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1、Unit 4,Earthquakes,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.,Earthqu
2、akes 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.,What happens before an earthquake?,The water in wells rises and falls, rises and falls again.,Fish jump out of the bowl.,Some other strange things before earthquake,Cr
3、acks appear in the ground.,cracks,cracks,What damages are done to the earthquake-hit area?,Buildings and houses collapse.,Useless broken railway tracks,Most of the bridges are down,Dams fall in an earthquake.,The quake-hit area lies in ruins.,How is the rescue work done?,Medical workers come to help
4、.,Other rescue workers come to help.,looking for the survivors,Digging out those who are trapped,Shelters are put up for the homeless.,Food ,medicine and water are taken by train ,truck and plane.,Warming up,1.Say something about these two cities. What will happen before an earthquake?,Tangshan is a
5、 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.,Tangshan,San Francisco,The
6、 earthquake which happened in Tangshan was the biggest and worst in China in the 20th century.,But terrible earthquakes have happened to these two cities.,A Night the Earth didnt Sleep,The city lay in ruins,Why didnt the earth sleep that night?,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?,What should we do before,during and after an earthquake?,The monument built after the Tangshan Eathquake,Thank you!,