Editors’ message: The housing crisis from underground—damage to a historic town by geothermal drillings through anhydrite, Staufen, Germany   总被引：2，自引：1，他引：1  

Nico Goldscheider  Timothy D. Bechtel 《Hydrogeology Journal》2009,17(3):491-493

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The production of unequal risk in hazardscapes: An explanatory frame applied to disaster at the US–Mexico border     

Timothy W. Collins   《Geoforum》2009,40(4):589-1806

This paper advances understanding of how unequal risks to environmental hazards are generated. Marginalization is the best known explanation for the production of risk. The concept of marginalization was elaborated through studies of hazards in the global South and connotes how social inequalities constrain livelihood options of less powerful social groups. Thus, marginal groups are pressured to degrade landscapes and occupy hazardous environments while they experience decreased capacities to cope with environmental change. This paper directs analytical attention beyond the material to include the discursive realm and demonstrates that the production of unequal risk is contingent upon how hazards are differentially perceived, represented, and contested in social spaces. Findings from a flood disaster case study in the El Paso (US)–Ciudad Juárez (Mexico) border metropolis highlight how hegemonic discourses reinforce material processes of marginalization in flood-prone social spaces. Findings also reveal how socially-powerful geographical groups of people have harnessed institutional resources in their efforts to externalize risks and capitalize on environmental opportunities in some flood-prone areas. The concept of facilitation is used to explain the material-discursive production of socially-elite, flood-prone spaces. Facilitation clarifies how powerful groups are provided privileged access to institutional resources in their pursuit of environmental rewards, contributing to unjust socioenvironmental outcomes. In conclusion, I outline key aspects of how unequal risks are materially and discursively (re)produced within hazardscapes through relational processes of marginalization/facilitation.  相似文献   

Early Palaeozoic orogenic events north of the Rheic suture (Brabant,Ardenne): A review     

Manuel Sintubin  Timothy Nick Debacker  Hervé Van Baelen 《Comptes Rendus Geoscience》2009,341(2-3):156-173

The Lower Palaeozoic rocks exposed in the Brabant-Ardenne region (Belgium, France) recorded the Early Palaeozoic history on the southern margin of the perigondwanan microcontinent of Avalonia, north of the Rheic suture. These rocks crop out in the Brabant basement and in the Ardenne basement inliers within the Variscan Ardenne allochthon. The two main unconformities are classically associated with distinct orogenic episodes, the Late Ordovician “Ardennian” event and the Early Devonian “Brabantian” event. A review of the current state-of-knowledge with respect to the reconstruction of Early Palaeozoic geodynamics in the Brabant-Ardenne region is presented. It is demonstrated that an unconformity does not necessarily represent an orogenic event, and that the hiatus related to an unconformity does not necessarily coincide with tectonic activity, especially when tectonism is diachronous in nature. The former applies to the Ardennian unconformity, while the latter applies to the Brabantian unconformity. Finally, the well-constrained Brabantian orogeny, as well as the Ardenne-Eifel basin development, is tentatively framed within the Early Palaeozoic geodynamic context of the northern margin of the Rheic realm. By doing so, it is shown that the Brabant-Ardenne region links, both in space and time, the Rheic and Rhenohercynian ocean.  相似文献   

Long-lived transpression in the Archean Bird River greenstone belt, western Superior Province, Southeastern Manitoba     

Manuel Duguet  Shoufa Lin  Don W. Davis  M. Timothy Corkery  Justin McDonald 《Precambrian Research》2009,174(3-4):381-407

The Archean Bird River greenstone belt (BRGB) is located on the southwestern edge of the Superior Province between the 3.2 Ga old Winnipeg River subprovince to the south and the metasedimentary belt of the English River subprovince (ERSP) to the north. This position between two major subprovinces makes the BRGB a primary target for investigating the geodynamic and kinematic evolution of a major structural boundary. New structural and geochronological data have allowed us to present an evolutionary framework for the southern boundary of the North Caribou superterrane. The BRGB underwent 3 main deformation phases. The D1 event took place ca. 2698 Ma and displays a north-side-up shearing. The D2 event, occurring at ca. 2684 Ma in a transpressive context, presents a complex structural pattern mixing vertical tectonics in the BRGB and strike-slip tectonics along the boundaries of the greenstone belt with other subprovinces. Between the BRGB and the ERSP, the 2832–2858 Ma old Maskwa batholith acted as a rigid passive block during the collision and marks the boundary between pure dextral strike-slip tectonics along his northern boundary with the ERSP and vertical south-side-up motion in the BRGB. The BRGB can be considered as a pop-up structure with anastomosed shear zones displaying different horizontal offset according to the orientation of the shear zones. The southern boundary with the Winnipeg River subprovince is represented by a sinistral south-side-up shear zone. The same pattern is found at the regional scale where major shear zones acted as a conjugate set in the horizontal plane. At ca. 2640 Ma, the D3 event occurred in a general dextral transpressive tectonic regime coeval with the emplacement of rare-elements pegmatitic plutons in a still hot (400–500 °C) country rock. The geodynamical and mechanical significance of the partitioning between pure strike-slip tectonics in the English River subprovince and vertical motion in the BRGB can be explained by the rheological behaviour of a hot and weak lithosphere undergoing transpressive strain. The structural framework of the BRGB is the result of strong interactions between hot and weak domains, coeval with widespread plutonism, and a rigid older domain (Maskwa batholith) during the D2 transpressive event.  相似文献   

