Moon: Origin and evolution of multi-ring basins   总被引：2，自引：0，他引：2  

W. K. Hartmann  C. A. Wood 《Earth, Moon, and Planets》1971,3(1):3-78

This paper summarizes current data and new observations on lunar basin systems. Parts 1–4 review earlier literature and give new crater-counts used to reconstruct basin histories. Among the results are: basin rings are defined by faults, hills, craters, and/or wrinkle ridges; all of these are inter-related; 2 plays a special role in the ratios of ring diameters; flooding occurred in many basins prior to the formation of the familiar front-side maria; 3 km is a typical depth of lava flooding in basins. Parts 5–11 interpret these results in terms of origin and evolution of basins. Polar concentrations of basins and old, large craters are found (Figures 28 and 29). Basins originated by impacts of very early planetesimals left over from or created during formation of the Moon (6). Concentric fractures were produced by the impacts. Concentric rings developed along fractures during subsequent sagging of the basin into partially melted substrata, along the lines of theory and experiments by Lance and Onat (1962) (Figures 36 and 37). There is marginal empirical evidence that some rings formed significantly after their basins (8). The structure of specific rings depended on the nature of volcanic products extruded. Wrinkle ridges, peak-rings, rings of craters, concentric graben, and central peaks are all consequences of basin-forming evolutionary processes (9, Figure 41), Flooding by lava was a final stage in basin evolution. Lava extruded from concentric ring-faults, wrinkle ridges, and crater and basin rims (10). Mascons are directly correlated with the amount of mare lava, but not correlated with basin age or morphology (11). Section 12 summarizes the results and compares them to those of other authors.  相似文献   

Strontium isotopic identification of water-rock interaction and ground water mixing   总被引：1，自引：0，他引：1  

Frost CD  Toner RN 《Ground water》2004,42(3):418-432

87Sr/86Sr ratios of ground waters in the Bighorn and Laramie basins' carbonate and carbonate-cemented aquifer systems, Wyoming, United States, reflect the distinctive strontium isotope signatures of the minerals in their respective aquifers. Well water samples from the Madison Aquifer (Bighorn Basin) have strontium isotopic ratios that match their carbonate host rocks. Casper Aquifer ground waters (Laramie Basin) have strontium isotopic ratios that differ from the bulk host rock; however, stepwise leaching of Casper Sandstone indicates that most of the strontium in Casper Aquifer ground waters is acquired from preferential dissolution of carbonate cement. Strontium isotope data from both Bighorn and Laramie basins, along with dye tracing experiments in the Bighorn Basin and tritium data from the Laramie Basin, suggest that waters in carbonate or carbonate-cemented aquifers acquire their strontium isotope composition very quickly--on the order of decades. Strontium isotopes were also used successfully to verify previously identified mixed Redbeds-Casper ground waters in the Laramie Basin. The strontium isotopic compositions of ground waters near Precambrian outcrops also suggest previously unrecognized mixing between Casper and Precambrian aquifers. These results demonstrate the utility of strontium isotopic ratio data in identifying ground water sources and aquifer interactions.  相似文献   

Polycyclic aromatic hydrocarbons (PAHs) in small island coastal environments: a case study from harbours in Guam, Micronesia     

Denton GR  Concepcion LP  Wood HR  Morrison RJ 《Marine pollution bulletin》2006,52(9):1090-1098

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Light-toned layered deposits in Juventae Chasma, Mars     

David C. Catling  Stephen E. Wood  David R. Montgomery  Christopher R. Glein 《Icarus》2006,181(1):26-51

