人教版（2020新） 必修第一册 unit4 Video Time 课件.ppt

1、Tsunami: Killer Wave Unit4 Video Time Tsunami waves can strike out of nowhere and cause a lot of destruction. Scientists study and track tsunamis in order to warn people and minimise deaths. Tsunami: Killer Wave Now, lets explore more about tsunami by a video. BEFORE YOU WATCH Read the sentences abo

2、ut the formation and effects of tsunamis. Then match each sentence with the correct picture. A: Tectonic plates push together. B: A series of waves expands in all directions. C: Whole sections of cities are destroyed. C A B 1. An earthquake occurs when plates below the earths surface push together/p

3、ull apart. 2. Tsunami waves deep at sea move fast and rise only a few /hundreds of feet. 3. As these killer waves enter shallow waters, their speed is reduced/raised. 4. Most tsunami damage is caused when the waves come in from/move back out to the sea. WHILE YOU WATCH 1. Decide whether the statemen

4、ts are true(T) or false(F). 1. There are few warning signs just before a tsunami hits. 2. A tsunami breaks just like an ordinary wave but is bigger. 3. Scientists at the Pacific Tsunami Warning Center monitor the earths movements 24 hours a day in order to track tsunamis. T F T F T F 2. Circle the c

5、orrect word(s) in each sentence. AFTER YOU WATCH 1. What have you learnt about tsunamis? 2. What kind of help do you think people who have suffered from a tsunami need? Possible answer: I have learnt that they are dangerous. / that they arent noticeable or strong until they hit the coast. / that the

6、y cause more damage when they recede. Possible answer: They need food, water, shelter, etc. They may also need medical help and emotional help if they have lost loved ones. Tapescript The warnings are few. The signs are sudden. The ground shakes. The tide goes into reverse. A great roaring sound fil

7、ls the air. And then It strikes. Wave after wave of crashing, crushing water. And when it is over, nothing is left. A tsunami. The word in Japanese meansharbour wave. Japan has been hit by many tsunamis in its history, as a result of its location. It lies across the edges of 4 tectonic plates. Most

8、earthquakes are born in such places. When two tectonic plates push together, the earthquake sends enormous amounts of energy up through the ocean. A series of waves expands in all directions. In deep water, these waves travel fast-up to 500 miles an hour-but reach a height of only a few feet. A pass

9、ing ship may not even notice them. But as the waves enter shallow waters and come into contact with the ocean floor, their speed is reduced but their height is raised. As they move onto land, the waves can rise as high as a 10-story building. A tsunami wave doesnt break like an ordinary wave. Instea

10、d, it advances like a wall of water, crashing over everything in its way, sometimes reaching more than a kilometre inland. More damage is caused when the wave moves back out to sea. It drags everything in its path underwater and out to sea. Most tsunamis have several waves. They arrive between 10 an

11、d 60 minutes after the first strike- just when survivors think the danger has passed. The deadliest tsunami ever recorded occurred in December of 2004. An earthquake off the coast of Indonesia caused a tsunami that rushed across the Indian Ocean and reached as far as the coast of Africa. Whole secti

12、ons of cities were destroyed. More than 200,000 people died. Most had no way of being warned. Five thousand miles away in Hawaii, scientists at the Pacific Tsunami Warning Centre monitor the earths movements 24 hours a day. They hope to prevent a similar disaster from happening in the Pacific region

13、. If they discover a quake big enough to cause a tsunami, the scientists try to find out where the wave will head and warn people in its path. Their advice is simple: leave the coastal areas and move to higher ground. Wait for news that the danger has passed. And be ready to deal with the damage that a tsunami leaves behind.