Journal of Conference Abstracts

Numerical Simulations of Mantle Dynamics and Evolution with Brittle Lithosphere

Viatcheslav Solomatov (slava@nmsu.edu)¹, Faez Bakalian (faezbaka@nmsu.edu)¹, Christopher Reese (creese@nmsu.edu)² & Louis Moresi (louis@ned.dem.csiro.au)³

¹Dept. of Physics, NMSU, Las Cruces, NM, 88003, U.S.A.

²CSIRO Dept. of Physics, 39NMSU, Las Cruces, NM, 88003, U.S.A.

³Exploration & Mining, 39 Fairway, PO Box 437, Nedlands, WA, 6009, Australia

One of the most striking observation in the Solar System is that Earth is the only planet which has plate tectonics. On Mars, Venus, Mercury and the Moon the lithosphere is stagnant. This is likely to be due to strongly temperature-dependent viscosity which makes the cold lithospheric plates stiff and immobile. On the other hand, some kind of plate tectonics could take place in the early history of Mars and Venus as suggested by recent interpretations of geological observations. Assuming that brittle fracture is an important factor for the initiation of plate tectonics we explore the mechanical conditions required for plate tectonics to occur on a planet and investigate how these conditions change during planetary evolution. We perform numerical simulations of mantle convection with strongly temperature dependent viscosity and brittle fracture modeled with the help of depth dependent yield stress similar to one suggested by Byerlee's friction law. We find that depending on the relative value of the yield stress the convective style can be plate tectonics, stagnant lid convection or episodic plate tectonics. During secular cooling, the convective regime can change from plate tectonics to stagnant lid as a result of variation of both the convective stresses and the critical stress necessary to break the lithosphere. At some moment, the stresses drop below the critical stress and convection style switches from plate tectonics to stagnant lid convection. The stress balance is so delicate that about 30% difference in the yield stress gradient is sufficient to ensure that the planets had only one regime during their entire evolution.