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951.
Managing wildland fire incidents can be fraught with complexity and uncertainty. Myriad human factors can exert significant influence on incident decision making, and can contribute additional uncertainty regarding programmatic evaluations of wildfire management and attainment of policy goals. This article develops a framework within which human sources of uncertainty in wildfire management can be classified and managed, specifically identifying social, institutional, and psychological factors that can affect wildland fire incident decision making. These factors are reviewed in the context of wildland fire incident management and the literature regarding fire manager decision making. I then provide specific recommendations for addressing these issues, with a focus on improving incident decision processes. Extending this framework to consider a broader set of human factors and to consider how human factors affect the broader wildfire management spectrum could lead to improved fire management outcomes.  相似文献   
952.
Compositional analyses of lunar pyroclastic deposits   总被引:1,自引:0,他引:1  
The 5-band Clementine UVVIS data at ∼100 m/pixel were used to examine the compositions of 75 large and small lunar pyroclastic deposits (LPDs), and these were compared to representative lunar maria and highlands deposits. Results show that the albedo, spectral color, and inferred composition of most LPDs are similar to those of low-titanium, mature lunar maria. These LPDs may have consisted largely of fragmented basalt, with substantial components of iron-bearing mafic minerals (pyroxenes, olivine) and smaller amounts (if any) of volcanic glass. Several smaller LPDs also show substantial highland components. Three classes of very large deposits can be distinguished from most LPDs and from each other on the basis of crystallinity and possible titanium content of their pyroclastic components. One class has spectral properties that are dominated by high-titanium, crystallized “black beads” (e.g., Taurus-Littrow), a second consists of a mixture of high-titanium glasses and beads with a higher glass/bead ratio (Sulpicius Gallus) than that of Taurus-Littrow, and a third has a significant component of quenched iron-bearing volcanic glasses (Aristarchus) with possible moderate titanium contents. Although areally extensive, these three classes of very large pyroclastic deposits compose only 20 of the 75 deposits studied (∼27%), and eruption of such materials was thus likely to have been less frequent on the Moon.  相似文献   
953.
954.
对采自苏北-胶南构造混杂岩带中的15个矿物样品进行了国内首次系统的多重扩散域~(40)Ar-~(39)Ar年龄谱研究,其中七个样品的冷却历史表明,这一地区存在着两个明显的快速冷却事件:172~196Ma(10~40℃/Ma)和105~123Ma(4~10℃/Ma)。采自南缘的样品给出的这一地区最早抬升事件的时间大约为260Ma。这些结果表明苏北-胶南碰撞带的剥蚀历史可能与秦岭-大别山造山带相一致。应用多重扩散域新理论可以从单一长石样品揭示较完整的热历史。  相似文献   
955.

