The volumes of volcanic seamounts as a factor determining the formation of the ocean floor’s morphostructure

The volumes of formed volcanoes are an important indicator of the formation intensity of the ocean floor volcanogenic morphostructure under different geodynamic conditions. The distribution of the volumes of volcanoes that formed within the oceanic lithosphere of different geological ages is considered to analyze the spatial and time dynamics of the scopes of the seamount formation. The greatest volumes of effused rocks concentrate in volcanoes of different heights on the different-age segments of the lithosphere. The total volumes of volcanogenic substance growing with increasing age and thickness of the lithosphere is caused by the increasing range of the heights of the formed volcanoes and the growing number of big seamounts. Despite that the volcanic seamounts formed within the mid-oceanic ridges, on the divergent boundaries of the lithospheric plates and in the transform faults most often, half of the volcanogenic material was emitted to the earth’s surface during the spreading of the intraplate volcanism. A leading part in the formation of the volcanogenic morphostructure of the ocean floor belongs to the formation of big seamounts with heights of 4–6 km and volumes from 1500 to 5100 km³, respectively, in the provinces with ages from 60 to 90 mln years.     

Experimental study of turbulent-wake expansion from a surface ship

We studied the time dynamics of a turbulent region excited by a moving surface vessel in a field experiment. The time dependences of the geometrical sizes of the turbulent region are obtained, and it is shown that the time dependence of the width of the turbulent wake at the initial stage is close to the power-law function with an exponent of 0.4 for different experiments (the depth of the wake remaining practically constant). In the semiempirical turbulence theory, we suggested a qualitative model describing the process of the initial expansion of a ship wake as a diffusion of a one-dimensional layer of turbulized liquid due to a pulsed source.     

Stratigraphy and formation conditions of the sedimentary cover in the Sea of Japan near the Bogorov Rise

The results of the complex study of the sedimentary cover (continuous seismic profiling and diatom analysis) in the northeastern part of the Sea of Japan, including the Bogorov Rise, the adjacent part of the Japan Basin, and the continental slope, are presented. Two varied-age complexes were distinguished in the sedimentary cover of Primorye’s continental slope, namely, the Middle Miocene and Late Miocene-Pleistocene; these complexes were formed in a stable tectonic environment with no significant vertical movements. The depression in the acoustic basement is located along the continental slope and it is divided from the Japan Basin by a group of volcanic structures, the most uplifted part of which forms the Bogorov Rise. The depression was formed, probably, before the Middle Miocene. In the Middle Miocene, the Bogorov Rise was already at the depths close to the modern ones. In the sedimentary cover near the Bogorov Rise, buried zones were found, which probably were channels for gas transportation in the pre-Pleistocene. Deformations of sediments that occurred in the beginning of the Pleistocene are established in the basin.     

Bottom fauna associated with <Emphasis Type="Italic">Bathymodiolus azoricus</Emphasis> (Mytilidae) mussel beds in the hydrothermal fields of the Mid-Atlantic Ridge

The structure of the assemblages associated with the mussel aggregations of Bathymodiolus azoricus was investigated. The mussel beds were found on the hydrothermal vent fields on the Mid-Atlantic Ridge (the Menez Gwen, Lucky Strike, and Rainbow areas) at the depths of 850–2400 m. The community structure of the mussel bed assemblages varied between the studied areas. Large number of species was unique to Menez Gwen mussel beds; the most observed taxa were not specialized hydrothermal species. All the other, nonunique species were found for the Lucky Strike region. The lowest mussel assemblage structure evenness was observed in the shallowest area, the Menez Gwen area (850 m depth). We assume that two types of mussel assemblages—nematode-dominated and copepod-dominated ones—exist in the Lucky Strike field. The assemblages of B. azoricus differ significantly from the assemblages of B. thermophilus inhabiting the Pacific hydrothermal vents.     

Simulating the influence of an atmospheric fine inhomogeneous structure on long-range propagation of pulsed acoustic signals

The results of simulating the influence of an atmospheric fine structure on the characteristics of acoustic signals propagating throughout the atmosphere for long distances from their sources are presented. A numerical model of an atmospheric fine inhomogeneous structure within the height range z = 20…120 km is proposed to perform calculations. This model and its numerical parameters are based on the current notions of the formation of an atmospheric fine structure due to internal gravity waves. The numerical calculations were performed using the parabolic-equation method. A spatial structure of the acoustic field and the structure of an acoustic signal at long distances from a pulsed source were calculated. It is shown that the presence of an atmospheric fine structure results in a scattering of acoustic signals and their recording in the geometric shadow region. The results of calculations of signal forms are in a satisfactory agreement with data on signals recorded in the geometric shadow region which is formed at a distance of about 300 km from an experimental explosion.     

