1. 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

3. 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

9. 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

10. 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

15. 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