00:00Presented for more than 3 billion years,
00:02a part of the oldest terrestrial crust disintegrates today.
00:06While the continents seem to be immobile,
00:09they have undergone significant displacement and rearrangement over time.
00:13This phenomenon is made possible by tectonic activity,
00:16which causes the slow sliding of terrestrial plates,
00:19like the pieces of a vast jigsaw puzzle in motion.
00:22The most stable parts of these jigsaw pieces are designated by the name of cratons.
00:26These rock formations, both very ancient and extremely resistant,
00:31constitute the roots of the continents and ensure their cohesion.
00:35The North American craton, for example,
00:37encompasses a large part of the United States,
00:39about half of Canada,
00:40as well as the majority of Greenland.
00:43Scientists have identified nearly 35 major cratons around the world.
00:48Thanks to their robustness,
00:49these structures have remained practically immutable for hundreds of millions of years.
00:54However, in 2014,
00:56it was discovered that their allegedly indestructible character was not absolute.
01:01Some cratons have lost part of their solid roots
01:05as a result of specific geological processes,
01:08resulting in a weakening and fragilization of their structures.
01:12These observations suggest that additional tectonic modifications
01:16could compromise their stability.
01:18In 2024,
01:20scientists from the University of Geosciences of China
01:22have analyzed an ancient terrestrial mass called the North China Craton,
01:26or NCC in abbreviated.
01:29They wanted to know more about how some of the oldest rock regions on Earth
01:33could dislocate.
01:35This process of disintegration of the cratons is called decratonization.
01:40The NCC arouses particular interest
01:42because it consists of three main subdivisions,
01:45the Western Block,
01:46the Eastern Block,
01:48and the Trans-North China Orogene,
01:50an intermediate zone located between these two blocks.
01:53Studies have shown that during the Mesozoic Era,
01:56the Eastern Block lost its ancient roots
01:59as a result of intense tectonic and magmatic movements,
02:02known as tectonomagmatic events.
02:05Scientists have sought to understand precisely
02:08how the processes within the terrestrial mantle
02:11and the movements of the tectonic plates
02:13led to the disintegration of the NCC.
02:16They have developed four-dimensional models
02:18to illustrate the evolution of its shape over time,
02:21including the changes in its surface,
02:23the stretching of its layers,
02:25as well as the propagation of seismic waves within it.
02:28They found that part of the tectonic plate
02:30had sunk under the craton before receding.
02:33This return movement accompanied by a stretch
02:36led to a softening of the solid rock,
02:38making it unstable.
02:40This process would have begun about 200 million years ago,
02:43during the Jurassic Period,
02:45at the time when dinosaurs reigned on the planet.
02:48The North China Craton is not the only region
02:51affected by the phenomenon of decratonization.
02:54Other cratons, such as those in North America,
02:56South America,
02:57or even the Yangtze region in China,
03:00could have experienced similar evolutions.
03:03Researchers believe that this illustrates
03:05the progressive transformations of terrestrial continents
03:08over billions of years.
03:09In geology,
03:10no place seems completely safe from such upheavals,
03:14but this is not a reason to worry.
03:17You may not notice it,
03:18but our planet is constantly moving.
03:21A perfectly natural phenomenon.
03:23However,
03:24these movements can sometimes lead to spectacular transformations.
03:29In 2017,
03:30scientists officially announced that Zealandia
03:33could be considered a new continent.
03:36The continental plateaus of this mysterious territory
03:39lie at a depth of about 1,000 meters
03:42below sea level.
03:43The oceanic crust plunges even deeper,
03:46reaching 3,000 meters.
03:48Geologists have explored these depths
03:51to retrieve samples from the ocean floor.
03:54They discovered
03:56that unlike the neighboring oceanic crust
03:58composed of recent basaltic rocks,
04:01the crust surrounding New Zealand
04:03is made up of a mixture of ancient granite,
04:05limestone, and grey,
04:07characteristic of a continental crust.
04:10In addition,
04:11researchers have discovered a narrow strip of oceanic crust
04:14that separates Australia from the concealed territory of Zealandia.
04:17This proves that these two regions are distinct continents.
04:2185 million years ago,
04:23Zealandia separated from the supercontinent Gondwana.
04:26Millions of years later,
04:27the powerful Pacific plate,
04:29a true champion of tectonic plates,
04:31plunged under the continental crust of Zealandia.
04:34This is how the root of Zealandia,
04:36this connection to its continental crust,
04:38broke,
04:39and sank into the sea depths.
04:42And this is not the only new tectonic plate
04:44from this region of the world.
04:46120 million years ago,
04:47Australia and Antarctica
04:49were one and the same piece of land.
04:52After having borrowed different trajectories,
04:54Antarctica did not leave without taking anything.
04:57Today,
04:58in the Indian Ocean,
04:59there is an oceanic plateau that,
05:01in the past,
05:02was linked to another lost continent,
05:04the microcontinent of Kerguelen.
