Geomorphology of coal seam fires     

Claudia Kuenzer  Glenn B. Stracher 《Geomorphology》2012,138(1):209-222

Coal fires occur in underground natural coal seams, in exposed surface seams, and in coal storage or waste piles. The fires ignite through spontaneous combustion or natural or anthropogenic causes. They are reported from China, India, USA, South Africa, Australia, and Russia, as well as many other countries. Coal fires lead to loss of a valuable resource (coal), the emission of greenhouse-relevant and toxic gases, and vegetation deterioration. A dangerous aspect of the fires is the threat to local mines, industries, and settlements through the volume loss underground. Surface collapse in coal fire areas is common. Thus, coal fires are significantly affecting the evolution of the landscape. Based on more than a decade of experience with in situ mapping of coal fire areas worldwide, a general classification system for coal fires is presented. Furthermore, coal seam fire geomorphology is explained in detail. The major landforms associated with, and induced by, these fires are presented. The landforms include manifestations resulting from bedrock surface fracturing, such as fissures, cracks, funnels, vents, and sponges. Further manifestations resulting from surface bedrock subsidence include sinkholes, trenches, depressions, partial surface subsidence, large surface subsidence, and slides. Additional geomorphologic coal fire manifestations include exposed ash layers, pyrometamorphic rocks, and fumarolic minerals. The origin, evolution, and possible future development of these features are explained, and examples from in situ surveys, as well as from high-resolution satellite data analyses, are presented. The geomorphology of coal fires has not been presented in a systematic manner. Knowledge of coal fire geomorphology enables the detection of underground coal fires based on distinct surface manifestations. Furthermore, it allows judgments about the safety of coal fire-affected terrain. Additionally, geomorphologic features are indicators of the burning stage of fires. Finally, coal fire geomorphology helps to explain landscape features whose occurrence would otherwise not be understood. Although coal fire-induced thermal anomalies and gas release are also indications of coal fire activity, as addressed by many investigators, no assessment is complete without sound geomorphologic mapping of the fire-induced geomorphologic features.  相似文献   

Associations between elevated atmospheric temperature and human mortality: a critical review of the literature   总被引：4，自引：1，他引：3  

Simon N. Gosling  Jason A. Lowe  Glenn R. McGregor  Mark Pelling  Bruce D. Malamud 《Climatic change》2009,92(3-4):299-341

The effects of the anomalously warm European summer of 2003 highlighted the importance of understanding the relationship between elevated atmospheric temperature and human mortality. This review is an extension of the brief evidence examining this relationship provided in the IPCC’s Assessment Reports. A comprehensive and critical review of the literature is presented, which highlights avenues for further research, and the respective merits and limitations of the methods used to analyse the relationships. In contrast to previous reviews that concentrate on the epidemiological evidence, this review acknowledges the inter-disciplinary nature of the topic and examines the evidence presented in epidemiological, environmental health, and climatological journals. As such, present temperature–mortality relationships are reviewed, followed by a discussion of how these are likely to change under climate change scenarios. The importance of uncertainty, and methods to include it in future work, are also considered.  相似文献   

Climate trends of the North American prairie pothole region 1906–2000     

Bruce Millett  W. Carter Johnson  Glenn Guntenspergen 《Climatic change》2009,93(1-2):243-267

The Prairie Pothole Region (PPR) is unique to North America. Its millions of wetlands and abundant ecosystem goods and services are highly sensitive to wide variations of temperature and precipitation in time and space characteristic of a strongly continental climate. Precipitation and temperature gradients across the PPR are orthogonal to each other. Precipitation nearly triples from west to east from approximately 300 mm/year to 900 mm/year, while mean annual temperature ranges from approximately 1°C in the north to nearly 10°C in the south. Twentieth-century weather records for 18 PPR weather stations representing 6 ecoregions revealed several trends. The climate generally has been getting warmer and wetter and the diurnal temperature range has decreased. Minimum daily temperatures warmed by 1.0°C, while maximum daily temperatures cooled by 0.15°C. Minimum temperature warmed more in winter than in summer, while maximum temperature cooled in summer and warmed in winter. Average annual precipitation increased by 49 mm or 9%. Palmer Drought Severity Index (PDSI) trends reflected increasing moisture availability for most weather stations; however, several stations in the western Canadian Prairies recorded effectively drier conditions. The east-west moisture gradient steepened during the twentieth century with stations in the west becoming drier and stations in the east becoming wetter. If the moisture gradient continues to steepen, the area of productive wetland ecosystems will shrink. Consequences for wetlands would be especially severe if the future climate does not provide supplemental moisture to offset higher evaporative demand.  相似文献   

