Retaltive age of topography (stage of denudational development) is introduced as a criterion of geological interpretation. The thesis is illustrated with examples from the Northern Urals and western Middle Siberia. The geological interpretation practice has been concluded to confirm Davis scheme, which states the topography correspondence to geological structure to change in the course of erosion cycle. A scheme of regionalization based on relative age of topography is necessary for automatization of geological deciphering. The author substantiates the necessity of general morphochronological scheme compilation by means of identification of natural stages in the topography development, which are independent on geological age.

Colluvial (slope) morpholithogenesis at the North-East of the USSR includes broad variety of slope proceses (about 20). According to the altitudinal zonality they form a special spectrum at each mountain belt. Slope processes are proved to depend on parent rocks composition. Special features are noted at each of mountain country under discussion (Chersky Range, Kolyma, Priokhotye). A genetic clasification of slope processes is introduced, which is based on differences in their mechanisms, the latter depending on composition, physical properties and consistency of loose slope (alluvial) deposits.

Two possible concepts about transition relief are suggested for the discussion: a) the relief reflects the appearance of the first signs of erogenous processes on the Earth's surface and indicates the increase of the process intensity up to the degree characteristic of the peripheral parts of mountain regions; b) relief is a complex which combines simultaneously features of erogenous and plain-platform regions. In accordance with the first concept the preorogenic zones of transitive relief are distinguished, in accordance with the second one the transition morphostructural zones are distinguished, two overlapped groups of morphostructures being formed within these zones. The forms of the first group follow ancient structures, which is typical for platform plains, morphostructures of the second are formed under the influence of geological structures of the same age of the neighbouring orogenic regions.

The gully danger has been estimated for the Middle Region of the USSR (West Siberian Plain, Kazakhstan and Middle Asia included) on the base of comparison of maps compiled by the authors, such as map of present gully distribution and map of potential gully erosion, i. e. possible erosion intensity in case of natural environment destruction due to the agricultural development of the territory. Present gully development has been estimated by indices of gully net density and frequency. Potential gully erosion has been calculated using solid discharge data at closing profiles of small drainage basins as well as data on main natural factors (catchment area, liquid precipitation, average slope of the territory, surface rock resistance to erosion).

At present the gully development at the region is not considerable (gully area is about 2 per cent of the whole territory), nevertheless in case of agricultural development about 50 per cent of the vast territory can undergo intensive and moderate erosion; the value may be increased in case of irrigation on account of the irrigation erosion at erodible soils. The study results can be used to work out anti-erosion measures and to chose the regions of economic development.

A development of channel change forecasting is a task of great significance for natural river usage, for man-made changes of their regime and for gravity flowing channel construction. The problem is especially urgent in relation to rivers with unstable channel in erodible sediments. The paper describes a channel reach of the upper Amu Darya where time and rate of relief transformation appears to be an economic problem of great importance. Detailed channel studies carried out by Laboratory of soil erosion and channel processes (Moscow State university) have revealed main regularities of channel changes and factors they are conditioned with. The results have been used as a basis for channel changes forecasting and as a ground for complex of measures preventing unfavourable consequences of the changes.

High degree of the forecasting reliability allows to suggest a complex of studies which is necessary to carry out at rivers with unstable channel at the points of irrigation channel diversion, near bridges, ports etc.

The paper discusses the authors experience of geomorphological – geodetic methods application to studies and mapping the relief dynamics at mountain areas. In essence the methods consist in delineation of sites characterized with different intensity of predominant exogenous processes. Denudation and accumulation rates had been valued by sediment run-off at large territories, instrumental survey being carried out at the places of the most active dynamics. The collected data enable to compile a complex synthetic map, representing quantitatively changes in relief. When colour variant of the map being prepared, the colour background shows morphometric index which summarizes density and depth of dissection, slope gradient and their exposition (by points, «relief energy» index or other synthetic indices). Areal denudation and accumulation supposed to be shown by colour shade or various sets of hachures, linear and local processes-by conventional signs. Two black-and-white hachure maps illustrate the paper.

A formula has been introduced for the calculation of morphographic index, the latter being mean arithmetic value of elevation ratio of terrace levels close in age. River valleys study has revealed the index to depend mainly on tectonic regime of the area in question and to exclude the influence of water discharge, flood height, lithology changes etc. Reflection of morphostructures in the morphographic indices values are illustrated with river valleys of the Northern Russian Plain. Possibilities of the indices application to geomorphology of mountain valleys has been noted.

The paper considers the results of experimental studies of pebble transport along the beach and reveals the role played by a submarine canyon near Pitsunda in the process. The coarse beach debris capture by the canyon head has not been analysed till now at neither Soviet nor foreign literature. The authors used the technique of colour indicators which was proved to -be effective enough. Quantitative estimations has been got for the rate and direction of natural debris longshore transport as well as for debris loss through the canyon head which is less than 10 m deep and cut the zone of longshore debris flow. The obtained data contribute into knowledge of the Pitsunda Peninsula coast dynamics and can be applied to coast protection designs.

Efate Island (New Hebrides) is characterized with great variety of landforms which differ by their genesis and age. The island topography had been developed in short geological time – during Pliocene-Pleistocene. The whole geomorphic cycle began after a group of volcanoes emerged from ocean at Pliocene. Fringing reefs encircled them and later on formed a succession at different hypsometric levels according to the volcanoes uplift. The uplift proceeded at high rare and the fringing reefs formed a series of steps from 0 to 400 m above sea level.

A geomorphological map of the island has been compiled, landforms and their complexes being briefly described. Absolute age of three terraces is given.

The author gives some quantitative characteristics of seasonal changes of spits and sediments at the Volga delta offshore margin, the characteristics are necessary for understanding its growth and forecasting its changes. The spits diminish during snow and ice .melting, and increase during floodtime (rapidly) and low water (slowly). The sediments become coarser and better sorted after flood time.

The paper discusses results of geological and geomorphological studies carried out by R/V «Academician Kurchatov» at the central Scotia Sea near a deep sea trough. Considering data of previous studies the existence of sub-latitudinal V-shaped seismic active troughs (Without sediments) is proved to be reflection of eastward shearing displacement of earthcrust blocks. Thus no expansion of the basin floor is possible, the conclusion is in full accordance with seismic stability of the northern and southern branches of the submarine South Antilles Ridge.

Three groups of planation surfaces were identified in Nigeria: the Gondwana and Post-Gondwana, the African and Post-African surfaces. The African and Post-African surfaces are of Cenozoic age and are associated with lateritic crusts of weathering, the latter being mostly of Pliocene-Pleistocene age. They are now undergoing erosion, rearrangement and removal.

A complex system .of earthcrust blocks of different order has been identified at the zone of the Amur-Zeya Plate and Turana Ridge junction. The block form mosaic structure pattern with singular block morphostructures representing elementary «cells». Since the Amur-Zeya depression came into being (Late Jurassic-Early Cretaceous) up to the end of Cenozoic time .the junction zone has been a kind of intermediate step between the destructed mountains of the Turana Ridge and forming plate due to gradual decrease in amplitude of contrast tectonic movements in the conjugated subsidence-uplift» system since the end of Early Cretaceous till Pleistocene.

The third discovery of the Earth

On the new aspect of practical application of structural-geomorplological (morphostructural) studies

Problems of erosion and channel processes study