Saviez-vous qu'il existe tout un monde antique enterré sous la glace de l'Antarctique ? Les scientifiques ont découvert les vestiges d'écosystèmes préhistoriques, y compris des rivières et des lacs, emprisonnés sous des kilomètres de surface gelée. C'est comme un fantôme du passé lointain de la Terre, conservé dans des capsules temporelles glacées depuis des millions d'années. Ce monde caché a peut-être autrefois abondé de vie, à l'époque où l'Antarctique était luxuriant et verdoyant au lieu du désert glacé qu'il est aujourd'hui. La partie la plus fascinante ? L'explorer pourrait nous donner des indices sur la manière dont la vie s'adapte à des conditions extrêmes—sur Terre et peut-être même sur d'autres planètes. C'est incroyable de penser que sous toute cette glace se trouve un instantané d'un monde que nous n'avons jamais connu ! Animation créée par Sympa.
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FunTranscript
00:00The South Pole is not limited to mangroves and an infinite extension of snow.
00:04A ghostly world is buried there.
00:06Observe, it is located precisely here on the Earth's globe.
00:10Do not confuse Antarctica with the Arctic, which is at the top of our maps,
00:14and much smaller and, let's be honest, much less enigmatic.
00:18The Antarctic ice cap measures 2 to 5 km in thickness,
00:22the equivalent of 16 Eiffel Towers stacked on top of each other.
00:26This immense layer of ice masks the real reliefs and contours of the Antarctic soil.
00:31Our knowledge of this mysterious continent remains limited,
00:35largely due to the omnipresence of ice and snow.
00:38We still do not know the exact shape and precise dimensions of this land.
00:43Mapping the Antarctic without titanic tools is a task of extreme complexity.
00:48However, satellites have learned to penetrate the ice thanks to their point cameras.
00:53Today, we know that an ancient, colossal and spectacular landscape
00:57rests under this snow, a kind of ghost of the past.
01:02About 90 million years ago, Antarctica was a much warmer place.
01:07This territory housed a luxurious tropical forest, rich in plant and life-eating species.
01:13Rivers flowed there, drawing an amazing landscape.
01:17Then the ice covered everything.
01:19This upheaval took place about 34 million years ago.
01:22During the transition from the Eocene to the Oligocene,
01:25a period marked by a significant cooling of our planet.
01:29It was the beginning of one of the many glacial eras.
01:32The earth subsisted, but was engulfed under an increasingly thick layer of ice and snow.
01:38To the naked eye, Antarctica has become a vast, uniform and devoid of relief white desert.
01:44The millennia passed, and the thick ice cap continued to move, polishing and transforming the soil.
01:51Over millions of years, it changed the appearance of the continent.
01:55Today, if we examined the subsurface,
01:57there would be virtually no remains of the original South Pole, with one exception.
02:04In regions where the ice is exceptionally thick and almost immobile,
02:08like in East Antarctica, it plays a reverse role.
02:12It acts as a particularly dense cover that protects the soil.
02:16In normal times, factors such as wind or rain progressively erode the soil,
02:21thus changing its shape over the centuries.
02:24However, thanks to this protective layer of ice,
02:27these natural processes fail to reach the underlying layers.
02:32Thus, the soil has remained almost intact for millions of years,
02:36as if it had been frozen over time.
02:38This specific area, located near the subglacial basins of Aurora and Schmidt,
02:43is now nicknamed the Spectre of the Antarctic Landscape.
02:47This place has remained almost intact since it was covered with snow.
02:5134 million years ago, it constitutes a unique historical trace,
02:56capable of revealing the appearance of the Antarctic soil before it becomes this frozen desert.
03:01When scientists explored East Antarctica, they highlighted a fascinating phantom.
03:07Traces of ancient rivers, various valleys, enigmatic small islands,
03:11as well as three vast U-shaped terrestrial formations.
03:15But what exactly do they mean?
03:19As you know, the continents of our planet are in constant motion,
03:23sliding on a lava mantle in fusion, like cereals in a bowl of milk.
03:27Over the geological eras, they have gathered and separated many times.
03:31Several hundred million years ago, a supercontinent named Gondwana
03:36brought together several lands, including Antarctica, which then formed a single mass.
03:41However, when Gondwana broke, Antarctica was subjected to powerful tectonic forces.
03:47Fragments of its territory were torn from each other and dispersed.
03:51This is how these large blocks of earth formed, hidden under the thick layer of ice.
03:56Today, scientists want to deepen the study of this phantom.
04:01To do this, they plan to drill the ice,
04:03a bit like using a straw to reach the bottom of a thick milkshake.
04:07This method will allow them to take samples of rocks and sediment in depth,
04:12in order to learn more about the history and climate of our planet.
