摘要:

The density profiles of stratospheric minor constituents are compiled from several one‐dimensional theoretical models that have appeared in the literature. The models are compared with each other and also with observations if data are available. The similarity and disparity of the models are clarified and discussed. If a large difference exists among the models, attempts are made to interpret it as much as possible in terms of the physical and chemical data employed in each model. The inadequacy of one‐dimensional models in calculating the realistic ozone density distributions and the problems related to it are briefly discus

ISSN:8755-1209    

DOI:10.1029/RG014i001p00001

年代:1976

数据来源: WILEY

摘要:

Through analysis of leveling data, rates of relative vertical motion have been determined for points of a grid of profiles over much of the eastern United States. The rates are commonly too large to be attributed to leveling errors and therefore must reflect true earth movements. With some exceptions, modern movements appear to be related to earlier Phanerozoic trends, but the rates of modern movements are much larger than average rates over the past 130 m.y. Thus movements are either episodic or oscillatory about a long‐term trend. If oscillatory, the periods must be less than about 106yr and may be much smaller. The spatial patterns of the rates of relative motion, or tilts, can be correlated with certain geological features. The Atlantic and Gulf coastal plains are tilting downward away from the continental interior. Along a profile from Savannah, Georgia, to Philadelphia, Pennsylvania, the Atlantic Coastal Plain is also tilting downward to the north, with a perturbation at the Cape Fear arch. The Appalachian Highlands are rising relative to the Atlantic Coast at rates of up to 6 mm/yr. The pattern of maxima and minima in relative velocities along the profiles crossing the Appalachian Highlands province suggests elongated zones of relative uplift and subsidence paralleling either the Appalachian drainage divide or the trend of Appalachian structure. The maxima correlate strongly with topographic highs. There is a suggestion of correlation of modern seismicity with extremes of relative velocities in the Appalachian Highlands province. The Interior Plains are tilting downward to the east at a rate of 2 × 10−8rad/yr, the implication being that glacial rebound is not an important factor south of the Great Lakes at the present time. The wavelength between successive zones of relative uplift in the Appalachian Highlands is about 300 km, suggesting that at least the entire thickness of the lithosphere is involved, and probably the asthenosphere as well. Possible explanations for these phenomena include the effects of hydrologic variations, phase transitions in the lower crust and/or the upper mantle, asthenospheric currents driven by ocean and ice loads or plate motions, and stresses derived from nonequilibrium crustal loads or crustal unloading by ero

ISSN:8755-1209    

DOI:10.1029/RG014i001p00013

年代:1976

数据来源: WILEY

摘要:

Recent crystal chemical research on rock‐forming silicate minerals has focused on the accurate refinement of room temperature and high‐temperature crystal structures. The data are of sufficient accuracy to allow detailed examination of structural topology and intracrystalline equilibria and to provide some insight into exsolution phenomena, chemical bonding, and phase transitions. This paper summarizes the results of recent research on olivines, humites, garnets, aluminosilicates, pyroxenes, pyroxenoids, amphiboles, micas, silica minerals, feldspars, feldspathoids, and scapoli

ISSN:8755-1209    

DOI:10.1029/RG014i001p00037

年代:1976

数据来源: WILEY

摘要:

We review some of the properties of surface gravity waves and look at their modification as they enter the littoral zone. Theoretical and experimental modeling of processes pertaining to the near shore are discussed and compared with field observations. In particular we review the present knowledge pertaining to the dynamics of rip currents, longshore currents, and computer modeling of beach deformation due to wave‐induced erosion or accretio

ISSN:8755-1209    

DOI:10.1029/RG014i001p00081

年代:1976

数据来源: WILEY

摘要:

The literature on earth noise over the spectrum of periods from 0.1 s to 12 h is reviewed and presented as accelerations which, when expressed as spectral‐noise density, allow all seismographs to be considered on a common basis of sensitivity. Their ultimate sensitivity is limited by thermal agitation of their suspended masses and is calculable by considering the energy flow to and from their lossy elements in accordance with principles elucidated by Nyquist. Practical instruments, including those with feedback loops, are considered as examples. Seismometers and accelerometers are treated here as resonant systems having one degree of freedom. The electrical outputs of their transducers are classified as ‘velocity’ or ‘displacement.’ The dynamic range required to record these outputs depends on the range of accelerations imposed on the instrument and upon the combined filtering effects of the resonant system and transducer. Gravitational variation, tilt, and tidal accelerations are considered as they affect the instrumenta

ISSN:8755-1209    

DOI:10.1029/RG014i001p00093

年代:1976

数据来源: WILEY

摘要:

The magnetic field of the magnetosheath is most naturally discussed in terms of its steady state and its fluctuating components. The theory of the steady state field is quite well developed, and its essential features have been confirmed by observations. The interplanetary field is converted through the bow shock where its magnitude is increased and its direction changed by the minimal amount necessary to preserve the normal component across the shock. Convection within the magnetosheath usually increases the magnitude still further near the subsolar point and further distorts the direction until the field is aligned approximately tangent to the magnetopause. Fluctuations of the magnetosheath field are very complex, variable, and not well understood. Power spectra of the field typically vary as 1/for 1/f² below and 1/f³ above the proton gyrofrequency. Spectral peaks are common features which occur at different frequencies at various times. Transverse waves are often dominant at frequencies ≲0.002 Hz, and compressional waves are often dominant at somewhat higher frequencies. Perturbation vectors of hydromagnetic waves tend to be aligned with the shock and magnetopause surfaces. Magnetosheath waves may be generated upstream, within the magnetosheath, at the bow shock, or at the magnetopause, but the relative importance of these sources is not kn

ISSN:8755-1209    

DOI:10.1029/RG014i001p00117

年代:1976

数据来源: WILEY

摘要:

A brief topical review of current knowledge available for predicting the characteristics of sandstorms is presented. Particular emphasis is placed on extrapolations to Mars where saltation of loose surface material appears to be a necessary condition for initiation of observed dust storms. Considerable data are now available to predict threshold winds under earth's environmental conditions, but techniques for predicting the quantity of material transported and the height and velocity to which it travels are still crude. Extrapolation of current knowledge to Mars is probably sufficient only for estimating purposes and landing craft design. The upcoming Viking landing mission on Mars will, it is hoped, shed additional light on the problem.

ISSN:8755-1209    

DOI:10.1029/RG014i001p00135

年代:1976

数据来源: WILEY