Background  

Forests can sequester carbon dioxide, thereby reducing atmospheric concentrations and slowing global warming. In the U.S., forest carbon stocks have increased as a result of regrowth following land abandonment and in-growth due to fire suppression, and they currently sequester approximately 10% of annual US emissions. This ecosystem service is recognized in greenhouse gas protocols and cap-and-trade mechanisms, yet forest carbon is valued equally regardless of forest type, an approach that fails to account for risk of carbon loss from disturbance.  相似文献   
956.
957.
The Waratah Fault is a northeast trending, high angle, reverse fault in the Late Paleozoic Lachlan Fold Belt at Cape Liptrap on the Southeastern Australian Coast. It is susceptible to reactivation in the modern intraplate stress field in Southeast Australia and exhibits Late Pliocene to Late Pleistocene reactivation. Radiocarbon, optically stimulated luminescence (OSL), and cosmogenic radionuclide (CRN) dating of marine terraces on Cape Liptrap are used to constrain rates of displacement across the reactivated Waratah Fault. Six marine terraces, numbered Qt6–Tt1 (youngest to oldest), are well developed at Cape Liptrap with altitudes ranging from ~1.5 m to ~170 m amsl, respectively. On the lowest terrace, Qt6, barnacles in wave-cut notches ~1.5 m amsl, yielded a radiocarbon age of 6090–5880 Cal BP, and reflect the local mid-Holocene sea level highstand. Qt5 yielded four OSL ages from scattered locations around the cape ranging from ~80 ka to ~130 ka. It formed during the Last Interglacial sea level highstand (MIS 5e) at ~125 ka. Inner edge elevations (approximate paleo high tide line) for Qt5 occur at distinctly different elevations on opposite sides of the Waratah Fault. Offsets of the inner edges across the fault range from 1.3 m to 5.1 m with displacement rates ranging from 0.01 mm/a to 0.04 mm/a. The most extensive terrace, Tt4, yielded four Early Pleistocene cosmogenic radionuclide (CRN) ages: two apparent burial ages of 0.858 Ma ± 0.16 Ma and 1.25 Ma ± 0.265 Ma, and two apparent exposure ages of 1.071 Ma ± 0.071 Ma (10Be) and 0.798 Ma ± 0.066 Ma (26Al). Allowing for muonic production effects from insufficient burial depths, the depth corrected CRN burial ages are 1.8 Ma ± 0.56 Ma and 2.52 Ma ± 0.88 Ma, or Late Pliocene. A Late Pliocene age is our preferred age. Offsets of Tt4 across the Waratah Fault range from a minimum of ~20 m for terrace surface treads to a maximum of ~70 m for terrace bedrock straths. Calculated displacement rates for Tt4 range from 0.01 mm/a to 0.04 mm/a (using a Late Pliocene age, ~2 Ma), identical to the rates calculated for the Last Interglacial terrace, Qt5. This indicates that deformation at Cape Liptrap has been ongoing at similar time-averaged rates at least since the Late Pliocene. The upper terraces in the sequence, Tt3 (~110 m amsl), Tt2 (~140 m) and Tt1 (~180 m) are undated, but most likely correlate to sea level highstands in the Neogene. Terraces Tt1–Tt4 show an increasing northward tilt with age.The Waratah Fault forms a prominent structural boundary in the Lachlan Fold Belt discernible from airborne magnetic and bouger gravity anomalies. Seismicity and deformation are episodic. Episodic movement on the Waratah Fault may be coincident with sea level highstands since the Late Pliocene, possibly from increased loading and elevated pore pressure within the fault zone. This suggests that intervals between major seismic events could be on the order of 100 ka.  相似文献   
958.
Abstract– We have carried out a sample‐correlated spectroscopic and mineralogical investigation of samples from seven different collection sites of the Tagish Lake C2 chondrite. Rietveld refinement of high‐resolution powder X‐ray diffraction (XRD) data was used to determine quantitative major mineral abundances. Thermal infrared (400–4500 cm−1, 2.2–25.0 μm) spectra of the same samples were obtained using diffuse (biconical) reflectance infrared Fourier transform spectroscopy (DRIFTS). Our results are in good agreement with previous studies of the mineralogy of the Tagish Lake meteorite; we find however that Tagish Lake is more varied in major mineralogy than has previously been reported. In particular, we observed two new distinct lithologies, an inclusion‐poor magnetite‐ and sulfide‐rich lithology, and a carbonate‐rich, siderite‐dominated lithology in addition to the previously documented carbonate‐rich and carbonate‐poor lithologies. Grain density for each Tagish Lake sample was calculated from the measured mineral modal abundances and known mineral densities. For powders from three originally intact inclusion‐rich samples, the calculated grain density is 2.77 ± 0.05 g cm−3, in excellent agreement with those reported in the literature for other intact inclusion‐rich Tagish Lake samples. Tagish Lake disaggregated samples have a significantly higher calculated grain density due to their lower saponite‐serpentine content, likely a result of mineral separation in the meltwater holes from which they were collected; the disaggregated samples may not therefore adequately represent bulk samples of the Tagish Lake meteorite. The predominance of very fine‐grained material in the Tagish Lake samples investigated in this study is expected to produce infrared spectra representative of asteroidal regolith. Gypsum and talc have been found by XRD in powders from the inclusion‐rich, intact Tagish Lake samples in this study, and may have been present in the parent body; if present, these hydrous sulfates would complicate the interpretation of possible hydrated mineral features in asteroid infrared spectra.  相似文献   
959.
The development of the National Aeronautics and Space Administration's Large Format Camera has added a new dimension to remote sensing. Offering inexpensive large area coverage imagery with excellent geometric fidelity, the LFC was successfully flown in late 1984 aboard the Space Shuttle. The success of this initial flight has encouraged scientists to propose that the LFC be included as part of the earth observation sensor bed on the planned space station.

The relatively low costs associated with LFC photography provide an opportunity for developing countries to learn more about the capabilities and advantages of exploiting remotely sensed imagery. In particular, by using LFC imagery to study an array of local and global phenomena, these developing countries can quickly increase their knowledge of earth observation techniques and join the “community”; of nations currently active in remote sensing efforts.  相似文献   
960.
The southeastern United States, including Florida, has been identified as a region of homogeneous response to the El Niño/Southern Oscillation (ENSO) climatic anomaly, in which mean monthly precipitation and discharge during winter is above or below normal following the onset of the warm (El Niño) or cold (La Niña) phase of ENSO, respectively. However, this understanding of the response is expanded through a study of the effects of the ENSO phenomenon on the probability distributions of mean monthly streamflows of the Santa Fe river. The Santa Fe river basin is situated between one region, which experiences the greatest proportion of annual streamflow during winter, and another where the largest percentage of annual flow occurs during late summer. The basin experiences both winter and summer peaks in precipitation and (subsequent) streamflow and may therefore display responses to ENSO during each season. A two-parameter lognormal distribution is employed to model these streamflows during warm and cold phases of ENSO. Increases in both the mean and the variance detected during warm phase winters are compatible with previous observations. Increases in variance apparent during cold phase summers have not been previously identified. These results, which have considerable bearing upon predictions of high and low flow probabilities during the year, suggest that the response in streamflow is not spatially homogeneous across the state.  相似文献   
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