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| Titel |
Conditions for Plate Tectonics on Super-Earths: Inferences From Convection Models With Damage |
| VerfasserIn |
B. J. Foley, D. Bercovici |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069485
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| Zusammenfassung |
| Numerical simulations of mantle convection with a damage-grainsize feedback are used to
develop scaling laws for predicting conditions at which super-Earths would have plate
tectonics. In particular, the numerical simulations are used to determine how large a viscosity
ratio between pristine lithosphere and mantle (μl-μm) can be offset by damage to allow
mobile (plate-like) convection. Regime diagrams of μl-μm versus the damage number (D)
show that the transition from stagnant lid to mobile convection occurs for higher
μl-μm as D increases; a similar trend occurs for increasing Rayleigh number. We
hypothesize a new criterion for the onset of plate tectonics on terrestrial planets: that
damage must reduce the viscosity of shear zones in the lithosphere to a critical
value equivalent to the underlying mantle viscosity; a scaling law based on this
hypothesis reproduces the numerical results. For the Earth, damage is efficient in the
lithosphere and provides a viable mechanism for the operation of plate tectonics. We
scale our theory to super-Earths and map out the transition between plate-like and
stagnant-lid convection with a “planetary plate-tectonic phase" diagram in planet
size-surface temperature space. Both size and surface conditions are found to be
important, with plate tectonics being favored for larger, cooler planets. This gives a
natural explanation for Earth, Venus, and Mars, and implies that plate tectonics on
exoplanets should correlate with size, incident solar radiation, and atmospheric
composition. |
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