Generation of plate-like behavior and mantle heterogeneity from a spherical, viscoplastic convection model

Bradford J. Foley, Thorsten W. Becker

Research output: Contribution to journalArticle

68 Citations (Scopus)

Abstract

How plate tectonics arises from mantle convection is a question that has only very recently become feasible to address with spherical, viscoplastic computations. We present mainly internally heated convection results with temperature-dependent viscosity and explore parts of the Rayleigh number (Ra)-yield stress (σy) phase space, as well as the effects of depth-dependent σy, bottom heating, and a lowviscosity asthenosphere. Convective planform and toroidal-poloidal velocity field ratio (TPR) are affected by near-surface viscosity variations, and TPR values are close to observed values for our most plate-like models. At the relatively low convective vigor that is accessible at present, most models favor spherical harmonic degree one convection, though models with a weaker surface viscosity form degree two patterns and reproduce tomographically observed power spectra. An asthenospheric viscosity reduction improves plate-like nature, as expected. For our incompressible computations, pure bottom heating produces strong plumes that tend to destroy plates at the surface. This implies that significant internal heating may be required, both to reduce the role of active upwellings and to form a low-viscosity zone beneath the upper boundary layer.

Original languageEnglish (US)
Article numberQ08001
JournalGeochemistry, Geophysics, Geosystems
Volume10
Issue number8
DOIs
StatePublished - Aug 1 2009

Fingerprint

Earth mantle
convection
viscosity
Viscosity
mantle
heating
Heating
planforms
Planforms
Rayleigh number
plates (tectonics)
asthenosphere
mantle convection
upwelling water
spherical harmonics
Tectonics
vigor
Power spectrum
plate tectonics
plumes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

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abstract = "How plate tectonics arises from mantle convection is a question that has only very recently become feasible to address with spherical, viscoplastic computations. We present mainly internally heated convection results with temperature-dependent viscosity and explore parts of the Rayleigh number (Ra)-yield stress (σy) phase space, as well as the effects of depth-dependent σy, bottom heating, and a lowviscosity asthenosphere. Convective planform and toroidal-poloidal velocity field ratio (TPR) are affected by near-surface viscosity variations, and TPR values are close to observed values for our most plate-like models. At the relatively low convective vigor that is accessible at present, most models favor spherical harmonic degree one convection, though models with a weaker surface viscosity form degree two patterns and reproduce tomographically observed power spectra. An asthenospheric viscosity reduction improves plate-like nature, as expected. For our incompressible computations, pure bottom heating produces strong plumes that tend to destroy plates at the surface. This implies that significant internal heating may be required, both to reduce the role of active upwellings and to form a low-viscosity zone beneath the upper boundary layer.",
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Generation of plate-like behavior and mantle heterogeneity from a spherical, viscoplastic convection model. / Foley, Bradford J.; Becker, Thorsten W.

In: Geochemistry, Geophysics, Geosystems, Vol. 10, No. 8, Q08001, 01.08.2009.

Research output: Contribution to journalArticle

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AB - How plate tectonics arises from mantle convection is a question that has only very recently become feasible to address with spherical, viscoplastic computations. We present mainly internally heated convection results with temperature-dependent viscosity and explore parts of the Rayleigh number (Ra)-yield stress (σy) phase space, as well as the effects of depth-dependent σy, bottom heating, and a lowviscosity asthenosphere. Convective planform and toroidal-poloidal velocity field ratio (TPR) are affected by near-surface viscosity variations, and TPR values are close to observed values for our most plate-like models. At the relatively low convective vigor that is accessible at present, most models favor spherical harmonic degree one convection, though models with a weaker surface viscosity form degree two patterns and reproduce tomographically observed power spectra. An asthenospheric viscosity reduction improves plate-like nature, as expected. For our incompressible computations, pure bottom heating produces strong plumes that tend to destroy plates at the surface. This implies that significant internal heating may be required, both to reduce the role of active upwellings and to form a low-viscosity zone beneath the upper boundary layer.

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