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.
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