La Croûte Terrestre se Fissure... Une Nouvelle ère Débute-t-Elle ?

Sympa

La croûte terrestre fait quelque chose d'assez intense—elle se casse lentement ! Les scientifiques disent que les plaques tectoniques, ces immenses pièces de puzzle qui composent la surface de notre planète, se déplacent et se fissurent plus que jamais. Cela pourrait signifier un grand changement dans la façon dont les continents et les océans sont formés sur des millions d'années. C'est comme si la Terre se préparait pour un tout nouveau chapitre. Ne vous inquiétez pas, cependant—ce n'est pas quelque chose qui arrive du jour au lendemain, pas de gouffres soudains ou de nouveaux océans demain. Cependant, c'est fascinant de penser que le sol sous nos pieds est toujours en mouvement, façonnant petit à petit l'avenir de la planète.  Animation créée par Sympa. ---------------------------------------------------------------------------------------- Musique par Epidemic Sound https://www.epidemicsound.com   Pour ne rien perdre de Sympa, abonnez-vous!: https://goo.gl/6E4Xna​ ---------------------------------------------------------------------------------------- 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 ----------------------------------------------------------------------------------------  Si tu en veux encore plus, fais un tour ici:  http://sympa-sympa.com

Transcript

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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