Across

1. Process where the average temperature of the earth increases (6,7).
4. Visible form of energy.
6. Liquid pollution from the skies that kills trees and lakes (4,4).
7. Greenhouse gas produced when fossil fuels are burnt (6,7).
10. Glass building where plants are grown.
11. Process used by green plants to convert light energy to chemical energy.
14. Valuable chemical compounds found in the earth's crust.
15. Raw materials on the earth.
17. Chemical or radioactive contamination of the environment by humans.
18. Type of light, just beyond the visible spectrum, that causes cataracts and skin cancer.

Down

2. Calcium carbonate as a sedimentary rock.
3. Chemical name of "natural gas". Also produced in large volumes by cattle.
5. Very high region of the atmoshere where jet airliners fly.
7. Banned liquid refrigerant that destroys the ozone layer.
8. Form of oxygen that protects us from harmful ultraviolet radiation.
9. An unwanted reaction between metals and the atmosphere and water.
12. Where all our energy originally came from.
13. Petrified (stony) remains of prehistoric plants and animals.
16. Substance like oil, coal or gas that is burnt in air to release chemical energy.