The deep wind structure of the giant planets: Results from an anelastic general circulation model     

Yohai Kaspi  Glenn R. Flierl 《Icarus》2009,202(2):525-542

The giant gas planets have hot convective interiors, and therefore a common assumption is that these deep atmospheres are close to a barotropic state. Here we show using a new anelastic general circulation model that baroclinic vorticity contributions are not negligible, and drive the system away from an isentropic and therefore barotropic state. The motion is still aligned with the direction of the axis of rotation as in a barotropic rotating fluid, but the wind structure has a vertical shear with stronger winds in the atmosphere than in the interior. This shear is associated with baroclinic compressibility effects. Most previous convection models of giant planets have used the Boussinesq approximation, which assumes the density is constant in depth; however, Jupiter's actual density varies by four orders of magnitude through its deep molecular envelope. We therefore developed a new general circulation model (based on the MITgcm) that is anelastic and thereby incorporates this density variation. The model's geometry is a full 3D sphere down to a small inner core. It is nonhydrostatic, uses an equation of state suitable for hydrogen-helium mixtures (SCVH), and is driven by an internal heating profile. We demonstrate the effect of compressibility by comparing anelastic and Boussinesq cases. The simulations develop a mean state that is geostrophic and hydrostatic including the often neglected, but significant, vertical Coriolis contribution. This leads to modification of the standard thermal wind relation for a deep compressible atmosphere. The interior flow organizes in large cyclonically rotating columnar eddies parallel to the rotation axis, which drive upgradient angular momentum eddy fluxes, generating the observed equatorial superrotation. Heat fluxes align with the axis of rotation, and provide a mechanism for the transport of heat poleward, which can cause the observed flat meridional emission. We address the issue of over-forcing which is common in such convection models and analyze the dependence of our results on this; showing that the vertical wind structure is not very sensitive to the Rayleigh number. We also study the effect of rotation, showing how the transition from a rapidly to a slowly rotating system affects the dynamics.  相似文献   

Magnetically-regulated fragmentation induced by nonlinear flows and ambipolar diffusion     

Shantanu Basu  Glenn E. Ciolek  Wolf B. Dapp  James Wurster 《New Astronomy》2009,14(5):483-495

We present a parameter study of simulations of fragmentation regulated by gravity, magnetic fields, ambipolar diffusion, and nonlinear flows. The thin-sheet approximation is employed with periodic lateral boundary conditions, and the nonlinear flow field (“turbulence”) is allowed to freely decay. In agreement with previous results in the literature, our results show that the onset of runaway collapse (formation of the first star) in subcritical clouds is significantly accelerated by nonlinear flows in which a large-scale wave mode dominates the power spectrum. In addition, we find that a power spectrum with equal energy on all scales also accelerates collapse, but by a lesser amount. For a highly super-Alfvénic initial velocity field with most power on the largest scales, the collapse occurs promptly during the initial compression wave. However, for trans-Alfvénic perturbations, a subcritical magnetic field causes a rebound from the initial compression, and the system undergoes several oscillations before runaway collapse occurs. Models that undergo prompt collapse have highly supersonic infall motions at the core boundaries. Cores in magnetically subcritical models with trans-Alfvénic initial perturbations also pick up significant systematic speeds by inheriting motions associated with magnetically-driven oscillations. Core mass distributions are much broader than in models with small-amplitude initial perturbations, although the disturbed structure of cores that form due to nonlinear flows does not guarantee subsequent monolithic collapse. Our simulations also demonstrate that significant power (if present initially) can be maintained with negligible dissipation in large-scale compressive modes of a magnetic thin sheet, in the limit of perfect flux freezing.  相似文献   

Late Pleistocene sea-level oscillations (MIS 10–2) recorded in shallow marine and coastal plain sediments of the southern Wanganui Basin, New Zealand     

