The Energetics of Earth’s Core and Mantle
IPGP - Îlot Cuvier
Séminaires Dynamique des fluides géologiques
I will reexamine the energetics of Earth's core and mantle, and discuss some implications for our planet's convective evolution. For the core, I will explore the potential information from the ~500-1000 kg m-3 seismically-inferred jump in density between the liquid outer core and solid inner core, which allows us to directly infer the core-freezing Clapeyron Slope for the outer core’s actual composition which contains ~8±2% lighter elements (S,Si,O,Al, H,…) mixed into a Fe-Ni alloy. A PREM 600 kg m-3-based Clapeyron Slope would imply, that if the entire inner core has frozen over the past ~3Ga, there has been ~774K of core cooling during the freezing and growth of the inner core, releasing ~24 TW of power during the past ~3 Ga. If so, core cooling can easily power Earth’s long-lived geodynamo. Another major implication of ~24 TW heatflow across the core-mantle boundary is that diapiric mantle plumes should dominate deep mantle upwelling. Finally, this mode of core heat supply to the base of the mantle is a simple way to have mantle convective evolution histories that are significantly closer to the 'steady-state' scenario assumed in several geochemical evolution models than any scenarios driven mainly by loss of radioactive heat generated within the mantle.