Geochemical modelling of a Zn–Pb skarn: Constraints from LA–ICP–MS analysis of fluid inclusions     

Martina Bertelli  Timothy Baker  James S. Cleverley  Thomas Ulrich 《Journal of Geochemical Exploration》2009

The Bismark deposit (northern Chihuahua, Mexico) is one of several base metal-rich high-temperature, carbonate-replacement deposits hosted in northern Mexico. Previous fluid inclusion studies based on microthermometry and PIXE have shown that the Zn-rich, Pb-poor Bismark deposit formed from a moderate salinity magmatic fluid [Baker, T. and Lang, J.R., 2003. Reconciling fluid inclusion types, fluid processes, and fluid sources in skarns: an example from the Bismark Deposit, Mexico. Mineralium Deposita 38(4), 474–495; Baker, T., van Achterberg, E., Ryan, C.G. and Lang, J.R., 2004. Composition and evolution of ore fluids in a magmatic-hydrothermal skarn deposit. Geology 32(2), 117–120]. The exact precipitation mechanisms are unclear and may have due to cooling, salinity decrease and wall rock reaction. Furthermore, PIXE data suggested that Pb and Zn concentrations were comparable and inconsistent with the Zn-rich nature of the ore. However, Pb was commonly below the limit of detection for PIXE and the data presented by Baker et al. [Baker, T., van Achterberg, E., Ryan, C.G. and Lang, J.R., 2004. Composition and evolution of ore fluids in a magmatic-hydrothermal skarn deposit. Geology 32(2), 117–120] are regarded as the maximum concentrations of Pb in the fluid. In this study new LA ICP MS analysis was carried out on the same fluid inclusion population to compare with the PIXE data in order to constrain the uncertainty related to the Pb data and the new results are used to model possible ore deposition mechanisms. The new laser ablation data reveal overall lower concentrations of Pb in the ore fluid (average value ~ 285 ppm) than previously indicated by PIXE analysis (average value ~ 713 ppm). Chemical modelling using the new laser ablation data tested the following ore deposition processes: 1) cooling; 2) fluid–rock reaction at constant temperature; 3) cooling and simultaneous fluid–rock interaction. Modelling results show that the gangue and ore minerals observed at Bismark are best reproduced by fluid–rock interaction and simultaneous cooling. Results from the simulations strongly indicate that ore deposition was mainly driven by a pH increase due to the neutralization of the acidic ore fluid (pH = 3.9) as the result of the reaction with the limestone. Modelling results also suggest that the deposit likely formed under cooling conditions, but do not support the hypothesis of a temperature decrease as the principal ore-forming process.  相似文献   

Change of collision efficiency with distance in bacterial transport experiments     

Dong H  Scheibe TD  Johnson WP  Monkman CM  Fuller ME 《Ground water》2006,44(3):415-429

Understanding the mechanisms of bacterial transport in aquifers is important in developing bioremediation strategies. Collision efficiency (alpha) is one important parameter used in modeling bacterial transport. This study was undertaken to measure change in alpha with distance by performing a bacterial transport experiment in Oyster, Virginia. Following injection of a bacterium, Comamonas sp., into a well, water samples were collected at various distances along the flowpath and injected into columns packed with homogenized South Oyster focus area sediment. Zeta potentials of the bacteria in the samples were measured. Values of alpha were determined at various locations in the field in two ways: based on field breakthrough concentrations at the sampling points and based on column breakthrough concentrations. The alpha values estimated from field breakthrough decreased with distance, whereas those estimated from column breakthrough increased with distance. Bacterial cell surface charge became progressively more negative with distance in the field. We hypothesize that the apparent contradiction between field and column alpha values was caused by differences in the flow of the two systems. Flow in the columns was forced to occur through fine-grained zones of iron and aluminum hydroxide coatings that selectively removed the most negatively charged bacteria. In contrast, in the field, the injected cells did not come into contact with the positively charged coatings because the bulk solution bypassed them due to heterogeneous hydraulic properties. These results suggest that laboratory-based models may underestimate bacterial transport distance in the field. A more realistic approach may be necessary to capture the degree of heterogeneity.  相似文献   

Downscaling large-scale NCEP CFS to resolve fine-scale seasonal precipitation and extremes for the crop growing seasons over the southeastern United States     

Young-Kwon Lim  Steven Cocke  D. W. Shin  Justin T. Schoof  Timothy E. LaRow  James J. O’Brien 《Climate Dynamics》2010,35(2-3):449-471

