Lecture 25-26 Earth's Structure(1)

Shearsecondarysurface s waves l travel more slowly

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Unformatted text preview: h massive structures as mountains. l༆  Drii would be impossible with this kind of rigid subterranean structure. l༆  Wegener died in 1930 on an expediHon and few believed his theory anymore. l༆  More about this later 13 Earthquakes l༆  The theory of ConHnental drii gained more favour as more about the interior structure of the Earth was revealed. l༆  Seismic waves, following earthquakes, reveal much about the Earth’s structure l༆  Earthquakes appear when fault lines move under stress to release energy (potenHal energy) l༆  hop://www.youtube.com/watch?v=Sn4t13uxJFQ 14 Earthquakes produce two types of wave: 1. Primary or P waves are compression waves l༆  P- Waves are the fastest – travelling on the order of 1 to 14 kms- 1 l༆  Compression waves are longitudinal waves l༆  Velocity depends on density of material as well as its elasHc properHes (think about sound waves – faster in water vs. air). l༆  Slowest speed is for P- waves (P for primary) travelling through water and higher speeds near centre of Earth 16 17 l༆  When a P- wave passes the ground is vibrate...
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