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  • 1
    Electronic Resource
    Electronic Resource
    AN UPPER LIMIT TO THE AGE OF THE WITWATERSRAND SYSTEM (1961)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 91 (1961), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1961.tb35516.x
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  • 2
    Electronic Resource
    Electronic Resource
    A Weak Layer in the Mantle? (1937)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 4 (1937), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The paper discusses the effect of a weak layer in the upper mantle on the deformation of the crust arising from atmospheric loading, and on the isostatic compensation process. It also points out that S phases with periods of I second are much more strongly damped than S phases with periods of 10 seconds or more, and than P phases with short periods. The damping arising from a liquid layer is proportional to the square root of the frequency and does not provide a satisfactory explanation. Scattering of the kind suggested by Jeffreys, or any other mechanism leading to the firmoviscous law, gives rise to damping proportional to the square of the frequency and is sufficiently frequency sensitive to be consistent with the observations. The differences between P and S can only be accounted for in terms of different behaviour of the elastic constants for dilatational and distortional movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1937.tb07122.x
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  • 3
    Electronic Resource
    Electronic Resource
    Upper mantle models and the thickness of the continental lithosphere (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 105 (1991), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Analysis of the Early Rise traveltimes in the United States shows that on several of the profiles there are features which can be interpreted as indicating a low-velocity zone above 200 km, i.e. that the continental lithosphere thickness is less than 200 km. The explosion data from the Nevada Test Site, GNOME and Early Rise are all consistent with Lehmann's suggestion that there is a discontinuity at a depth of about 200 km. Comparison of the observed data between 15° and 23° with model calculations shows that the major differences between the western and central-eastern United States upper mantles occur above 200 km. It appears that the only reasonable explanation for the 200 km discontinuity is that it represents the termination of a zone of partial melting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1991.tb06718.x
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  • 4
    Electronic Resource
    Electronic Resource
    THE THERMAL CONTRACTION THEORY OF MOUNTAIN BUILDING (Second Paper) (1953)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 6 (1953), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In an earlier paper it was suggested that it was failure in the region between 250 and 600 km below the surface which determined the periodicity of orogenic phenomena. In this paper estimates of the cross-sectional areas of the oceanic troughs and of the mass deficiencies reflected in the strips of large negative gravity anomalies are given and it is inferred that the interval between successive periods of failure is 50 million years.It is pointed out that if the troughs are formed in the manner described in the earlier paper then a regression of sea-level of about 70 metres will occur as a result of their formation. Finally some aspects of the development of the trough regions into mountain ranges are discussed qualitatively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1953.tb03035.x
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  • 5
    Electronic Resource
    Electronic Resource
    THE THERMAL CONTRACTION THEORY OF MOUNTAIN BUILDING (1953)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 6 (1953), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The depth of the level of no strain and the stress distribution have been calculated using Jeffreys's temperature distribution. It is found that the depth of the level of no strain is 59 km, that the stress difference in the crust increases at the rate of 0.6 dyn/cm2 year and that the decrease in the radius in 200 million years is 0.6 km. A relation between the decrease in radius and the heat loss per unit area is derived and from this relation it is shown that the possible changes in the parameters will not bring the contraction into accord with geological estimates. It is pointed out that the stress differences increase much more rapidly in relation to the strength at depths of 250 to 600 km and that failure should begin in this region. On this basis the cross-sectional area of an ocean deep is found to be 1400 km2.The lower mantle and the core are compressed as a result of cooling between the surface and 700 km. This compression is relieved when deep-focus earthquakes occur. It is calculated that increases in the length of the day totalling about 31/2 sec will occur in a period of failure of the mantle. Using a formula of Lapwood it is shown that the heating effect associated with the compression of the core is of the order of 1017 erg/sec, and that during failure of the mantle the cooling effect is likely to be much greater. Finally it is shown that the present rate of dissipation of energy in earthquakes is very much greater than the rate of generation of strain energy as a result of cooling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1953.tb03032.x
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  • 6
    Electronic Resource
    Electronic Resource
    A STUDY OF THE PALAEOMAGNETISM OF THE PILANSBERG DYKES (1956)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 7 (1956), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: iA detailed study has been made of the remanent magnetization of five Pilansberg dykes, by means of measurements on oriented specimens of the rocks. Outcrops of the dykes prove to have suffered magnetic disturbance of their original thermo-remanent magnetization. Specimens from depths of a few thousand feet, taken in Witwatersrand gold mines, show highly consistent magnetisation of the basic parts of the dykes over considerable distances between sampling sites. The mean directions given by the five dykes agree well, and the mean direction from the five dykes gives a North-seeking magnetic pole with inclination +69.3 and azimuth N 24° E. Assuming thermo-remanent magnetisation by a geocentric dipole field, this places a North magnetic pole in latitude 71/2° N, longitude 421/ E at the time of intrusion of the dykes. The age of the dykes is uncertain, but is probably about 300 to 400 million years. Some of the specimens have been subjected to alternating magnetic fields in order to test the stability of their magnetisations. The basic specimens are found to be highly stable, being only slightly affected by fields of 100 to 300 oersteds. The possible implications of the results are discussed, in terms of hypotheses of polar wandering and continental drift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1956.tb05564.x
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  • 7
    Electronic Resource
    Electronic Resource
    Convection Currents in Geysers. (1937)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 4 (1937), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1937.tb00414.x
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  • 8
    Electronic Resource
    Electronic Resource
    CONVECTION CURRENTS IN THE EARTH. (1936)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 3 (1936), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1936.tb01744.x
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  • 9
    Electronic Resource
    Electronic Resource
    Crustal Layers of the Earth (1951)
    [s.l.] : Nature Publishing Group
    Nature 168 (1951), S. 163-164 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In a seismic study of the crustal layers in the western Transvaal2, it was found that between 220 and 300 km. there was a large and well-defined phase which was rather more than 1 second early with respect to the Pt line (V-^ = 6-09 km./sec). It was pointed out that the early onsets could be ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/168163a0
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  • 10
    Electronic Resource
    Electronic Resource
    Blackett's Fundamental Theory of the Earth's Magnetic Field (1947)
    [s.l.] : Nature Publishing Group
    Nature 160 (1947), S. 746-746 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SOON after the publication of Prof. P. M. S. Blackett's paper1, Dr. E. C. Bullard suggested to us that it should be possible to test Blackett's theory against other theories by measurements of the magnetic field of the earth in the mines of the Witwaters-rand. By courtesy of the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/160746a0
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