Activa JavaScript para disfrutar de los vídeos de la Mediateca.
HOW TSUNAMIS WORK - Contenido educativo
Ajuste de pantallaEl ajuste de pantalla se aprecia al ver el vídeo en pantalla completa. Elige la presentación que más te guste:
In 479 BC, when Persian soldiers besieged the Greek city of Potidaea, the tide retreated
00:00:00
much farther than usual, leaving a convenient invasion route.
00:00:13
But this wasn't a stroke of luck.
00:00:17
Before they had crossed halfway, the water returned in a wave higher than anyone had
00:00:19
ever seen, drowning the attackers.
00:00:23
The Potidaeans believed they had been saved by the wrath of Poseidon, but what really
00:00:26
saved them was likely the same phenomenon that has destroyed countless others, a tsunami.
00:00:31
Although tsunamis are commonly known as tidal waves, they're actually unrelated to the tidal
00:00:36
activity caused by the gravitational forces of the sun and moon. In many ways, tsunamis are just
00:00:41
larger versions of regular waves. They have a trough and a crest, and consist not of moving
00:00:47
water, but the movement of energy through water. The difference is in where this energy comes from.
00:00:52
For normal ocean waves, it comes from wind.
00:00:58
Because this only affects the surface, the waves are limited in size and speed.
00:01:01
But tsunamis are caused by energy originating underwater,
00:01:05
from a volcanic eruption, a submarine landslide,
00:01:09
or, most commonly, an earthquake on the ocean floor,
00:01:12
caused when the tectonic plates of the Earth's surface slip,
00:01:15
releasing a massive amount of energy into the water.
00:01:18
This energy travels up to the surface,
00:01:21
displacing water and raising it above the normal sea level.
00:01:24
But gravity pulls it back down, which makes the energy ripple outwards horizontally.
00:01:27
Thus, the tsunami is born, moving at over 500 miles per hour.
00:01:33
When it's far from shore, a tsunami can be barely detectable,
00:01:37
since it moves through the entire depth of the water.
00:01:40
But when it reaches shallow water, something called wave shoaling occurs.
00:01:43
Because there is less water to move through, this still massive amount of energy is compressed.
00:01:47
The wave's speed slows down while its height rises to as much as 100 feet.
00:01:53
The word tsunami, Japanese for harbor wave, comes from the fact that it only seems to appear near the coast.
00:01:58
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.
00:02:04
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.
00:02:13
As if that weren't enough, the water then retreats, dragging with it the newly created
00:02:21
debris and anything or anyone unfortunate enough to be caught in its path. The 2004
00:02:26
Indian Ocean tsunami was one of the deadliest natural disasters in history,
00:02:32
killing over 200,000 people throughout South Asia. So how can we protect ourselves against
00:02:37
this destructive force of nature? People in some areas have attempted to stop tsunamis with sea
00:02:42
walls, floodgates, and channels to divert the water. But these are not always effective. In 2011,
00:02:47
a tsunami surpassed the flood wall protecting Japan's Fukushima power plant, causing a nuclear
00:02:54
disaster in addition to claiming over 18,000 lives. Many scientists and policymakers are
00:02:59
instead focusing on early detection, monitoring underwater pressure and seismic activity,
00:03:06
and establishing global communication networks for quickly distributing alerts.
00:03:11
When nature is too powerful to stop, the safest course is to get out of its way.
00:03:15
- Subido por:
- Alicia M.
- Licencia:
- Dominio público
- Visualizaciones:
- 87
- Fecha:
- 17 de marzo de 2022 - 16:33
- Visibilidad:
- Público
- Centro:
- IES LA SENDA
- Duración:
- 03′ 37″
- Relación de aspecto:
- 1.78:1
- Resolución:
- 1920x1080 píxeles
- Tamaño:
- 95.56 MBytes