Core-Mantle Boundary Heat Flow

Core-Mantle Boundary Heat Flow Cut-away Earth schematic indicating dynamic regimes in the mantle and core, along with variation in heat flux through the core-mantle boundary. Heat flux from the core into the mantle (represented by red arrows) is highest in areas cooled by downwellings, and lowest in hot upwelling regions.
The current total heat flow at Earth’s surface, 46 ± 3 TW (10**12 J/s), involves contributions from secular cooling, radiogenic heating from decay of U, Th and K, heat entering the mantle from the core, and various minor processes such as tidal deformation, chemical segregation and thermal contraction. Over the past decade, estimates of the heat flow across the core-mantle boundary (CMB), or across a chemical boundary layer above the CMB, have generally increased by a factor of 2 to 3, yielding values in the range 5-15 TW from independent considerations of core temperature, geodynamo energetics, buoyancy flux of lower mantle thermal plumes, and direct temperature determinations in the lowermost mantle enabled by relating seismic velocity discontinuities to a laboratory-calibrated phase change in magnesium-silicate perovskite (MgSiO3) (Lay et al., 2008). Relative to earlier ideas, the increased estimates of deep mantle heat flow indicate a more prominent role for thermal plumes in mantle dynamics, more extensive partial melting of the lowermost mantle in the past, and a more rapidly growing and younger inner core and/or presence of significant radiogenic material in the outer core or lowermost mantle.
</p><p>Lay, T., J. Hernlund, and B. A. Buffett (2008). Core-mantle boundary heat flow, Nature Geosci., 1, 25-32.</p>


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