Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.t11c0725m&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #T11C-0725
Physics
8120 Dynamics Of Lithosphere And Mantle: General (1213), 8121 Dynamics: Convection Currents, And Mantle Plumes, 8147 Planetary Interiors (5430, 5724, 6024), 8149 Planetary Tectonics (5475), 8160 Rheology: General (1236, 8032)
Scientific paper
Mantle convection systems with periodic events of subduction exhibit two different kinds of upwelling currents: plumes and thermals. Plumes are strong upwelling currents with a well-defined head and tail structure. Thermals having only little buoyancy do not develop this typical structure and are strongly influenced by the large- scale convection. In vigorous convection thermals are driven towards the locations of the plumes. In this study we numerically investigate the structure and evolution of the rising mantle currents in a 2D Rayleigh- Benard set-up. Periodic events of the subduction occur due to the application of a temperature- and stress- dependent rheology. Model calculations in a Cartesian geometry with large aspect ratios are run with variations in the Rayleigh number, the viscosity contrast (measure of the temperature dependence) and the yield stress (measure of the stress dependence). Our study indicates that a system with periodic subduction events is characterised by three phases. In the first phase the cold thick lid at the surface has no influence on the upwelling currents. Strong, stationary plumes drive the convection. In the second phase the subducted cold material suppresses upwellings. Only small transient currents rise in front of the cold slab. In the third phase the cold material at the bottom is heated up allowing for the formation of strong upwelling currents again.
Hansen Ulrich
Moeller Angela
Stein Cliff
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