1. Chapter 8

2. Earth’s Core Lithosphere Lithosphere- solid outer crust of Earth – Rock and hot plastic-like upper mantle Three major parts or layers: – Earth’s core: Outer liquid portion Inner solid portion Composition believed to be iron and nickel

3. Earth’s Core (continued) 1,800 miles to outer core 1,300 miles to inner core Core is extremely hot – 8,000 F Used seismic waves to reveal composition Impossible to observe directly

4. Makes up most of Earth’s volume Composed of hot solid material – Silicon, oxygen, iron, aluminum, and magnesium – 1,800 miles think and extremely high pressure – Heat moves upward through mantle Forms convection cells

5. Extreme heat comes from: – Radioactive decay – Friction – Residual heat Upper mantle called the asthenosphere – Flows like thick syrup

6. Outer portion is composed of solid rock Thickness from 40 miles to 3 miles – 40 miles under mountains Continental crust- density 2.7 gm/cc – 3 miles under parts of the ocean Oceanic crust- density 3gm/cc Denser because of pressure of ocean

7. Oceanic crust made of basalt Earth floats on top of upper mantle – Like a cracker floating on soup Seven elements make up 99 percent of crust – Oxygen and silicon form 72 percent of the crust – Aluminum, iron, calcium, magnesium, sodium form the remainder Lower crust and upper mantle form the asthenosphere

8. Model developed using seismic waves Also studied inner composition of meteorites – Helps in understanding Earth’s interior Deepest penetration by drilling is 9 miles Deepest mine is slightly over 2 miles Model is constructed by inference

9. Inference- conclusion based on gathered evidence Can only infer because can’t travel there Many theories based on inference – Earth is so large – Much cannot be studied by direct observation Oceans Atmosphere

10. Earth’s Interior