The present chemical structure of the Earth and other terrestrial bodies is the result of segregation of material phases into chemically distinct but interacting layers. Engineered intervention (e.g. carbon sequestration) may be able to take this process in reverse, with benefits for humans. In the shallow mantle beneath mid-ocean ridges, magmatic segregation leads to formation of the oceanic crust and modification of the residual mantle. Natural or man-made, (de)segregation processes from the Earth's surface to its core are the result of two-phase dynamics.

This session will explore two-phase dynamics throughout the Earth system, with an emphasis on magmatic processes beneath mid-ocean ridges. Theoretical models and measurement/observation both play important roles in this exploration, and recent progress has lead to new insights from both approaches.

Recent progress in long term observation technology on the seafloor enables the imaging of mantle structure beneath mid-ocean ridges using both seismological and electromagnetic techniques. The ensuing velocity and resistivity structures provide important constraints toward understanding melt generation and mantle dynamics among ridge systems. Observational talks in this session will 1) exchange the latest mantle structure results and laboratory experiments on mantle rocks, 2) address variability of crustal formation through investigations of structural, geophysical, petrological and geochemical characteristics of the crust, and 3) link investigations from numerical simulations to identify the parameters controlling crustal formation and mantle structure.

The dynamics of these processes are typically modeled using two-phase flow theory, in which a continuum composed of two interpenetrating, immiscible fluids of different viscosities react dynamically to stresses within and between phases. Thermal, mechanical and chemical interactions between phases lead to complex, nonlinear behaviour. Theoretical/modelling talks in this session will 1) present recent extensions to the theory of two-phase dynamics, 2) apply two-phase theory to model a variety of systems, including mid-ocean ridges, 3) suggest testable predictions that can inspire the next generation of observations.