Seasonally predicted precipitation at a resolution of 2.5° was statistically downscaled to a fine spatial scale of ~20 km over the southeastern United States. The downscaling was conducted for spring and summer, when the fine-scale prediction of precipitation is typically very challenging in this region. We obtained the global model precipitation for downscaling from the National Center for Environmental Prediction/Climate Forecast System (NCEP/CFS) retrospective forecasts. Ten member integration data with time-lagged initial conditions centered on mid- or late February each year were used for downscaling, covering the period from 1987 to 2005. The primary techniques involved in downscaling are Cyclostationary Empirical Orthogonal Function (CSEOF) analysis, multiple regression, and stochastic time series generation. Trained with observations and CFS data, CSEOF and multiple regression facilitated the identification of the statistical relationship between coarse-scale and fine-scale climate variability, leading to improved prediction of climate at a fine resolution. Downscaled precipitation produced seasonal and annual patterns that closely resemble the fine resolution observations. Prediction of long-term variation within two decades was improved by the downscaling in terms of variance, root mean square error, and correlation. Relative to the coarsely resolved unskillful CFS forecasts, the proposed downscaling drove a significant reduction in wet biases, and correlation increased by 0.1–0.5. Categorical predictability of seasonal precipitation and extremes (frequency of heavy rainfall days), measured with the Heidke skill score (HSS), was also improved by the downscaling. For instance, domain averaged HSS for two category predictability by the downscaling are at least 0.20, while the scores by the CFS are near zero and never exceed 0.1. On the other hand, prediction of the frequency of subseasonal dry spells showed limited improvement over half of the Georgia and Alabama region.  相似文献   

Climate change mitigation: trade-offs between delay and strength of action required     

Naomi E. Vaughan  Timothy M. Lenton  John G. Shepherd 《Climatic change》2009,96(1-2):29-43

Climate change mitigation via a reduction in the anthropogenic emissions of carbon dioxide (CO₂) is the principle requirement for reducing global warming, its impacts, and the degree of adaptation required. We present a simple conceptual model of anthropogenic CO₂ emissions to highlight the trade off between delay in commencing mitigation, and the strength of mitigation then required to meet specific atmospheric CO₂ stabilization targets. We calculate the effects of alternative emission profiles on atmospheric CO₂ and global temperature change over a millennial timescale using a simple coupled carbon cycle-climate model. For example, if it takes 50 years to transform the energy sector and the maximum rate at which emissions can be reduced is ?2.5% $\text{year}^{-1}$ , delaying action until 2020 would lead to stabilization at 540 ppm. A further 20 year delay would result in a stabilization level of 730 ppm, and a delay until 2060 would mean stabilising at over 1,000 ppm. If stabilization targets are met through delayed action, combined with strong rates of mitigation, the emissions profiles result in transient peaks of atmospheric CO₂ (and potentially temperature) that exceed the stabilization targets. Stabilization at 450 ppm requires maximum mitigation rates of ?3% to ?5% $\text{year}^{-1}$ , and when delay exceeds 2020, transient peaks in excess of 550 ppm occur. Consequently tipping points for certain Earth system components may be transgressed. Avoiding dangerous climate change is more easily achievable if global mitigation action commences as soon as possible. Starting mitigation earlier is also more effective than acting more aggressively once mitigation has begun.  相似文献   

Changes in frost, snow and Baltic sea ice by the end of the twenty-first century based on climate model projections for Europe     

Kirsti Jylhä  Stefan Fronzek  Heikki Tuomenvirta  Timothy R. Carter  Kimmo Ruosteenoja 《Climatic change》2008,86(3-4):441-462

Changes in indices related to frost and snow in Europe by the end of the twenty-first century were analyzed based on experiments performed with seven regional climate models (RCMs). All the RCMs regionalized information from the same general circulation model (GCM), applying the IPCC-SRES A2 radiative forcing scenario. In addition, some simulations used SRES B2 radiative forcing and/or boundary conditions provided by an alternative GCM. Ice cover over the Baltic Sea was examined using a statistical model that related the annual maximum extent of ice to wintertime coastal temperatures. Fewer days with frost and snow, shorter frost seasons, a smaller liquid water equivalent of snow, and milder sea ice conditions were produced by all model simulations, irrespective of the forcing scenario and the driving GCM. The projected changes have implications across a diverse range of human activities. Details of the projections were subject to differences in RCM design, deviations between the boundary conditions of the driving GCMs, uncertainties in future emissions and random effects due to internal climate variability. A larger number of GCMs as drivers of the RCMs would most likely have resulted in somewhat wider ranges in the frost, snow and sea ice estimates than those presented in this paper.  相似文献   

Enhanced visualization of the flat landscape of the Cambridgeshire Fenlands          下载免费PDF全文

Oliver Pritchard  Timothy Farewell  Stephen Hallett 《Geology Today》2015,31(5):187-192

The Fenlands of East Anglia, England, represent a subtle landscape, where topographic highs rarely exceed 30 m above sea level. However, the fens represent an almost full sequence of Quaternary deposits which, together with islands of Cretaceous and Jurassic outcrops, make the area of geological importance. This feature discusses the advantages of using 3D visualization coupled with high‐resolution topographical data, over traditional 2D techniques, when undertaking an analysis of the landscape. Conclusions suggest that the use of 3D visualization will result in a higher level of engagement, particularly when communicating geological information to a wider public.  相似文献