05:07Scientists estimate that it served as a terrestrial bridge
05:10between India and Antarctica.
05:12To better understand,
05:13just observe the Kerguelen archipelago,
05:15located in the South Indian Ocean.
05:18These islands are the last remains of this ancient continent.
05:21They have a cold climate
05:22and are covered with glaciers
05:24due to their proximity to Antarctica.
05:27However,
05:27in the past,
05:28the climate there was more temperate,
05:30with abundant rainfall.
05:33The fauna and flora there were undoubtedly similar
05:36to those currently found in tropical regions.
05:39Another lost continent,
05:40as for it,
05:41does not hide under the waves,
05:42but under Europe itself.
05:44It bears the name of Great Adria
05:46and collided with the European continent
05:49before starting to sink under it,
05:51about 100 million years ago.
05:53Currently,
05:54it is located under Italy,
05:56Greece and the Balkans.
05:58Its size,
05:58and even its shape,
05:59recalls that of Greenland,
06:01the largest island in the world.
06:03Great Adria is no longer visible today,
06:05but it has left many traces.
06:07Some of its parts have been integrated into the Alps,
06:10other fragments are found in Italy and present-day Croatia,
06:13on the other side of the Adriatic Sea.
06:16The limestone rocks from this ancient continent
06:18began to transform once buried
06:21under the European terrestrial mass.
06:23The intense heat
06:24and the pressure exerted for tens of millions of years
06:27have altered their structure.
06:29This is how limestone disappeared to the benefit of marble.
06:32Great Adria
06:33was not a solid land
06:34like the continent we know today,
06:37but rather
06:38an immense shallow underwater platform.
06:41Over time,
06:41sand, mud and various materials
06:44have accumulated on this platform
06:46to gradually turn into rock.
06:48Great Adria could have looked like Zealandia
06:51or the Keys of Florida,
06:53an island chain located in a shallow sea.
06:56Above the water,
06:57there were probably many islets and archipelagos,
07:00while under the waves,
07:01multicolored coral reefs
07:03were full of life.
07:05If you had lived there at that time
07:06and had diving equipment,
07:08this place would have offered an ideal setting
07:11for underwater exploration.
07:12With all the upheavals related to the craton,
07:15who knows,
07:16we could witness the emergence
07:18of a new continent in the future.
07:20The in-depth study of the terrestrial crust
07:22could shake our understanding
07:23of the history of the planet.
07:25In Copenhagen,
07:26scientists made a fascinating discovery
07:29about the real origin of Scandinavia.
07:31And it is not where we thought it was.
07:34After analyzing the sand and rocks
07:36from isolated regions of Finland,
07:39they concluded that the roots of Scandinavia
07:42actually came from Greenland,
07:44more than 3.75 billion years ago.
07:48This means that the current region
07:50of the Nordic countries,
07:51Denmark, Sweden, Norway and Finland,
07:54is actually 250 million years older
07:57than what scientists had previously imagined.
08:00This discovery was made possible
08:02thanks to tiny crystals called zircons,
08:05discovered in the sands of the Finnish rivers.
08:08By studying their chemical composition,
08:10researchers found that the age of the crystals
08:12corresponded to that of the rocks of Greenland
08:14and not Scandinavia.
08:16Scientists used specific techniques
08:19to analyze elements such as uranium,
08:21lead,
08:22lutetium
08:23and afnium,
08:24and thus determined that the rocky base
08:26of Scandinavia
08:28was probably detached from Greenland
08:30several billion years ago.
08:32A small grain of earth
08:34would then have drifted through the earth's surface
08:37for hundreds of millions of years.
08:39This fragment would have finally settled
08:41where Finland is today.
08:44Over time,
08:45new rocky layers formed around this grain,
08:48giving birth to the Scandinavia
08:50that we know on current maps.
08:52This same study could encourage us
08:54to review the way in which the continents of the Earth
08:57were initially formed.
08:59The most widespread theory suggests
09:01that continental crust
09:03began to develop
09:04as soon as the planet was formed,
09:06about 4.6 billion years ago.
09:09However,
09:10recent research shows
09:11that the growth of continents
09:12began only a billion years later.
09:14According to scientists,
09:16terrestrial continents
09:17may have emerged
09:19from small grains
09:21of ancient crust
09:22distributed in various parts of the planet.
09:25These grains developed over time,
09:27forming the current terrestrial masses.
09:29They are not only found in Scandinavia,
09:32but also in Australia,
09:33South Africa and India.
09:35However,
09:36researchers do not know
09:37if all these grains come from the same place,
09:40or if they developed independently
09:42in different regions.
09:43There is therefore a lot to discover,
09:45and it is essential
09:46that scientists
09:48continue their research
09:49to determine
09:50whether all these ancient grains
09:51are connected.
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