Main forms of the Earth's mega-relief are considered in reference to their relation to main geostructures types which age distinguished by the plate tectonics theory. Main geotectures groups include oceans, mterplate transition zones (active oceanic margins), interpolate orogens, intraplate transition zones (passive oceanic margins), 29 types of mega-relief are distinguished within the groups. The systematics of the mega-relief types is described, and their spatial distribution over the Earth's surface is shown. The importance of works of I. P. Gerasimov is stressed, who was the first to apply the plate tectonics' concept to the global geomorphology.

The paper presents results of the trend-analysis of the present-day surface topography, pre-Riphaean basement surface and the Mohorovicic discontinuity within the limits of the Russian Plain. Landiforms of different ranks are shown to differ in the interrelation between the surfaces. Mega forms (average radius 500 km) most clearly show an inverse relation of the present-day surface to the basement surface topography, while in macroforms (average radius about 250 km) the basement surface in inversely related to the Moho discontinuity. The author speculates conserning the deep processes character which account for the mentioned relations.

Morphogenetic analysis of transition areas (mostly of those in the Pacific ocean) revealed a sequence in their evolution. Several stages are distinguished, most consideration being given t o the youngest one, which is the island arc formation.

The paper deals with processes of sea coast and delta evolution modified as a result of water reservoirs construction and regulation of rivers which supply the coast with sediments. The rivers have been divided into groups according to the significance of the flow control by the reservoirs. Most influenced appear the coasts which are fed by rivers devoid of deltas. In a short time after reservoirs construction the marine erosion removes alluvium from the river mouth and extends along the sea coast. A new delta of the Rioni River is taken as a reference case of the terrestrial water management (including reservoirs construction and flow diversion) influence on the delta formation, the delta in question is continuously eroded and degrades. Some measures are recommended to lessen or prevent the erosion and to make the coast stable.

The paper summarizes results of channel processes studies which had been carried out in the Lena drainage basin, on the Lena, Aldan, Kirenga and Vilui rivers. The studies show the channel evolution and regularities of the channel deformation in sandy channels are different from those in gravel and boulder channels. The composition of the recent alluvium is discussed as well as channel types and dynamics. The studies results permit to develop both theoretical schemes and practical measures of channels control for the navigability improvement.

The paper gives the solution of the volcanic islands slope geometry problem which has been obtained within the scope of a mathematical model developed on the basis of the hypothesis by G. F. Becker. The latter assumed volcanoes to be bodies of equal strength (resistance). The suggested equations describe the volcanic constructions profiles as a function of their height, crater's radius and the volcanic rock properties. The computer calculations results were used to construct theoretical contours of volcanic islands. Possible causes of terrace formation on the islands slopes are also discussed, as well as conditions of collapse caldera formation.

Geomorphological regions, singled out within the limits of plains and mountains of the Altai Territory, differ from each other in structure, erosion network pattern, in density and bepth of dissection. The general direction of most forms in erosional system is predetermined by tectonics. In most regions NE direction of erosional landforms prevails which is controlled by mid- and late Quaternary faults or recent folds. The increase of minor erosional form instability and lateral channel erosion is traced from Kulunda Plain towards the Altai and Sal air foothills. The dynamics of erosion in the Altai Mountains depends directly on the land use of the territory.

New data on the Corner High (SE Newfoundland) seamounts relief are presented. Main detections of lineaments are determined. The structure proved to indergo a considerable descent (about 1700 m). It is also shown that the seamounts had not been turned into guyots because of short duration of the subaerial stage of their development.

Several stages of the eolian morphogenesis are distinguished; the youngest one is dated back to the Pleistocene-Holocene boundary, older one- about 15,000 years ago, and the third - at the beginning of the Karginsk (mid-Late Pleistocene) interstadial. Still earlier phases of eolian processes can be traced in sequences of loess and similar deposits. Stages of eolian morphogenesis and loess sedimentation are supposed to correspond to certain regime of the atmospheric circulation.

A very complicated pattern of tectonic blocks is typical for the Western Caucasus because of many faultlines of different rank crossing each other. Within the limits of western Mountain Caucasian karst area (belonging to Crimean-Caucasian province) geostructural features permit to distinguish 3 karst districts, 7 sub-districts, 22 regions and 64 sub-regions. The region is considered to be the main unit in the scheme of the karst territorial subdivision. It corresponds to an individual crustal block with a separate ground water reservoir and shows a certain complex of karst processes and resulting landforms.

General features of the Cenozoic evolution of the Barents and Kara seas floor relief are considered. The maps have been compiled showing the present position of the Late Miocene (pre-Pliocene) and Late Pleistocene (pre-Holocene) relief on the Barents and Kara shelves. The leading part of the neotectonics in the formation of the relief and correlate sediments is argued. The principal stages of relief formation and sedimentation through the Cenozoic are shown to correspond to certain phases of the tectonic evolution of Arctic geodepression.

Main stages of post-glacial development of the shelf topography in the East Siberian and Chukchi seas are considered. New data permit to trace the submerged coastlines (dated back to the last transgression) and to understand the neotectonic and environmental impact on the relief evolution. Sedimentary formations structure indicates that the sea shelves in the Eastern Soviet Arctic are not only zones of transit of sediments but also a very large area of sedimentation.

Values and rate of changes in coastal morphology characteristics are shown to be essentially different when defined on different time scale (hours, months, years, millennia). Each estimate indicates the significance of a single f actor which controls coastal processes and acts within a certain time interval. With reference to longs fore sediment transport estimation in different parts of the World Ocean, strong storms (with frequence about once per year) have been proved to be f actor controlling coasts evolution within time interval of a few years to a few hundreds of years. By means of assessment of horizontal migration of the shoreline in a bay of the White Sea it was ascertained that tidal fluctuations of the sea level controlled the coast dynamics during the whole Holocene.

In the Vanch valley moraines were formed under conditions of plastic ice flow (by layers) with incidental thrusting is scales, they consist of monolithic and scaly f acres of basal till. The moraines on the valley slopes do not fit the term «Lateral moraine», being a part of a single body of basal till; a new term is suggested which emphasizes the position of the deposit on the valley slope («slope moraine» or «border moraine»). A kind of moraine terraces was formed by meltwater during the glacier downwasting, during phases of temporal stability of the ice surf ace. Similar regularities are typical for the till structure and morphology in other valleys in Pamir where large glaciers existed during the Pleistocene

Geomorphological studies in the Physical Geography Department, Kazan University (to the centennial anniversary of the Department)

Problems of morphotectonics and geomorphological mapping at the international symposium in Italy