Rapid deglaciation as an initiator of volcanic activity: An hypothesis     

Kevin Hall 《地球表面变化过程与地形》1982,7(1):45-51

Volcanic activity on sub-Antarctic Marion Island is found to have occurred only during the interglacials. The present volcano distribution is associated with a radial and peripheral fault system, the location of which appears to be related to the former glacier distribution. An hypothesis is presented suggesting that the faulting is a result of deglaciation and that the specific location of the faults is due to the differential stresses occurring between ice-covered and ice-free areas during isostatic uplift. The faulting initiates volcanism due to the location of the island within a volcanic region.  相似文献   

Middle-fan deposits from the late precambrian kongsfjord formation submarine fan,Northeast Finnmark,Northern Norway     

Kevin T. Pickering 《Sedimentary Geology》1982,33(2):79-110

The 3.2 km-thick late Precambrian Kongsfjord Formation Submarine Fan shows well-developed middle-fan facies-associations. Channel deposits are characterised by discrete packets of coarse-grained, medium to thick-bedded, amalgamated sandstone turbidites and other mass-flow deposits, generally 10 to 30 m thick. Individual beds, or packets of beds, wedge out and channel bases cut down by up to 11 m over a lateral distance of 150 m. Channel deposits often comprise a thinning-and-fining-upward sequence although they vary greatly in clarity. Interchannel deposits occur as packets, tens of centimetres to 25 m thick, of thin and very thin bedded Bouma T_cde siltstones and mudstones. Palaeocurrents within interchannel deposits commonly diverge from those of adjacent channel sandstones. Within the interchannel deposits, isolated beds or packets of beds occur that are both thicker bedded and coarser grained than the surrounding beds; these unusual deposits are sheet-like or fill small channels, and are interpreted as crevasse splays, lobes and channels. Packets, up to a few metres thick, of laterally discontinuous siltstone turbidites occur immediately above some of the channel sandstones, rarely below, and in some cases within interchannel deposits. These siltstones are thin to medium-bedded, show Bouma T_cd, with T_c often as climbing-ripple lamination, and commonly show soft-sediment deformation as slides, slumps, liquefaction and fluidisation structures. Palaeoflow within these packets, compared to adjacent channel sandstones, diverges by up to 90°, and in some cases channel sandstones are seen to pass laterally into these deposits with a swing in palaeocurrents from parallel to the inferred channel axis, to perpendicular to it. These deposits are thought to be levees. Channel-margin deposits are most distinctive, and they are recognised by extreme lateral wedging of channel sandstones, with concomitant thinning and fining of individual beds and their amalgamation towards the channel axis. Sliding and slumping of channel margin deposits is common. Throughout the Kongsfjord Formation Submarine Fan, channel sandstone palaeocurrents suggest a sediment-transport direction to the NE quadrant, although some channels funnelled sediment towards the southeast.  相似文献   

The present day formation of apatite in Mexican continental margin sediments     

Richard A. Jahnke  Steven R. Emerson  Kevin K. Roe  William C. Burnett 《Geochimica et cosmochimica acta》1983,47(2):259-266

Results of pore water and sediment analyses from the western Mexican continental margin strongly suggest the present day formation of apatite. The interstitial water phosphate and fluoride profiles indicate chemical removal at a depth which corresponds to a large maximum in the phosphorus content of the sediments. Apatite is identified within this maximum via X-ray diffraction but is elsewhere undetectable in the core. Radioisotopic thorium, uranium, and radium data support the conclusion that this deposit is modern. The present day depositional environment is consistent with those reported by other workers for phosphorite formation with the exception that pore water magnesium is not depleted below its seawater value.  相似文献   

Mapping the Globalization of the Temporary Staffing Industry*     

Neil M. Coe  Jennifer Johns  Kevin Ward 《The Professional geographer》2007,59(4):503-520

Very little is currently known about the globalization of the temporary staffing industry, a strategically significant sector given its role in promulgating wider labor market flexibility. This article starts to rectify this research lacuna in four ways: by conceptualizing the international expansion of temporary staffing and comparing it to other business service sectors, by identifying and mapping the top twenty transnational staffing agencies, by offering a typology of the leading transnational agencies based on their functional and geographic characteristics, and by charting a research agenda for future work on this sector.  相似文献   

In Situ Dechlorination of TCE during Aquifer Heating     

M. Truex  T. Powell  K. Lynch 《Ground Water Monitoring & Remediation》2007,27(2):96-105

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Searching for the Stonyhurst discs     

Kevin Kilburn  Finton O''Reilly 《Astronomy& Geophysics》2007,48(6):6.06-6.06

Projects to drill into and recover samples from active faults are progressing in two widely separated locations: off the coast of Japan and in California.  相似文献   

