ISSN:0273-8457    

DOI:10.1080/10889378409377216

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Volcanic activity has stamped its mark on the history of the Icelanders. The damaging factors of volcanic eruptions and the range of their effects are shown in Table 1. The four factors causing the most serious damage in Iceland are tephra, lava, gases, and jokulhlaups. The most damaging tephra falls were from Hekla in 1104 and from Myrdalsjökull, a hitherto unknown eruption, in about 1375. In lowland areas, a tephra fall leads to long abandonment of farms, when the thickness of the tephra layer, as freshly fallen, exceeds 25 cm. Two lava flows were exceptionally destructive, the Lakagigar lava flow in 1783 and that on Heimaey in 1973. Most destructive among the numerous jokulhlaups were probably those from Öraefajökull in 1362 and from Katla shortly before 1179. The worst disaster in Iceland's history was caused by the gases—mainly fluorine and sulphuric compounds—emitted during the Lakagigar eruption in 1783. This disaster excluded, volcanic eruptions have directly caused fewer losses of life than snow avalanches have done. And bearing in mind the utilization of the natural heat, it seems safe to claim that in spite of severe blows from eruptions and earthquakes, the volcanic character of Iceland makes it now a better country to live in than it would otherwise be. (Translated by U.S. Department of State; further translation and editing by Richard S.Williams, Jr., U.S. Geological Survey, Reston, Virginia 22092).

ISSN:0273-8457    

DOI:10.1080/10889378409377217

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

All fiords and trough‐shaped submarine valleys occur within glaciated coastal mountains or adjacent glaciated shelves and are completely absent from other coasts or shelf areas. This distribution strongly suggests that these landforms are of glacial origin and hence their dimensions can be used for assessing the rate of glacial scour. The total volume of these forms in the eastern North Atlantic measures about 750,000 km3, equivalent to a mass of 280 • 1013tonnes; this would be equivalent to the removal of a layer of rock 240 m thick. As for the distribution of the resultant drift, 30% of its mass can be explained in terms of lateglacial in‐filling of the troughs, 63% to 65% was dumped on the continental slopes and rises, about 1% was deposited on the polar abyssal plain, and 4 to 5% was rafted by icebergs to subpolar areas of the abyssal plain. Rates of scour in fiords and glacial submarine valleys ranged from 2.7 to 6.0 mm/year, which is an order of magnitude higher than the rate of erosion by land‐based glaciers. Data on glaciomarine sedimentation in the western North Atlantic and in deepsea trenches off southwest Alaska and southern Chile tally with these figures.

ISSN:0273-8457    

DOI:10.1080/10889378409377218

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

During glacio‐eustatic lowering of sea level, the shallow northeastern portion of the Bering Sea became a part of the Bering Land Bridge while the sea's deep southwestern portion remained part of the ocean. Judging by indirect evidence, the deep portion was glaciated. Our analysis stresses a multifacetted analogy between the Bering Sea and the Norwegian‐Greenland Sea which strongly suggests that the conditions conducive to ice‐sheet growth existed over both seas. The intensified polar front in the “glacial”; North Pacific, like that in the “glacial”; North Atlantic, acted as a barrier to northward flow of subtropical water; also branches of the Kuroshio Current ceased to enter the Bering Sea. This resulted in a negative heat balance in the sea, which must have forced the inception of a marine ice sheet through an ice‐shelf mechanism. The South‐Beringian Ice Sheet is visualized as a single dynamic system of marine and terrestrial glaciers with a total area of 2.6–2.7 million km2; its central portion was the Bering Ice Shelf constrained north of the Aleutian‐Commander Ridge and resting on the Shirshov and Bowers ridges. The large submarine canyons of southern Beringia, the flattened tops of the above ridges, and “submerged”; terraces on the continental slopes were connected with glacial scouring, while the system of coalescing turbidite fans at depth are considered to be glaciomarine. In reconstructions of sea‐surface summer temperatures for the North Pacific 18,000 years ago, the 0° isotherm should be plotted south of the Aleutian‐Commander Ridge and a separate zone of steep thermal gradient is interpolated immediately south of that isotherm.

ISSN:0273-8457    

DOI:10.1080/10889378409377219

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The article addresses the topic of prediction of vegetation recovery in areas disturbed by industrial activities in northern West Siberia, depending on such factors as initial vegetation cover and drainage conditions. The author has developed a system for mapping vegetation zones in terms of their capability for recovery after disturbance.

ISSN:0273-8457    

DOI:10.1080/10889378409377220

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The author maintains that there are no glacial deposits present in the northern part of Western Siberia. The extensive till‐like deposits, which have formed the basis for earlier hypotheses as to glaciation of this area, are in fact water‐laid. There are in fact two varieties of till‐like deposits: the first lying at the base of the Quaternary sequence, consists of a concentration of megaclast material. It was formed in a nearshore marine environment during extremely rapid sediment accumulation which permitted little reworking by water‐action prior to burial. The second variety of till‐like deposits is characterized by better sorting of the fines and a more even distribution of megaclasts throughout the section. This material was deposited offshore, the megaclasts having been transported by floating ice.

ISSN:0273-8457    

DOI:10.1080/10889378409377221

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0273-8457    

DOI:10.1080/10889378409377222

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0273-8457    

DOI:10.1080/10889378409377215

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor