Bottom Morphostructure of the Valaam Archipelago in Lake Ladoga: First Video Images and Quantitative Assessments

Doklady Earth Sciences - Based on the first created digital model of the Valaam archipelago (Lake Ladoga) with a spatial resolution of 25 × 25 m, a quantitative assessment of the spatial...     

Morphostructural features of the Butakov Guyot (Magellan Seamounts, Pacific Ocean)

The structural features of the Butakov Guyot are interpreted based on the comparison of telephoto-profiling (approximately 8000 photos of the oceanic floor) and multibeam echo sounding data. The network of linear structures of the guyot is outlined and their regular orientation is visualized in rose charts. Several structural steps complicating the slopes and summit plateau of the guyot are identified, and a scenario of its possible initiation and evolution is suggested. The data imply elevated tectonic activity of the Butakov Guyot relative to other guyots and its subdivision into the northern and southern bocks. It is shown that the main systems of the linear structures in the Butakov Guyot are oriented in consistence with four global fracture networks.     

Regularities in the orientation of bottom lineaments and faults in the Russian segment of the Sea of Japan

The configuration of the lineament-disjunctive network in the Russian segment of the Sea of Japan (sheets K-52 and K-53) was studied with structural zoning of the region using geophysical and geomorphologic data. The constructed rose diagrams revealed systematic orientation of lineaments and faults in the region as a whole and some of its areas. The orientation of linear structures in the Russian segment of the Sea of Japan is compared with that characteristic of the global disjunctive network. This allowed the following inferences: (1) the region is characterized by a single lineament-disjunctive system with four main directions of dislocations: submeridional (0–5°), sublatitudinal (86–90°), diagonal northeastern (36–65°), and diagonal southeastern (136–140°); (2) the directions of these dislocations coincide with the orientation of four main systems in the global disjunctive network (planetary fracturing); (3) the revealed disjunctive network is substantially of the Earth’s rotation genesis; (4) regularities in the distribution and orientation of faults and lineaments are determined by two interacting factors: the stress concentration in areas of the layer thickness gradient and variations in the Earth’s rotation velocity (the former controls localization of faults and the latter, their orientation).     

The fourth assessment report of the intergovernmental panel on climate change: Working group II contribution

Basic results of IPCC Working Group II, derived in the process of the work at the Fourth Assessment Report, are considered in brief. The results are given in conformity with the Summary for Policymakers adopted at the Plenary Meeting of Working Group II in Brussels on April 6, 2007. The authors’ comments on some results connected with the key vulnerable elements of natural and socioeconomic systems are given in the conclusion.     

Volcanic edifices on guyots of the Magellan Seamounts (Pacific Ocean)

Analysis of detailed bathymetric charts and records of phototelevision profiling over the surfaces of the guyots of the Magellan Seamounts reveals many cones and domes. Their diameters and heights vary from a few hundreds of meters to 10 km and from 30 to 350 m, respectively. The age generations of these mesomorphic structures correspond to the Campanian–Maastrichtian, Late Paleocene–Eocene, and Miocene. The formation of complicating volcanic edifices is most likely determined by late phases of volcanic activity related to differentiation of magmatic melts. At the same time, the tectonic factor responsible for their formation is also sufficiently well evident: volcanic edifices on plateau summits are associated spatially with linear morphostructures and lineaments.     

Structural features of the northeastern slope of Govorov Guyot,Magellan Seamounts,Pacific Ocean

Photo/TV surveying (approximately 4500 photographs of the oceanic floor) and multibeam echo sounding data were compared to analyze the structural features of the northeastern slope of Govorov Guyot. A network of linear structures complicating this slope was visualized. The trajectories of the linear structures were determined and shown in rose diagrams. It was demonstrated that the photo/TV surveying of the oceanic floor represents an effective tool for studying its topography. The blocks bordered by linear fractures are characterized by different parameters of ferromanganese ore mineralization of the crust type, which may be explained by the determining role of the tectonic factor in the relief-forming process. The combination of the topographic features and the hydrodynamic regime within the blocks provides conditions favorable to different extents for the accumulation of Mn hydroxides.     

X-Ray fluorescence analysis of the principal elements of the seawater salt composition in the tropical Atlantic

This paper reports on the results of determining the chlorine, potassium, calcium and sulphur concentrations obtained by X-ray fluorescence (XRF) during the 37th cruise of the R/VAkademik Vernadsky in the tropical Atlantic. The determination accuracies for the ratios of K/Cl, Ca/Cl, and S/Cl were 0.45, 0.58, and 2.5%, respectively. As follows from the data obtained, the variations of these ratios exceed the accuracy of the measurements at all stations, and they are connected with the structural features of the hydrochemical fields.Translated by Mikhail M. Trufanov.