Geomagnetism in Marine Geology: V. Vacquier, 1972. Elsevier,Amsterdam, 1972, 200 pp., Ofl.42.50     

D. McKenzie 《Earth》1973,9(3):289-290

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Geology and physics of the moon: A study of some fundamental problems: edited by G. Fielder. Elsevier,Amsterdam, 1971, 167 pp. $22.00     

Grant Heiken  Wendell Mendell 《Geochimica et cosmochimica acta》1973,37(5):1407-1408

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Pacific Science Association Congress     

A. Grant Anderson 《The Professional geographer》1983,35(4):476-476

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Spectral development of a solar X-ray burst observed on OSO-7     

D. L. McKenzie  D. W. Datlowe  L. E. Peterson 《Solar physics》1973,28(1):175-185

The UCSD solar X-ray instrument on the OSO-7 satellite observes X-ray bursts in the 2–300 keV range with 10.24 s time resolution. Spectra obtained from the proportional counter and scintillation counter are analyzed for the event of November 16, 1971, at 0519 UT in terms of thermal (exponential spectrum) and non-thermal (power law) components. The energy content of the approximately 20 × 10⁶K thermal plasma increased with the 60 s duration hard X-ray burst which entirely preceded the 5 keV soft X-ray maximum. If the hard X-rays arise by thick target bremsstrahlung, the nonthermal electrons above 10 keV have sufficient energy to heat the thermally emitting plasma. In the thin target case the collisional energy transfer from non-thermal electrons suffices if the power law electron spectrum is extrapolated below 10 keV, or if the ambient plasma density exceeds 4 × 10¹⁰ cm^–3.Formerly at UCSD.  相似文献   

Observations of 1000 km s −1 Doppler shifts in 107 K solar flare supra-arcade     

Innes  D.E.  McKenzie  D.E.  Wang  Tongjiang 《Solar physics》2003,217(2):267-279

An X1.5 flare on the west limb of the Sun on 21 April 2002 developed a large supra-arcade about 30 min after flare onset. The growth of the supra-arcade can be followed in both TRACE 195 Å images and SUMER spectra. Its growth seems to be associated with dark (in TRACE images), sunward moving channels that descend onto the arcade from above. SUMER recorded Doppler shifts of 800–1000 km s^–1 in Fexxi 1354 Å from positions where this sunward flow interacts with the arcade tops. We describe the observations, focusing on the relationship of the high Fexxi line shifts to the sunward moving dark flows.  相似文献   

Modeling Forest Emissivity at L-Band and a Comparison With Multitemporal Measurements     

Della Vecchia  A. Ferrazzoli  P. Wigneron  J.-P. Grant  J.P. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(4):508-512

This letter describes recent advances in modeling forest emissivity at L-band. The formulation is based on a previously developed discrete model and includes a new representation of forest litter. Comparisons with multitemporal radiometric data collected in the framework of the ldquoBray 2004rdquo experiment, which was carried out within Les Landes forest, are shown and discussed. Input variables are given by using detailed ground measurements. In general, the model reproduces both absolute values and temporal variations of measured brightness temperature. The contribution of the litter to overall emission was found to be important.  相似文献   

Recently increased tropical cyclone activity and inferences concerning coastal erosion and inland hydrological regimes in New Zealand and Eastern Australia     

Patrick J. Grant 《Climatic change》1981,3(3):317-332

For the area bounded by 0–35 °S latitude and 105 °E–105 °W longitude a significant increase of tropical cyclone frequency occurred about 1954–55 and this regime persisted throughout the 1960s and 1970s. Probably this frequency increase was accompanied by an increase of cyclonic storm intensity. It was related to an atmospheric pressure regime change over Australasia which commenced in early 1954. Tropical cyclones produce large rainfall amounts and strong winds which generate high-energy sea waves. Severe damage can result on land and at sea. However, much recently recorded damage has resulted from extra-tropical cyclones. Therefore it is postulated that extra-tropical cyclones also increased in frequency after the mid 1950s and that both types of cyclone contributed to a significant increase in total storminess. In eastern Australia and around both islands of New Zealand a major coastal regime change occurred in the 1950s and has persisted to the present;erosion has been the dominant process. In eastern Australia there was a significant increase in the magnitude of river floods after the late 1940s. After the mid 1950s most of the North Island of New Zealand experienced the wettest years of this century which caused large closed lakes to reach the highest levels for several centuries. Throughout the North Island the majority of the greatest recorded stream floods of this century have occurred during the 1950s, 1960s and 1970s. And in forested mountain areas of the North Island the average rate of erosion and alluvial sedimentation increased markedly after the mid 1950s. The regime change of each natural phenomenon is explicable in terms of increased storminess since the mid 1950s. Consequently it is hypothesised that the coastal and inland environmental regime changes discussed were either initiated or accentuated after the mid 1950s as a result of increased activity of both tropical and extra-tropical cyclones. Some further studies, necessary to test the links in the overall hypothesis, are mentioned.  相似文献   

