Daytime ionosphere of Venus as studied with Veneras 9 and 10 dual-frequency radio occultation experiments

We present results of the dual-frequency radio sounding of the Venusian ionosphere carried out by the Venera 9 and 10 satellites in 1975. Thirteen height profiles of electron density for different solar zenith angles varying from 10 to 87° have been obtained by analyzing the refraction bending of radiorays in the sounded ionssphere. The main maximum of electron density at a height of 140–150 km depends on the solar zenith angle and is 1.4 to 5 × 10⁵ cm^?3. The lower maximum is determined definitely to be at ～130 km high. In the main and lower maxima the electron density variations with solar zenith angle are in good agreement with the Chapman layer theory. For the first time it is found that the height of the upper boundary for the daytime ionosphere (h_i) depends regularly on the solar zenith angle. At Z_⊙ < 60°, h_i does not exceed 300 km while at Z_⊙ > 60°, it increases with Z_⊙ and comes up to ～ 600 km at Z_⊙ ～ 80°.     

Studies of hydrophysical processes during monitoring of the anthropogenic impact on coastal basins using the example of Mamala Bay of Oahu Island in Hawaii

This paper presents the main results of processing the data obtained in the study of hydrophysical processes during multidisciplinary monitoring of the anthropogenic impact on the coastal basin of Mamala Bay (Oahu Island, Hawaii). The results of the hydrophysical measurements carried out in August–September of 2002–2004 using stationary moorings and dropped and towed ship sensors were analyzed as the initial data. On the basis of these measurements, spatiotemporal, statistical, and spectral characteristics of different hydrophysical parameters of the marine envrionement in the basin of Mamala Bay were calculated, including three-dimensional components of the velocity vectors, the spectra of different components of velocities, the spectra of temperature fluctuations, and the characteristics of internal waves. The variability of the temperature fields and the correlation of the tidal phenomena with the temperature measurements and fluctuations caused by internal waves were analyzed. The materials and methods of the oceanographic studies and the results of the analysis of the meteorological and hydrological conditions are presented. The results obtained are used for a multidisciplinary analysis of the satellite and sea truth data.     

Wave responses from oil reservoirs in the Arctic shelf zone

We consider the appearance of scattered PP-waves, SS-waves, scattered converted PS-waves, and SP-waves reflected from the reservoirs in the Arctic shelf zone and wave responses from them in the water column when the source and receiver are located near the water surface. We obtained a numerical solution of the direct problems of seismic prospecting in the shelf zone with a reservoir and without it. The solution was obtained using the grid-characteristic method, which makes possible to model the wave processes in detail.     

New data on the composition and age of granitoids in the northern part of the Tagil structure (Ural Mountains)

The Tagil structure representing a large fragment of the Paleozoic island arc on the eastern slope of the Urals has been sufficiently well studied in its southern part (Middle Urals). In contrast, reliable data on the age and geochemical properties of various, including granitoid, rock complexes available for its northern part are scarce. The first data on the U–Pb LA–ICP–MS age of zircons from quartz diorites of the Man’ya massif of the Petropavlovsk Complex (436 ± 3 Ma, MSWD = 1.3), tonalites of the same complex (439.4 ± 1.3 Ma, MSWD = 1.3), granites of the Yuzhno-Pomur massif of the Severorudnichnyi Complex (422.4 ± 3 Ma, MSWD = 1.5), and titanite of the same massif (423.4 ± 4.4 Ma, MSWD = 0.84) have been obtained. Based on these data combined with the geochemical properties of the host rocks, the conclusion that they were crystallized at the initial stages of the formation of comagmatic volcanic series is supported; by their composition, granitoids correspond to island arc igneous rocks.     

Subsidences and erosion in loess soils

The properties of loesses are very peculiar. The formation of loess is stable in the dry state, but under the effect of moisture it could present great subsidence. Sometimes in loess some processes are in progress. Similar to karst formation in the water-soluble rocks, but chiefly connected with mechanical suffosion (loess pseudokarst). In the water saturated condition loess soils are of a lower bearing capacity. Locally the loess is characterized by some self-progressing processes of underflooding by underground waters. Provoked by earthquakes and explosions some thixotropical liquefaction of loess soils may occur. All these processes have drawn the attention of researchers, engineers and agronomists of different countries to loess. In the first part of this paper we consider the collapse deformations and wash-outs of loess (Savvateev 1974), in the second part — pseudokarst processes (Kriger; Lavrusevich; Petrov 1983).     

Systematics of rare earth elements, Th, Hf, Sc, Co, Cr, and Ni in the vendian pelitic rocks of the Serebryanka and Sylvitsa groups from the western slope of the Central Urals: A tool for monitoring provenance composition

This paper presents the first data on the systematics of rare earth elements (REE), Th, Hf, Sc, Co, Cr, and Ni and the Nd model ages of fine-grained aluminosilicate clastic rocks of the Serebryanka and Sylvitsa groups of the Vendian from the Kvarkushsko-Kamennogorskii meganticlinorium (western slope of the Central Urals). It was found that the REE distribution patterns of shales and mudstones of the two groups are similar to those of the majority of post-Archean fine-grained terrigenous complexes. The presence of pelitic rocks with Gd_N/Yb_N > 2.0 in a number of Vendian levels suggests a contribution from an Archean component in the composition of the fine aluminosilicate clastic material. This is probably also indicated by the high degree of heavy REE depletion in some mudstone samples. The REE systematics allow us to suppose a heterogeneity of Vendian paleocatchments and variations in their composition with time. The eroded areas had the most mature composition in the beginning of Serebryanka. Starting from the second half of Serebryanka, mafic and/or ultramafic rocks started playing a significant role in the provenances. The rocks of the lower portion of the Serebryanka Group show T_Nd(DM) values of about 2.0 Ga, whereas the upper part of the section is dominated by rocks with T_Nd(DM) ? 1.77–1.73 Ga. This indicates that during the Taninskaya and Koiva time periods, fine aluminosilicate clastic material was supplied into the sedimentation region mainly from the west, from the eastern areas of the east European platform, where Archean and Early Proterozoic crystalline complexes dominated. A decrease in model ages was related to the addition of juvenile mantle material to the mature continental crust. Such processes can be illustrated by the mafic-ultramafic complexes (Dvoretskii, Shpalorezovskii, Vil’vinskii, etc.) located in the field of Vendian sedimentary sequences, which show T_Nd(DM) values from 824 to 707 Ma. It was concluded that the history of the formation of an Early Vendian rift in the western slope of the central Urals included only one rifting event (rather than three, as was previously supposed), which was supported by a variety of recent geological and isotope geochemical data.     

Late Pleistocene Catastrophic Landslide from the Balaganchik Ridge: Evidence from the Mitoga 2 Reference Section (Western Kamchatka)

Lithology and Mineral Resources - A new reference section of the Okhotsk seaside of Kamchatka in the Mitoga 2 River area is studied and dated for the first time (14C and 230Th/U). Sedimentary...     

Numerical Simulation of Seismic Wave Propagation in Coastal Zones

Doklady Earth Sciences - The problem of tsunami warning and the use of the grid-characteristic method developed for studying wave processes in heterogeneous media is addressed. A multilayer...