tsunami：killerwave公开课教案教学设计课件资料.docx

Tsunami: Killer WaveThe warnings are few. The signs are sudden. The ground shakes. The tide goes into reverse. A great roaring sound fills 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 means "harbour 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（ 壳板块） Most 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 fastup to 500 miles an hour but reach a height of only a few feet. A passing 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-storey building.A tsunami wave doesn't break like an ordinary wave. Instead7 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 and 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 xxx coast of Indonesia caused a tsunami that rushed across xxx Indian Ocean and reached as far as xxx coast of Africa. Whole sections 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 xxxxxxx Tsunami Warning Centre monitor the earth's movements 24 hours a day. They hope to prevent a similar disaster from happening in the xxxxxxx region. Ifthey 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.