HR: 17:30h
AN: T44B-07    [Abstracts]
TI: Transitions in convective behavior as a function of damage: an explanation for the difference between Earth and Venus
AU: * Landuyt, W
EM: william.landuyt@yale.edu
AF: Department of Geology and Geophysics, Yale University, Kline Geology Lab. 210 Whitney Ave., New Haven, CT 06520, United States
AU: Bercovici, D
EM: david.bercovici@yale.edu
AF: Department of Geology and Geophysics, Yale University, Kline Geology Lab. 210 Whitney Ave., New Haven, CT 06520, United States
AB: The generation of plate tectonics from mantle convection requires shear localization in order to form narrow, weak zones that separate the broad, strong plate interiors. The existence of plate tectonics on Earth and its absence on the other terrestrial planets remains a significant conundrum for geophysicists. Two-phase damage theory provides a theoretical framework to describe the failure and weakening that leads to shear localization by allowing for the development of damage to be manifested in two distinct ways: void generation associated with dilation of the matrix and increasing the fineness of the mixture (e.g. grain size reduction). This work will examine the application of two-phase damage theory in two-dimensional convection simulations to model mantle convection. We find that by varying the healing rate for grain-growth the convective model undergoes significant transitions in convective style; by increasing the healing rate for grain growth the system will transition from stable plate-like behavior to episodic behavior, and further increases in healing rate eventually force the system to stagnant-lid behavior. The various states of convection observed in our simulations are similar to the different modes of convection seen in our solar system: stagnant lid (Mars), episodic (possibly Venus), and stable plate- like (Earth). The numerical experiments are used to test a simple conceptual model whose underlying hypothesis is that the transitions are due to grain size variations controlling subduction lubrication, hence either allowing for unimpeded subduction or the cessation of subduction altogether. Finally, we propose a model for the generation of plate tectonics that explains the convective transitions by coupling a planet's lithosphere and atmosphere/ocean climate system. The model suggests a criteria to determine if a planet will develop Earth-like plate tectonics.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8149 Planetary tectonics (5475)
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting