EFFECT OF COMPOSITION DEPENDENT PROPERTIES ON SURFACE MOBILITY IN THE EARLY EARTH

Numerical models of the Earth's interior are helpful for understanding present day mantle dynamics. These models are often constrained by surface observations. The much hotter early Earth is less well constrained and consequently the dynamics are less well understood. One theory about the early Earth is that a large hot magma ocean was trapped near the core-mantle boundary during differentiation. This basal magma ocean would likely contain different elements from the surrounding mantle and therefore have different properties. It could even be iron-rich from the core. A large, hot, low viscosity magma layer at the base of the mantle is likely to influence the type of surface motion present in the early Earth. We examine how the physical properties of a basal component affect mantle convection in an early Earth setting using numerical models. We vary the viscosity, thermal conductivity, and internal heating in the basal layer to explore different properties and elements that might be present and explore the effect on surface properties and mobility. We find that increased conductivity and decreased viscosity in the basal layer flattens the basal topography. However, we also find that increased conductivity in the basal layer also increases the potential for surface yielding. Using these results, we explore the parameters which will yield the kind of mobile surfaces we see in present day plate tectonics.