[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:07.14,0:00:10.72,Default,,0000,0000,0000,,In 479 BC, when Persian soldiers beseiged
Dialogue: 0,0:00:10.72,0:00:12.83,Default,,0000,0000,0000,,the Greek city of Potidaea,
Dialogue: 0,0:00:12.83,0:00:15.14,Default,,0000,0000,0000,,the tide retreated much farther than usual,
Dialogue: 0,0:00:15.14,0:00:17.96,Default,,0000,0000,0000,,leaving a convenient invasion route.
Dialogue: 0,0:00:17.96,0:00:19.81,Default,,0000,0000,0000,,But this wasn't a struck of luck.
Dialogue: 0,0:00:19.81,0:00:21.34,Default,,0000,0000,0000,,Before they had crossed half way,
Dialogue: 0,0:00:21.34,0:00:23.05,Default,,0000,0000,0000,,the water returned in a wave higher
Dialogue: 0,0:00:23.05,0:00:25.14,Default,,0000,0000,0000,,than anyone had ever seen,
Dialogue: 0,0:00:25.14,0:00:27.06,Default,,0000,0000,0000,,drowning the attackers.
Dialogue: 0,0:00:27.06,0:00:29.15,Default,,0000,0000,0000,,The Potiidaeans believed they had been saved
Dialogue: 0,0:00:29.15,0:00:31.21,Default,,0000,0000,0000,,by the wrath of Poseidon.
Dialogue: 0,0:00:31.21,0:00:32.85,Default,,0000,0000,0000,,But what really saved them was likely
Dialogue: 0,0:00:32.85,0:00:35.82,Default,,0000,0000,0000,,the same phenomenon that has destroyed countless others:
Dialogue: 0,0:00:35.82,0:00:37.10,Default,,0000,0000,0000,,a tsunami.
Dialogue: 0,0:00:37.10,0:00:39.81,Default,,0000,0000,0000,,Although tsunamis are commenly known as tidal waves,
Dialogue: 0,0:00:39.81,0:00:42.48,Default,,0000,0000,0000,,they're actually unrelated to the tidal activity caused
Dialogue: 0,0:00:42.48,0:00:45.62,Default,,0000,0000,0000,,by the gravitational forces of the sun and moon.
Dialogue: 0,0:00:45.62,0:00:48.10,Default,,0000,0000,0000,,In many ways, tsunamis are just larger versions
Dialogue: 0,0:00:48.10,0:00:49.55,Default,,0000,0000,0000,,of regular waves.
Dialogue: 0,0:00:49.55,0:00:51.33,Default,,0000,0000,0000,,They have a trough and a crest,
Dialogue: 0,0:00:51.33,0:00:53.30,Default,,0000,0000,0000,,and consist not of moving water,
Dialogue: 0,0:00:53.30,0:00:56.38,Default,,0000,0000,0000,,but the movement of energy through water.
Dialogue: 0,0:00:56.38,0:00:58.88,Default,,0000,0000,0000,,The difference is in where this energy comes from.
Dialogue: 0,0:00:58.88,0:01:00.19,Default,,0000,0000,0000,,For normal ocean waves,
Dialogue: 0,0:01:00.19,0:01:01.79,Default,,0000,0000,0000,,it comes from wind.
Dialogue: 0,0:01:01.79,0:01:03.57,Default,,0000,0000,0000,,Because this only affects the surface,
Dialogue: 0,0:01:03.57,0:01:06.02,Default,,0000,0000,0000,,the waves are limited in size and speed.
Dialogue: 0,0:01:06.02,0:01:07.62,Default,,0000,0000,0000,,But tsunamis are caused by energy
Dialogue: 0,0:01:07.62,0:01:09.60,Default,,0000,0000,0000,,originating underwater,
Dialogue: 0,0:01:09.60,0:01:10.83,Default,,0000,0000,0000,,from a volcanic erruption,
Dialogue: 0,0:01:10.83,0:01:12.50,Default,,0000,0000,0000,,a submarine landslide,
Dialogue: 0,0:01:12.50,0:01:13.90,Default,,0000,0000,0000,,or most commonly,
Dialogue: 0,0:01:13.90,0:01:15.61,Default,,0000,0000,0000,,an earthquake on the ocean floor
Dialogue: 0,0:01:15.61,0:01:18.79,Default,,0000,0000,0000,,caused when the tectonic plates of the Earth's surface slip,
Dialogue: 0,0:01:18.79,0:01:21.99,Default,,0000,0000,0000,,releasing a massive amount of energy into the water.
Dialogue: 0,0:01:21.99,0:01:24.15,Default,,0000,0000,0000,,This energy travels up to the surface,
Dialogue: 0,0:01:24.15,0:01:26.12,Default,,0000,0000,0000,,displacing water and raising it above
Dialogue: 0,0:01:26.12,0:01:27.95,Default,,0000,0000,0000,,the normal sea level,
Dialogue: 0,0:01:27.95,0:01:29.78,Default,,0000,0000,0000,,but gravity pulls it back down,
Dialogue: 0,0:01:29.78,0:01:33.13,Default,,0000,0000,0000,,which makes the energy rippel outwards horizontally.
Dialogue: 0,0:01:33.13,0:01:34.78,Default,,0000,0000,0000,,Thus, the tsunami is born,
Dialogue: 0,0:01:34.78,0:01:37.58,Default,,0000,0000,0000,,moving at over 500 miles per hour.
