Title: "Melting Earth's core: Implications for structure and an early dynamo"
Abstract: At ~2900 km beneath the surface, the core is among the least known parts of Earth due to its inaccessibility by direct probe. However, despite its relatively small size (~15 vol%) and isolation, the core plays an important role in sustaining life on Earth by generating and maintaining the geodynamo. Many geochemical arguments rely on a balance between Earth reservoirs and chondritic abundances by assuming certain elemental abundances in the core. These assumptions do not robustly agree with seismological observations and geodynamical constraints, so mineral physical experiments and complementary first-principles computations are needed to simulate the compositions and conditions needed to match observations.
At the top of the core lies a region of anomalously low velocity, dubbed the E' layer, with typical thickness estimates on the order of 100 km. This buoyant layer cannot be explained via simple mechanisms such as enrichment in light elements, as convention would suggest that a lower density iron alloy would have higher velocities because of the inverse relationship between density and velocity. Recent studies have explained this apparent conundrum through the exchange of light elements between the E' layer and the bulk outer core thus necessitating more than one light element present in the liquid outer core iron alloy. The mechanism by which this might occur is less constrained. In this talk I will revisit the likelihood of immiscible iron melts (e.g., Fe-Si-O system) at high pressures as motivation to understanding their possible influence on the evolution of the core and present-day structure.