Plinian-type eruptions in the medicine lake highland, california, and the nature of the underlying magma     

Grant Heiken 《Journal of Volcanology and Geothermal Research》1978,4(3-4)

Contemporaneous Plinian eruptions of rhyolite pumice from Glass Mountain and Little Glass Mountain during the last 1100 years B.P. were followed by extrusion of lava flows. 1.2 km of material was erupted and 10% by volume is tephra. All of the tephra deposits consist of very poorly sorted coarse ash and lapilli that are mostly pumice pyroclasts.Eruptive sequences, chemical composition and petrographic character of the rhyolites at Little Glass Mountain and Glass Mountain suggest that they came from the same magma body. The 1:9 ratio of tephra to lavas is typical of small silicic magma chambers. Eruption from a small chamber, 4–6 km deep, at vents 15 km apart is possible if magma rose along cone sheets with dips of 45–60°. The caldera rim and arcuate lines of vents near it may represent the surface expression of several concentric cone sheets.Pumice pyroclasts erupted at Glass Mountain and Little Glass Mountain may have formed in the following manner: (1) vesicle growth and coalescence beginning at 1–2 km depths; (2) elongation of the vesicles by flow within the cone sheets; (3) disruption of the vesiculated magma when it reached the surface by an expansion wave passing down through it; and (4) eruption of comminution products as pumice pyroclasts. Plinian activity at Little Glass Mountain and Glass Mountain continued until the volatile-rich top of the magma chamber had been depleted.  相似文献   

Some remarks on the development of sedimentary basins   总被引：15，自引：0，他引：15  

Dan McKenzie 《Earth and Planetary Science Letters》1978,40(1):25-32

A simple model for the development and evolution of sedimentary basins is proposed. The first event consists of a rapid stretching of continental lithosphere, which produces thinning and passive upwelling of hot asthenosphere. This stage is associated with block faulting and subsidence. The lithosphere then thickens by heat conduction to the surface, and further slow subsidence occurs which is not associated with faulting. The slow subsidence and the heat flow depend only on the amount of stretching, which can be estimated from these quantities and from the change in thickness of the continental crust caused by the extension. The model is therefore easily tested. Preliminary investigations of the Great Basin, the Aegean, the North Sea and the Michigan Basin suggest that the model can account for the major events in their evolution.  相似文献   

Evaluation of biogeochemical prospecting methods in the search for sulfide deposits in the Appalachian piedmont, Virginia, U.S.A.     

Steven W. Leavitt  H.Grant Goodell 《Journal of Geochemical Exploration》1979,11(1):89-100

Soil and stream sediment sampling have been the primary geochemical exploration tools in the Appalachian piedmont to date. However, the great thicknesses of soil and saprolite found in the region coupled with the dense vegetation frequently encountered favor biogeochemistry as an alternative or supplemental method since deep-rooted plants sample closer to bedrock. To evaluate this method, an orientation survey was performed in which soils and vegetation at 17 sites north of Mineral, Virginia, were sampled and analyzed for Ag, Cd, Cu, Pb and Zn. The traverse included stations over the host rocks of massive sulfide mineralization, as well as over apparent “barren” country rock. Samples were analyzed by atomic absorption spectrophotometry using standard digestion and analytical techniques.Both A- and B-horizon soil metals generally appear to be reliable indicators of mineralization, with soils developed over sulfides showing up to three-fold enrichment in metal content relative to the average soils developed on the country rock. Correlation of metal concentrations in vegetation to soil metal concentrations reveal plant concentrations expressed on a dry-weight basis correlate stronger and more frequently to soil metals than do ash-weight concentrations. Copper shows some promise in selected organs and species, Ag appears fair but data are limited to one organ of one species, and plant Pb seems totally unresponsive to soil metal concentrations perhaps because foliar absorption is an important plant uptake mechanism here. However, Zn and Cd in organs of the oak group, especially mature leaves and twigs of the current year's growth show the greatest promise as prospecting tools. They correlate well with soil metals and when compared directly to the geology they reliably reflect mineralization. Although results using White oak were slightly less profound than those obtained from the Black-Red oak group, White oak may be preferred as it is a single, more widespread, easily-identifiable species. Copper and especially Zn although essential elements to plants, do not appear to be “difficult” elements for biogeochemical prospecting in the Appalachian piedmont.  相似文献