Does lunisolar gravitational tide affect the activity of animals?

Multiyear time series obtained by the continuous instrumental monitoring of the electrical activity (EA) of weakly electric fish Gnathonemus leopoldianus and the motor activity (MA) of the freshwater catfish Hoplosternum thoracatum and the cockroach Blaberus craniifer are compared to the parameters of the lunisolar gravitational tide. These curves are observed to be very similar for a large number of time intervals. However, a more detailed analysis shows this to be only a superficial resemblance caused by the closeness of the periods of diurnal and semidiurnal rhythms of bioindicator activity (the dominant rhythms in EA and MA patterns) and the periods of main gravitational tidal waves. It is concluded that the lunisolar gravitational tide has no significant effect on animal behavior in our experiment.     

Stationary waves in the flow of a homogeneous fluid with vertical shear of the velocity

A plane problem of free stationary gravitational waves in a horizontal current with vertical shear of the velocity is studied in the linear statement. The determination of the parameters of waves is reduced to the solution of the Sturm–Liouville boundary-value problem. For some vertical distributions of current velocity, we obtain analytic solutions. We propose a numerical algorithm for finding the parameters of waves. On the basis of the performed analysis, we establish the possibility of existence of stationary surface waves in currents for certain ranges of the Froude number. As the Froude number decreases, the waves become shorter, which leads to a faster attenuation of waves disturbances with depth. Under the actual conditions, the waves are short and suffer the influence of shear currents only in the subsurface layer of the ocean.     

Factors governing abundance of hydrolyzable amino acids in the sediments from the N.W. European Continental Margin (47–50°N)

Fifty-six samples representing 6 sediment cores taken along the N.W. European Continental Margin from the shelf, slope and abyssal plain of the Goban Spur and Meriadzek Terrace were quantitatively analysed for total hydrolyzable amino acids (THAA) and clay minerals. In descending order, the five most abundant amino acids making up more than 70% of the total were: aspartic acid, glycine, serine, alanine and glutamic acid. Clay mineral proportions were typical for the N.E. Atlantic, in order of descending abundance: illite, kaolinite, chlorite, smectite and mixed layers.The Meriadzek Terrace area is characterised by fine grain suspension sedimentation with a low pelagic carbonate input and the lowest content of THAA. In contrast, the Goban Spur transect is characterised by much higher carbonate inputs and more vigorous hydrodynamics as judged from granulometry and the high abundance of minerals of shelf and continental origin and a generally higher THAA content. The pelagic portion of THAA deposited at the sea floor is more readily mineralised during early diagenesis than the more ‘refractory', clay mineral-associated continental portion. Along this margin the average mineralization of THAA down to 25 cm in the sediment is about 54%. There is a significant affinity between chlorites and amino acids which we suggest may involve the formation of ionic bonds between the octahedral layers of the clay and the amino acids.     

Evaluation of drift current parameters using an analytical model

The paper is concerned with the evaluation of the drift current parameters derived through the use of an analytical model. In this model, effective when stratification is stable and indifferent, the vertical turbulence coefficient profile is prescribed by the power function, and hydrodynamic quantities are prescribed using the external parameters of the problem (wind stress, the Coriolis parameter, and the dimensionless stratification parameter). Model data are compared with the observations of the upper mixed layer in the vicinity of the oceanic Station C, conducted during one year. It is shown that, under the spring-summer-time warming conditions, the model at issue is capable of adequately simulating the upper ocean layer dynamics. Translated by Vladimir A. Puchkin.     

Potential of the regional centre for reception and treatment of satellite data

In application to the Crimean regional centre for satellite data reception, treatment, and dissemination, we have identified the earth’s satellite-surveyed areas, with orbital heights (H) ranging from 650 to 750 km. This paper shows that for the Ukrainian territory and the Sea of Azov-Black Sea environment to be monitored, the regional centre’s receiving station must be capable of receiving radar signals from a range of about 1500 km. For typical high-speed radio lines, this may be achieved through the use of a satellite data-receiving station, with the antenna’s diameter being about 3 m. Translated by Vladimir A. Puchkin.