may be formalized and presented as geosystems of various order. The formalization and the system approach can produce and result only on the condition that the aims of the analysis are strictly defined.
Scientific Research Methods
Present-day topography of the Caucasus has been studied using trend analysis. When compared with geological and geophysical data, and with data on paleostructures in particular (such as thickness and facies of Alpine stage sediments), the models of topography (both of regional and local components) proved to be adequate. As the comparison reveals, the trend analysis models of topography bear the information on both the relief's morphology and on all heterogeneous elements of structure which contribute to the regional morphostructure.
The authors used the mathematics of the fluctuations theory to show the depths field dispersions distribution to be equivalent to vertically directed tectonic forces. A boundary is drawn following maximum values of dispersions gradient; it divides the Pacific lithosphere into two provinces, differing considerably in vertical movements rate. Topographic field dispersion and geological-geophysical data if considered together clearly indicate the Western Pacific to be a separate tectonic formation, or lithospheric block, which the authors suggest to name Darwin plate. The area between Darwin plate and continental plates of North and South America is a region of active tangential movements; the region is similar tectonically to the Atlantic and is about of the same dimensions.
Short communications
River systems has been reconstructed which existed at the Caspian Lowland during different epochs of the late Pleistocene. Watercourses direction often did not correspond to the general southward slope of the lowland. Types of deltas and coastlines also changed in the course of time, mostly due to differentiated tectonic movements. Three main trends can be traced in the tectonic evolution of the region: gradual increase in general slow upwarping of the territory, continuous tectonic activity of extensive lineaments (mostly NW strike), corresponding to deep-seated faults, increase in the rate of differentiated tectonics of both platformian type (large arch-block uplifts and graben-like troughs) and salt tectonics. The noted features in drainage network evolution essentially contribute to knowledge of the Caspian Lowland paleogeography during the late Pleistocene.
Lineaments scheme of the Turan Plain has been constructed on» the basis of only topographic maps using simple technique. Some types of relief are identified as unfavorable for lineaments interpretation, those include table plateaus, sloping and sub horizontal plains modeled by wind action.
The lineaments distribution is analyzed with view to their length and direction, lineaments of NW and NE trend being dominant. As far as their distribution, direction and precise position is concerned, the lineaments correspond to known fault lines within the Turan Plain which is considered to be an evidence of their connection with tectonics; the lineaments pronounced in the modern topography are likely active during the neotectonic stage.
A quantitative expression of the mudflow wash over the Transcaucasian area is analyzed. From the mountains 6.7 mln. tons or 3.3 mln. m3 of solid matter are carried out annually. The overall water erosion rate is about 105 mln. tons, the mudflows erosion being 6.4% of the total value.
All the principal factors of erosion beinf taken into consideration, a quantitative estimate of arable lands erodibility has been calculated for geomorphic regions of the Central Chernozemic provinces. The order of erosion preventive measures is determined after the calculated index of erosion hazard.
Computer modeling permits to study river terraces response on different types of tectonic movements. If the .rate of uplift increases upstream, the resulting terraces are of chord type, altitudes of synchronous terraces fluctuate due to self-oscillattion. The river's response to differentiated uplifts is pronounced not only within the raised area, but in the adjacent parts of the valley as well. Besides, all the responses of the valley and its terraces to the tectonics have prolonged aftereffects. Deformations of terrace series bring about destruction of most of earlier levels.
For the first time a morphostructural scheme of the lower Mekong plain has been compiled based on new geological, geomorphological and geophysical data and space photoes as well as on deep drilling data. Three units have been recognised, such as structural-erosional low mountains, basalt plateau and marginal continental plain corresponding to tectonic down warping. The latter consists of denudational and erosional-accumulative plains, and sedimentary delta plain. Both positive and negative neotectonic structures are identified within the sedimentary plain, they are well pronounced in the topography and to a certain extent in geophysical fields pattern.
Comparative analysis of morphostructures of Mekong and Hanoi (North Viet-Nam) plains indicates moderate down warping at vast areas of Southern Viet-Nam, the process rate increasing through the Quaternary. The climatic factor significance for morpho- and lithogenesis is elucidated.
The author puts the Mekong plain to the class of down warping plains adjoining marginal seas (Western Pacific type).
Morphology due to the Moscow ise sheet appeared to be complicated and but slightly reworked, marginal zones being more Widespread than it has been previously believed. Marginal landforms fix the active ice margin position during its retreat. Ice-detached masses and deformations due to ice pressure are characteristic of the terminal moraines.
Glacial topography of that time differs both from the Valdai glacial landforms and Dnieper ones. Reconstructions of the Moscow ice sheet structures became possible on the basis of the landforms direction and debris included in the till. The debris petrography of the Moscow till differs both from those of younger and older glacial till which argues the Moscow ise sheet to be an independent one.
Reviews
Everything on the coastal zone: The Encyclopedia of Beaches and Coastal Environments. Ed. Hutchinson, Ross, Publ. USA, 1982, 940 p.
Obituaries
ISSN 2949-1797 (Online)
