Il existe des preuves qu'un tremblement de terre a en fait duré plus de 200 ans ! Ce n'était pas votre secousse typique - c'était un événement super lent le long de la zone de subduction. Les scientifiques ont découvert cela en étudiant les sédiments anciens et ont trouvé des signes d'activité sismique continue sur des siècles. Imaginez un grondement constant sous vos pieds qui ne s'arrête jamais. C'est une découverte époustouflante qui change notre manière de penser aux tremblements de terre ! Examinons cela et d'autres phénomènes naturels qui ont duré plus longtemps qu'ils n'auraient dû. Animation créée par Sympa.
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Musique par Epidemic Sound https://www.epidemicsound.com
Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna
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Nos réseaux sociaux :
Facebook: https://www.facebook.com/sympasympacom/
Instagram: https://www.instagram.com/sympa.officiel/
Stock de fichiers (photos, vidéos et autres):
https://www.depositphotos.com
https://www.shutterstock.com
https://www.eastnews.ru
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Si tu en veux encore plus, fais un tour ici:
http://sympa-sympa.com
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FunTranscript
00:00The most powerful earthquake ever recorded in the east of the Mississippi River,
00:05which occurred more than 200 years ago, is never finished, according to some scientists.
00:10Most earthquakes last from a few seconds to a few minutes,
00:14and the official record so far is a silent earthquake in Sumatra that lasted 32 years.
00:19This event of slow gliding triggered a massive earthquake and a tsunami.
00:23So, if it's true that the earthquake in New Madrid is still sending replicas,
00:28we'll have a new name for this sad list.
00:31The earthquake began in December 1811,
00:35by a powerful quake in a small part of northeastern Arkansas.
00:39The quakes were felt at a distance of 1,600 km from the White House,
00:44and the towers' bells rang in Boston, even further away.
00:47It even made the powerful Mississippi flow upside down for a few minutes
00:51on new waterfalls formed by the displaced soil.
00:54The city of New Madrid, in Missouri, completely disappeared in the disaster.
01:00The earth would not remain still until the end of January of the following year,
01:04when things became serious again.
01:07A huge earthquake struck, this time near the Ohio River junction and the Mississippi Rivers,
01:13right in the heel of the Missouri Bottom.
01:16Geologists think it was a rupture on the New Madrid fault,
01:20putting even more pressure on the Real Foot fault nearby.
01:23Just when people thought it couldn't get any worse,
01:26two more weeks of tremors passed,
01:28and the Real Foot fault sank deep under New Madrid.
01:31In Tennessee, about 24 km south of New Madrid,
01:35the rise of the ground created the Real Foot Lake.
01:38Steamboats sailed along the river,
01:41with thousands of floating trees and hectares of wood torn by the earthquake.
01:45In St. Louis, Missouri, which is 257 km away,
01:50the buildings were seriously damaged,
01:52and the chimneys fell in Cincinnati, Ohio, 644 km away.
01:58People up to Montreal, Canada, more than 1,600 km away,
02:03felt the earthquake.
02:07Seismologists have recorded about 200 small earthquakes
02:11in the New Madrid seismic zone each year since 1974.
02:16Some researchers estimate that up to 30% of these
02:20were replicas of these great earthquakes that occurred in 1811 and 1812.
02:26In some parts of the United States, where there is not much tectonic activity,
02:30these replicas could continue to grow for years,
02:33perhaps even centuries, after the great earthquakes.
02:36The replicas are the way the Earth releases all this accumulated tension
02:40from the main earthquake.
02:42When the ground shakes because of the first earthquake,
02:45it exerts a ton of pressure on the nearby rocks.
02:48And when these rocks can no longer withstand this pressure,
02:51they crack, causing even more shakings,
02:54this is the replica.
02:55They can be quite intense, especially just after the main earthquake,
02:59but they weaken over time.
03:03All scientists do not agree that contemporary earthquakes
03:07have a link with those of 200 years ago.
03:10We mainly associate the faults with these lines where the terrestrial plates meet,
03:14but there is an entire network of these just below the center of the North American plate.
03:19They are like relics dating from 750 million years ago,
03:22when North America was part of a supercontinent called Rodinia.
03:26When Rodinia began to dislocate, it left behind its rifts,
03:30weak points of the terrestrial crust that extend in depth,
03:34under modern Midwest.
03:36This could explain the seismic activity.
03:38An international team of geologists decided to take a new look
03:42at three major earthquakes that shook North America,
03:46and put an end to the debate.
03:48They used a new mathematical method called the nearest neighbor.
