1. How do we know? Rock Samples Seismic Waves 2 ways –Rock Samples –Seismic Waves Holes in the earth up to 12.3 km (7.6 miles) –Brings samples –Gives clues –Volcanoes shoot up rocks –Labs recreate rock conditions Earthquake Waves –How they travel through the earth –Speed and path shows the material inside

2. Features of Crust Pressure –Results from force pressing on an area –Deeper in the earth = greater the pressure Temperature –Temperature increases as depth increases –Rock is cool for about 20 m down (65 ft) –Every 40 m after, temp increases 1° C (131 ft, 33.8° F) –Some heat left over from Earth formation The outermost layer of the Earth –Solid rock that includes dry land and ocean floor –5 – 40 km thick (3.1-29 miles) on avg –2 types of crust Continental crust (thickest at mountains) Oceanic crust (thinnest)

3. Mantle Core Made 3 layers –Lithosphere (rock sphere) Brittle rock like the crust Strong, rigid 100 Km thick –Asthenosphere Less rigid, more putty like –Mesosphere Hotter, but rigid again due to pressure Center of the Earth –below the mantle –Believed to be nickel & iron –Outer core: 2,258 km liquid –Inner core: 1,222 km solid Intense pressure makes it solid

4. Why is the Inner Core solid?

5. Magnetic Field –Believed to be caused by movement in the liquid outer core –Makes Earth behave like bar magnet http://pubs.usgs.gov/gip/dynamic/inside.html