Across
- 1. Sinking of the ground due to underground material removal
- 6. A propeller-like device for moving a vehicle, e.g., underwater
- 8. Not able to be maintained at the current rate
- 10. A synthetic polymer used in plastic bags
- 12. Chemical process causing gradual destruction, e.g., of metal
- 15. Willing to take risks; courageous
- 16. Site where waste is buried under the ground
- 18. The outer areas of a town or city
- 20. The process of using things up, like resources or energy
Down
- 2. In a way that achieves maximum productivity with minimum waste
- 3. An opening in a wall, door, or vehicle
- 4. A ship or large boat
- 5. Obeying rules or commands
- 7. Able to find quick and clever ways to overcome difficulties (from personal qualities in space exploration)
- 9. Acting in accordance with one's conscience; diligent
- 11. The study of human history through excavation
- 13. Positive and confident about the future
- 14. Basic physical and organizational structures needed for society
- 17. Able to make decisions quickly
- 19. Grammatical structure where subject and verb switch places for emphasis