04:18Antarctica would be the 5th largest continent in the world,
04:21surpassing the whole of Europe or Australia in size,
04:23and rivaling all of South America.
04:26In addition to the already mentioned Eastern Antarctic,
04:29it houses other emblematic regions,
04:31such as the Antarctic Peninsula, the South Pole, the Western Antarctic and the Sea of Ross.
04:36This continent is, in a way, a huge frozen land,
04:40whose mysterious and buried landscapes remain less explored than those of Mars.
04:45What we know for sure is that without its ice cover,
04:49it would reveal a world rich in relief,
04:51composed of vast mountains, gigantic canyons and even active volcanoes.
04:56Some of these volcanoes, of a colossal size, emerge above thick layers of snow.
05:01In the Western Antarctic alone, there are at least 138,
05:06although only 8 or 9 are still active today.
05:12One of the most fascinating volcanoes is Mount Erebus,
05:15the southernmost of the continent and also the highest,
05:18culminating at about 4,000 meters.
05:21Under the thick ice cover, this giant houses undervolcanic caves of exceptional beauty,
05:26where the temperatures are soft enough to stay in t-shirts.
05:30The Antarctic Peninsula is like a mountain range of islands,
05:34deeply buried under the surface.
05:36It is composed of relatively recent volcanic rocks,
05:40which are part of the Pacific Ring of Fire.
05:42A gigantic circle,
05:44grouping volcanoes and seismic zones around the Pacific Ocean.
05:48The Eastern Antarctic, on the other hand,
05:50represents an immense region, almost as vast as Australia.
05:54It extends from the eastern coast of the continent to the South Pole.
05:57Under these glaciers, we find extremely ancient rock formations,
06:01some of which were located in the area mentioned earlier.
06:06You probably know that the Antarctic is almost completely devoid of humans.
06:10Nothing surprising about that,
06:12given the average temperature approaching minus 43 degrees Celsius.
06:16But despite these extreme conditions and the desolation of the place,
06:20life persists, and guess where?
06:22In the depths of the earth.
06:24In 2017, researchers discovered traces of algae DNA,
06:28moss, and even unknown small animals in deep caves.
06:32This proves that, despite such hostile conditions,
06:35unique ecosystems manage to thrive in pockets of isolated heat under the snow.
06:43Another incredible discovery took place under the ice platform of Ross,
06:48a flourishing ecosystem within an underground river.
06:51Scientists suspected for a long time that lakes and freshwater rivers
06:55could exist in the Antarctic subsoil.
06:58One day, a satellite detected a fault,
07:01and after deciding to explore it,
07:03they used a drill fed by hot water to melt the ice and sink into it.
07:08Upon arriving in these depths,
07:10they plunged a camera into one of these hidden rivers.
07:13At first, they thought they were simply discovering rocks or similar formations.
07:18But on the contrary, they came across hundreds of amphipods,
07:22tiny creatures resembling shrimps.
07:25The small creatures immediately grouped around the lens,
07:29obstructing the camera and preventing scientists from carrying out the planned observations.
07:34This may seem funny,
07:36but it confirms that there is indeed an ecosystem in the heart of Antarctica.
07:40Researchers now plan to explore it in depth.
07:44And all this is just the beginning of this mysterious underground world.
07:48Under the snow, this continent also hides the deepest canyon,
07:52located under the Denman Glacier.
07:54Although the Marian Fault remains the deepest point in the globe,
07:58it should be noted that, geologically, it belongs to the oceanic crust.
08:03In 1958,
08:05explorers updated a vast mountain range buried under the ice,
08:09comparable to the Alps in terms of altitude.
08:12This chain extends over nearly 1,200 kilometers,
08:15with peaks culminating at 2,700 meters in altitude.
08:19And this splendor is nestled under tons of ice.
08:22Who knows what else we could discover here.
08:27Antarctica houses about 60% of the planet's fresh water.
08:31This means that a total meltdown of these glaciers would have dramatic consequences.
08:36As an example, there is an apocalyptic glacier,
08:40officially known as Glacier Thwaites.
08:43This gigantic block of ice, the size of Florida,
08:46is currently melting.
08:48Each year, this contributes to an elevation of 4% of sea levels.
08:52If this glacier were to melt completely,
08:55the ocean level would increase by 60 centimeters.
08:58A rise that may seem modest,
09:00but would be devastating for the coastal regions of the world.
09:04Fortunately, researchers have found that,
09:06even if its glacial platform disintegrated in the next 50 years,
09:10the glacier itself would not disappear as quickly as it was feared.
09:14Although it is still losing ice at a sustained rate,
09:17this process would remain rather slow.