Different Types of Island-Arcs in the Pacific

1945 ◽  
Vol 106 (5/6) ◽  
pp. 198 ◽  
Author(s):  
J. H. F. Umbgrove
Keyword(s):  
Island Arcs ◽  
The Pacific ◽  
Different Types

scholarly journals Особенности спектров ЯМР -=SUP=-63,65-=/SUP=-Cu в локальном поле образцов полупроводникового минерала CuFeS-=SUB=-2-=/SUB=- из сульфидных месторождений океана

2018 ◽  
Vol 52 (8) ◽  
pp. 836
Author(s):  
В.Л. Матухин ◽  
А.И. Погорельцев ◽  
А.Н. Гавриленко ◽  
С.О. Гарькавый ◽  
Е.В. Шмидт ◽  
...  
Keyword(s):  
Room Temperature ◽  
Global Ocean ◽  
Island Arcs ◽  
Nmr Spectrum ◽  
Nmr Method ◽  
The Pacific ◽  
Different Types ◽  
Asymmetric Shape ◽  
The Pacific Ocean ◽  
Polymetallic Sulfides

AbstractThe results of studying natural samples of CuFeS_2 chalcopyrite mineral from hydrothermal ore manifestations of island arcs of the Pacific Ocean by ^63Cu nuclear magnetic resonance (^63Cu NMR) in a local field at room temperature are presented. The asymmetric shape of the detected resonance lines in the ^63Cu NMR spectrum indicates the presence of at least two overlapping lines. The presence of two overlapping central components can be a consequence of the occurrence of regions with different types of structural distortion near the resonant nuclei. These results show that the pulsed ^63Cu NMR method can be an effective method for studying the physical properties of deep-sea polymetallic sulfides of the global ocean.

Evolution of Antarctic prospective sedimentary basins

1989 ◽  
Vol 1 (1) ◽  
pp. 51-56 ◽  
Author(s):  
V.L. Ivanov
Keyword(s):  
Sedimentary Basins ◽  
Passive Margin ◽  
Mobile Belt ◽  
Continental Shelves ◽  
The Pacific ◽  
Different Types ◽  
Tectonic Features ◽  
Stratigraphic Evolution ◽  
Continental Glaciation ◽  
The Antarctic

No less than 15–20 sedimentary basins are now known on the Antarctic continental landmass and surrounding continental shelves. Reconstruction of their tectonic and stratigraphic evolution is a specialized task. Owing to the polar position of the continent, the Pacific and Atlantic global geostructures are closely spaced there and the interplay between them is strong enough to result in hybridization of the characteristic tectonic features of the various basins. The present morphostructure of the southern polar region of the Earth is characterized by a prominent circumpolar zoning. Therefore, the sedimentary basins form a gigantic ring along the continental margin, including both the shelf proper and the edge of the continent. Within the ring, the basins are associated with different types of margins successively replacing each other, from the Mesozoic magmatic are in the Pacific segment to the classic passive margin off East Antarctica. The formation of the sedimentary basins in the Antarctic segment of the Pacific mobile belt was a part of a single process of geosynclinal development, whereas on the craton flank the process was superposed on the continental structures by rifting during Gondwana fragmentation. During post-break-up tectonism, continental glaciation played an important part in the formation of the sedimentary basins.

Fishing Vessels of the Pacific Northwest: The Past 30 Years

1988 ◽  
Vol 25 (02) ◽  
pp. 105-117
Author(s):  
James A. Cole
Keyword(s):  
Pacific Northwest ◽  
Carrying Capacity ◽  
Principal Characteristics ◽  
Stability Problems ◽  
The Past ◽  
Fishing Vessels ◽  
Technological Advances ◽  
The Pacific ◽  
Different Types ◽  
Hull Design

This paper reviews the evolution of the design of fishing vessels of the Pacific Northwest over the past three decades. Since the vessels are designed to suit their particular fishery or fisheries, five different types are reviewed: gillnet boat, trollers, combination fishing vessels over a range of several sizes, tuna seiners, and stern trawlers. The paper shows how evolution has brought bigger vessels with increased carrying capacity, range, and endurance. Stability problems that have arisen with some of the types are also discussed. A section is devoted to each type summarizing its origins, its evolution, the fishery, fishing method, etc. This is followed by comparisons in hull design of the types reviewed with drawings of the vessels accompanied by their principal characteristics. The conclusion covers the technological advances in design and construction of the vessels and the increased sophistication of their machinery and equipment. An Appendix illustrates the operating areas and seasons of the Pacific Northwest fisheries and includes photographs of typical vessels of the region.

