1. Heat flow, thermal regime, energy budget of the Earth Definitions Measuring heat flow Kelvin and the age of the Earth Radioactivity Continental heat flow (1) Oceanic heat flow (1) Global budget (1) Continental vs oceanic heat flow Plate model for the oceans Continental heat flow (2) Global budget (2) Constraints on the temperature regime

2. Thermodynamics 1 st law: heat is a form of energy dU = dQ -PdV ΔQ = C ρ ΔT 2 nd law (simple form): heat goes from hot to cold (Entropy can only increase unless work is done. Work can be extracted from system only if there are a cold and a hot source). Conduction of heat (Fourier): q = -k grad T Other mechanisms of heat transport (radiation, convection).

4. Some numbers k (thermal conductivity) 3 W/m/K (average for most rocks) Temperature gradient 20-30 K/km Heat flow If gradient does not decrease with depth, temperature at 100km >2000K and temperature at CMB > 60,000K

9. Radioactivity

12. Oceanic heat flow

13. Surprise !!! Continental crust is radioactive and thick Oceanic crust is thin with almost no heat generation Oceanic heat flow < Continental heat flow ? NO difference?

15. Energy Budget of the earth (1) Birch (1951) Total flux = 30 TW Heat production in chondrites = 5 pW/kg Mass of earth = 6 10 24 kg Coincidence?

32. Thermal model for continents