ASTR 151 1st Edition Lecture 13 Outline of Last Lecture I II Chapter 7 Structure of Earth Chapter 7 Atmosphere of Earth Outline of Current Lecture III Chapter 7 Section 1 Structure of Earth Continued IV Chapter 7 Section 3 Earth s Interior V Chapter 7 Section 4 Surface Activity Current Lecture I Chapter 7 Section 1 Continued a Body Waves i Travels through the interior of the crust ii Gets refracted depending on the density b Surface Waves i Slower than body waves ii Travels across the surface c Shear Waves i Produced by earthquakes sometimes ii Also called pressured waves II Chapter 7 Section 3 Earth s Interior a We use patterns of reflections during earthquakes to deduce interior of the Earth 1 Mantle is less dense than core 80 of the Earth 2 Core is metallic 3 Outer core is liquid inner core is solid due to pressure ii Radioactivity provides heat 1 Radioactivity Decay These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 2 Radioactive Dating 3 Half Lives after one half of life is expended decay begins iii Earth may have been molten when it was formed and remelted due to bombardment by space debris 1 Heavier materials sank to the center b Carbon Dating i When plants or animals die they equal 14 C it decays due to radioactivity 1 The ratio of 12 C to 14 C changes over time that s what you measure and compare to atmosphere 2 Not useful for things older than 60 000 years old not enough 14 C ii To measure much older things you need longer half lives iii Continental Drift 1 Earth s surface is covered with crustal plates which can move independently 2 Plate Boundaries a Collisions two plates crunch b Subduction one plate goes under other 3 Tectonics Pangea meaning all lands III Chapter 7 Section 4 Surface Activity a Ring of Fire i Circum Pacific seismic belt 1 90 earthquakes b Shearing i Plates move on each other causing faults c Rifts i Plates move away from each other d Plates are moved by convection
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