Belts of regenerated mountains including large arched uplifts, linear deformations and rift zones are widely distributed over Eurasia and North America. Mongolian-Siberian mountain belt is an example of such system.
Mountain belts of the Mongolian-Siberian type with complete set of zones are characterised with general arch-like uplifts of the socle due to isostatic upheavals above anomalous mantle lenses. Within isolated mountain belts individual forms replace each other across the belt. In the mountain belts associated with epigeosynclinal constructions the forms replace each other along the system's axis. «Uncomplete» mountain belts include only large arches and linear deformation zones and have no general socle uplifts.
Mountain belts of the Mongolian-Siberian type have their own elements of power supply in the deep structure, lateral movements of adjacent geoblocks influence the formation of their structure and act as an additional factor of the orogenesis.
The paper considers some possibilities of the mountains' morphostructural analysis on the basis of space data. Regional examples of space photoes interpretation are given, folds, blocks and volcanic structures were identified within Pacific and Mediterranean belts. The examples testify to the scientific and technological efficiency of the remote sensing application to geotectural and morphostructural studies of lineaments, linear and isometric structures on various scales. Space morphostructural analysis indicates the lineaments cross each other within the orogenic belts which is the evidence for more complicated pattern of deformations there as compared with island arcs.
Discussions
Mountain belts origin is discussed with special reference to transcontinental belts (Alps-Hymalayas and Andes-Cordilleras) and mid-oceanic ridges, the plate tectonics hypothesis being critically reviewed, Mountain belts belong to different taxonomic categories, but have many topographic features in common in spite of differences in lithospheric structure. Reconstructions based on the plate tectonics cannot explain most essential morphological features of mountains regions such as the Alps, the Carpathians, the Hymalayas, the Andes and others. The comparison between transoceanic and transcontinental belts reveals in the latter two classes of mountain-forming processes: geosynclinal and riftogenous ones. Convection processes in the mantle and stratification of the upper mantle and the earthcrust are but in small degree maifested in the mountain belts present morphology and outlines. The mantle's control over the earthcrusts's structural layers development on continents seems to lessen gradually upwards.
The paper discusses the problem of the origin of a large depression west of the Baikal Lake. It is argued that the depression was not due to tectonics (the earthcrust down-warping) but resulted from karst processes and the loss of soluble matter (halyte) from the sedimentary cover, which brought about the sediments shrinkage and the surface lowering, the deep depression thus being formed.
Short communications
An account is given of the techniques and results of measurements of the mass movement (defluction) rate on slopes in Armenia. The maximum rate has been recorded on the surface of the soil in subalpine and alpine belts-about 1.5 to 2 cm per year. Rate of stone field’s movement downslope is up to 4 to 5 cm per year.
Stationary observations of soil erosion on arable lands have been carried out on several watersheds within the drainage basin of the Protva River (tributary of the Oka River). Results obtained during the meltwater and heavy rains runoff appeared to be close. The paper discusses special features of deposition of eroded soil matter within the upper links of the drainage network as well as the influence of erosion and alluviation on slopes modelling.
Structural position of the Amsterdam basin is clarified and geomorphological scheme has been compiled using geological and geophysical data obtained during the cruise of «Dm. Laptev» RV. The basin first appeared in the Holocene as a system of sutural grabens. The further subsidence rate was controlled by the age of the oceanic crust.
A scheme of incised meandering channel evolution is introduced. The river valley's sinuosity, and valley meanders in particular, are of polygenetic nature. Their development is based on the meandering process which results (in the course of geological time) in valley asymmetry and local broadening of valley near the incised meanders bend and later in the incised channel transformation and development of a valley with a broad floodplain. Various types of valley bends are considered. A relationship is established between the meanders dimensions and bedload size.
The detailed aerial and space geological studies aimed for searches for structural oil and gas traps at the Volgograd region consisted in morphostructural analysis and structural-tectonic schemes compilation, The morphostructural analysis is most important and has been applied at all the stages of the work. The studies confirmed the ancient structures had been reactivated in the Pleistocene and Holocene, relief-forming processes dynamics were proved to bear a direct relationship to the buried structures stratigraphic scope and to their distance from large paleodepressions axes.
A case study of the Obshchy Syrt upland near Orenburg is discussed to demonstrate that the system of faults and fissures can be traced from the basernentand deep horizons of the sedimentary cover up to the Earth's surface where it forms lineaments. The lineaments direction is closely associated with regional tectonic elements, with flexuresin particular. The lineaments direction is proved to be bound up with the local structures morphology. Parts of the earthcrust, which are tectonically active at present, are note ceable in the topography as zones of high density of lineaments.
The mechanism of mountain rivers solid discharge formation and the significance of individual external factors are analyzed on the basis of data obtained by long-term stationary observations at the Black Sea coast in western Georgia. The rivers' bed load supply into the coastal zone is controlled by the erosion intensity in the drainage basin and depends considerably on cyclic fluctuations of precipitations at the area under study. A forecast of the alluvium supply into the coastal zone may be derived from the erosion characteristics within the drainage basins at the Black Sea coast.
History of Science
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Problems- of geomorphology discussed at the VIII All-Union conference on the placers geology
ISSN 2949-1797 (Online)
