EAPS

John W. Crowley, Harvard University
Mar 30 | 3:45 - 5:00 pm | 54-915

Convection in the presence of strong plates: multiple solutions, hysteresis, and the dynamic state of a planet

Abstract:

Plate tectonics regulates the thermal and chemical state of a planet and may be a necessary condition for a stable surface environment and a habitable planet. Predicting the rate at which tectonic plates move is crucial for understanding both the thermal and chemical evolution of a planet.

A new analytic boundary layer model for thermal convection with a finite-strength plate and depth-dependent viscosity has been developed. The model permits solutions in which convective flow rates in the mantle exceed the plate velocity. Multiple solutions are present with three solution branches for the plate velocity representing three distinct modes of thermal convection. All three modes emerge naturally from the model, and have varying degrees of plate-mantle coupling and different dominant plate driving forces. The branch of solutions with the largest plate velocity reproduces the classic convective scaling laws for an isoviscous fluid while two new branches of solutions with slower plate velocities represent sluggish-lid convection cells with strong plate-like boundary layers.

Together with numerical simulations, the model is used to explore and gain physical insight into several issues including: how the asthenosphere affects plate-mantle coupling; whether or not exoplanets will have plate tectonics; and the thermal evolution of the Earth.


A reception in Building 54, Room 923 precedes the talk.

All are welcome.

If you have any questions regarding the lecture, please contact Jen Fentress at 617.253.2127 or provaire@mit.edu. Reservations not required.

Sponsored by the Department of Earth, Atmospheric and Planetary Science, MIT.