ASTRO-110 Lecture Notes - Lecture 8: Mantle Convection, Gravitational Energy, Himalayas
9 Sep 2020
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Only upper layer of mantle is liquid (volcanism); core: inner is solid, outer is liquid. How we sample this: earthquakes are perfect! Heating and cooling of the interior; release of energy. When planets were young: accretion and differentiation. Nowadays, radioactive decay is most important heat source. Differentiation: gravity pulls high-density material to center; lower- density material rises to surface; material ends up separated by density. Gravitational potential energy is converted to thermal energy of interior. Convection transports heat as hot material rises and cool material falls. Conduction transfers heat from hot material to cool material. Smaller worlds cool off faster and harden earlier. Moon and mercury are now geologically dead . Earth is distinct from all in having plate tectonics. Sea floor is different from continental crust. Mid-ocean ridges, discovered mid-1950"s as third evidence for plate tectonics. Thin (5 10 km) seafloor crust differs from thick (20 70 km) continental crust.