03:52It states that if earthquakes are too close in space,
03:56time and magnitude could be considered as background independent events,
04:01then we suppose that one triggered the other.
04:04According to the way you look at the figures,
04:06between 10 and 65% of recent earthquakes in the region
04:10could be replicas of these historical earthquakes.
04:13And a huge earthquake that struck Charleston in South Carolina
04:17at the end of the 19th century
04:19could explain up to 72% of earthquakes in the region since then.
04:24But not all places are the same, so the scientific debate continues.
04:31In 1774, the British explorer James Cook noticed a glow in the distance.
04:37It was the volcano of Mount Yassur, Yassur, in Vanuatu.
04:40This ugly boy has been spitting lava and ashes since then,
04:44and it is very likely that he has been doing this for much longer.
04:47The volcano has been on alert since October 2016,
04:50which means that things are really unstable there.
04:53They even delimited a radius of 610 meters around the crater
04:57to keep people safe.
04:59There were low to moderate intensity eruptions,
05:02projecting ashes, gases and steam,
05:05and a few more major explosions
05:07that propelled materials out of the crater.
05:10Satellite images detected some hot spots of sulfur dioxide panning,
05:14showing that Yassur is still a big storm there.
05:18Stromboli, one of the volcanic islands near Sicily,
05:21officially holds the Guinness World Record
05:24as the longest erupting volcano.
05:27It has been a fire show for more than 2,400 years in a row.
05:31The ancient sailors nicknamed it the lighthouse of the Mediterranean.
05:35Most of the time, Stromboli is content to spit splashes.
05:39But from time to time, it spills lava
05:42or projects moderately high fountains.
05:45Sometimes, you could also see eruptions caused by steam.
05:51More than 200 million years ago,
05:53the world underwent a major transformation,
05:56with not one, not two,
05:58but four massive volcanic eruptions that changed everything.
06:01All this happened in Wrangelia,
06:03a large piece of land that was once a supermassive volcano
06:07stretching across what is now British Columbia and Alaska.
06:11This volcanic activity could have helped dinosaurs
06:14to go from the size of a kitten
06:16to that of the giants we saw in Jurassic Park.
06:19It triggered a rainy season of 2 million years.
06:23It made the whole world hot and humid,
06:26and the dinosaurs simply loved it.
06:29Researchers dug deep into the layers of sediment
06:32under an old lake in China to discover its secrets.
06:35They found traces of volcanic ash and mercury,
06:38clear signs of these epic eruptions.
06:41There were carbon signatures showing huge peaks of carbon dioxide levels,
06:45making the atmosphere hot and the rain falling down.
06:49All this happened in four distinct impulses,
06:52each triggered by these monstrous volcanic explosions.
06:57There is a place in a national park not far from Sydney, Australia,
07:01where a fire has been raging deeply underground for at least 6,000 years.
07:06It is called Burning Mountain,
07:08and it is a layer of coal fire
07:10that burns its way through a layer of coal under the surface of the earth.
07:14Once these underground fires begin,
07:16they are almost impossible to put out.
07:19This ball of fire is up to 9 meters wide
07:22and is extremely hot.
07:24But there is no flame. It is burning.
07:26The fire progresses slowly at a rate of about 1 meter per year.
07:30A local farmer saw it for the first time in the 19th century
07:34and believed it to be a volcano.
07:36People who have lived here since the Enlightenment
07:38believe that this place is sacred.
07:40They used it to cook and make tools,
07:43and say that it was born from the tears of a widow
07:45or the torch of a hero.
07:47But experts think it could be a flash of lightning,
07:50a piece of coal that heats up like a summer barbecue
07:52because of the interaction with oxygen.
07:57Some say that it could have burned
07:59long before the time when dinosaurs roamed the earth.
08:02No one knows exactly how long this mountain will burn
08:05or in which direction it will move.
08:08At the moment, coal has enough oxygen to burn for centuries,
08:12even millennia, without human intervention.
08:15The fire heats the mountain like a gigantic oven,
08:18making it crack and crumble,
08:20inviting more oxygen to feed on it.
08:23Even if humans decide to act,
08:25these fires of coal veins require water trucks
08:28and liquid nitrogen to control them.
08:30Several years ago,
08:31explorers noticed that the embers were approaching
08:34a cliff overlooking a small river.
08:36And depending on what the coal vein decides to do next,
08:39we could see spectacular changes here
08:41in the decades to come.
08:43There could be flames there with much more heat,
08:46and the coal veins could sink,
08:48extinguish and extinguish.