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  • 1
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    In:  Earth planet. Sci. Lett., Edmonton, Conseil de l'Europe, vol. 150, no. 3-4, pp. 233-243, pp. B10410, (ISSN: 1340-4202)
    Publication Date: 1997
    Keywords: Modelling ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Gravimetry, Gravitation ; Plate tectonics ; ConvolutionE ; Three dimensional ; mantle ; isostasy ; continents ; Mohorovicic ; discontinuity ; orogeny ; gravity ; anomalies ; tectonics
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  • 2
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    In:  Geophys. Res. Lett., Luxembourg, Conseil de l'Europe, vol. 18, no. 1-3, pp. 2209-2212, pp. B02405, (ISSN: 1340-4202)
    Publication Date: 1991
    Keywords: Planetology ; Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Tectonics ; GRL
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  • 3
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    In:  J. Geophys. Res., Luxembourg, Conseil de l'Europe, vol. 100, no. 1-3, pp. 15193-15203, pp. B02405, (ISSN: 1340-4202)
    Publication Date: 1995
    Keywords: China ; Plate tectonics ; Tectonics ; Geol. aspects ; JGR
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 378 (1995), S. 709-711 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The behaviour shown in Fig. 1 has previously been interpreted as evidence of additional heat input into the base of old continental lithosphere due to a secondary scale of convection-that is, one of a smaller scale than that associated directly with the formation of tectonic plates at mid-ocean ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Chemical differentiation and convective removal of internal heat make the Earth's lithosphere a thermal and a chemical boundary layer. Thin layers of chemically light material form near the Earth's surface and become embedded within the cold thermal boundary layer associated with interior heat removal. The likelihood of near-surface thermal and chemical boundary layer interactions influencing the Earth's thermotectonic evolution prompts the models presented herein. A simplified system, consisting of a chemically light layer within the upper thermal boundary layer of a denser thermally convecting layer, is explored through a suite of numerical experiments to see how its dynamic behaviour differs from similar, well-studied, thermal boundary layer systems. A major cause of differences between the two systems resides in the ability of the deformable near-surface chemical layer to alter the effective upper thermal boundary condition imposed on the convectively unstable layer below. In thermal equilibrium, regions of chemical boundary layer accumulation locally enforce an effectively near-constant heat-flux condition on the thermally convecting layer due to the finite thermal conductivity of chemical boundary layer material. For cases in which chemical accumulations translate laterally above the unstable layer, the thermal coupling condition between chemical boundary layer material and the unstable layer below is one of non-equilibrium type, i.e. the thermal condition at the top of the convectively unstable layer is time-, as well as space-, variable. A second major cause of differences is that, for the thermal/chemical system, chemically induced rheologic variations can offset, or compete with, those due to temperature. More specifically, the presence of chemically weak material can lubricate convective downwellings allowing for enhanced overturn of an, on average, strong upper thermal boundary layer. Both of these factors have low-order effects on internal flow structure and heat loss and lead to dynamic behaviour in which chemical boundary layer deformation is not only driven by flow in the thermally convecting interior layer but also feeds back and alters this flow. Some implications of this, in regard to elucidating how near-surface chemical boundary layer deformation, e.g. continental tectonics, might interact with, and influence, mantle convection, are discussed.
