The Origin of Outer Topographic Rises Associated with Trenches     

Barry Parsons  Peter Molnar 《Geophysical Journal International》1958,1(4):707-712

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On the thermal evolution of the terrestrial planets     

Peter E. Fricker  Ray T. Reynolds  Audrey L. Summers 《Earth, Moon, and Planets》1974,9(1-2):211-218

Physical and chemical constraints for such different planetary objects as the Earth, the Moon and meteorite parent bodies can best be satisfied by thermal history models having high initial temperatures. On the basis of thermal calculations it is suggested that the evolution of the other terrestrial planets (Mars, Venus and Mercury) was also characterized by high initial temperatures. Under these conditions, melting and, consequently, fractionation would set in at an early stage. Because of the resulting redistribution of the long-lived radioactive heat sources and the concentration of these elements in the surface layers, large-scale differentiation could be achieved by partial melting.Paper presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.  相似文献   

Some tests of the Vaníček Method of spectral analysis     

J. Taylor  S. Hamilton 《Astrophysics and Space Science》1972,17(2):357-367

One of the chief claims of the Vaníček Method of spectrum analysis is its, ability to remove ‘systematic noise’ from a time series with minimal distortion of the spectrum of the remaining series. In this paper, comparisons are made between the Vaníček Method and the more usual method consisting of preliminary removal of the systematic noise followed by fourier analysis. Formulas relating the two methods are developed and a series of comparative plots of simple spectra are presented. Results indicate that the Vaníček Method does not displace a spectral peak falling close to the systematic noise, that it distorts the amplitude of the peak less than the conventional method of analysis, and that it tends to intensify the side lobes.  相似文献   

Occultation of ε Geminorum by Mars: IV. Oblateness of the martian upper atmosphere     

Richard G. French  Gordon E. Taylor 《Icarus》1981,45(3):577-585

The oblateness of the Martian upper atmosphere was determined from analysis of photoelectric observations of the 8 April 1976 occultation of ε Geminorum by Mars at seven stations. The oblatness is 0.0096 ± 0.0023, consistent with a mean equator-to-pole temperature difference in excess of ～ 50°K, vertically averaged from the surface to the occulation altitude of ～70 km. The astrometric solution provides precise determination of the occultation path relative to the Martian shadow, and absolute vertical alignment of upper atmospheric temperature profiles obtained by inversion of occultation light curves. The observations can be compared directly with models of atmospheric tides computed for the conditions at the suboccultation regions on Mars.  相似文献   

Observed composition of the ionosphere of Venus: Implications for the ionization peak and the maintenance of the nightside ionosphere     

H.A. Taylor  R.E. Hartle  H.B. Niemann  L.H. Brace  R.E. Daniell  S.J. Bauer  A.J. Kliore 《Icarus》1982,51(2):283-295

Across the nightside of Venus, daily measurements from the PV Orbiter Ion Mass Spectrometer often indicate an ionosphere of relatively abundant concentration, with a composition characteristic of the dayside ionosphere. Such conditions are interspersed by other days on which the ionosphere appears to largely “disappear” down to about 200 km, with ion concentrations at lower heights also much reduced. These characteristics, coupled with observations of strong day to night flows of O⁺ in the upper ionosphere, support arguments that ion transport from the dayside is important for the maintenance of the nightside ionosphere. Also, U.S. and Soviet observations of nightside energetic electron fluxes have prompted consideration of impact ionization as an additional nightside ion source. The details of the ion and neutral composition at low altitudes on the nightside provide an important input for further analysis of the maintenance process. In the range 140–160 km, strong concentrations of O₂⁺ and NO⁺ indicate that the ionization peak is at times composed of at least two prominent ion species. Nightside concentrations of O₂⁺ and NO⁺ as large as 10⁵ and 10⁴/cm³, respectively, appear to require sources in addition to that provided by transport. The most probable sources are considered briefly, and no satisfactory explanation is yet found for the observed NO⁺ concentrations. Further analysis beyond the scope of this paper is required to resolve this issue.  相似文献   

A paleomagnetic study of the Mull lava succession   总被引：1，自引：0，他引：1  

James M. Hall  R. L. Wilson  Peter Dagley 《Geophysical Journal International》1977,49(2):499-514

Summary. A paleomagnetic study has been made of a succession of 139 non-overlapping basaltic lavas, representing 91 per cent of the longest remaining succession of flows associated with the Paleogene Mull volcano. All the lavas have experienced considerable hydrothermal alteration, probably at up to several million years after initial magnetization and frequently with alteration to the opaque minerals and the production of new potentially magnetic phases. The question of whether directional remagnetization has taken place while preserving within-unit directional consistency and discreteness of unit mean direction is discussed. Extensive directional remagnetization is excluded as an explanation for the data. If stable directions obtained by alternating field remanence cleaning coincide with original TRM directions then a mean pole position for all temporally independent lava directions from the British Tertiary igneous province is at 71.9° N, 167.2° E, with k:22 and α₉₅:3.0°. This pole is significantly different from the geographic pole. If the difference in palaeomagnetic and geographic poles is interpreted in terms of absolute plate motion, then 2010 km of northwards motion of the western part of the Eurasian Plate, at 3.7 cm/yr, has taken place over the last 55 Myr. This motion has implications for the geological history of the Arctic and for the complexity of mantle motions.  相似文献   

IGU working group on applied geography     

Peter H. Nash 《GeoJournal》1983,7(3):313-315

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Provenances of naturalised plants in Australasia     

Peter Holland  Sherry Olson 《The Australian geographer》1989,20(2):136-143

In both Australia and New Zealand, numbers of naturalised flowering plant species have increased steadily since the start of European settlement, and this process shows no sign of abating. Plants native to Western Europe, the Mediterranean basin and the Middle East predominated during the mid‐nineteenth century, but in recent decades other geographical areas (notably the Western Hemisphere, Asia and Southern Africa) have become important sources of adventive plants. Today, the composition of ensembles of naturalised species more closely conforms to the diversity of physical environments in the host area. Species native to mediterranean‐type climates tend to dominate in Victoria, species from the Asian and American tropics are especially significant in Queensland, and species from cool temperate regions compose the bulk of the naturalised flora of south‐western New Zealand.  相似文献   

Multigenetic gravity couple across a modern convergent margin: inheritance from Cretaceous asymmetric extension     

Peter J. J. Kamp  Kerry A. Hegarty 《Geophysical Journal International》1989,96(1):33-41

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Dryland salinity in a subcatchment at Glenthompson,Victoria     

Peter Dixon 《The Australian geographer》1989,20(2):144-152

Dryland salinity is a widespread and serious environmental problem in western Victoria. As a result river environs and farmland have been seriously degraded with loss of habitat, reduced farm production and increased erosion. Until recently, the preferred method of salinity investigation was centred around expensive drilling programs to obtain information on groundwater provinces. More recently, electromagnetic surveys have provided the means of rapidly assessing the levels of soil and water salinities present within the landscape. At a site south of Glenthompson, Victoria, the results of an electromagnetic survey together with an investigation of relevant soil properties are being used to plan salinity control options. High recharge areas do not appear to be present in the study district. The effects of agronomic control options, such as the establishment of perennial grasses, can be predicted by the use of a monthly water balance whereby climatic factors and the crop's efficiency in plant water use can be related. The likely reduction in deep infiltration can then be estimated.  相似文献