Saviez-vous que la Terre avait autrefois des continents qui n'existent plus aujourd'hui ? Il y a des millions d'années, il y avait d'immenses masses terrestres qui ont depuis disparu, soit en sombrant sous l'océan, soit en se fragmentant pour former de nouveaux continents. L'un de ces continents perdus s'appelle Zealandia, dont la majeure partie est maintenant submergée sous l'océan Pacifique ! Il y en a aussi un célèbre appelé Gondwana, qui finit par se diviser en Afrique, Amérique du Sud, Australie et Antarctique. Ces changements se produisent en raison de la tectonique des plaques, où la croûte terrestre se déplace au fil du temps. C'est comme un puzzle géant qui ne cesse de bouger, et nous découvrons encore des morceaux de cette histoire ancienne ! Animation créée par Sympa.
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Musique par Epidemic Sound https://www.epidemicsound.com
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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:
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FunTranscript
00:00Do you know the number of continents on Earth?
00:04The answer seems obvious, 6.
00:07But for a moment, doesn't Europe and Asia form a vast set called Eurasia?
00:12This could seem to be the case if we observe a map of the world.
00:15However, scientists have a different approach.
00:18They do not just consider the emerged lands.
00:20Geologists also examine the composition of the rocks that form the continents.
00:24By adopting their perspective, the number of continents can even increase.
00:28Lost continents are therefore not a legend.
00:31Some have existed, or at least, have existed in the past.
00:34And these continents are not always submerged.
00:37They are sometimes buried under other emerged lands.
00:40Surprise!
00:41Researchers have recently discovered a continent of this type, the Great Adria.
00:46This may be familiar to you.
00:48Indeed, there is a link with the Adriatic Sea.
00:51This disappeared continent is entirely buried under Europe.
00:54It collided with this one and began to sink about 140 million years ago.
01:00Nowadays, it lies under Italy, Greece and the Balkans.
01:04Its size and shape are comparable to that of Greenland, the largest island in the world.
01:09But how did geologists identify the Great Adria?
01:12Although it is no longer visible, it has left traces.
01:16Fragments have been found integrated into the Alps,
01:19while others have been incorporated into Italy and present-day Croatia, on the other side of the Adriatic Sea.
01:25The limestone rocks of this disappeared continent have undergone transformations once buried under Europe.
01:31Millions of years of intense heat and enormous pressures have modified their structure.
01:36The limestone has given way to marble.
01:38The Greek and Roman temples that you admire during your holidays have been built with the same marble,
01:43heritage of a continent long forgotten.
01:47The Great Adria has thus remained hidden for millennia.
01:51Yet other disappeared continents were within view.
01:55Do you know the 7th continent of the Earth, Zealandia?
01:58Probably not, as it lies under the Pacific Ocean.
02:01Today, 35% of this continent is submerged.
02:05Can you guess its exact location?
02:07Its name gives you a clue.
02:09It is located under New Zealand.
02:11If you google maps, you can discern its outline.
02:15Visible as a zone of a lighter blue, extending from New Caledonia to New Zealand.
02:21In the past, this elevation exceeded sea level and represented about two-thirds of Australia,
02:27more than double the area of the Great Adria.
02:30We can locate Zealandia today because it has not been submerged too deeply.
02:36It is also the best way to identify other lost continents.
02:40Imagine the Earth without its oceans.
02:42The seabed is not uniform.
02:44It is composed of mountains and trenches.
02:47We could plunge Mount Everest into the deepest of them, the Marian Falls.
02:52And it would remain another 2,000 meters up to sea level.
02:56This extreme depth results from a geological process called subduction,
03:01where the Pacific plate sank under the Philippine plate.
03:05The earth's crust is made up of plates floating in a fusion rock mantle.
03:10When they collide, one sinks while the other rises.
03:14This is how the Great Adria ended under the European continent.
03:18Our planet is in perpetual motion.
03:20But we do not notice this phenomenon because it takes place deeply under our feet.
03:24120 million years ago, Australia and Antarctica formed a single and same territory.
03:29Yes, the coldest regions and one of the warmest places on Earth were once united.
03:34Antarctica separated from Australia, but it did not go empty-handed.
03:39Today, an oceanic plateau is located in the Indian Ocean.
03:43The term plateau means a flat, elevated area of land.