    Type of Medium: Electronic Resource
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  • 6
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    Springer Nature
    Publication Date: 2017-01-05
    Description: Nature Geoscience 10, 4 (2017). doi:10.1038/ngeo2862 Author: Adrian Lenardic 180 million years ago Earth's continents were amalgamated into one supercontinent called Pangaea. Analysis of oceanic crust formed since that time suggests that the cooling rate of Earth was enhanced in the wake of Pangaea's dispersal.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 7
    Publication Date: 2016-08-27
    Description: We use a suite of 3-D numerical experiments to test and expand 2-D planar isoviscous scaling relationships of Moore [ 2008 ] for mixed heating convection in spherical geometry mantles. The internal temperature scaling of Moore [ 2008 ], when modified to account for spherical geometry, matches our experimental results to a high degree of fit. The heatflux through the boundary layers scale as a linear combination of internal (Q) and basal heating and the modified theory predictions match our experimental results. Our results indicate that boundary layer thickness and surface heat flux are not controlled by a local boundary layer stability condition (in agreement with the results of Moore [ 2008 ]), and are instead strongly influenced by boundary layer interactions. Subadiabtic mantle temperature gradients, in spherical 3D, are well described by a vertical velocity scaling based on discrete drips as opposed to a scaling based on coherent sinking sheets, which was found to describe 2D planar results. Root Mean Square (RMS) velocities are asymptotic for both low Q and high Q, with a region of rapid adjustment between asymptotes for moderate Q. RMS velocities are highest in the low Q asymptote, and decrease as internal heating is applied. The scaling laws derived by Moore [ 2008 ], and extended here, are robust and highlight the importance of differing boundary layer processes acting over variable Q and moderate Ra.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
    Publication Date: 2016-08-28
    Description: Interactions among tectonics, volcanism, and surface weathering are critical to the long term climatic state of a terrestrial planet. Volcanism cycles greenhouse gasses into the atmosphere. Tectonics creates weatherable topography and weathering reactions draw greenhouse gasses out of the atmosphere. Weathering depends on physical processes governed partly by surface temperature, which allows for the potential that climate-tectonic coupling can buffer the surface conditions of a planet in a manner that allows liquid water to exist over extended time scales (a condition that allows a planet to be habitable by life as we know it). We discuss modeling efforts to explore the level to which climate-tectonic coupling can, or cannot, regulate the surface temperature of a planet over geologic time. Thematically we focus on how coupled climate-tectonic systems respond to: 1) Changes in the mean pace of tectonics and associated variations in mantle melting and volcanism; 2) Large amplitude fluctuations about mean properties such as mantle temperature and surface plate velocities; and 3) Changes in tectonic mode. We consider models that map the conditions under which plate tectonics can or can not provide climate buffering as well as models that explore the potential that alternate tectonic modes can provide a level of climate buffering that allows liquid water to be present at a planets surface over geological time scales. We also discuss the possibility that changes in the long-term climate state of a planet can feed back into the coupled system and initiate changes in tectonic mode.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
    Publication Date: 2016-06-02
    Description: Nature Geoscience 9, 417 (2016). doi:10.1038/ngeo2707 Authors: Cin-Ty A. Lee, Laurence Y. Yeung, N. Ryan McKenzie, Yusuke Yokoyama, Kazumi Ozaki & Adrian Lenardic
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 10
    Publication Date: 2016-08-30
    Description: The discovery of large terrestrial (~1 Earth mass (M e ) to 〈 10 M e ) extrasolar planets has prompted a debate as to the likelihood of plate tectonics on these planets. Canonical models assume classic basal heating scaling relationships remain valid for mixed heating systems with an appropriate internal temperature shift. Those scalings predict a rapid increase of convective velocities ( V rms ) with increasing Rayleigh numbers ( Ra ) and non-dimensional heating rates ( Q ). To test this we conduct a sweep of 3-D numerical parameter space for mixed heating convection in isoviscous spherical shells. Our results show that while V rms increases with increasing thermal Ra it does so at a slower rate than predicted by bottom heated scaling relationships. Further, the V rms decreases asymptotically with increasing Q . These results show that independent of specific rheologic assumptions (e.g., viscosity formulations, water effects, lithosphere yielding), the differing energetics of mixed and basally heated systems can explain the discrepancy between different modeling groups. High temperature, or young, planets with a large contribution from internal heating will operate in different scaling regimes compared to cooler temperature, or older, planets that may have a larger relative contribution from basal heating. Thus, differences in predictions as to the likelihood of plate tectonics on exoplanets may well result from different models being more appropriate to different times in the thermal evolution of a terrestrial planet (as opposed to different rheologic assumptions as has often been assumed).
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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