PHYS 183 Lecture Notes - Lecture 30: Arecibo Observatory, Observability, Geochemistry
21 Apr 2018
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Document Summary
Central to origin and evolution is age. First estimates based on religion, not science, suggested few thousand years old. Ongoing radioactive decays in centre of earth produce lots of heat. Use seismic waves produced by this activity to study interior. Structure largely determined by gravity: slowly pulls denser objects inward. Earth structure: dense solid metal core at centre, surrounded by dense liquid metal core, surrounded by mantle of dense rock, surrounded by crust of less dense rock. From ocean floor to highest mountain peak is 0. 1% of earth"s radius. Seismometers left by astronauts on moon allow similar studies. They find: many fewer earthquakes, much smaller core, surrounded by liquid mantle, surrounded by solid mantle, then crust. Easy to estimate moon less dense than earth; consistent with seismic data. Heat of radioactivity deep within earth drives evolution of geological features. Crust stressed: buckling, folding can create mountains, stretching produces faults, cracking produces earthquakes, volcanism when molten rock (lava) comes to surface.
