MANTLE PHASE-TRANSITIONS AND LAYERED CHAOTIC CONVECTION

We report preliminary results from a sequence of very high resolution simulations of the mantle convection process based upon an axisymmetric anelastically compressible spherical model with both Olivine-Spinel and Spinel-post Spinel phase transitions. Our analyses strongly suggest that at Earth-like Rayleigh numbers near 10(7) the circulation may be quite strongly layered, although a very long timescale transient exists that is characterized by brief excursions into the whole mantle state. We suggest the use of a new diagnostic tool that may be employed to determine whether or not the layered state is characteristic of the present day earth.