原版英语RAZ 教案(S) Tsunamis.pdf

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1、www.readinga-TsunamisA Reading AZ Level S Leveled BookWord Count:889TsunamisVisit www.readinga- for thousands of books and materials.Written by Shaun TaylorLEVELED BOOK SWritten by Shaun TaylorTsunamisLevel S Leveled Book Learning AZWritten by Shaun TaylorIllustrated by Cende HillAll rights reserved

2、.www.readinga-Photo Credits:Front cover:Paul Topp/Acclaim Images;back cover:REUTERS/Tarmizy Harva;title page,page 6:REUTERS;page 4:REUTERS/Yuriko Nakao;page 5:Reuters/Landov;page 7:ArtToday;page 8:courtesy of USGS;page 15:iS 16:courtesy of NOAA;page 17:Jupiterimages Corporation;page 18:REUTERS/Beawi

3、harta www.readinga-TsunamisCorrelationLEVEL SO3434Fountas&PinnellReading RecoveryDRA34Table of ContentsThe Indian Ocean Tsunami .4History of Tsunamis .7Causes of Tsunamis.8Areas at Risk for Tsunamis .14Warning Systems.15How to Survive a Tsunami .17Conclusion .18Glossary .19Index .20The Indian Ocean

4、TsunamiOn December 26,2004,a powerful earthquake shook the ocean floor near the coast of Sumatra,Indonesia.People in nearby villages felt the earth shake.They didnt know that within minutes a massive wave,known as a tsunami,would flood their homes.The giant wall of moving water washed away entire to

5、wns.Within hours,the waves had pounded thousands of miles of coast in Indonesia,India,Africa,Thailand,Bangladesh,Malaysia,Maldives,Myanmar,and Singapore,among others.The 2004 Indian Ocean tsunami washed away much of Banda Aceh,Indonesia.Epicenter of the 2004 earthquake that produced a tsunamiTsunami

6、s Level S56People around the world were stunned each day as the reported death toll increased from 20,000 to 100,000 to 226,000.We will probably never know how many people died because many bodies were buried by the mud and debris or washed out to sea.Scientists think that the death toll would have

7、been lower if more people had known about the danger of tsunamis and how to escape them.Banda Aceh after tsunamiBanda Aceh before tsunamiTsunami Survivor StoriesAmid the stories of loss were amazing stories of survival.One man from Indonesia was washed out to sea by the tsunami,but he was able to cr

8、awl onto a wooden raft.He survived by eating coconuts and drinking rainwater.A ship rescued him after two weeks at sea.Some people outran the water or were washed inland by the wave.Others survived by hanging onto trees or by climbing to the tops of strong buildings.The people who headed for higher

9、ground as soon as they felt the earthquake were most likely to survive.Experts say moving to higher ground or inland are the only true safe places to go when a tsunami hits.Wooden raft used by one tsunami survivorTsunamis Level S78Causes of TsunamisEarthquakes on the ocean floor cause most tsunamis.

10、Underwater landslides,volcanic explosions,and meteor impacts also cause tsunamis.Not every earthquake in or near the ocean causes a tsunami.It depends on the strength of the earthquake and the kind of movement that occurs in Earths crust.An earthquake has to be at least 6.75 on the Richter scale to

11、result in a tsunami.The Indian Ocean tsunami of 2004 was caused by a“mega-earthquake”with a magnitude of 9.0.History of TsunamisThe word tsunami is Japanese and means“harbor wave.”It originated with Japanese fishermen who would return to port to find their towns destroyed by unusually large ocean wa

12、ves that they hadnt even noticed while out at sea.Tsunamis can be devastating when they occur.Fortunately,they are very rare.There are usually six major tsunamis every 100 years worldwide.In 1883 in Indonesia,the volcano Krakatoa exploded and caused a tsunami that killed 36,000 people.In 1958,a land

13、slide in Alaska splashed into Lituya Bay,creating a wave 1,720 feet(524.26 meters)high.An earthquake off the coast of Chile caused a tsunami in 1960,devastating parts of South America,Hawaii,and Japan.Krakatoa erupting in 1943How Strong Is It?The force of an earthquake is described with the Richter

14、scale.People do not feel a 2.0 earthquake at all.Seismographs all around the world can measure a 4.5 quake.With each step up the Richter scale,force increases rapidly.A magnitude 6.0 earthquake has 10 times the power of a 5.0 quake.So when you hear about a magnitude 7,8,or 9 quake,remember that each

15、 unit is actually 10 times the strength of the unit before.Tsunamis Level S910Earthquakes occur when sections of Earths crust suddenly slide against each other along a fault.If an up-and-down shift occurs on the seafloor,all the water above the seafloor moves,too,creating an enormous bulge of water,

16、a tsunami.The tsunami moves almost invisibly in the open ocean because it is broad and very low compared to surface waves.Tsunamis are sometimes called tidal waves because they rush in like a high tide,but in truth they have nothing to do with tides.Tsunamis are also different from normal surface wa

17、ves caused by wind.Surface waves tend to roll onto shore in a circular motion.Tsunami waves act much as surface waves do.The bottom of the tsunami wave drags on the ocean floor slowing it down while the upper part pours onto the shore.Because tsunami waves are taller and farther apart,much more wate

18、r pours onto shore at one time.Surface Waves vs.Tsunami WavesSurface waves roll onto shore fairly close together.As waves approach shallower water,the lower part of the wave drags on the ocean floor,slowing it down.The upper part of the wave pours onto land.Antarctic PlateSections of Earths crustAus

19、tralian PlateAfrican PlateEurasian PlateIndian Plate*Arabian PlateNorth American Plateland above sea levelfaultsorigin of December 2004 tsunami*KEYNPhilippine Plate Pacific Plate Tsunamis Level S1112A tsunami can move as fast as a jet plane at speeds of 200-500 miles per hour (321-643 kph).Tsunamis

