Earth History
After protoplanet stage
- Heat (infall and radioactive decay) ==> molten Earth
- heavy elements (Fe, Ni) sink to center Z 59
- light elements (rocks) float
- Cooling (black-body radiation from surface
- crust forms (solid rock)
- mantle below (hot, plastic, rock)
- Fe core remains molten
- All this happens within first 1 billion y
- same processes for all terrestrial planets
- Thereafter, stored heat drives convection, leading to tectonic activity
- recall convection, mag. fields, sunspots in Sun
- upwelling at sea floor
- new crust produced
- continents pushed apart TA 56
- continents are light granite floating on denser basalt