Glenn R. Hughes  David M. Kennedy   《Quaternary Research》2009,71(3):477-489

The northern Wanganui Basin, New Zealand, is one of the key global sites for understanding marine cyclic sedimentation during the Quaternary. This paper presents the first evidence of marine cyclic sedimentation from its central-southern parts. Sedimentological, micropalaeontological and palynological analyses on a 280-m-deep borehole encountered units dating back to MIS 10. The sequence includes four marine cycles spanning MIS 9–5, which are overlain by terrestrial fluvial aggradation surfaces dating from MIS 4–2. Each marine unit represents a progressively shallowing depositional environment from the mid-shelf to coastal plain. This is overlain by a terrestrial sequence of lowstand fluvial terraces. Localized fault movements appear to have influenced the sedimentary character of the sequence during MIS 7a and 5e producing basement highs which provided protection to the shoreline. The cyclothems described in this paper now extend the already extensive, previously described record from MIS 17–10 to produce a combined eustatic record of Quaternary sea level change within the basin to MIS 5. They also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space.  相似文献   

The Effects of Fault-Zone Cementation on Groundwater Flow at the Field Scale     

Tyler G. Sproule  Glenn A. Spinelli  John L. Wilson  Michael D. Fort  Peter S. Mozley  Jared Ciarico 《Ground water》2021,59(3):396-409

Fault zones are an important control on fluid flow, affecting groundwater supply, contaminant migration, and carbon storage. However, most models of fault seal do not consider fault zone cementation, despite the recognition that it is common and can dramatically reduce permeability. In order to study the field-scale hydrogeologic effects of fault zone cementation, we conducted a series of aquifer pumping tests in wells installed within tens of meters of the variably cemented Loma Blanca Fault, a normal fault in the Rio Grande Rift. In the southern half of the study area, the fault zone is cemented by calcite; the cemented zone is 2-8 m wide. In the center of the study area, the cemented fault zone is truncated at a buttress unconformity that laterally separates hydrostratigraphic units with a ∼40X difference in permeability. The fault zone north of the unconformity is not cemented. Constant rate pumping tests indicate that where the fault is cemented, it is a barrier to groundwater flow. This is an important demonstration that a fault with no clay in its core and similar sediment on both sides can be a barrier to groundwater flow by virtue of its cementation; most conceptual models for the hydrogeology of faults would predict that it would not be a barrier to groundwater flow. Additionally, the lateral permeability heterogeneity across the unconformity imposes another important control on the local flow field. This permeability discontinuity acts as either a no-flow boundary or a constant head boundary, depending on the location of pumping.  相似文献   

First Spitzer observations of Neptune: Detection of new hydrocarbons     

Victoria S. Meadows  Glenn Orton  Mao-Chang Liang  Jeffrey Van Cleve 《Icarus》2008,197(2):585-589

We present the first spectra of Neptune taken with the Spitzer Space Telescope, highlighting the high-sensitivity, moderate-resolution 10-20 μm (500-1000 cm⁻¹) spectra. We report the discovery of methylacetylene (CH₃C₂H) and diacetylene (C₄H₂) with derived 0.1-mbar volume mixing ratios of (1.2±0.1)×¹⁰⁻¹⁰ and (3±1)×¹⁰⁻¹² respectively.  相似文献   

Dreading CRISPR: GMOs,Honest Brokers,And Mertonian Transgressions          下载免费PDF全文

Glenn Davis Stone 《Geographical review》2017,107(4):584-591

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Photonic dating of prehistoric irrigation canals at Phoenix,Arizona, U.S.A.*     

Glenn W. Berger  T. Kathleen Henderson  D. Banerjee  Fred L. Nials 《Geoarchaeology》2004,19(1):1-19

A number of archeological features, including in‐filled irrigation canals of uncertain prehistoric age, occur within the Holocene floodplain of the Salt River at Phoenix, Arizona. In the first attempt to date irrigation‐canal sediments using luminescence methods, we obtained age estimates of 1640 ± 190 yr B.P. (1σ) (multi‐aliquot or MA) and 1621 ± 95 yr B.P. (post‐IR single‐aliquot‐regenerative‐dose or SAR) for a single sample from the base of the oldest canal‐infilling deposits (all IR‐PSL ages reported in this article are in calendar years before A.D. 2001). For the remaining canal samples, weighted mean luminescence ages of 819 ± 45 yr (MA) and 826 ± 32 yr (post‐IR SAR) were obtained. Thus from photonic dating we can resolve the first and last phases of canal use at this Phoenix site: initiation at ca. 1600 years ago and final use at ca. 800 years ago. These results demonstrate the power of SAR luminescence sediment dating to enhance our understanding of prehistoric irrigation‐canal development and usage here and elsewhere in the world. © 2004 Wiley Periodicals, Inc.  相似文献