Thermal convection with non-Newtonian plates

SUMMARY The coupling between plate motions and mantle convection is investigated using a fully dynamic numerical model consisting of a thin non-Newtonian layer which is dynamically coupled to a thick Newtonian viscous layer. The non-Newtonian layer has a simple power-law rheology characterized by power-law index n and stiffness constant pp. A systematic investigation of steady, single cell configurations demonstrates that under certain conditions (n > 7 being one of them) the nonNewtonian layer behaves like a mobile tectonic plate. Time-dependent calculations with multicellular configurations show the ability of the plate-mantle coupling model to adjust the number of plates and their sizes in accordance with the flow in the Newtonian layer. These calculations show that the geometry and number of plates do not necessarily resemble the planform of convection below.

[1]  N. Weiss,et al.  Convection in the earth's mantle: towards a numerical simulation , 1974, Journal of Fluid Mechanics.

[2]  S. Stein,et al.  Implications of oceanic intraplate seismicity for plate stresses, driving forces and rheology , 1985 .

[3]  L. Cserepes.  Numerical studies of non-Newtonian mantle convection , 1982 .

[4]  M. F. Ashby,et al.  On the rheology of the upper mantle , 1973 .

[5]  T. Tanimoto,et al.  Ridges, hotspots and their interaction as observed in seismic velocity maps , 1992, Nature.

[6]  Guust Nolet,et al.  Tomographic imaging of subducted lithosphere below northwest Pacific island arcs , 1991, Nature.

[7]  Neil M. Ribe,et al.  The dynamics of thin shells with variable viscosity and the origin of toroidal flow in the mantle , 1992 .

[8]  T. Jordan,et al.  Slab penetration into the lower mantle beneath the Mariana and other island arcs of the northwest Pacific , 1986 .

[9]  D. Yuen,et al.  Time-dependent large aspect-ratio thermal convection in the earth's mantle , 1989 .

[10]  Thomas H. Jordan,et al.  Present‐day plate motions , 1977 .

[11]  U. Kopitzke.  Finite element convection models: comparison of shallow and deep mantle convection, and temperatures in the mantle , 1979 .

[12]  G. Davies.  Role of the lithosphere in mantle convection , 1988 .

[13]  J. Weertman,et al.  High Temperature Creep of Rock and Mantle Viscosity , 1975 .

[14]  B. Parsons,et al.  An analysis of the variation of ocean floor bathymetry and heat flow with age , 1977 .

[15]  G. M. Corcos,et al.  A boundary layer model for mantle convection with surface plates , 1980 .

[16]  A. Dziewoński,et al.  Global Images of the Earth's Interior , 1987, Science.

[17]  Ulrich R. Christensen,et al.  3‐D Convection With Variable Viscosity , 1991 .

[18]  Bradford H. Hager,et al.  The relationship between plate velocity and trench viscosity in Newtonian and power‐law subduction calculations , 1990 .

[19]  Ulrich R. Christensen,et al.  Convection in a variable-viscosity fluid: Newtonian versus power-law rheology , 1983 .

[20]  C. Goetze.  The mechanisms of creep in olivine , 1978, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[21]  C. G. Chase.  Plate kinematics: The Americas, East Africa, and the rest of the world , 1978 .

[22]  Bradford H. Hager,et al.  A simple global model of plate dynamics and mantle convection , 1981 .

[23]  G. Davies,et al.  Mantle convection model with a dynamic plate: topography, heat flow and gravity anomalies , 1989 .

[24]  Ulrich R. Christensen,et al.  Convection with pressure- and temperature-dependent non-Newtonian rheology , 1984 .

[25]  C. Froidevaux,et al.  Transient and steady-state creep of pure forsterite at low stress , 1979 .

[26]  Michael Gurnis,et al.  Large-scale mantle convection and the aggregation and dispersal of supercontinents , 1988, Nature.

[27]  S. Stein,et al.  Intraplate seismicity and stresses in young oceanic lithosphere , 1984 .

[28]  B. Hager,et al.  Controls of the structure of subducted slabs , 1988, Nature.

[29]  W. Peltier,et al.  Low-wavenumber signatures of time-dependent mantle convection , 1990 .

[30]  Richard G. Gordon,et al.  Current plate motions , 1990 .

[31]  J. Weertman.  The creep strength of the Earth's mantle , 1970 .

[32]  E. R. Oxburgh,et al.  Mid-plate Tectonics , 1973, Nature.

[33]  G. Jarvis.  Time-dependent convection in the Earth's mantle , 1984 .