[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.14,0:00:10.66,Default,,0000,0000,0000,,In 479 BC, when Persian soldiers besieged
Dialogue: 0,0:00:10.68,0:00:12.64,Default,,0000,0000,0000,,the Greek city of Potidaea,
Dialogue: 0,0:00:12.66,0:00:14.94,Default,,0000,0000,0000,,the tide retreated\Nmuch farther than usual,
Dialogue: 0,0:00:14.97,0:00:17.53,Default,,0000,0000,0000,,leaving a convenient invasion route.
Dialogue: 0,0:00:17.55,0:00:19.55,Default,,0000,0000,0000,,But this wasn't a stroke of luck.
Dialogue: 0,0:00:19.58,0:00:21.10,Default,,0000,0000,0000,,Before they had crossed halfway,
Dialogue: 0,0:00:21.12,0:00:24.95,Default,,0000,0000,0000,,the water returned in a wave higher\Nthan anyone had ever seen,
Dialogue: 0,0:00:24.98,0:00:26.77,Default,,0000,0000,0000,,drowning the attackers.
Dialogue: 0,0:00:26.79,0:00:29.01,Default,,0000,0000,0000,,The Potiidaeans believed\Nthey had been saved
Dialogue: 0,0:00:29.03,0:00:30.71,Default,,0000,0000,0000,,by the wrath of Poseidon.
Dialogue: 0,0:00:30.73,0:00:32.24,Default,,0000,0000,0000,,But what really saved them
Dialogue: 0,0:00:32.26,0:00:35.80,Default,,0000,0000,0000,,was likely the same phenomenon\Nthat has destroyed countless others:
Dialogue: 0,0:00:35.82,0:00:36.92,Default,,0000,0000,0000,,a tsunami.
Dialogue: 0,0:00:36.94,0:00:39.79,Default,,0000,0000,0000,,Although tsunamis are commonly\Nknown as tidal waves,
Dialogue: 0,0:00:39.81,0:00:42.45,Default,,0000,0000,0000,,they're actually unrelated\Nto the tidal activity caused
Dialogue: 0,0:00:42.48,0:00:45.60,Default,,0000,0000,0000,,by the gravitational forces\Nof the Sun and Moon.
Dialogue: 0,0:00:45.62,0:00:49.24,Default,,0000,0000,0000,,In many ways, tsunamis are just\Nlarger versions of regular waves.
Dialogue: 0,0:00:49.26,0:00:51.14,Default,,0000,0000,0000,,They have a trough and a crest,
Dialogue: 0,0:00:51.16,0:00:53.28,Default,,0000,0000,0000,,and consist not of moving water,
Dialogue: 0,0:00:53.30,0:00:55.42,Default,,0000,0000,0000,,but the movement of energy through water.
Dialogue: 0,0:00:56.23,0:00:58.71,Default,,0000,0000,0000,,The difference is\Nin where this energy comes from.
Dialogue: 0,0:00:58.73,0:01:01.52,Default,,0000,0000,0000,,For normal ocean waves,\Nit comes from wind.
Dialogue: 0,0:01:01.55,0:01:05.81,Default,,0000,0000,0000,,Because this only affects the surface,\Nthe waves are limited in size and speed.
Dialogue: 0,0:01:05.84,0:01:09.22,Default,,0000,0000,0000,,But tsunamis are caused by energy\Noriginating underwater,
Dialogue: 0,0:01:09.25,0:01:10.81,Default,,0000,0000,0000,,from a volcanic eruption,
Dialogue: 0,0:01:10.83,0:01:12.48,Default,,0000,0000,0000,,a submarine landslide,
Dialogue: 0,0:01:12.50,0:01:15.40,Default,,0000,0000,0000,,or most commonly,\Nan earthquake on the ocean floor
Dialogue: 0,0:01:15.42,0:01:18.77,Default,,0000,0000,0000,,caused when the tectonic plates\Nof the Earth's surface slip,
Dialogue: 0,0:01:18.79,0:01:21.96,Default,,0000,0000,0000,,releasing a massive amount\Nof energy into the water.
Dialogue: 0,0:01:21.99,0:01:24.13,Default,,0000,0000,0000,,This energy travels up to the surface,
Dialogue: 0,0:01:24.15,0:01:27.93,Default,,0000,0000,0000,,displacing water and raising it above\Nthe normal sea level,
Dialogue: 0,0:01:27.95,0:01:29.75,Default,,0000,0000,0000,,but gravity pulls it back down,
Dialogue: 0,0:01:29.78,0:01:32.69,Default,,0000,0000,0000,,which makes the energy ripple\Noutwards horizontally.
Dialogue: 0,0:01:32.71,0:01:34.76,Default,,0000,0000,0000,,Thus, the tsunami is born,
Dialogue: 0,0:01:34.78,0:01:37.38,Default,,0000,0000,0000,,moving at over 500 miles per hour.
Dialogue: 0,0:01:37.40,0:01:40.97,Default,,0000,0000,0000,,When it's far from shore,\Na tsunami can be barely detectable
Dialogue: 0,0:01:40.99,0:01:43.65,Default,,0000,0000,0000,,since it moves through\Nthe entire depth of the water.
