英語(yǔ)聽力文摘 在海嘯中航行
海嘯是一種具有強(qiáng)大破壞力的海浪。當(dāng)?shù)卣鸢l(fā)生于海底，因震波的動(dòng)力而引起海水劇烈的起伏，形成強(qiáng)大的波浪，向前推進(jìn)，將沿海地帶一一淹沒的災(zāi)害，稱之為海嘯。海嘯通常由震源在海底下50千米以內(nèi)、里氏地震規(guī)模6.5以上的海底地震引起。海嘯波長(zhǎng)比海洋的最大深度還要大，在海底附近傳播也沒受多大阻滯，不管海洋深度如何，波都可以傳播過去，海嘯在海洋的傳播速度大約每小時(shí)五百到一千公里，而相鄰兩個(gè)浪頭的距離也可能遠(yuǎn)達(dá)500到650公里，當(dāng)海嘯波進(jìn)入陸棚后，由于深度變淺，波高突然增大，它的這種波浪運(yùn)動(dòng)所卷起的海濤，波高可達(dá)數(shù)十米，并形成“水墻”。由地震引起的波動(dòng)與海面上的海浪不同，一般海浪只在一定深度的水層波動(dòng)，而地震所引起的水體波動(dòng)是從海面到海底整個(gè)水層的起伏。
Tsunamis are powerful waves caused by underwater earthquakes or eruptions that can crash over ten stories tall into a coastline.
If you were sailing far from shore, how would you feel about a tremendous tsunami heading your way?
Actually, you wouldn’t notice a tsunami at all. In deep water, a tsunami raises the ocean’s surface only about one or two feet—much less than ordinary ocean waves. What’s more, it takes up to an hour for a single tsunami to roll by. How can a wave be so deadly to a coastline, but so tame in the open ocean?
The energy of a wave has more to do with how deep the water churns than how tall the wave rises. Ordinary waves can be rather tall, but they don’t go very deep. What’s more there’s never much distance between one ordinary wave’s crest and the one following it. The distance between waves is called “wavelength,” and it’s another secret of a tsunami’s strength.
While ordinary waves only tug at the surface water, tsunamischurn the water all the way to the deepest ocean floor! They also have very long wavelengths—a hundred miles or more. Although tsunamis raise the surface only a foot or so in deep water, they carry a lot of energy.
When a tsunami approaches a coastline, the water gets shallower. This causes friction at the front of the wave and slows it down. The faster moving back of the wave piles into the slower front, squeezing the whole hundred mile tsunami like an accordion. Just as a rug will crumple and rise if it’s scrunched by an opening door, the tsunami gets taller. By the time it hits the beach, it can be a hundred feet high!
譯文：
海嘯是由海底的地震或者火山噴發(fā)引起的足以把一個(gè)十層高樓淹沒的強(qiáng)大海浪。
如果你正遠(yuǎn)離海岸航行，這時(shí)遭遇了海嘯，是什么樣的感覺呢?
事實(shí)上，你根本不會(huì)注意到海嘯。在深海中，海嘯只會(huì)掀起一或兩英尺的海浪-遠(yuǎn)遠(yuǎn)低于普通的海浪。更重要的是，一次海嘯最多一個(gè)小時(shí)就過去了。為什么對(duì)于海岸如此致命的海浪在公海中如此溫馴呢?
海浪的力量與水層波動(dòng)的深度而不是海浪的高度有關(guān)。常波可能很高，但是它們水體波動(dòng)的深度并不深。更重要的是常波前后的波峰之間并沒有太大的距離。波之間的距離被稱為“波長(zhǎng)”，這是海嘯力量的另一個(gè)秘密。
盡管常波只是在水表面生成，但是海嘯可以在最深的海底引起水層波動(dòng)使其產(chǎn)生。它們同樣有很長(zhǎng)的波長(zhǎng)-一百英里或更多。雖然海嘯通過深海中的水層波動(dòng)只能提升水平面一英尺左右，但是它們帶來(lái)了大量的能量。
當(dāng)海嘯接近海岸線時(shí)，水的深度逐漸變淺，導(dǎo)致波前摩擦，使其速度變慢?？焖偾斑M(jìn)的波浪與前面速度較慢的波浪重疊，像手風(fēng)琴那樣擠壓這些整個(gè)百里長(zhǎng)的海嘯，正如由于門開時(shí)被壓住而弄皺卷起的地毯，海浪就越來(lái)越高。當(dāng)它到達(dá)海灘的時(shí)候，它可以達(dá)到一百英尺。