03:46And this plateau bears the evocative name of Broken Ridge,
03:49a bit like a Hollywood movie title.
03:52In the past, it was linked to another lost continent, the microcontinent of Kerguelen,
03:57and would have constituted a terrestrial bridge between India and Antarctica.
04:01But what was the aspect of this territory?
04:03The answer could be found in this small archipelago located in the Indian Ocean,
04:07the Kerguelen Islands.
04:09These islands are the remains of the ancient terrestrial mass.
04:13Their climate is cold, and they shelter glaciers due to their proximity to Antarctica.
04:19However, at the time, the climate had to be temperate, with abundant rainfall.
04:24The fauna and flora of this lost continent were probably similar to those of the current tropical regions,
04:30and its landscape had to resemble that of New Zealand.
04:35Speaking of this region, can you guess which continent the island state of Madagascar once belonged to?
04:41If you answered Africa, you are wrong.
04:44But no one will blame you.
04:46Look at the top right of the map.
04:49The right answer is India.
04:51About 120 million years ago, it detached from the African continent and headed northeast.
04:57Madagascar did not succeed in following and found itself as an island off the southeast coast of Africa.
05:03However, traces of an even larger terrestrial mass have been discovered.
05:08Mauritius' lost continent.
05:11Scientists have found remains of this ancient land under the island of Mauritius.
05:15Today, it is a fairly popular tourist destination,
05:18but millions of years ago, it was a real hot spot sprinkled with volcanoes.
05:23Scientists were able to find the remains of Mauritius thanks to a mineral, zircon, present in the volcanic rocks.
05:29This lost land once covered an area from the island of Mauritius to the west coast of India.
05:35If this territory existed today, it would offer a rich combination of Indian and African cultures,
05:40with local dishes that are certainly spicy.
05:43Speaking of spices, have you ever tasted Indonesian cuisine?
05:46Only 50,000 years ago, Southeast Asia had a very different face.
05:51Sumatra, Borneo, Java, and even Australia did not yet exist in their current form.
05:57There were then two continental masses, Sunda and Sahul, separated by a deep oceanic pit.
06:04On one side, there was the extension of the Asian continent, Sunda, and on the other, the great Australia, Sahul.
06:12At that time, Bali was still located at the southern end of Asia.
06:17Biologists were among the first to observe this separation,
06:21because the species developed distinctively on Sunda and Sahul.
06:26This is why Australia houses unique animals such as kangaroos, wombats, and ornithorhynchus.
06:32Did you know that a giant kangaroo used to live in New Guinea?
06:36This is explained by the fact that a terrestrial bridge connected Australia to the end of the last glaciation.
06:42Today, the two islands are separated by the Torres Strait, which is relatively shallow, with barely 20 meters of water.
06:49This reminds us that this region used to form a single continental mass called Sahul.
06:55Another oceanic strait barely 50 meters deep separates North America from Asia.
07:00The Bering Strait is now located at the site of the former Bering Sea.
07:04This former terrestrial mass was not particularly extensive, stretching about 1,600 km north to south,
07:11which is only a third of the distance between Los Angeles and New York.
07:15The Bering Sea was of additional importance.
07:18During the glaciations, it formed a bridge between the continents.
07:21At that time, the sea levels were below 90 meters today.
07:26If the water level had dropped further,
07:29it would have been possible to walk from Cape Good Hope in Africa to Cape Horn in South America.
07:35So this is a truly exceptional hiking route.
07:39Today, it is possible to take a plane to go almost everywhere in the world.
07:44Has the globe ever seemed so small?
07:46Well, to tell the truth, it has been.
07:48About two to three hundred million years ago, all continents formed only one supercontinent, called Pangaea.
07:55Its name, which comes from Greek, means the whole Earth.
07:59But Pangaea began to fragment.
08:01The biggest gap formed between America on one side and Europe, as well as Africa on the other.
08:07The sea water quickly invaded this space, giving birth to the Atlantic Ocean.
08:12This process is far from over.
08:14While you are watching this video,
08:16North America is gradually moving away from Europe by 2 or 3 centimeters per year.
08:21This may seem little compared to the average lifespan of a human being who is about 70 years old.
08:26However, in the long run, all continents will reconnect, forming a new supercontinent.
08:31This would not be the first time in the history of the Earth.
08:34But personally, I will not wait for this to happen.