Experimental Investigations of the Dynamics of Thermochemical Boundary Layers in the Mantles of Terrestrial Planets

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Manga 0124972 Heat and mass transfer across thermal and chemical boundary layers at the top and bottom of the mantles of the terrestrial planets govern the chemical and geodynamic evolution these planets. The dynamics of the top, lithospheric boundary layers of terrestrial planets are dominated by multi-mode (brittle/ductile) rheological behavior, e.g., plate tectonics on Earth and immobile lithosphere on Mars, which are at least readily observed if not completely "understood". Although deep mantle dynamics are less accessible to observation, there are still seismological, mineral physics and geochemical data that provide constraints on mantle dynamics. Near the core-mantle boundary, flow probably involves both a thermal and chemical boundary layer. Laboratory experiments can play an important role in treating problems involving vigorous multi-component convection in which dynamical interactions across continuous viscosity and density interfaces determine the flow. The investigators will carry out a series of laboratory experiments aimed at achieving a better understanding of the dynamics of mantle flow at the Earth's core-mantle boundary. Over the course of the proposed work they will forge a better fundamental understanding of thermochemical boundary layers in all aspects of mantle convection. The investigation will focus on two classes of experiments: (1) Basic studies of thermochemical convection to elucidate the coupling of heat transfer and flow across chemical boundary layers, quantify entrainment rates across viscosity interfaces, and better understand the dynamics controlling the formation of thermo-chemical plumes. (2) Focussed studies of plume/plate interactions using controlled large-scale flow as a proxy for the effects of plate motions. The investigators also plan to complement their laboratory experiments with theoretical and 3-D numerical modeling studies. For the latter, the laboratory experiments will form valuable benchmarks.