Том 55, № 7 (2019)

The evolution of the continental lithosphere, unlike the oceanic one, lasts more than 3.5 Ga. This evolution was largely determined by thermal factors, such as the removal of heat from the Earth’s surface, the interaction of the conductive layer of the lithosphere with mantle thermal convection, and the strong dependence of the viscosity of the upper layers of the Earth on temperature. The aim of this work was to simulate the long-term interaction of these factors over a period of several Ga on the basis of the whole-mantle thermal convection equations. In our evolutionary model, the nucleus of continental lithosphere with a thickness of 50 kilometers was inserted in the mantle, which then began to grow in depth due to the reorganization of convection under the continental lid with a conductive heat transfer mechanism. For the self-consistent modeling of the lithosphere thickness changes in time we set the condition of viscosity jump by three orders of magnitude with a decrease in local temperature below 1200°C. The results of successive calculations demonstrated that the initial period of growth of the continental lithosphere due to its cooling, which takes about one Ga, is subsequently replaced by its slow thinning due to the accumulation of heat under a thick heat-insulating lithospheric cover. The calculated maximum of the average thickness of the growing lithosphere, estimated by temperature and viscosity, is 162 kilometers, however, when estimated by the conventional point of intersection of the lithospheric geotherms with mantle adiabat, it is 100 kilometers more. The increase in the average mantle temperature from the heat-insulating effect is about 100 K/Ga and continues both at the stage of the lithosphere thickening and at the subsequent stage of its slow thinning. The mantle warming up due to the presence of continents is one of the competing factors in the global process of the Earth’s secular cooling. The conclusion about the presence of two stages in the evolution of the continental lithosphere clarifies existing ideas about the formation of the current state of the outer layers of the Earth.

Fluxes of anthropogenic heavy metals (Pb, Cd, As, Zn, Ni, Cr, and Cu) to the surface of four seas (White, Pechora, Kara, and Laptev seas) in the Russian Arctic have been estimated in this work using previously calculated concentrations of these elements in the surface atmosphere in some island and continental points of the Arctic Ocean. The obtained values were compared with the published data on the fluxes of the same components carried by waters flowing into the seas. Based on EMEP reports, we made some corrections for the data on lead and cadmium fluxes from the atmosphere to White and Pechora sea waters, taking into account pollution sources from European countries and the contribution of processes of the raising of dust and soil particles by wind to the pollution of the European part of Russia. On the whole, the contribution of atmospheric fluxes of HMs to the formation of the environment composition of northern Russian seas is significantly lower than that of the runoff of rivers flowing into the seas. The White Sea is the exception; it is exposed to numerous anthropogenic sources of HM emissions into the atmosphere. It is also reasonable to expect the atmospheric transport of HMs to make a significant contribution to these waters. One can also expect a significant contribution of the atmospheric transport of HMs to waters of distant seas (the Kara and Laptev seas), namely, in the parts of these seas where the influence of largest Siberian rivers (Ob, Yenisei, and Lena) is insignificant.

The results of the fractal analysis of a drainage network reconstructed using a digital elevation model and the structural and geomorphological analysis of the relief of the Kerch Peninsula are compared. Three sectors with different geomorphological expression and the uplifts and depressions associated with them have been identified by the results of the structural and geomorphological analysis. At the same time, the newest structural geometry does not coincide with the structural geometry that developed until the Late Pliocene period. The neotectonic structures of several orders are distinguished according to the results of the structural and geomorphological analysis. The relationship between the magnitude of the fractal dimension D of the drainage network and the movement direction was found: higher values correspond to uplifts and lower values correspond to depressions. This is due to the fact that the areas of neotectonic uplifts are characterized by the active restructuring of the drainage system and the formation of new streambeds and valleys as well as the branching of streams. The increasing complexity of the river network is seen in the higher values of the fractal dimension D, which is a quantitative measure of the complexity of objects. At the same time, the increased values of the D field correlate with rather large first-order structures. It is also found that the results of fractal analysis are subject to the scale effect, and the sensitivity depends on the accuracy and scale of the data. This should be taken into account in further research. It is shown that the fractal approach is promising for the quantitative analysis of the drainage pattern in the study of the newest tectonic structures.

A review of the literature suggests that the seismic process in Fennoscandia (the Baltic Shield) is affected by at least four mechanisms: (1) northwest-to-southeast movement of the lithospheric plate under the Norwegian and Barents seas by spreading of the Mid-Atlantic Ridge from Iceland to Spitsbergen; (2) postglacial isostatic uplift; (3) local recent neotectonic movements; and (4) gravitational bending deformations on continental contact with the sea shelf along the Norwegian coast due to strong erosion from the rising crystalline domain of the Baltic Shield. The current seismicity of Fennoscandia is relatively low. The strongest earthquake in this area over the last 1000 years was the earthquake of 1627 which had a magnitude of M ≈ 6.5 and occurred in the Kandalaksha graben in the White Sea. However, Fennoscandia, including the Kola Peninsula and eastern Karelia, has a reliable history of a significant number of Pleistocene and even Holocene paleoseismic dislocations, whose parameters allow them to be associated with strong earthquakes which occurred at that time with magnitudes of 7–8 and even higher. It is likely that these paleo-events occurred at the last stage of the glacial age (9000–10 000 years ago) during the intense postglacial isostatic uplift of the Fennoscandia domain. Their possible recurrence can be estimated as tens of thousands of years from the time interval between consecutive glaciations. One should therefore recognize that the nature of current seismicity of Fennoscandia is determined by tectonic stresses caused by both the global effect of the northwestern uplifting lithospheric plate under the Norwegian Sea (a constant source of tectonic stress accumulation) and local tectonic uplifts (the north coast of Norway) or lowerings (the Swedish coast of the Gulf of Bothnia), rather than by postglacial stresses. In addition, the increased seismicity of southwestern Norway and the adjacent North Sea shelf is most likely caused by the formation of crest-like structures under the action of tensile stresses revealed here.

The earthquake and tsunami that occurred in 1185 in the North Azov region is considered here using the multidisciplinary approach for the first time in professional literature, based on indications from the Old Russian written source, The Tale of Igor’s Campaign. Problems such as the relationship between earthquake and tsunami, shaking intensity, geographic position, and other location conditions are addressed. The epicenter area is established to be the northeastern shore of the Sea of Azov. Information is given about earthquakes in the region for 200 years and their confinement to the sublatitudinally extending northeastern shore of the sea is found. The revealed seismogenic zone is correlated with the North-Azov fault, a large tectonic structure of the same orientation. Finally, based on archeoseismic data, which have not been previously employed in a seismic hazard assessment in the framework of making General Seismic Zoning maps, the question is raised of assessing the seismic potential of the zone.

Instrumental observation data on acoustic oscillations in Moscow for 2014–2017 have been analyzed. The difference in amplitude and spectral characteristics of acoustic noise between the megalopolis and an outside area has been demonstrated. Data testifying to an increase in acoustic noise during strong atmospheric phenomena such as hurricanes and squalls are presented. Specific features of infrasound oscillations and acoustic–gravity waves have been considered separately.