Post on 20-Jan-2016
A Layered Earth•Solid inner core- 6,370 km deep
•Liquid outer core- 2,900 km deep
•Mantle – 100-200 km deep
•Brittle crust- Surface to 100-200 km
Evidence from Earthquakes
• Two Types of Seismic Waves– P Waves: Compressional– S Waves: Transverse
• Seismic waves do not travel at the same speed through the earth
• S Waves cannot pass through liquid– Shadow zone develops behind the liquid core
• P Waves slow down through liquid
Lithosphere and Asthenosphere
• Lithosphere (litho=rock)– 100-200 km thick– Oceanic and Continental Crust
• Asthenosphere (asthenes=week)– Below Lithosphere to 350-650 km– Hot, partially liquid upper part of the Mantle
Continents
• Continents are made of low density crust rock (like granite) that floats on denser crust
• Oceanic crust is more dense than continental crust so it sits lower
Continental Drift
• Continents look like they fit together– S. America and Africa
• 1912-Alfred Wegener proposes that continents move. – Everyone thought he was nuts
• 1960- Seafloor spreading