Across
- 3. tiny rock pieces broken off larger rocks
- 8. water falling down onto Earth's surface
- 9. how ice can break rocks
- 11. gas layer surrounding the Earth
- 13. water on Earth's surface moving downhill
- 14. the gas in the air that humans need the most
- 16. hard rocky layer of earth
- 19. when tiny rock pieces are carried away by water or wind
- 20. an underground rock formation caused by weathering
- 21. when ice changes to liquid
- 22. area of Earth that has living things
Down
- 1. when rocks break down into new substances
- 2. vapor molecules change into liquid
- 4. the most common gas in the air
- 5. the breakdown of rocks into smaller pieces
- 6. after water seeps into the ground
- 7. a substance with a very low pH
- 10. liquid molecules fly away
- 12. parts of a tree that can break down rock
- 15. a collection of water droplets floating in sky
- 17. liquid layer surrounding the Earth
- 18. when liquid molecules lock into place