Structure and development of transition zones between the continents and oceans

1968 ◽  
Vol 5 (4) ◽  
pp. 1011-1026 ◽  
Author(s):  
V. V. Beloussov ◽  
I. P. Kosminskaya
Keyword(s):  
Mechanical Properties ◽  
Deep Structure ◽  
Island Arcs ◽  
Transition Zones ◽  
Marginal Seas ◽  
The Pacific ◽  
Marginal Part ◽  
The Difference ◽  
Marginal Zones ◽  
Cretaceous Period

A set of geological-geophysical data provides a good basis for the recognition of two basic types of marginal zones: Atlantic and Pacific. The analysis of the tectonics and deep structure of the crust allows us to characterize their development in time, proceeding from a basic, well-grounded conception that beginning with the Cretaceous Period processes of crustal subsidence were dominant in the marginal zones of both types. In connection with the different structure of margins on the continental side and their correspondingly different mechanical properties, i.e., strength and monolithic quality, it is evident that the effects of crustal subsidence in different zones should have different manifestations.The Atlantic type of margins is characterized on the continental side by the platform regime, and the development of the marginal zones was here accompanied by the subsidence of the marginal part of the pre-Mesozoic foundation with an increase of its tilt towards the ocean. The M boundary in this zone is observed to have a steep rise of the scarp type, approximately 15 km for every 100 km. The inhomogeneity of the foundation structure and the possible irregularity of the processes of its subsidence in certain areas resulted in the formation of small plateaus detached from the shelf. The zones of the Atlantic type were evidently unconnected with considerable reduction of land, and they are mainly located within the boundaries of the pre-Mesozoic shelf.The margins of the Pacific type are characterized by another mechanical regime, which develops on the background of largely differing geosynclinal structures of continents. Sinking of large blocks is here followed by their disintegration into smaller blocks, as well as by volcanism with which the formation of island arcs of the second type and of the accompanying troughs is associated, etc. Starting with the Neogene in the zones of this type, the areas of the ocean expanded and in place of land vast marginal seas were formed with a thinned continental and suboceanic crust.The connection between the primary mechanical properties of the earth's crust of the marginal zones and the character of structures which evolved as the result of its subsidence is only one side of the phenomena causing the difference in the types of margins. As the subsidences of the crust are succeeded by its regeneration under the influence of the processes in the mantle, it might also be supposed that in the Atlantic zones with platform conditions these phenomena developed more regularly, while in the Pacific zones in the conditions of the geosynclinal state of the interior the same process had a more complicated and diverse development.

scholarly journals Differences in Epicentral Location of Mexican Earthquakes between Local and Global Catalogs: An update

2016 ◽  
Vol 55 (1) ◽  
Author(s):  
Vala Hjörleifsdóttir ◽  
Shri Krishna Singh ◽  
Allen Husker
Keyword(s):  
Subduction Zone ◽  
Velocity Structure ◽  
The United States ◽  
The State ◽  
The Pacific ◽  
Different Types ◽  
The Pacific Ocean ◽  
Epicentral Location ◽  
Large Earthquakes ◽  
Mexican Subduction Zone

Differences in epicentral locations between local and global catalogs for earthquakes in the Mexican subduction zone were first observed to be biased in the 1980s, based on a few well studied events. In this study we compare locations between two local catalogs; (1) a recent high precision catalog of events in the state of Guerrero and (2) the catalog of the Servicio Sismológico Nacional (SSN), to the global catalog of the United States Geological Service (USGS). We find that on average epicentral locations in the global catalog of earthquakes larger than M 5 in the Mexican subduction zone are 26 km towards N54°E of those in the local catalogs. We investigate how the errors vary for different types of earthquakes in Guerrero, and how they vary along the trench, from the state of Jalisco to the state of Chiapas. The average differences are largest for thrust events occurring close to the trench, and for events in Michoacán. The differences are greater on average for large earthquakes than for small. There is a trade-off between the distance from the trench and timing, suggesting a poor resolution of these parameters, due to the lack of stations the Pacific Ocean. We attribute the differences in locations to systematic patterns in the velocity structure of the mantle, with consistently fast paths to the northeast and relatively slow paths towards the southwest.

