Name: 【TED-Ed】3分鐘搞懂海嘯是怎麼發生的 (How tsunamis work - Alex Gendler)
Uploaded: 2022-04-18T21:01:10.000Z
Duration: 3 min 37 s
Description: 海嘯的巨浪可高達100英呎，時速超過500英哩—對任何在它所經之處的人或物，這樣的組合都是非常危險的。愛麗克絲 • 珍德勒 (Alex Gendler) 詳述這些高聳駭人巨浪的成因，並說明科學家如何尋找未來可望降低其破壞程度的方法。 課程由愛麗克絲 • 珍德勒 (Alex Gendler) 講授，動畫由 Augenblick...

In 479 BC, when Persian soldiers besieged the Greek city of Potidaea, the tide retreated much farther than usual, leaving a convenient invasion route.

西元前 479 年波斯士兵要圍攻波提狄亞的希臘城邦時，海潮退得比平時還遠，給了波斯士兵方便入侵的路徑。

Before they had crossed halfway, the water returned in a wave higher than anyone had ever seen, drowning the attackers.

在他們穿越到一半前，退去的海水以沒人見過的浪高衝了回來，淹死了進攻的波斯士兵。

The Potiidaeans believed they had been saved by the wrath of Poseidon.

波提狄亞人相信是海神的天譴救了他們。

But what really saved them was likely the same phenomenon that has destroyed countless others: a tsunami.

但真正救了他們的其實是摧毀無數生命的自然現象： 海嘯。

Although tsunamis are commonly known as tidal waves, they're actually unrelated to the tidal activity caused by the gravitational forces of the sun and moon.

雖然海嘯通常被認為是潮汐，但它們其實與受太陽、月球引力作用所形成的潮汐活動沒有關聯。

In many ways, tsunamis are just larger versions of regular waves.

從許多方面來看，海嘯只不過是放大版的正常海浪。

They have a trough and a crest, and consist not of moving water, but the movement of energy through water.

它們都有波谷及波峰，靠的不是流動的海水， 而是海水中能量的變動。

The difference is in where this energy comes from.

For normal ocean waves, it comes from wind.

風是一般海浪形成的能量來源。

Because this only affects the surface, the waves are limited in size and speed.

由於風的影響僅止於海平面，海浪的大小和流速因此有限。

But tsunamis are caused by energy originating underwater, from a volcanic eruption, a submarine landslide,

海嘯的形成則是源於水底下的能量，如火山爆發、 海底滑坡、

or, most commonly, an earthquake on the ocean floor caused when the tectonic plates of the Earth's surface slip, releasing a massive amount of energy into the water.

或最常見的，由地球表面的地殼板塊滑動時，釋放大量能量至水中而產生的海底地震。

This energy travels up to the surface, displacing water and raising it above the normal sea level, but gravity pulls it back down, which makes the energy ripple outwards horizontally.

這些能量傳達到海面上，排出大量的水，使水位高過一般海平面。然而，地心引力造成的拉力， 使得能量以水平方向波動。

Thus, the tsunami is born, moving at over 500 miles per hour.

海嘯因此而生，移動時速超過 500 英哩。

When it's far from shore, a tsunami can be barely detectable, since it moves through the entire depth of the water.

當海嘯離岸邊較遠時，很難被人察覺， 因為它是從整個深水層移動。

But when it reaches shallow water, something called "wave shoaling" occurs.

然而，當海嘯到達淺水域時，會出現「波浪淺化效應」。

Because there is less water to move through, this still massive amount of energy is compressed.

因為可移動的海水變少，不變的巨大能量被壓縮。

The wave's speed slows down, while its height rises to as much as 100 feet.

海浪的流速因此變慢，而浪高則可高達 100 英呎。

The word tsunami, Japanese for "harbor wave", comes from the fact that it only seems to appear near the coast.

海嘯一詞在日文意指「港口的波浪」， 因為它似乎只出現在靠近海岸的地方。

If the trough of a tsunami reaches shore first, the water will withdraw farther than normal before the wave hits, which can be misleadingly dangerous.

如果海嘯的波谷先抵達海岸，在浪打過來前，海水會退得比平時更遠， 會有誤導性的危險。

A tsunami will not only drown people near the coast, but level buildings and trees for a mile inland or more, especially in low-lying areas.

海嘯不僅會淹沒岸邊的人，內陸一英哩或以上的建築物和樹木也會被摧毀，尤其是低窪地區。

As if that weren't enough, the water then retreats, dragging with it the newly-created debris, and anything⏤or anyone⏤unfortunate enough to be caught in its path.

如果這還不夠糟，當海水退去時， 將一併帶走新的殘骸、 以及不幸在它所經之處的任何東西和人。

The 2004 Indian Ocean tsunami was one of the deadliest natural disasters in history, killing over 200,000 people throughout South Asia.

2004 年的印度洋海嘯是史上最致命的自然災害之一， 造成整個南亞地區超過 20 萬人喪命。

So, how can we protect ourselves against this destructive force of nature?

所以在面對大自然的破壞力時，我們該如何自保？

People in some areas have attempted to stop tsunamis with sea walls, flood gates, and channels to divert the water.

有些地區的人們試圖靠海堤、防洪閘門和渠道來疏導海水，藉以抵擋海嘯。

In 2011, a tsunami surpassed the flood wall protecting Japan's Fukushima Power Plant, causing a nuclear disaster in addition to claiming over 18,000 lives.

2011 年的一次海嘯，便越過用來保護日本福島核電廠的防洪牆，導致核災事故，同時帶走超過 1 萬 8 千多條人命。

Many scientists and policy-makers are, instead, focusing on early detection, monitoring underwater pressure and seismic activity, and establishing global communication networks for quickly distributing alerts.

許多科學家和決策者將重點放在早期預警系統， 監測水面下壓力及地震活動， 並建立全球通訊網絡以利快速發佈警報。

When nature is too powerful to stop, the safest course is to get out of its way.

當大自然的力量強大到無法阻擋時，最安全的作法就是逃離現場。

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【TED-Ed】3分鐘搞懂海嘯是怎麼發生的 (How tsunamis work - Alex Gendler)

massive

phenomenon

effective

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