Nationalism, Populism, Dependency: Southeast Asia and Responses to the Asian Crisis     

Kevin Hewison 《Singapore journal of tropical geography》2001,22(3):219-236

Opposition to neoliberal globalisation has been especially intense since the Asian crisis. This paper assesses three responses to the crisis: a broad localist reaction in Thailand, and the approaches adopted by two major Asian-based organisations, the Third World Network (TWN) and the Focus on the Global South. The discussion of these approaches focuses on the issues of nationalism and populism; dependency; industrialisation and the state; and liberalisation, international institutions, and local society. Their critiques range from the conservative populism of the localists, to reformism of TWN, and to the more radical "deglobalisation" approach of the Focus group. However, none have been able to free themselves of the influence of dependency models. Their populism and "progressive nationalism" prevents an accurate location of the causes of exploitation in capitalist processes. This paper questions whether the national-global dichotomy of these approaches is an adequate way to conceptualise capitalist production and exploitation in the era of globalisation.  相似文献   

Evaluation of response and energy in actively controlled structures     

Kevin K. F. Wong  Rong Yang 《地震工程与结构动力学》2001,30(10):1495-1510

A computational method of energy evaluation is derived to study the elastic responses and energy distribution of actively controlled single‐degree‐of‐freedom (SDOF) structures during earthquakes. Contrary to the common perception that applying active control force pumps energy into the structure, the applied control force can actually reduce the energy in the structure by reducing the input energy from earthquakes to the structure. In addition, applying control force can dissipate a large amount of energy in the structure when this control force is applied in the direction opposite to the displacement and velocity responses. To demonstrate this energy mechanism in active controlled structures, the two most popular control algorithms, optimal linear control (OLC) and instantaneous optimal control (IOC) algorithms, are used to calculate the control response and energy spectra. One‐step time delay is incorporated into the algorithms to take into consideration the practical aspect of active control. The effects of different earthquakes and damping ratios on control energy and response spectra are studied. These studies show that both OLC and IOC are very effective in reducing the structural displacement and velocity responses by reducing the input earthquake energy as well as dissipating a large amount of energy in the structure. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Effectiveness of structural control based on control energy perspectives     

Kevin K. F. Wong  Rong Yang 《地震工程与结构动力学》2001,30(12):1747-1768

A computational algorithm for maximizing the control efficiency in actively controlling the elastic structural responses during earthquake is proposed. Study of optimal linear control using a single degree of freedom shows that applying active control is very effective in reducing the structural displacement and velocity responses for long‐period structures, but at the same time it has an adverse effect in increasing the absolute acceleration response. The extent of this adverse effect reduces the effectiveness of the control system, and therefore it poses a limit on the maximum control force in order to provide maximum control efficiency. In view of this shortcoming, maximum control energy dissipation is used to define the most effective optimal linear control law. Less displacement and velocity response are expected as larger control force is applied, but there is always a limit that maximum control energy can be dissipated. This study shows that this limit depends on the structural characteristics as well as the input ground motion, and a general trend is that the maximum control energy decreases as damping increases. Finally, application of the proposed algorithm on a six‐storey hospital building is presented to show the effectiveness of using optimal linear control on a multi‐degree‐of‐freedom system from the control energy perspectives. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Organic matter, putative nannobacteria and the formation of ooids and hardgrounds   总被引：3，自引：0，他引：3  

Robert L. Folk  & F. Leo Lynch 《Sedimentology》2001,48(2):215-229

Modern ooids from Joulters Cay, when baked at 500 °C, turn various shades of black depending upon the organic content. Mucus-rich laminae occur at quasi-regular intervals of a few micrometres within the cortex. When mucus is still present, it turns black; when it is absent, there is a gap. The cortex consists of two types of aragonite: (1) 'batons' of circular cross-section capped by a single 0·1-μm (100-nm) ball, which can be interpreted as a single nannobacteria cell that precipitated the baton; (2) elongate crystals made of multiple rows of minute balls of about 0·03 μm (30 nm), which may or may not have been small organisms in the size range of viruses. There are also some crystals that show no evidence of organic precipitation. Hardground cementation begins with the formation of a terminal mucus-rich ring on the ooid that bakes black and is crowded with 0·1-μm (100-nm) balls. Some ooids are then joined by a meniscus also made of mucus with aragonite crystals. The final, most abundant hardground cement forms a fur of inorganic aragonite crystals often shaped like plywood sheets, although some 'organic', elongate crystals composed of ≈0·03 μm (≈30 nm) balls are also found in the later cement. For a century, ooids have been known to be closely associated with organic matter; this paper goes further and proposes that the bulk of the ooid may be precipitated by nannobacterial processes. Hardground formation, in the beginning, may also be a microbiological process, but most cementation is accomplished inorganically.  相似文献