Dialogue: 0,0:01:37.58,0:01:38.95,Default,,0000,0000,0000,,When it's far from shore,
Dialogue: 0,0:01:38.95,0:01:40.99,Default,,0000,0000,0000,,a tsunami can be barley detectable
Dialogue: 0,0:01:40.99,0:01:43.67,Default,,0000,0000,0000,,since it moves through the entire depth of the water.
Dialogue: 0,0:01:43.67,0:01:45.08,Default,,0000,0000,0000,,But when it reaches shallow water,
Dialogue: 0,0:01:45.08,0:01:47.53,Default,,0000,0000,0000,,something called wave shoaling occurs.
Dialogue: 0,0:01:47.53,0:01:49.79,Default,,0000,0000,0000,,Because there is less water to move through,
Dialogue: 0,0:01:49.79,0:01:53.27,Default,,0000,0000,0000,,this still massive amount of energy is compressed.
Dialogue: 0,0:01:53.27,0:01:55.12,Default,,0000,0000,0000,,The wave's speed slows down,
Dialogue: 0,0:01:55.12,0:01:58.55,Default,,0000,0000,0000,,while its height rises to as much as 100 feet.
Dialogue: 0,0:01:58.55,0:01:59.56,Default,,0000,0000,0000,,The word tsunami,
Dialogue: 0,0:01:59.56,0:02:01.63,Default,,0000,0000,0000,,Japanese for "harbor wave",
Dialogue: 0,0:02:01.63,0:02:03.76,Default,,0000,0000,0000,,comes from the fact that it only seems to appear
Dialogue: 0,0:02:03.76,0:02:05.25,Default,,0000,0000,0000,,near the coast.
Dialogue: 0,0:02:05.25,0:02:07.88,Default,,0000,0000,0000,,If the trough of a tsunami reaches shore first,
Dialogue: 0,0:02:07.88,0:02:09.92,Default,,0000,0000,0000,,the water will withdraw farther than normal
Dialogue: 0,0:02:09.92,0:02:13.07,Default,,0000,0000,0000,,before the wave hits, which can be misleadingly dangerous.
Dialogue: 0,0:02:13.07,0:02:16.32,Default,,0000,0000,0000,,A tsunami will not only drown people near the coast,
Dialogue: 0,0:02:16.32,0:02:20.13,Default,,0000,0000,0000,,but level buildings and trees for a mile inland or more,
Dialogue: 0,0:02:20.13,0:02:22.16,Default,,0000,0000,0000,,especially in low-lying areas.
Dialogue: 0,0:02:22.16,0:02:23.45,Default,,0000,0000,0000,,As if that weren't enough,
Dialogue: 0,0:02:23.45,0:02:24.96,Default,,0000,0000,0000,,the water then retreats,
Dialogue: 0,0:02:24.96,0:02:27.21,Default,,0000,0000,0000,,dragging with it the newly created debris,
Dialogue: 0,0:02:27.21,0:02:29.74,Default,,0000,0000,0000,,and anything, or anyone, unfortunate enough
Dialogue: 0,0:02:29.74,0:02:31.48,Default,,0000,0000,0000,,to be caught in its path.
Dialogue: 0,0:02:31.48,0:02:33.91,Default,,0000,0000,0000,,The 2004 Indian Ocean tsunami
Dialogue: 0,0:02:33.91,0:02:37.00,Default,,0000,0000,0000,,was one of the deadliest natural disasters in history,
Dialogue: 0,0:02:37.00,0:02:40.18,Default,,0000,0000,0000,,killing over 200,000 people throughout South Asia.
Dialogue: 0,0:02:40.18,0:02:42.08,Default,,0000,0000,0000,,So how can we protect ourselves
Dialogue: 0,0:02:42.08,0:02:44.65,Default,,0000,0000,0000,,against this destructive force of nature?
Dialogue: 0,0:02:44.65,0:02:46.38,Default,,0000,0000,0000,,People in some areas have attempted
Dialogue: 0,0:02:46.38,0:02:50.21,Default,,0000,0000,0000,,to stop tsunamis with sea walls, flood gate,
Dialogue: 0,0:02:50.21,0:02:51.72,Default,,0000,0000,0000,,and channels to divert the water.
Dialogue: 0,0:02:51.72,0:02:53.28,Default,,0000,0000,0000,,But these are not always effective.
Dialogue: 0,0:02:53.28,0:02:56.16,Default,,0000,0000,0000,,In 2011, a tsunami surpassed the flood wall
Dialogue: 0,0:02:56.16,0:02:58.88,Default,,0000,0000,0000,,protecting Japan's Fukushima Power Plant,
Dialogue: 0,0:02:58.88,0:03:01.47,Default,,0000,0000,0000,,causing a nuclear disaster in addition to claiming
Dialogue: 0,0:03:01.47,0:03:04.14,Default,,0000,0000,0000,,over 18,000 lives.
Dialogue: 0,0:03:04.14,0:03:06.47,Default,,0000,0000,0000,,Many scientists and policy makers are instead
Dialogue: 0,0:03:06.47,0:03:08.57,Default,,0000,0000,0000,,focusing on early detection,
Dialogue: 0,0:03:08.57,0:03:11.75,Default,,0000,0000,0000,,monitoring underwater pressure and seismic activity,
Dialogue: 0,0:03:11.75,0:03:14.12,Default,,0000,0000,0000,,and establishing global communication networks
Dialogue: 0,0:03:14.12,0:03:15.74,Default,,0000,0000,0000,,for quickly distributing alerts.
Dialogue: 0,0:03:15.74,0:03:18.47,Default,,0000,0000,0000,,When nature is too powerful to stop,
Dialogue: 0,0:03:18.47,0:03:21.88,Default,,0000,0000,0000,,the safest course is to get out of its way.