'Nature disasters'

6. poisonous or dirty substances that are polluting the water, air or land somewhere
8. a shaking of the ground caused by movement of the earth's crust
10. it's extremely destructive form of pollution, and the enviroment suffers from it's effects
13. responsible for causing the greenhouse effect
14. a very large wave, often caused by an earthquake, that flows onto the land and destroys things
15. thick layers of ice and snow that cover the North and South Poles

1. the average level of the sea with respect to the land
2. this mud or mud-stone flow suddenly emerging in the course of mountain rivers as a result of rainfall, rapid melting of glaciers or seasonal snow cover
3. long period of time during which no rain falls
4. the gradual rise in the earth's temperature
5. an extremely violent wind or storm
7. all trees are cut down or destroyed
9. the death of all animal or plant remaining living members
11. ...effect the problem caused by increased quantities of gases such carbon dioxide in the air
12. a large amount of water covers an area which is usually dry, for example when a river flows over its banks or a pipe bursts