The heat flux density in a non-homogeneous bare loessial soil   总被引：2，自引：0，他引：2  

Marcel Fuchs  Amos Hadas 《Boundary-Layer Meteorology》1972,3(2):191-200

This work describes the relationship between the diurnal patterns of the radiant energy exchange in the atmospheric surface layer and the soil heat flux density of a bare irrigated soil in an arid environment. The measurements show that the soil heat flux density is a large fraction of the net radiation. The soil moisture content has little effect on this fraction but modifies the phase relationship between the net radiation and the soil heat flux density waves. Differences between the thermal regimes of the wet and dry soil appear to be caused by latent heat exchanges rather than changes of the soil thermal properties. The data also show that the variation with depth of the soil thermal properties strongly influences the propagation of the temperature and heat flux density waves in the soil. A heat diffusion theory for non-homogeneous conductors (Lettau, 1962) which enables the thermal properties of the soil to be predicted is tested by comparison with experimental determinations in the field.  相似文献   

Paleomagnetism of tertiary and recent lavas of Israel     

Amos Nur 《Earth and Planetary Science Letters》1971

Magnetizations in 24 flows of Tertiary age in Israel indicate two stable directions, each of which has both normal and reversed polarities. AF demagnetization decreases the scatter of the NRM results. Typical Tertiary poles are near 70°N 110°W and another set of anomalous poles are near 34°N 50°W. These are similar to other reported Tertiary and Cretaceous poles.  相似文献   

Distribution of hydrocarbons in the oyster,Pinctada margaratifera,along the coast of Kuwait     

Victor C Anderlini  Layla Al-Harmi  Brock W De Lappe  Robert W Risebrough  Wayman Walker  Bernd R.T Simoneit  Amos S Newton 《Marine pollution bulletin》1981,12(2):57-62

Concentrations of total hydrocarbons within the boiling point range of the alkanes n-C₁₄ and n-C₃₂ were determined in oysters, Pinctada margaratifera, from coastal waters of Kuwait. Levels of petroleum-derived hydrocarbons were highest in an area adjacent to the major oil loading facilities. Whether the use of dispersants to treat minor spills increases levels of incorporation of petroleum compounds into the food webs could not be concluded from the data of this study. Levels of total petroleum-type hydrocarbons in the oysters at this site were equivalent to those in mussels, Mytilus sp., from harbours, bays and urban coastal areas of California. The Kuwaiti oysters lacked a C₂₈ pentacyclic triterpane that was present in extracts of mussels from southern California that had been recently exposed to a minor spill or to a natural seepage. Levels of DDE and PCB were comparable to those in relatively unpolluted areas of North America.  相似文献   

Using dissolved gas analysis to investigate the performance of an organic carbon permeable reactive barrier for the treatment of mine drainage     

R.L. Williams  K.U. Mayer  R.T. Amos  D.W. Blowes  C.J. Ptacek  J.G. Bain 《Applied Geochemistry》2007

The strongly reducing nature of permeable reactive barrier (PRB) treatment materials can lead to gas production, potentially resulting in the formation of gas bubbles and ebullition. Degassing in organic C based PRB systems due to the production of gases (primarily CO₂ and CH₄) is investigated using the depletion of naturally occurring non-reactive gases Ar and N₂, to identify, confirm, and quantify chemical and physical processes. Sampling and analysis of dissolved gases were performed at the Nickel Rim Mine Organic Carbon PRB, which was designed for the treatment of groundwater contaminated by low quality mine drainage characterized by slightly acidic pH, and elevated Fe(II) and SO₄ concentrations. A simple 4-gas degassing model was used to analyze the dissolved gas data, and the results indicate that SO₄ reduction is by far the dominant process of organic C consumption within the barrier. The data provided additional information to delineate rates of microbially mediated SO₄ reduction and confirm the presence of slow and fast flow zones within the barrier. Degassing was incorporated into multicomponent reactive transport simulations for the barrier and the simulations were successful in reproducing observed dissolved gas trends.  相似文献   

Late Quaternary environmental and human events at En Gedi, reflected by the geology and archaeology of the Moringa Cave (Dead Sea area, Israel)     

Sorin Lisker  Roi Porat  Hanan Eshel  Amos Frumkin 《Quaternary Research》2007,68(2):203-212