We examine hypotheses for the formation of light-toned layered deposits in Juventae Chasma using a combination of data from Mars Global Surveyor's Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Emission Spectrometer (TES), as well as Mars Odyssey's Thermal Emission Imaging System (THEMIS). We divide Juventae Chasma into geomorphic units of (i) chasm wall rock, (ii) heavily cratered hummocky terrain, (iii) a mobile and largely crater-free sand sheet on the chasm floor, (iv) light-toned layered outcrop (LLO) material, and (v) chaotic terrain. Using surface temperatures derived from THEMIS infrared data and slopes from MOLA, we derive maps of thermal inertia, which are consistent with the geomorphic units that we identify. LLO thermal inertias range from ∼400 to 850 J m⁻² K⁻¹ s^−1/2. Light-toned layered outcrops are distributed over a remarkably wide elevation range () from the chasm floor to the adjacent plateau surface. Geomorphic features, the absence of small craters, and high thermal inertia show that the LLOs are composed of sedimentary rock that is eroding relatively rapidly in the present epoch. We also present evidence for exhumation of LLO material from the west wall of the chasm, within chaotic and hummocky terrains, and within a small depression in the adjacent plateau. The data imply that at least some of the LLO material was deposited long before the adjacent Hesperian plateau basalts, and that Juventae Chasma underwent, and may still be undergoing, enlargement along its west wall due to wall rock collapse, chaotic terrain evolution, and exposure and removal of LLO material. The new data allow us to reassess possible origins of the LLOs. Gypsum, one of the minerals reported elsewhere as found in Juventae Chasma LLO material, forms only at low temperatures () and thus excludes a volcanic origin. Instead, the data are consistent with either multiple occurrences of lacustrine or airfall deposition over an extended period of time prior to emplacement of Hesperian lava flows on the plateau above the chasm.  相似文献   

Partnering between a geography department and a community initiative to provide a wind resource assessment for the Blueskin Bay region,Otago, New Zealand     

Nicolas Cullen  Alice Bowden  Rachel Spronken‐Smith 《New Zealand geographer》2012,68(1):49-61

This paper explores the partnership between a community group and a geography department to assess the wind energy potential of the Blueskin Bay region in southern New Zealand. The partnership has provided opportunities for research and is of strategic importance. Year‐long wind observations and numerical modelling have revealed that the hills surrounding Blueskin Bay show potential for wind energy generation. Despite challenges for both parties, the university–community partnership has allowed a successful research platform to be established.  相似文献   

Growing up and cleaning up: The environmental Kuznets curve redux   总被引：1，自引：0，他引：1  

Rachel S. Franklin  Matthias Ruth 《Applied geography (Sevenoaks, England)》2012,32(1):29-39

Borrowing from the Kuznets curve literature, researchers have coined the term “environmental Kuznets curve” or EKC to characterize the relationship between pollution levels and income: pollution levels will increase with income but some threshold of income will eventually be reached, beyond which pollution levels will decrease. The link between the original Kuznets curve, which posited a similar relationship between income and inequality, and its pollution-concerned offspring lies primarily with the shape of both curves (an upside-down U) and the central role played by income change. Although the EKC literature has burgeoned over the past several years, few concrete conclusions have been drawn, the main themes of the literature have remained constant, and no consensus has been reached regarding the existence of an environmental Kuznets curve. EKC research has used a variety of types of data and a range of geographical units to examine the effects of income levels on pollution. Changes in pollution levels might also be at least partly explained by countries’ position in the demographic transition and their general population structure, however little research has included this important aspect in the analysis. In addition, few analyses confine themselves to an evaluation for one country of the long-term relationship between income and pollution. Using United States CO₂ emissions as well as demographic, employment, trade and energy price data, this paper seeks to highlight the potential impact of population and economic structure in explaining the relationship between income and pollution levels.  相似文献   

Climate change and agriculture in computable general equilibrium models: alternative modeling strategies and data needs     

Ruslana Rachel Palatnik  Roberto Roson 《Climatic change》2012,112(3-4):1085-1100

Agricultural sectors play a key role in the economics of climate change. Land as an input to agricultural production is one of the most important links between economy and the biosphere, representing a direct projection of human action on the natural environment. Agricultural management practices and cropping patterns exert an enormous effect on biogeochemical cycles, freshwater availability and soil quality. Agriculture also plays an important role in emitting and storing greenhouse gases. To consistently investigate climate policy and future pathways for the economic and natural environment, a realistic representation of agricultural land use is essential. Top—down Computable General Equilibrium (CGE) models have increasingly been used for this purpose. CGE models simulate the simultaneous equilibrium in a set of interdependent markets, and are especially suited to analyze agricultural markets from a global perspective. However, modeling agricultural sectors in CGE models is not a trivial task, mainly because of differences in temporal and geographic aggregation scales. This study surveys some proposed modeling strategies and highlights different tradeoffs involved in the various approaches. Coupling of top-down and bottom-up models is found to be the most applicable for comprehensive analysis of agriculture in prism of climate change. However, linking interdisciplinary data, methods and outputs is still the major obstacle to be solved for wide-scale implementation.  相似文献   

