Across
- 4. liquid mixture of hydrocarbons that are present in certain rock
- 6. resources which continue to exists despite being consumed
- 7. formed from the remains of living organisms
- 8. accumulation of valuable minerals formed by gravity
- 10. energy generated in a way that does not deplete natural resources
- 11. using less energy to perform the same task
- 13. extraction of metal from its ore by using heating and melting
- 17. nuclear reaction where the nuclei fuses
- 18. natural substances that are not replenished or replaced
- 19. energy that uses the power of water to generate electricity
- 20. energy from the sun's rays
Down
- 1. nuclear reaction where the heavy nucleus splits
- 2. mining beneath the surface of the earth
- 3. energy formed or produced by living organisms
- 5. cultivation of forest for farming
- 9. energy that is taken from the earth's core
- 12. mining on top of the earth
- 14. prevention of the waste of electricity
- 15. natural occurrence of rock or sediment which contains ore
- 16. a solid inorganic substance of natural occurrence