Across
- 5. Occurs naturally in nature
- 6. A layer of the upper atmosphere
- 7. Process by which people cut down woodlands to harvest timber and to clear the land for farms or ranches
- 9. Human made gases that contain chlorine and fluorine
- 12. Mixture of rock fragments, nutrients, water, air, and decaying animal and plant matter
- 14. Process in which large areas of land are developed as more people move into cities and suburbs
- 16. A layer of warm air prevents the rising air from escaping
- 18. Precipitation that is more acidic than normal due to air pollution
- 19. Synonym for pollutants
- 21. Rock that makes up Earth's crust
Down
- 1. Process by which water, wind, and ice particles moves particles of rocks or soil
- 2. Advance of desert-like conditions into areas that were previously fertile
- 3. A situation when the soil becomes less fertile
- 4. Process of restoring an area of land to a more productive state
- 8. Happens when certain gases in the air react to sunlight
- 10. A form on oxygen that has three oxygen atoms instead of two atoms
- 11. Includes nutrients that help crops grow better
- 13. Top layer of soil
- 15. Period of time when there is less rain fall than normal
- 17. Colorless, odorless gas that is radioactive
- 20. Contains rock fragments, water, air, and less animal and plant matter