Natural Resources

4. a form of rain that is unusually acidic, meaning that it has elevated levels of hydrogen ions
5. a silvery white, weakly radioactive metal
9. naturally occurring water that is not salty, and is suitable for consumption if clean or processed
10. the action of clearing a wide area of trees
11. a natural fuel such as coal or gas, formed in the geological past from the remains of living organisms
13. the draining away of water (or substances carried in it) from the surface of an area of land
14. a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane
16. the science, art, or practice of cultivating the soil, producing crops, and raising livestock
17. the energy released during nuclear fission or fusion, especially when used to generate electricity
19. a group of wind turbines in the same location used to produce electricity
20. the process of claiming something back

1. the introduction of harmful materials into the environment
2. radiant light and heat from the Sun that is harnessed to generate electricity
3. a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown haze above cities
6. the generation of electricity using flowing water
7. a brown deposit resembling soil, formed by the partial decomposition of vegetable matter in wet acidic conditions
8. a naturally occurring solid material from which a metal or valuable mineral can be profitably extracted
12. a large area covered chiefly with trees and undergrowth
13. capable of being renewed
15. thermal energy in the Earth's crust
18. organic matter used as a fuel, especially in a power station for the generation of electricity.