70 лет Советской геоморфологии

Present-day ideas on the topography-field (field of elevations) are considered at the conceptual, methodical and technical levels. A conceptual apparatus of analytic geomorphology is introduced which is to represent adequately main components and aspects of the topography-field morphology. Notions of the external and internal forms (i. e. morphology and structure) are elaborated, the former being subdivided into topology and metrics, the latter-into vertical and horizontal structure. Metrics include, in turn, external a lTd internal geometry. Definitions are given for symmetry, hierarchy and structural position. The topographic structure is shown to be of importance for the topography functioning as a material system. The morphological study of the topography is shown to be of current concern with a view to the automatic processing of the remote sensing data and development of the computer-based geoinformation systems and geomorphological cadastres.

The paper analyses methodical approaches and discusses results obtained by regional stationary and experimental geomorphological studies carried out in Turkmenian deserts with a view to choice of industrial construction sites and gas pipes routes. The studies resulted in maps of eolian topography and wind-erosion processes, as well as in the territory's subdivision based on engineering-geomorphological characteristics. Practical advices are given as to optimum position of the sites and routes as well as to the construction work organisation and technology considering the topography preservation and protection.

Problems of paleotopographic oil and gas traps are discussed with special reference to the Perm region at the western border of the Urals. Prospects of searches for various types of traps are estimated as well as the degree of the methods elaboration.

The authors discuss the theoretical bases and methods of the automatic compilation of slope angles and exposure maps using aerial photoes. The mapping was carried out by the automatic cartographic system «AKS-MGU». The basic data are taken from digital photogrammetric models of topography. The algorithm is explained which had been used to approximate the basic digital data by cubic splines.

Maps and aerial and space photoes of various scales when simultaneously analysed permit to evaluate some features of the loess topography and engineering characteristics of loess. Most reliable data on the loess areas subsidence properties can be obtained from maps and aerial photoes on the scale of l:25000. The aerial photoes permit to discern minor depressions 20 meters and more in diameter, the depressions' average diameter within the area being 25 to 30 meters.

The rate of chemical, mechanical and total «transit» erosion of the Crimean moun'tains was calculated and corresponding schematic maps were compiled on the basis of data on rivers solid and chemical discharge. The chemical erosion rate averages to 0.007 mm per year, it is prevalent over the karst region of the Main Ridge (about 20% of the total area of the Crimean mountains) where the Upper Jurassic limestones are prone to both surficial and subterraneous dissolution. Mechanical erosion proceeds at a rate of 0.05 mm per year and reaches its maximum in the regions built of terrigenous ilysch. Total «transit» erosion on the average is about 0.06 mm per year, with allowance for flash floods and mudilows it may be high as 0.08 mm per year. Rivers remove from the Crimean mountains about 0,7 mln tons of solid and dissolved substance per year, almost 90% of the quantity being debris produced by the mechanical erosion.

A two-dimensional problem of the cliff surface evolution is considered taking into account the marine abrasion and denudation processes. The evolution is described using a set of three differential equations. When analysed the equations revealed the existence of two regimes of the marine erosion and denudation process, one of the regime being unstable. Occasional increase in debris supply to the beach may cause the transition from erosional to accumulative type of coast. Numerical solutions of the equations are obtained which describe the cliff evolution at two sites of the Black Sea coast. A technique of the erosion coefficient calculation is introduced, field observations data being used in the calculations.

Repeated levelling of high precision was carried out in 1948 to 1975 along the Garm geodynamical test site profile (right bank of the Obikhingow River) 35 km long. The profile runs across two large morphostructures, such as Sukhob-Vakhsh intermontane trough and erogenous uplift of the Peter the 1st Ridge. The Holocene tectonic movements of the morphostructures are estimated on the basis of the young fluvial terraces distortions, Geodetic data (usually of relative character) on the recent tectonic movements rates indicate mostly tendencies of the block morphostructures evolution during the Late Holocene.

Some features of gully formation are analysed, the gullies' characteristics are cited which distinguish them from balkas, erosional furrows and other linear erosional landforms. The gully considered to be a link in the drainage network which is in the state of active growth. The position of gullies within the whole system of linear erosional landforms is tentatively defined.

Within the limits of Byelorussia neotectonic processes controlled the pattern of the drainage net belonging both to the Black and Baltic sea drainage basins to a considerable degree. Differentiated neotectonic movements up to 150 to 170 meter range resulted in a regional monocline sloping towards the Baltic Sea, the main water divide thus having come into being. The present day river valleys inherited the Neogene valleys only in small fragments and have different direction over considerable areas. Some of lake depressions and local features of river valleys are due to local structures evolution. The hydrographic net often reflects structure of the glacial complexes.

Once the terms «geomorphic system stability» and «geomorphic system's state stabiLity» have been introduced and defined, mathematical techniques of the catastrophe's theory can be applied to the geomorphic processes study. It permits to construct mathematical models of situations connected with morphogenesis regimes transformation (the possibility is illustrated by the case of the sheet wash transformed into the linear erosion process) and to approach the problem of forecasting the extreme events in the relief's evolution.

A history is considered of the planation surfaces studies in the SE Caucasus mountains. Each surface morphology is described in details and reliability of its identification 'is discussed. In the author's opinion not more than 4 planation surfaces really exist in the region. Numerous surfaces (5 to 6 and more) which have been distinguished by other research workers are due to tectonic distortions of a single surface. The auf tor does not consider the Shahdag summit level to be a planation surface; ancient (Oligocene or Oligocene-Miocene) placation surfaces do not persist within the high mountain zone.

Обсуждение проблем теоретической геоморфологии на Иркутском геоморфологическом семинаре

Всесоюзное совещание по проблеме геоморфологической корреляции — ХVІІІ пленум Геоморфологической комиссии АН СССР