Across
- 1. The state that results when something has died out completely
- 3. Relating to the natural heat produced inside the Earth
- 7. Energy that is created by the splitting of nuclei
- 11. Water that is underground
- 12. The place where a plant of animal normally lives
- 14. Not harmful or less harmful to the environment
- 18. The act of producing or sending out something from a source
- 19. Something that makes a place or substance no longer suitable for use
- 20. Capable of slowly being broken down by natural processes
- 21. A kind of species that is non-native to an area and likely to cause harm
Down
- 2. Someone who works to protect animals and natural resources
- 4. Made or grown without artificial chemicals
- 5. The warming of the Earth's atmosphere when solar energy is trapped
- 6. Anything occurring naturally that humans use
- 8. A system in which materials are buried under the ground
- 9. An area composed of marshes or swamps that act as natural filters
- 10. A chemical used to destroy unwanted plants
- 13. A decayed mixture of plants that is use to improve soil
- 15. Able to be restored naturally in a relatively short period of time
- 16. Made to be thrown away
- 17. A substance that can cause cancer
- 22. Fog mixed with smoke