Dialogue: 0,0:01:43.67,0:01:47.51,Default,,0000,0000,0000,,But when it reaches shallow water,\Nsomething called wave shoaling occurs.
Dialogue: 0,0:01:47.53,0:01:49.76,Default,,0000,0000,0000,,Because there is less water\Nto move through,
Dialogue: 0,0:01:49.79,0:01:53.16,Default,,0000,0000,0000,,this still massive amount\Nof energy is compressed.
Dialogue: 0,0:01:53.18,0:01:55.09,Default,,0000,0000,0000,,The wave's speed slows down,
Dialogue: 0,0:01:55.12,0:01:58.09,Default,,0000,0000,0000,,while its height rises\Nto as much as 100 feet.
Dialogue: 0,0:01:58.11,0:02:01.61,Default,,0000,0000,0000,,The word tsunami,\NJapanese for "harbor wave,"
Dialogue: 0,0:02:01.63,0:02:04.68,Default,,0000,0000,0000,,comes from the fact that it only seems\Nto appear near the coast.
Dialogue: 0,0:02:04.70,0:02:07.86,Default,,0000,0000,0000,,If the trough of a tsunami\Nreaches shore first,
Dialogue: 0,0:02:07.88,0:02:09.93,Default,,0000,0000,0000,,the water will withdraw\Nfarther than normal
Dialogue: 0,0:02:09.95,0:02:11.12,Default,,0000,0000,0000,,before the wave hits,
Dialogue: 0,0:02:11.14,0:02:13.16,Default,,0000,0000,0000,,which can be misleadingly dangerous.
Dialogue: 0,0:02:13.18,0:02:16.21,Default,,0000,0000,0000,,A tsunami will not only drown\Npeople near the coast,
Dialogue: 0,0:02:16.23,0:02:19.55,Default,,0000,0000,0000,,but level buildings and trees\Nfor a mile inland or more,
Dialogue: 0,0:02:19.58,0:02:21.93,Default,,0000,0000,0000,,especially in low-lying areas.
Dialogue: 0,0:02:21.96,0:02:24.94,Default,,0000,0000,0000,,As if that weren't enough,\Nthe water then retreats,
Dialogue: 0,0:02:24.96,0:02:26.98,Default,,0000,0000,0000,,dragging with it the newly created debris,
Dialogue: 0,0:02:27.00,0:02:29.71,Default,,0000,0000,0000,,and anything, or anyone,\Nunfortunate enough
Dialogue: 0,0:02:29.74,0:02:31.14,Default,,0000,0000,0000,,to be caught in its path.
Dialogue: 0,0:02:31.17,0:02:33.89,Default,,0000,0000,0000,,The 2004 Indian Ocean tsunami
Dialogue: 0,0:02:33.91,0:02:36.57,Default,,0000,0000,0000,,was one of the deadliest\Nnatural disasters in history,
Dialogue: 0,0:02:36.60,0:02:40.24,Default,,0000,0000,0000,,killing over 200,000 people\Nthroughout South Asia.
Dialogue: 0,0:02:40.26,0:02:44.62,Default,,0000,0000,0000,,So how can we protect ourselves\Nagainst this destructive force of nature?
Dialogue: 0,0:02:44.65,0:02:46.36,Default,,0000,0000,0000,,People in some areas have attempted
Dialogue: 0,0:02:46.38,0:02:49.40,Default,,0000,0000,0000,,to stop tsunamis\Nwith sea walls, flood gates,
Dialogue: 0,0:02:49.42,0:02:51.17,Default,,0000,0000,0000,,and channels to divert the water.
Dialogue: 0,0:02:51.19,0:02:52.86,Default,,0000,0000,0000,,But these are not always effective.
Dialogue: 0,0:02:52.88,0:02:56.49,Default,,0000,0000,0000,,In 2011, a tsunami\Nsurpassed the flood wall
Dialogue: 0,0:02:56.52,0:02:58.73,Default,,0000,0000,0000,,protecting Japan's Fukushima Power Plant,
Dialogue: 0,0:02:58.75,0:03:00.86,Default,,0000,0000,0000,,causing a nuclear disaster
Dialogue: 0,0:03:00.88,0:03:03.43,Default,,0000,0000,0000,,in addition to claiming over 18,000 lives.
Dialogue: 0,0:03:04.24,0:03:08.54,Default,,0000,0000,0000,,Many scientists and policy makers\Nare instead focusing on early detection,
Dialogue: 0,0:03:08.57,0:03:11.73,Default,,0000,0000,0000,,monitoring underwater pressure\Nand seismic activity,
Dialogue: 0,0:03:11.75,0:03:14.09,Default,,0000,0000,0000,,and establishing global\Ncommunication networks
Dialogue: 0,0:03:14.12,0:03:15.71,Default,,0000,0000,0000,,for quickly distributing alerts.
Dialogue: 0,0:03:16.29,0:03:18.44,Default,,0000,0000,0000,,When nature is too powerful to stop,
Dialogue: 0,0:03:18.47,0:03:21.10,Default,,0000,0000,0000,,the safest course\Nis to get out of its way.