20、retain their strength as they spread out over thousands of miles of ocean,like ripples in a pond.They can travel from one side of the Pacific Ocean to the other in less than a day.AntarcticaIndiaAustraliaNThe numbers show how many hours it took the 2004 tsunami to reach land.Indonesia1234567890ablan

21、dseaarea of pressureLand bubbles as pressure builds from one plate“sticking”to another.“bubble”Sudden movement of land causes a surge of water above the fault line.Water rises as a tsunami.Tsunami waves spread away from the fault line.fault lineOrigin of EarthquakeOne plate of Earths crust pushes un

22、der another plate.Pressure releases,or pops,in an earthquakeINDIAN OCEANHow long did it take the tsunami to reach Australia?Tsunamis Level S1314When the wave runs into the shallow shoreline,it grows much higher and it slows down.First,the sea recedes as the wave approaches.Next,the sea floods in pas

23、t the normal shoreline and gushes inland,sometimes far up rivers and streams that open to the ocean.Tsunami waves often come in sets.Observers report the first wave of the Indian Ocean tsunami was smaller than the second wave.Some people survived the first wave but did not keep running and were over

24、whelmed by the larger,second wave.Areas At Risk for TsunamisLow-lying coastlines in areas where earthquakes are common are most at risk for tsunamis.The Ring of Fire is a line of volcanoes stretching around the entire Pacific Ocean.Where there are volcanoes,frequent earthquakes occur with the moveme

25、nt of Earths crust.Indonesia is also an area where Earths crust moves often.Although we cant predict the exact time or location of an earthquake,we can estimate when an area is overdue for one.PACIFIC OCEANNINDIAN OCEANSouth AmericaAsiaNorth AmericaAustraliaRing of Firerunupsea levelocean floorocean

26、top of wave moves fastershoreHow a Tsunami Hits Shorefriction with ocean floor slows bottom of waveTsunamis Level S1516Warning SystemsThere is no practical way to protect property from tsunami devastation,but with early warning,we can save lives.When an earthquake occurs at sea,there is usually some

27、 time before the resulting tsunami reaches land.Unfortunately for the people of Banda Aceh,Indonesia,there were only a few minutes between the quake and the wave.It took about three or four hours for the tsunami to reach India and Sri Lanka.This would have been enough time to radio a message ahead.G

28、overnments and scientists are working to build warning systems for future tsunamis around the world.On the Pacific Coast of the United States,a tsunami warning system is in place.Seismographs all along the Pacific Coast detect earthquakes.A tsunami warning is issued any time there is an earthquake o

29、f 6.8 in Alaska or 7.5 in the western United States.Buoys that are anchored at sea can detect a tsunamis wave speed and direction and radio this information back to land.Radio messages and loud sirens warn people in seaside communities that a tsunami is coming.Signs along the highways label areas at

30、 high risk and suggest evacuation routes.Signs,such as this one,line areas near the coast in the western United States to warn people of the danger of tsunamis.More buoys,such as this one in the Pacific Ocean,will be placed to help scientists monitor tsunamis and to provide warnings to areas at risk

31、.Tsunamis Level S1718ConclusionEarthquakes and tsunamis are scary reminders of the power of nature.We cant prevent these events from happening,but we can prepare for them.Knowing what to do and getting an early warning can save lives.An elephant helps clean up debris left by the devastating December

32、 2004 tsunami in Banda Aceh.How to Survive a TsunamiPeople who live in areas at risk for tsunamis should keep these rules in mind:Find out what the safe evacuation routes are and develop a family emergency plan.Follow the evacuation directions if a tsunami warning is issued.Dont waste time saving pr

33、operty.Depending on the earthquake location,you may have hours or only minutes to leave.If an earthquake occurs,head immediately to higher ground.Make sure that everyone in the house knows to leave.Dont wait for evidence of an approaching tsunami.Outrunning a tsunami that has already arrived should

34、be a last resort.Flee on foot.Traffic jams can quickly form,causing the waste of precious minutes.Dont stay in small buildings close to the coast.Most houses cannot withstand the force of a tsunami.Stay away from rivers near the coast.Tsunamis can wash far inland along river channels.Stay in a safe

35、location until the authorities give an all-clear message.Remember,the first wave may not be the biggest,or the last.Tsunamis Level S1920Africa,4Alaska,7,16areas,at risk,14,16,17buoys,16Chile,7death toll,5earthquake(s),4,6,7,8,14-16,18Earths crust,8,10,14fault,10,11Hawaii,7India,4,12,15Indian Ocean,4

36、,8,12-14Indonesia,4,6,7,12,15Japan,7tsunami huge sea wave,or set of sea waves,caused by the movement of the earth under the ocean,such as in strong earthquakes(p.4)IndexGlossarybuoys floating objects anchored in bodies of water,such as the ocean;some buoys can send information about an area back to

37、scientists(p.16)devastating causing ruin(p.7)earthquake the shaking of Earth where parts of the crust meet(p.4)evacuation removal of people from a place of danger(p.16)fault a crack in Earths crust along which movement occurs(p.10)magnitude greatness of size or intensity(p.8)Richter scale a scale fr

38、om 1 to 10 that measures the strength of an earthquake(p.8)sirens devices used to make shrill warning sounds during emergencies(p.16)tidal of or relating to tides caused twice daily by the attraction of the sun and moon on the surface of the ocean(p.9)landslide,7,8major tsunamis,7meteor,8Pacific Coast,16Pacific Ocean,12,14Richter scale,8Ring of Fire,14Sri Lanka,15surface waves,9-10survivor,6volcano(es)(volcanic eruption),7,8,14water,wall of,4warning,15-17Tsunamis Level S