scholarly journals SUBDUCTION EROSION AT PACIFIC-TYPE CONVERGENT MARGINS

2021 ◽  
Vol 40 (6) ◽  
pp. 3-19
Author(s):  
I.Yu. Safonova ◽  
◽  
А.I. Khanchuk ◽  
Keyword(s):  
Continental Crust ◽  
Driving Forces ◽  
Accretionary Prism ◽  
Convergent Margins ◽  
Island Arcs ◽  
The Pacific ◽  
Tectonic Erosion ◽  
Definition Of ◽  
Orogenic Belts ◽  
Oceanic Slab

The paper presents a review of processes of subduction or tectonic erosion at the Pacific-type convergent margins (PTCM) including definition of “tectonic erosion”, its triggers, driving forces and consequences. We review examples of tectonic erosion at the Circum-Pacific PTCMs and at the fossil PTCMs of the Paleo-Asian Ocean (PAO) currently hosted by the Central-Asian Orogenic Belt (CAOB). Recent geological and stratigraphic studies have shown two types of PTCMs: accreting and eroding. Accreting PTCMs consist of older deposits of accretionary and frontal prisms and grow oceanward, i.e. the trench retreats. Eroding PTCMs are characterized by the destruction of the prism, approaching arc and trench and typically form during shallow-angle and fast subduction of an oceanic slab with oceanic floor topographic highs. The mechanism of tectonic erosion includes destruction of oceanic slab, island arcs, accretionary prism, fore-arc and related prism. Tectonic erosion is a common phenomenon at many Circum-Pacific PTCMs, e.g., in South America, Tonga and Nankai troughs, Alaska. Accretion and subduction of oceanic rises contributes greatly to the processes of formation, transformation and destruction of continental crust at PTCM. The episodes of tectonic erosion can be also reconstructed for an ancient ocean, for example, for the PAO, which evolution and suturing formed the CAOB. Many CAOB foldbelts (Altai, Tienshan, eastern Kazakhstan, Transbaikalia, Mongolia) carry signs of disap-pearance of big volumes of continental crust (arcs). Studying processes responsible not only for the formation of continental crust, but also for the disappearance of big volumes of crustal mate-rial is important for correct evaluation of the nature of intra-continental orogenic belts, e.g., CAOB, and development of reliable tectonic models.

Plate Tectonics

2021 ◽  
pp. 114-136
Author(s):  
Elisabeth Ervin-Blankenheim
Keyword(s):  
Plate Tectonics ◽  
Plastic Material ◽  
Convergent Margins ◽  
Island Arcs ◽  
Mountain Ranges ◽  
Ocean Ridges ◽  
Rock Types ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Many

Plate tectonics, the grand unifying theory of geology, and its relation to the Earth is explained in this chapter. The planet transforms through time by means of the movement of rigid plates carrying the continents riding on the plastic material in the Earth’s upper mantle. Three major plate boundaries are divergent margins, where new ocean floor is being created along mid-ocean ridges and plates separate from one another; convergent margins, where the material is subducted and consumed as different types of plates collide, creating trenches, island arcs or mountain ranges, and transform boundaries; and where plates slide past one another. Besides the three predominant boundaries, hot spots caused by mantle plumes and diffuse boundaries make up additional dynamic forces in tectonics. Beyond these categories, geologists still are learning about tectonics; some boundaries are unknown or speculative. Plate tectonics explains why many of the Earth’s hazards are found where there are. Earthquakes trace many plate margins, as do volcanoes. The area around the Pacific Ocean is called the “Ring of Fire” because of the many volcanoes related to subducting plates. Tectonics accounts for why certain rocks are located where they are; for example, all rock types are found at convergent margins. The theory also predicts where valuable mineral and economic deposits are located.

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