The Moringa Cave within Pleistocene sediments in the En Gedi area of the Dead Sea Fault Escarpment contains a sequence of various Pleistocene lacustrine deposits associated with higher-than-today lake levels at the Dead Sea basin. In addition it contains Chalcolithic remains and 5th century BC burials attributed to the Persian period, cemented and covered by Late Holocene travertine flowstone. These deposits represent a chain of Late Pleistocene and Holocene interconnected environmental and human events, echoing broader scale regional and global climate events. A major shift between depositional environments is associated with the rapid fall of Lake Lisan level during the latest Pleistocene. This exposed the sediments, providing for cave formation processes sometime between the latest Pleistocene (ca. 15 ka) and the Middle Holocene (ca. 4500 BC), eventually leading to human use of the cave. The Chalcolithic use of the cave can be related to a relatively moist desert environment, probably related to a shift in the location of the northern boundary of the Saharo-Arabian desert belt. The travertine layer was U-Th dated 2.46 ± 0.10 to 2.10 ± 0.04 ka, in agreement with the archaeological finds from the Persian period. Together with the inner consistency of the dating results, this strongly supports the reliability of the radiometric ages. The 2.46-2.10 ka travertine deposition within the presently dry cave suggests a higher recharge of the Judean Desert aquifer, correlative to a rising Dead Sea towards the end of the 1st millennium BC. This suggests a relatively moist local and regional climate facilitating human habitation of the desert.  相似文献   

Solar and anthropogenic imprints on Lake Masoko (southern Tanzania) during the last 500 years   总被引：1，自引：0，他引：1  

Yannick Garcin  David Williamson  Laurent Bergonzini  Olivier Radakovitch  Annie Vincens  Guillaume Buchet  Joël Guiot  Simon Brewer  Pierre-Etienne Mathé  Amos Majule 《Journal of Paleolimnology》2007,37(4):475-490

The Masoko crater-lake in southern Tanzania provides a continuous record of environmental changes covering the last 500 years. Multi-proxy studies were performed on a 52 cm sediment core retrieved from the deepest part of the lake. Magnetic, organic carbon, geochemical proxies and pollen assemblages indicate a dry climate during the ‘Little Ice Age’ (AD 1550–1850), confirming that the LIA in eastern Africa resulted in marked and synchronous hydrological changes. However, the direction of response varies between different African lakes (low versus high lake-levels), indicating strong regional contrasts that prevent the clear identification of climate trends over eastern Africa at this time. Inferred changes in Masoko lake-levels closely resemble the record of solar activity cycles, indicating a possible control of solar activity on the climate in this area. This observation supports previous results from East African lakes, and extends this relationship southward. Finally, anthropogenic impact is observed in the Masoko sediments during the last 60 years, suggesting that human disturbance significantly affected this remote basin during colonial and post-colonial times.  相似文献   

Seismotectonics of the Sinai subplate – the eastern Mediterranean region     

Amos Salamon  Avraham Hofstetter  Zvi Garfunkel  Hagai Ron 《Geophysical Journal International》2003,155(1):149-173

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Neogene dextral transpression due to oblique convergence across the Andes of northwestern Patagonia, Argentina     

M. Diraison  P. R. Cobbold  E. A. Rossello  A. J. Amos 《Journal of South American Earth Sciences》1998,11(6):519-532

Between Bariloche (41°S) and El Bolsón (42°S), Neogene sediments of the Ñirihuau foreland basin and Paleogene volcanoclastic rocks have been thrust westward beneath basement rocks of the Andean cordillera. North of Bariloche (40°–41°S), Paleogene volcanoclastic rocks within the main cordillera show Neogene deformation. The large-scale Neogene tectonics of the area are revealed by superimposing geological maps with digital topographic data. Fault-slip data provide information on the relative amount of crustal thickening and strike-slip faulting. Throughout the area, major reverse faults and thrusts trend northwest, forming the edges to Cenozoic basins of foreland or ramp styles. Some of these are inverted grabens of Mesozoic age. The dominant strike-slip faults are right-lateral and trend nearly north, parallel to the cordillera. Conjugate left-lateral faults trend nearly east. At a regional scale, based on the fault-slip data, the principal direction of shortening is northeast, in areas where thrusts predominate, but swings around to the north in areas where strike-slip faults predominate. Thus the results indicate a degree of strain partitioning, but they are broadly compatible with the oblique direction of convergence between the Nazca and South American plates. This tectonic style seems to have lasted throughout the Neogene.

