1. The Earth as a Terrestrial Planet Mass -- 6 x 10 27 gm (6 x 10 24 kg) Size -- diameter 12,756 km (eq.) Density – mean 5.5 gm/cm 3 Surface -- 71% water

2. Interior Crust Mantle Core Densities – crust < 3 gm/cm 3 -- mantle 3.5 gm/cm 3  ? Very dense core ~ 15 gm/cm 3  Fe/Ni Outer core – molten (5000-7000K) Inner core – solid ~ 7000K Rotating molten core produces magnetic field Why ? – differentiation of elements

3. Age Dating of Earth Radioactive decay -- uranium, plutonium, thorium U 238  Pb 206 Th 232  Pb 208 using known half-life Rocks on Earth -- newly formed to ~ 3.5 - 4 x 10 9 yrs Oldest Moon rocks – 4.5 – 4.6 x 10 9 yrs

4. Our Active Earth – Plate Tectonics or Continental Drift

6. Consequences– earthquakes, volcanoes, mountain building

7. San Andreas Fault

9. Caused by convective currents in mantle transfers heat to crust

10. The Earth at Night

11. The Earth and Moon as a Double Planet Mmoon/Mearth = 0.012 (1/80 th ) Rmoon/Rearth = 0.27 (1/4 th ) Largest in Solar System

12. Surface Features Craters Mare Highlands

13. Origin of the Moon Sister planet – by fission Co-accretion – at same distance, same material Capture – not dynamically feasible Current theory – massive collision – computer modeling

14. Lunar rocks and soil samples

15. Age Dating Lunar rocks and soil samples Mare – 3.8 x 10 9 yrs Highlands – 4.3 – 4.6 x 10 9 yrs What does this imply?