A study of charge structure sensitivity in simulated thunderstorms     

Rumjana Mitzeva  Boryana Tsenova  Rachel Albrecht  Walt Petersen 《Atmospheric Research》2009,91(2-4):299-309

Two different thunderstorms are simulated by two distinct one-dimensional cloud models using four different parameterisations of the non-inductive mechanism of electric charging, based on laboratory studies. The results demonstrate that during the early (pre-lightning) stage of thunderstorm electrification, simulated charge density depends not only on the model charging parameterisation employed, but also on the specific representations of the kinematics and microphysical characteristics of the model itself. Though no conclusions are drawn regarding the physical suitability of the charging parameterisations themselves, the analysis indicates that the most significant differences between the simulated charge structures of the clouds produced in each particular model are the result of different distributions of model cloud characteristics and of the type of parameterisation of the microphysical processes. The study reveals that it is too early to make any conclusion regarding which, if any, of the existing parameterisation schemes are better suited to the realistic simulation of electrical charging in real clouds.  相似文献   

Observed changes in pan-arctic cold-season minimum monthly river discharge     

Asa K. Rennermalm  Eric F. Wood  Tara J. Troy 《Climate Dynamics》2010,35(6):923-939

Recent changes in pan-arctic land-surface hydrology may significantly affect ecosystems and the built environment. While spatial and temporal patterns in land-surface hydrology trends can be identified using in situ observations of river discharge, the existing studies of cold-season river discharge are often inconsistent and incomparable because they use different methodologies, time periods and geographic regions. By using a comprehensive dataset of river discharge and a trend analysis applying one algorithm over a range of temporal and spatial scales, a synthesis of pan-arctic cold-season low-flow was performed. Cold-season low-flow is increasing over most of the pan-arctic, with decreasing flow in eastern North America and unchanged flow in small basins in the late twentieth century in eastern Eurasia as the main exceptions. This study provides the first synthesis of spatially distributed cold-season low-flow trends in the pan-arctic and indicates that widespread changes in pan-arctic subsurface hydrology are occurring.  相似文献   

Halo masses for optically selected and for radio-loud AGN from clustering and galaxy–galaxy lensing     

Rachel Mandelbaum †  Cheng Li  Guinevere Kauffmann  Simon D. M. White 《Monthly notices of the Royal Astronomical Society》2009,393(2):377-392

We compute two-point correlation functions and measure the shear signal due to galaxy–galaxy lensing for 80 000 optically identified and 5700 radio-loud active galactic nuclei (AGN) from Data Release 4 of the Sloan Digital Sky Survey. Halo occupation models are used to estimate halo masses and satellite fractions for these two types of AGN. The large sample size allows us to separate AGN according to the stellar mass of their host galaxies. We study how the halo masses of optical and radio AGN differ from those of the parent population at fixed   M _*  . Halo masses deduced from clustering and from lensing agree satisfactorily. Radio AGN are found in more massive haloes than optical AGN: in our samples, their mean halo masses are  1.6 × 10¹³  and  8 × 10¹¹  h ⁻¹ M_⊙  , respectively. Optical AGN follow the same relation between stellar mass and halo mass as galaxies selected without regard to nuclear properties, but radio-loud AGN deviate significantly from this relation. The dark matter haloes of radio-loud AGN are about twice as massive as those of control galaxies of the same stellar mass. This boost is independent of radio luminosity, and persists even when our analysis is restricted to field galaxies. The large-scale gaseous environment of the galaxy clearly plays a crucial role in producing observable radio emission. The dark matter halo masses that we derive for the AGN in our two samples are in good agreement with recent models in which feedback from radio AGN becomes dominant in haloes where gas cools quasi-statically.  相似文献