HR: 1340h
AN: P33A-0230    [Abstracts]
TI: The conditions for plate tectonics: what went wrong everywhere else
AU: Jellinek, M
EM: mjellinek@eos.ubc.ca
AF: University of British Columbia, 6339 Stores Road , Vancouver, BC V6T 1Z4 Canada
AU: * O'Neill, C
EM: cjoneill@rice.edu
AF: Rice University, Department of Earth Sciences, MS-126, Rice University, 6100 Main St, Houston, TX 77005 United States
AU: Lenardic, A
EM: adrian@geophysics.rice.edu
AF: Rice University, Department of Earth Sciences, MS-126, Rice University, 6100 Main St, Houston, TX 77005 United States
AB: A necessary precursor for the onset of plate tectonics on a terrestrial planet is that the intrinsic system stresses, generally associated with buoyancy anomalies, are great enough to overcome the resistance of the lithosphere to deformation. On Earth, these stresses are generally associated with the subduction of oceanic lithosphere - leading to the notion that the plates drive themselves. On planets without existing plate tectonics, the most significant buoyancy anomalies are associated with the formation and sinking of cold downwelling 'thermals'. The question we address is under what conditions are stresses associated these cold thermals sufficient to initiate failure of the lithosphere? Lithospheric strength is a function of its friction coefficient and elastic thickness (or, equivalently, the depth to the brittle-ductile transition). Both and plate's yield strength, and convective stresses, depend critically on the size and thermal evolution of a planet. We use numerical simulations and scaling theory to identify conditions under which mantle convection generates lithospheric failure, for parameters appropriate to the terrestrial planets. While the Moon and Mercury are predicted to have always been in a stagnant lid regime, Earth is, predictably, in a 'failed-lid' regime. Venus and Io currently fall on the transition between the two regimes. This is consistent with an episodic-style of convection on Venus, and suggests a tectonic component of deformation on Io. Mars is in a stagnant lid regime now, and probably was for most its history; however, early Martian plate tectonics is plausible if the lithosphere was weakened by the presence of surface water during the first 500Myr of its history.
DE: 5475 Tectonics (8149)
DE: 6225 Mars
DE: 6295 Venus
DE: 8121 Dynamics: convection currents, and mantle plumes
SC: Planetary Sciences [P]
MN: Fall Meeting 2005