Abstract

Entre las localidades de Bariloche (41°S) y El Bolsón (42°S), sedimentos Neógenos de la cuenca de antepaís Ñirihuau y volcanoclastitas Paleógenas han sido cabalgados desde el oeste por el basamento de la Cordillera de los Andes. Al norte de Bariloche (40°–41°S), volcanoclastitas Paleógenas de la Cordillera también muestran deformación. La tectónica neógena de gran escala se destaca por la superposición de mapas geológicos y topográficos digitalizados. A la escala de los afloramientos, los datos de deslizamientos de falla proveen información relativa a las relaciones entre el espesamiento cortical y el fallamiento de rumbo. En este sentido, a través de toda el área, las fallas inversas y los cabalgamientos mayores se disponen con rumbos noroeste, controlando las cuencas Cenozoicas de antepaís o de tipo rampa. Algunas de ellas invierten grábenes Mesozoicos. Por su parte, las fallas transcurrentes son dominantemente dextrales y se disponen submeridianalmente de modo paralelo a la Cordillera. Juegos conjugados senestrales se orientan sublatitudinalmente. A escala regional, la dirección principal de acortamiento, a partir de datos de desplazamiento de fallas, es noreste donde dominan los cabalgamientos, aunque se desvía hacia el norte donde predominan las fallas transcurrentes. Estos resultados indican un grado de particionamiento de la deformación, que resulta compatible con la dirección oblícua de convergencia entre las placas de Nazca y Sudamérica; estilo tectónico que parece haberse instalado a partir del Neógeno.  相似文献   

Spatial gaps in arc volcanism: The effect of collision or subduction of oceanic plateaus   总被引：2，自引：0，他引：2  

Susan McGeary  Amos Nur  Zvi Ben-Avraham 《Tectonophysics》1985,119(1-4)

One of the major processes in the formation and deformation of continental lithosphere is the process of arc volcanism. The plate-tectonic theory predicts that a continuous chain of arc volcanoes lies parallel to any continuous subduction zone. However, the map pattern of active volcanoes shows at least 24 areas where there are major spatial gaps in the volcanic chains (> 200 km). A significant proportion (~ 30%) of oceanic crust is subducted at these gaps. All but three of these gaps coincide with the collision or subduction of a large aseismic plateau or ridge.The idea that the collision of such features may have a major tectonic impact on the arc lithosphere, including cessation of volcanism, is not new. However, it is not clear how the collision or subduction of an oceanic plateau perturbs the system to the extent of inhibiting arc volcanism. Three main factors necessary for arc volcanism are (1) source materials for the volcanics—either volatiles or melt from the subducting slab and/or melt from the overlying asthenospheric wedge, (2) a heat source, either for the dehydration or the melting of the slab, or the melting within the asthenosphere and (3) a favorable state of stress in the overlying lithosphere. The absence of any one of these features may cause a volcanic gap to form.There are several ways in which the collision or subduction of an oceanic plateau may affect arc volcanism. The clearest and most common cases considered are those where the feature completely resists subduction, causing local plate boundaries to reorganize. This includes the formation of new plate-bounding transform faults or a flip in subduction polarity. In these cases, subduction has slowed down or stopped and the lack of source material has created a volcanic gap.There are a few cases, most notably in Peru, Chile, and the Nankai trough, where the dip of subduction is so shallow that effectively no asthenospheric wedge exists to produce source material for volcanism. The shallow dip of the slab may be a buoyant effect of the plateau imbedded in the oceanic lithosphere.The cases which are the most enigmatic are those where subduction is continuous, the oceanic plateau is subducted along with the slab, and the dip of the slab is clearly steep enough to allow arc volcanism; yet a volcanic gap exists. In these areas, the subducted plateau may have a fundamental effect on the physical process of arc volcanism itself. The presence of a large topographic feature on the subducting plate may affect the stress state in the are by increasing the amount of decoupling between the two plates. Alternatively, the subduction of the plateau may change the chemical processes at depth if either the water-rich top of the plateau with accompanying sediments are scraped off during subduction or if the ridge is compositionally different.  相似文献   

The Quaternary： its character and definition   总被引：5，自引：0，他引：5  

Martin J. Head Philip Gibbard Amos Salvador 《《幕》》2008,31(2):234-238

The Quaternary, is characterised by the development of widespread glaciations in mid-northern latitudes. As a chronostratigraphic term it has attracted vigorous debate. The Quaternao; as accepted by the International Union for Quaternary Research and proposed by the International Commission on Stratigraphy, begins at 2.6 Ma within a 2.8-2.4 Ma interval of profound change in Earth＇s climate system.  相似文献