1. Unit 4
Earthquakes

4. The top layer(层) of the earth,its crust(地壳),is made up of huge pieces of rock.They move past each other all the time along fault lines（断层带）.But sometimes two pieces get stuck（挤压）together.
When they finally move away from each other,they move suddenly.　An earthquake is felt.

5. Earthquakes are measured on a scale(等级) of 0-9 called the Richter scale(里氏震级). A size 9 earthquake is the strongest and the most dangerous.

6. What happens before an earthquake?

7. The water in wells rises and falls, rises and falls again.

8. Fish jump out of the bowl.

9. Some other strange things before earthquake

10. Cracks appear in the ground.

11. cracks

12. cracks

13. What damages are done to the earthquake-hit area?

15. Buildings and houses collapse.

16. Useless broken railway tracks

17. Most of the bridges are down

19. Dams fall in an earthquake.

20. The quake-hit area lies in ruins.

21. How is the rescue work done?

22. Medical workers come to help.

23. Other rescue workers come to help.

24. looking for the survivors

25. Digging out those who are trapped

26. Shelters are put up for the homeless.

27. Food ,medicine and water are taken by train ,truck and plane.

28. Warming up

29. 1.Say something about these two cities.
What will happen before an earthquake?
Tangshan
San Francisco
Tangshan is a beautiful city with gardens, wide roads.
San Francisco is a city with tall buildings thickly standing on the earth.
These two cities are famous for their earthquakes during a period of calm.
So we should not trust situations that seem peaceful since bad things may happen.

30. But terrible earthquakes have happened to these two cities.
The earthquake which happened in Tangshan was the biggest and worst in China in the 20th century.

31. A Night the Earth didn’t Sleep

34. The city lay in ruins

40. Why didn’t the earth sleep that night?

41. What happened during the earthquake?
1.Where did the earthquake began?
2.How many people felt it?
3.How long was the huge crack?
4.How soon was the city destroyed?
5.How many people were killed and injured?

42. What should we do before,during and after an earthquake?

43. The monument built after the
Tangshan Eathquake

44. Thank you!