Using a Gaussian mathematical model to define eruptive stages of young volcanic rocks in Tengchong based on laser 40Ar/39Ar dating

Reconstruction of Quaternary environments, late Cenozoic geodynamics and evaluation of volcanic hazards, all depend on the precise delineation of eruptive stages. In recent years, laser ~(40)Ar/~(39)Ar dating methods have been widely used for dating young volcanic rocks, given their stable automated testing process, very low background level and high sensitivity, which meet the requirements for precise dating of young samples. This paper applied high-precision laser ~(40)Ar/~(39)Ar dating to the main volcanic units in the Tengchong area and obtained ages in the range of 0.025–5.1 Ma using conventional data processing methods. However, conventional dating highlighted issues related to very low radiogenic ~(40)Ar content, accidental errors and poor data stability, which led to huge age deviations. Moreover, lacking a unified timescale, conventional methods were unable to strictly define the stages of the Tengchong volcanic eruptions, leading to ongoing controversy. In this study, we applied a Gaussian mathematical model to deal with all 378 original ages from 13 samples. An apparent age-probability diagram,consisting of three independent waveforms, have been obtained. The corresponding isochron ages of these three waveforms suggest there were three volcanic eruptive stages, namely during the Pliocene(3.78±0.04 Ma), early Middle Pleistocene(0.63±0.03 Ma) and late Middle Pleistocene to early Late Pleistocene(0.139±0.005 Ma). These results accurately define eruptive stages in the Tengchong area.     

Earthquake risk assessment of buildings accounting for human evacuation

A primary goal of earthquake engineering is to protect society from the possible negative consequences of future earthquakes. Conventionally, this goal has been achieved indirectly by reducing seismic damage of the built environment through better building codes, or more comprehensibly, by minimizing seismic risk. However, the effect that building damage has on occupants is not explicitly taken into account while designing infrastructure. Consequently, this paper introduces a conceptual framework and numerical algorithm to assess earthquake risk on building occupants during seismic events, considering the evacuation process of the structure. The framework combines probabilistic seismic hazard analysis, inelastic structural response analysis and damage assessment, and couples these results with the response of evacuating agents. The results are cast as probability distributions of variables that measure the overall performance of the system (e.g., evacuation times, number of injured people, and repair costs) for specific time windows. As a testbed, the framework was applied to the response of a reinforced concrete frame building that exemplifies the use of all steps of the methodology. The results suggest that this seismic risk evaluation framework of structural systems that combine the response of a physical model with human agents can be extended to a wide variety of other situations, including the assessment of mitigation actions in communities and people to improve their earthquake resilience. Copyright © 2016 John Wiley & Sons, Ltd.     

Wondering about …. Geography—Its nature and its relevance?

In the context of the current review of New Zealand's National Certificate of Educational Achievement (NCEA), the paper reflects on the nature and relevance of geography in education, life and work. The context of school geography programmes is critically examined, and a checklist of points for further consideration and action is presented.     

水下喷发火山碎屑岩储层特征及主控因素:以新西兰Taranaki盆地中新世Kora火山为例

新西兰Taranaki盆地中新世Kora火山是海底喷发形成的碎屑岩型火山,可代表浅埋藏火山岩的储层特征.本文根据5口钻井的孔隙度、渗透率、孔隙孔径和铸体薄片开展Kora火山的储层特征、储集空间组成、缝宽以及原生和次生孔隙之间关系的分析.研究结果如下:(1)储集空间主要为次生孔隙,然后是裂缝和原生孔隙;Kora火山具有高...     

Physiological responses of transplants of the freshwater angiosperm Vallisneria americana along a salinity gradient in the Caloosahatchee Estuary (Southwestern Florida)

Fluctuations in freshwater input may affect the physiology and survival of submerged aquatic vegetation (SAV) occurring in oligoaline to mesohaline estuarine regions. Controls on the distribution of the freshwater angiosperm Vallisneria americana, were investigated by transplanting ramets. Pots (3.8-1) containing ramets were distributed among four sites (upstream site [least saline], donor site, near downstream site, and far downstream site [most saline]) in the Caloosahatchee Estuary (Southwest Florida) during wet (May–August) and dry (October–February) seasons. During 2–4 mo of each season, physiological indicators were monitored, including photosynthesis, glutamine synthetase activity, and protein content in shoots, and carbohydrates and total nitrogen and carbon in shoot and subterranean tissues. Where the physical environment (light or salinity) was suboptimal, all physiological indices, except photosynthetic rate, showed similar stress responses, which ranged from a slow decline to a rapid drop in physiological function. Levels of soluble carbohydrates decreased in response to unfavorable conditions more rapidly than did insoluble carbohydrates. Shoot protein of V. americana declined prior to transplant death, suggesting that measuring protein content may provide a rapid assessment of physiological health. V. americana transplants at the low-salinity upstream site died during both wet and dry season experiments, likely in response to light limitation and/or partial burial by sediments. At the far downstream site, death occurred within 2–4 wk, and was attributable to elevated salinities (>ca. 15‰). Comparison of physiological responses with salinity and light regimes at the donor and near downstream sites suggest that light may ameliorate salinity stress. This study demonstrates that V. americana, nominally classed as a freshwater macrophyte, is capable of a remarkable degree of halotolerance.     

Powers of engagement: on being engaged, being indifferent; and urban life

Summary This paper explores the dynamics of engagement and disengagement within urban space. It argues that a certain capacity to encounter the world around the self in an active, creative way is central to the self's ability to recognize and care about the places it inhabits and the people encountered within those places. Drawing on the work of Donald Winnicott and Jessica Benjamin, it outlines a framework of self-other psycho-dynamics through which this active, creative encountering may be understood, and examines the violence of indifference that occurs when this everyday creativity is absent.     

Estimating the Time Since Final Stabilization of a Perched Dune Field Along Lake Superior

The Nodaway dune field is perched along Lake Superior in Upper Michigan. This study uses absolute and relative‐age dating methods to test the hypothesis that the dune field finally stabilized after the Nipissing high stand, about 4,000 years ago. Surface soils on snouts of all dunes are moderately developed Spodosols, indicating that dunes stabilized within a few hundred years of each other. One thermoluminescence date provided an age of 8 ka from soil parent material, but is probably overestimated due to residual thermoluminescence. Subsequent optical stimulated luminescence and accelerator mass spectrometry age estimates indicate that the most recent accumulation of sand occurred between ?3.7 and 3.0 ka. This interval suggests one of three possibilities: 1) that the dune field was reactivated during the Algoma high stand and then stabilized; 2) that the dune field stabilized gradually, probably as sand supply diminished after the Nipissing high stand; and 3) that a combination of these two processes occurred.