什么是海啸？
Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the deep ocean, tsunami waves are not very tall. But as they travel toward land and the water becomes shallower, they build up to greater and greater heights.
The speed of a tsunami depends on the depth of the ocean, not on how far it is from where it started. In deep water, tsunami waves can travel as fast as a jet plane, and they only slow down when they reach shallow water.
Tsunamis are often called "tidal waves", but oceanographers discourage this name, because tides have very little to do with these giant waves.
In September 2009, for example, a large earthquake in the southern Pacific Ocean caused a tsunami that brought serious damage and loss of life to Samoa, American Samoa and Tonga.
海啸是由海底地震或火山喷发引起的巨浪。在深海里，海啸的浪并不太高；可是当它们向陆地推进、海水越来越浅时，浪就会变得越来越高。
海啸的速度取决于海水的深度，而不是离发源地有多远。在深海中，海啸的速度可以和喷气式飞机一样快，只有到了浅水区才会慢下来。
海啸常常被叫作“潮汐波”（tidal wave），但海洋学家不赞成这个叫法，因为潮汐和这种巨浪几乎没有关系。
例如，2009 年 9 月，南太平洋发生了一次大地震，引发的海啸给萨摩亚、美属萨摩亚和汤加造成了严重的破坏和人员伤亡。