Across
- 2. nearly 90% of Earth ozone
- 6. amount of water vapor in air
- 7. solar wind and Earth's magnetic field
- 9. makes air impure
- 10. less than 220 dobson units
- 14. harmful to breathe
- 15. N2O
- 17. contains all water
- 18. rocky outer layer of Earth
- 19. view and map Earth
- 20. outermost layer of atmosphere
Down
- 1. representation of Earth's processes
- 3. invisible gas
- 4. second lowest layer
- 5. prolonged dry period
- 8. meteors burn up
- 11. other term for biosphere
- 12. can be studied separately
- 13. a closed system
- 16. high temperature